source: downloads/tcl8.5.2/generic/tclDictObj.c @ 63

/*
 * tclDictObj.c --
 *
 *      This file contains functions that implement the Tcl dict object type
 *      and its accessor command.
 *
 * Copyright (c) 2002 by Donal K. Fellows.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclDictObj.c,v 1.56 2007/12/13 15:23:16 dgp Exp $
 */

#include "tclInt.h"
#include "tommath.h"

/*
 * Forward declaration.
 */
struct Dict;

/*
 * Prototypes for functions defined later in this file:
 */

static void             DeleteDict(struct Dict *dict);
static int              DictAppendCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictCreateCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictExistsCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictFilterCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictForCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictGetCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictIncrCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictInfoCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictKeysCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictLappendCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictMergeCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictRemoveCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictReplaceCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictSetCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictSizeCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictUnsetCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictUpdateCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictValuesCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static int              DictWithCmd(ClientData dummy, Tcl_Interp *interp,
                            int objc, Tcl_Obj *const *objv);
static void             DupDictInternalRep(Tcl_Obj *srcPtr, Tcl_Obj *copyPtr);
static void             FreeDictInternalRep(Tcl_Obj *dictPtr);
static void             InvalidateDictChain(Tcl_Obj *dictObj);
static int              SetDictFromAny(Tcl_Interp *interp, Tcl_Obj *objPtr);
static void             UpdateStringOfDict(Tcl_Obj *dictPtr);
static Tcl_HashEntry *  AllocChainEntry(Tcl_HashTable *tablePtr,void *keyPtr);
static inline void      InitChainTable(struct Dict *dict);
static inline void      DeleteChainTable(struct Dict *dict);
static inline Tcl_HashEntry *CreateChainEntry(struct Dict *dict,
                            Tcl_Obj *keyPtr, int *newPtr);
static inline int       DeleteChainEntry(struct Dict *dict, Tcl_Obj *keyPtr);

/*
 * Table of dict subcommand names and implementations.
 */

static const EnsembleImplMap implementationMap[] = {
    {"append",  DictAppendCmd,  TclCompileDictAppendCmd },
    {"create",  DictCreateCmd,  NULL },
    {"exists",  DictExistsCmd,  NULL },
    {"filter",  DictFilterCmd,  NULL },
    {"for",     DictForCmd,     TclCompileDictForCmd },
    {"get",     DictGetCmd,     TclCompileDictGetCmd },
    {"incr",    DictIncrCmd,    TclCompileDictIncrCmd },
    {"info",    DictInfoCmd,    NULL },
    {"keys",    DictKeysCmd,    NULL },
    {"lappend", DictLappendCmd, TclCompileDictLappendCmd },
    {"merge",   DictMergeCmd,   NULL },
    {"remove",  DictRemoveCmd,  NULL },
    {"replace", DictReplaceCmd, NULL },
    {"set",     DictSetCmd,     TclCompileDictSetCmd },
    {"size",    DictSizeCmd,    NULL },
    {"unset",   DictUnsetCmd,   NULL },
    {"update",  DictUpdateCmd,  TclCompileDictUpdateCmd },
    {"values",  DictValuesCmd,  NULL },
    {"with",    DictWithCmd,    NULL },
    {NULL}
};

/*
 * Internal representation of the entries in the hash table that backs a
 * dictionary.
 */

typedef struct ChainEntry {
    Tcl_HashEntry entry;
    struct ChainEntry *prevPtr;
    struct ChainEntry *nextPtr;
} ChainEntry;

/*
 * Internal representation of a dictionary.
 *
 * The internal representation of a dictionary object is a hash table (with
 * Tcl_Objs for both keys and values), a reference count and epoch number for
 * detecting concurrent modifications of the dictionary, and a pointer to the
 * parent object (used when invalidating string reps of pathed dictionary
 * trees) which is NULL in normal use. The fact that hash tables know (with
 * appropriate initialisation) already about objects makes key management /so/
 * much easier!
 *
 * Reference counts are used to enable safe iteration across hashes while
 * allowing the type of the containing object to be modified.
 */

typedef struct Dict {
    Tcl_HashTable table;        /* Object hash table to store mapping in. */
    ChainEntry *entryChainHead; /* Linked list of all entries in the
                                 * dictionary. Used for doing traversal of the
                                 * entries in the order that they are
                                 * created. */
    ChainEntry *entryChainTail; /* Other end of linked list of all entries in
                                 * the dictionary. Used for doing traversal of
                                 * the entries in the order that they are
                                 * created. */
    int epoch;                  /* Epoch counter */
    int refcount;               /* Reference counter (see above) */
    Tcl_Obj *chain;             /* Linked list used for invalidating the
                                 * string representations of updated nested
                                 * dictionaries. */
} Dict;

/*
 * The structure below defines the dictionary object type by means of
 * functions that can be invoked by generic object code.
 */

Tcl_ObjType tclDictType = {
    "dict",
    FreeDictInternalRep,                /* freeIntRepProc */
    DupDictInternalRep,                 /* dupIntRepProc */
    UpdateStringOfDict,                 /* updateStringProc */
    SetDictFromAny                      /* setFromAnyProc */
};

/*
 * The type of the specially adapted version of the Tcl_Obj*-containing hash
 * table defined in the tclObj.c code. This version differs in that it
 * allocates a bit more space in each hash entry in order to hold the pointers
 * used to keep the hash entries in a linked list.
 *
 * Note that this type of hash table is *only* suitable for direct use in
 * *this* file. Everything else should use the dict iterator API.
 */

static Tcl_HashKeyType chainHashType = {
    TCL_HASH_KEY_TYPE_VERSION,
    0,
    TclHashObjKey,
    TclCompareObjKeys,
    AllocChainEntry,
    TclFreeObjEntry
};

/***** START OF FUNCTIONS IMPLEMENTING DICT CORE API *****/

/*
 *----------------------------------------------------------------------
 *
 * AllocChainEntry --
 *
 *      Allocate space for a Tcl_HashEntry containing the Tcl_Obj * key, and
 *      which has a bit of extra space afterwards for storing pointers to the
 *      rest of the chain of entries (the extra pointers are left NULL).
 *
 * Results:
 *      The return value is a pointer to the created entry.
 *
 * Side effects:
 *      Increments the reference count on the object.
 *
 *----------------------------------------------------------------------
 */

static Tcl_HashEntry *
AllocChainEntry(
    Tcl_HashTable *tablePtr,
    void *keyPtr)
{
    Tcl_Obj *objPtr = keyPtr;
    ChainEntry *cPtr;

    cPtr = (ChainEntry *) ckalloc(sizeof(ChainEntry));
    cPtr->entry.key.oneWordValue = (char *) objPtr;
    Tcl_IncrRefCount(objPtr);
    cPtr->entry.clientData = NULL;
    cPtr->prevPtr = cPtr->nextPtr = NULL;

    return &cPtr->entry;
}

/*
 * Helper functions that disguise most of the details relating to how the
 * linked list of hash entries is managed. In particular, these manage the
 * creation of the table and initializing of the chain, the deletion of the
 * table and chain, the adding of an entry to the chain, and the removal of an
 * entry from the chain.
 */

static inline void
InitChainTable(
    Dict *dict)
{
    Tcl_InitCustomHashTable(&dict->table, TCL_CUSTOM_PTR_KEYS,
            &chainHashType);
    dict->entryChainHead = dict->entryChainTail = NULL;
}

static inline void
DeleteChainTable(
    Dict *dict)
{
    ChainEntry *cPtr;

    for (cPtr=dict->entryChainHead ; cPtr!=NULL ; cPtr=cPtr->nextPtr) {
        Tcl_Obj *valuePtr = Tcl_GetHashValue(&cPtr->entry);

        TclDecrRefCount(valuePtr);
    }
    Tcl_DeleteHashTable(&dict->table);
}

static inline Tcl_HashEntry *
CreateChainEntry(
    Dict *dict,
    Tcl_Obj *keyPtr,
    int *newPtr)
{
    ChainEntry *cPtr = (ChainEntry *)
            Tcl_CreateHashEntry(&dict->table, (char *) keyPtr, newPtr);

    /*
     * If this is a new entry in the hash table, stitch it into the chain.
     */

    if (*newPtr) {
        cPtr->nextPtr = NULL;
        if (dict->entryChainHead == NULL) {
            cPtr->prevPtr = NULL;
            dict->entryChainHead = cPtr;
            dict->entryChainTail = cPtr;
        } else {
            cPtr->prevPtr = dict->entryChainTail;
            dict->entryChainTail->nextPtr = cPtr;
            dict->entryChainTail = cPtr;
        }
    }

    return &cPtr->entry;
}

static inline int
DeleteChainEntry(
    Dict *dict,
    Tcl_Obj *keyPtr)
{
    ChainEntry *cPtr = (ChainEntry *)
            Tcl_FindHashEntry(&dict->table, (char *) keyPtr);

    if (cPtr == NULL) {
        return 0;
    } else {
        Tcl_Obj *valuePtr = Tcl_GetHashValue(&cPtr->entry);
        TclDecrRefCount(valuePtr);
    }

    /*
     * Unstitch from the chain.
     */

    if (cPtr->nextPtr) {
        cPtr->nextPtr->prevPtr = cPtr->prevPtr;
    } else {
        dict->entryChainTail = cPtr->prevPtr;
    }
    if (cPtr->prevPtr) {
        cPtr->prevPtr->nextPtr = cPtr->nextPtr;
    } else {
        dict->entryChainHead = cPtr->nextPtr;
    }

    Tcl_DeleteHashEntry(&cPtr->entry);
    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * DupDictInternalRep --
 *
 *      Initialize the internal representation of a dictionary Tcl_Obj to a
 *      copy of the internal representation of an existing dictionary object.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      "srcPtr"s dictionary internal rep pointer should not be NULL and we
 *      assume it is not NULL. We set "copyPtr"s internal rep to a pointer to
 *      a newly allocated dictionary rep that, in turn, points to "srcPtr"s
 *      key and value objects. Those objects are not actually copied but are
 *      shared between "srcPtr" and "copyPtr". The ref count of each key and
 *      value object is incremented.
 *
 *----------------------------------------------------------------------
 */

static void
DupDictInternalRep(
    Tcl_Obj *srcPtr,
    Tcl_Obj *copyPtr)
{
    Dict *oldDict = srcPtr->internalRep.otherValuePtr;
    Dict *newDict = (Dict *) ckalloc(sizeof(Dict));
    ChainEntry *cPtr;

    /*
     * Copy values across from the old hash table.
     */

    InitChainTable(newDict);
    for (cPtr=oldDict->entryChainHead ; cPtr!=NULL ; cPtr=cPtr->nextPtr) {
        void *key = Tcl_GetHashKey(&oldDict->table, &cPtr->entry);
        Tcl_Obj *valuePtr = Tcl_GetHashValue(&cPtr->entry);
        int n;
        Tcl_HashEntry *hPtr = CreateChainEntry(newDict, key, &n);

        /*
         * Fill in the contents.
         */

        Tcl_SetHashValue(hPtr, (ClientData) valuePtr);
        Tcl_IncrRefCount(valuePtr);
    }

    /*
     * Initialise other fields.
     */

    newDict->epoch = 0;
    newDict->chain = NULL;
    newDict->refcount = 1;

    /*
     * Store in the object.
     */

    copyPtr->internalRep.otherValuePtr = newDict;
    copyPtr->typePtr = &tclDictType;
}

/*
 *----------------------------------------------------------------------
 *
 * FreeDictInternalRep --
 *
 *      Deallocate the storage associated with a dictionary object's internal
 *      representation.
 *
 * Results:
 *      None
 *
 * Side effects:
 *      Frees the memory holding the dictionary's internal hash table unless
 *      it is locked by an iteration going over it.
 *
 *----------------------------------------------------------------------
 */

static void
FreeDictInternalRep(
    Tcl_Obj *dictPtr)
{
    Dict *dict = dictPtr->internalRep.otherValuePtr;

    --dict->refcount;
    if (dict->refcount <= 0) {
        DeleteDict(dict);
    }

    dictPtr->internalRep.otherValuePtr = NULL;  /* Belt and braces! */
}

/*
 *----------------------------------------------------------------------
 *
 * DeleteDict --
 *
 *      Delete the structure that is used to implement a dictionary's internal
 *      representation. Called when either the dictionary object loses its
 *      internal representation or when the last iteration over the dictionary
 *      completes.
 *
 * Results:
 *      None
 *
 * Side effects:
 *      Decrements the reference count of all key and value objects in the
 *      dictionary, which may free them.
 *
 *----------------------------------------------------------------------
 */

static void
DeleteDict(
    Dict *dict)
{
    DeleteChainTable(dict);
    ckfree((char *) dict);
}

/*
 *----------------------------------------------------------------------
 *
 * UpdateStringOfDict --
 *
 *      Update the string representation for a dictionary object. Note: This
 *      function does not invalidate an existing old string rep so storage
 *      will be lost if this has not already been done. This code is based on
 *      UpdateStringOfList in tclListObj.c
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The object's string is set to a valid string that results from the
 *      dict-to-string conversion. This string will be empty if the dictionary
 *      has no key/value pairs. The dictionary internal representation should
 *      not be NULL and we assume it is not NULL.
 *
 *----------------------------------------------------------------------
 */

static void
UpdateStringOfDict(
    Tcl_Obj *dictPtr)
{
#define LOCAL_SIZE 20
    int localFlags[LOCAL_SIZE], *flagPtr;
    Dict *dict = dictPtr->internalRep.otherValuePtr;
    ChainEntry *cPtr;
    Tcl_Obj *keyPtr, *valuePtr;
    int numElems, i, length;
    char *elem, *dst;

    /*
     * This field is the most useful one in the whole hash structure, and it
     * is not exposed by any API function...
     */

    numElems = dict->table.numEntries * 2;

    /*
     * Pass 1: estimate space, gather flags.
     */

    if (numElems <= LOCAL_SIZE) {
        flagPtr = localFlags;
    } else {
        flagPtr = (int *) ckalloc((unsigned) numElems*sizeof(int));
    }
    dictPtr->length = 1;
    for (i=0,cPtr=dict->entryChainHead; i<numElems; i+=2,cPtr=cPtr->nextPtr) {
        /*
         * Assume that cPtr is never NULL since we know the number of array
         * elements already.
         */

        keyPtr = (Tcl_Obj *) Tcl_GetHashKey(&dict->table, &cPtr->entry);
        elem = TclGetStringFromObj(keyPtr, &length);
        dictPtr->length += Tcl_ScanCountedElement(elem, length,
                &flagPtr[i]) + 1;

        valuePtr = Tcl_GetHashValue(&cPtr->entry);
        elem = TclGetStringFromObj(valuePtr, &length);
        dictPtr->length += Tcl_ScanCountedElement(elem, length,
                &flagPtr[i+1]) + 1;
    }

    /*
     * Pass 2: copy into string rep buffer.
     */

    dictPtr->bytes = ckalloc((unsigned) dictPtr->length);
    dst = dictPtr->bytes;
    for (i=0,cPtr=dict->entryChainHead; i<numElems; i+=2,cPtr=cPtr->nextPtr) {
        keyPtr = (Tcl_Obj *) Tcl_GetHashKey(&dict->table, &cPtr->entry);
        elem = TclGetStringFromObj(keyPtr, &length);
        dst += Tcl_ConvertCountedElement(elem, length, dst,
                flagPtr[i] | (i==0 ? 0 : TCL_DONT_QUOTE_HASH));
        *(dst++) = ' ';

        valuePtr = Tcl_GetHashValue(&cPtr->entry);
        elem = TclGetStringFromObj(valuePtr, &length);
        dst += Tcl_ConvertCountedElement(elem, length, dst,
                flagPtr[i+1] | TCL_DONT_QUOTE_HASH);
        *(dst++) = ' ';
    }
    if (flagPtr != localFlags) {
        ckfree((char *) flagPtr);
    }
    if (dst == dictPtr->bytes) {
        *dst = 0;
    } else {
        *(--dst) = 0;
    }
    dictPtr->length = dst - dictPtr->bytes;
}

/*
 *----------------------------------------------------------------------
 *
 * SetDictFromAny --
 *
 *      Convert a non-dictionary object into a dictionary object. This code is
 *      very closely related to SetListFromAny in tclListObj.c but does not
 *      actually guarantee that a dictionary object will have a string rep (as
 *      conversions from lists are handled with a special case.)
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      If the string can be converted, it loses any old internal
 *      representation that it had and gains a dictionary's internalRep.
 *
 *----------------------------------------------------------------------
 */

static int
SetDictFromAny(
    Tcl_Interp *interp,
    Tcl_Obj *objPtr)
{
    char *string, *s;
    const char *elemStart, *nextElem;
    int lenRemain, length, elemSize, hasBrace, result, isNew;
    char *limit;                /* Points just after string's last byte. */
    register const char *p;
    register Tcl_Obj *keyPtr, *valuePtr;
    Dict *dict;
    Tcl_HashEntry *hPtr;

    /*
     * Since lists and dictionaries have very closely-related string
     * representations (i.e. the same parsing code) we can safely special-case
     * the conversion from lists to dictionaries.
     */

    if (objPtr->typePtr == &tclListType) {
        int objc, i;
        Tcl_Obj **objv;

        if (TclListObjGetElements(interp, objPtr, &objc, &objv) != TCL_OK) {
            return TCL_ERROR;
        }
        if (objc & 1) {
            if (interp != NULL) {
                Tcl_SetResult(interp, "missing value to go with key",
                        TCL_STATIC);
            }
            return TCL_ERROR;
        }

        /*
         * If the list is shared its string rep must not be lost so it still
         * is the same list.
         */

        if (Tcl_IsShared(objPtr)) {
            (void) TclGetString(objPtr);
        }

        /*
         * Build the hash of key/value pairs.
         */

        dict = (Dict *) ckalloc(sizeof(Dict));
        InitChainTable(dict);
        for (i=0 ; i<objc ; i+=2) {
            /*
             * Store key and value in the hash table we're building.
             */

            hPtr = CreateChainEntry(dict, objv[i], &isNew);
            if (!isNew) {
                Tcl_Obj *discardedValue = Tcl_GetHashValue(hPtr);

                TclDecrRefCount(discardedValue);
            }
            Tcl_SetHashValue(hPtr, objv[i+1]);
            Tcl_IncrRefCount(objv[i+1]); /* Since hash now holds ref to it */
        }

        /*
         * Share type-setting code with the string-conversion case.
         */

        goto installHash;
    }

    /*
     * Get the string representation. Make it up-to-date if necessary.
     */

    string = TclGetStringFromObj(objPtr, &length);
    limit = (string + length);

    /*
     * Allocate a new HashTable that has objects for keys and objects for
     * values.
     */

    dict = (Dict *) ckalloc(sizeof(Dict));
    InitChainTable(dict);
    for (p = string, lenRemain = length;
            lenRemain > 0;
            p = nextElem, lenRemain = (limit - nextElem)) {
        result = TclFindElement(interp, p, lenRemain,
                &elemStart, &nextElem, &elemSize, &hasBrace);
        if (result != TCL_OK) {
            goto errorExit;
        }
        if (elemStart >= limit) {
            break;
        }

        /*
         * Allocate a Tcl object for the element and initialize it from the
         * "elemSize" bytes starting at "elemStart".
         */

        s = ckalloc((unsigned) elemSize + 1);
        if (hasBrace) {
            memcpy(s, elemStart, (size_t) elemSize);
            s[elemSize] = 0;
        } else {
            elemSize = TclCopyAndCollapse(elemSize, elemStart, s);
        }

        TclNewObj(keyPtr);
        keyPtr->bytes = s;
        keyPtr->length = elemSize;

        p = nextElem;
        lenRemain = (limit - nextElem);
        if (lenRemain <= 0) {
            goto missingKey;
        }

        result = TclFindElement(interp, p, lenRemain,
                &elemStart, &nextElem, &elemSize, &hasBrace);
        if (result != TCL_OK) {
            TclDecrRefCount(keyPtr);
            goto errorExit;
        }
        if (elemStart >= limit) {
            goto missingKey;
        }

        /*
         * Allocate a Tcl object for the element and initialize it from the
         * "elemSize" bytes starting at "elemStart".
         */

        s = ckalloc((unsigned) elemSize + 1);
        if (hasBrace) {
            memcpy((void *) s, (void *) elemStart, (size_t) elemSize);
            s[elemSize] = 0;
        } else {
            elemSize = TclCopyAndCollapse(elemSize, elemStart, s);
        }

        TclNewObj(valuePtr);
        valuePtr->bytes = s;
        valuePtr->length = elemSize;

        /*
         * Store key and value in the hash table we're building.
         */

        hPtr = CreateChainEntry(dict, keyPtr, &isNew);
        if (!isNew) {
            Tcl_Obj *discardedValue = Tcl_GetHashValue(hPtr);

            TclDecrRefCount(keyPtr);
            TclDecrRefCount(discardedValue);
        }
        Tcl_SetHashValue(hPtr, valuePtr);
        Tcl_IncrRefCount(valuePtr); /* since hash now holds ref to it */
    }

  installHash:
    /*
     * Free the old internalRep before setting the new one. We do this as late
     * as possible to allow the conversion code, in particular
     * Tcl_GetStringFromObj, to use that old internalRep.
     */

    TclFreeIntRep(objPtr);
    dict->epoch = 0;
    dict->chain = NULL;
    dict->refcount = 1;
    objPtr->internalRep.otherValuePtr = dict;
    objPtr->typePtr = &tclDictType;
    return TCL_OK;

  missingKey:
    if (interp != NULL) {
        Tcl_SetResult(interp, "missing value to go with key", TCL_STATIC);
    }
    TclDecrRefCount(keyPtr);
    result = TCL_ERROR;

  errorExit:
    DeleteChainTable(dict);
    ckfree((char *) dict);
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * TclTraceDictPath --
 *
 *      Trace through a tree of dictionaries using the array of keys given. If
 *      the flags argument has the DICT_PATH_UPDATE flag is set, a
 *      backward-pointing chain of dictionaries is also built (in the Dict's
 *      chain field) and the chained dictionaries are made into unshared
 *      dictionaries (if they aren't already.)
 *
 * Results:
 *      The object at the end of the path, or NULL if there was an error. Note
 *      that this it is an error for an intermediate dictionary on the path to
 *      not exist. If the flags argument has the DICT_PATH_EXISTS set, a
 *      non-existent path gives a DICT_PATH_NON_EXISTENT result.
 *
 * Side effects:
 *      If the flags argument is zero or DICT_PATH_EXISTS, there are no side
 *      effects (other than potential conversion of objects to dictionaries.)
 *      If the flags argument is DICT_PATH_UPDATE, the following additional
 *      side effects occur. Shared dictionaries along the path are converted
 *      into unshared objects, and a backward-pointing chain is built using
 *      the chain fields of the dictionaries (for easy invalidation of string
 *      representations using InvalidateDictChain). If the flags argument has
 *      the DICT_PATH_CREATE bits set (and not the DICT_PATH_EXISTS bit),
 *      non-existant keys will be inserted with a value of an empty
 *      dictionary, resulting in the path being built.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclTraceDictPath(
    Tcl_Interp *interp,
    Tcl_Obj *dictPtr,
    int keyc,
    Tcl_Obj *const keyv[],
    int flags)
{
    Dict *dict, *newDict;
    int i;

    if (dictPtr->typePtr != &tclDictType) {
        if (SetDictFromAny(interp, dictPtr) != TCL_OK) {
            return NULL;
        }
    }
    dict = dictPtr->internalRep.otherValuePtr;
    if (flags & DICT_PATH_UPDATE) {
        dict->chain = NULL;
    }

    for (i=0 ; i<keyc ; i++) {
        Tcl_HashEntry *hPtr = Tcl_FindHashEntry(&dict->table, (char *)keyv[i]);
        Tcl_Obj *tmpObj;

        if (hPtr == NULL) {
            int isNew;                  /* Dummy */

            if (flags & DICT_PATH_EXISTS) {
                return DICT_PATH_NON_EXISTENT;
            }
            if ((flags & DICT_PATH_CREATE) != DICT_PATH_CREATE) {
                if (interp != NULL) {
                    Tcl_ResetResult(interp);
                    Tcl_AppendResult(interp, "key \"", TclGetString(keyv[i]),
                            "\" not known in dictionary", NULL);
                    Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "DICT",
                            TclGetString(keyv[i]), NULL);
                }
                return NULL;
            }

            /*
             * The next line should always set isNew to 1.
             */

            hPtr = CreateChainEntry(dict, keyv[i], &isNew);
            tmpObj = Tcl_NewDictObj();
            Tcl_IncrRefCount(tmpObj);
            Tcl_SetHashValue(hPtr, tmpObj);
        } else {
            tmpObj = Tcl_GetHashValue(hPtr);
            if (tmpObj->typePtr != &tclDictType) {
                if (SetDictFromAny(interp, tmpObj) != TCL_OK) {
                    return NULL;
                }
            }
        }

        newDict = tmpObj->internalRep.otherValuePtr;
        if (flags & DICT_PATH_UPDATE) {
            if (Tcl_IsShared(tmpObj)) {
                TclDecrRefCount(tmpObj);
                tmpObj = Tcl_DuplicateObj(tmpObj);
                Tcl_IncrRefCount(tmpObj);
                Tcl_SetHashValue(hPtr, (ClientData) tmpObj);
                dict->epoch++;
                newDict = tmpObj->internalRep.otherValuePtr;
            }

            newDict->chain = dictPtr;
        }
        dict = newDict;
        dictPtr = tmpObj;
    }
    return dictPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * InvalidateDictChain --
 *
 *      Go through a dictionary chain (built by an updating invokation of
 *      TclTraceDictPath) and invalidate the string representations of all the
 *      dictionaries on the chain.
 *
 * Results:
 *      None
 *
 * Side effects:
 *      String reps are invalidated and epoch counters (for detecting illegal
 *      concurrent modifications) are updated through the chain of updated
 *      dictionaries.
 *
 *----------------------------------------------------------------------
 */

static void
InvalidateDictChain(
    Tcl_Obj *dictObj)
{
    Dict *dict = dictObj->internalRep.otherValuePtr;

    do {
        Tcl_InvalidateStringRep(dictObj);
        dict->epoch++;
        dictObj = dict->chain;
        if (dictObj == NULL) {
            break;
        }
        dict->chain = NULL;
        dict = dictObj->internalRep.otherValuePtr;
    } while (dict != NULL);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DictObjPut --
 *
 *      Add a key,value pair to a dictionary, or update the value for a key if
 *      that key already has a mapping in the dictionary.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      The object pointed to by dictPtr is converted to a dictionary if it is
 *      not already one, and any string representation that it has is
 *      invalidated.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_DictObjPut(
    Tcl_Interp *interp,
    Tcl_Obj *dictPtr,
    Tcl_Obj *keyPtr,
    Tcl_Obj *valuePtr)
{
    Dict *dict;
    Tcl_HashEntry *hPtr;
    int isNew;

    if (Tcl_IsShared(dictPtr)) {
        Tcl_Panic("%s called with shared object", "Tcl_DictObjPut");
    }

    if (dictPtr->typePtr != &tclDictType) {
        int result = SetDictFromAny(interp, dictPtr);

        if (result != TCL_OK) {
            return result;
        }
    }

    if (dictPtr->bytes != NULL) {
        Tcl_InvalidateStringRep(dictPtr);
    }
    dict = dictPtr->internalRep.otherValuePtr;
    hPtr = CreateChainEntry(dict, keyPtr, &isNew);
    Tcl_IncrRefCount(valuePtr);
    if (!isNew) {
        Tcl_Obj *oldValuePtr = Tcl_GetHashValue(hPtr);

        TclDecrRefCount(oldValuePtr);
    }
    Tcl_SetHashValue(hPtr, valuePtr);
    dict->epoch++;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DictObjGet --
 *
 *      Given a key, get its value from the dictionary (or NULL if key is not
 *      found in dictionary.)
 *
 * Results:
 *      A standard Tcl result. The variable pointed to by valuePtrPtr is
 *      updated with the value for the key. Note that it is not an error for
 *      the key to have no mapping in the dictionary.
 *
 * Side effects:
 *      The object pointed to by dictPtr is converted to a dictionary if it is
 *      not already one.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_DictObjGet(
    Tcl_Interp *interp,
    Tcl_Obj *dictPtr,
    Tcl_Obj *keyPtr,
    Tcl_Obj **valuePtrPtr)
{
    Dict *dict;
    Tcl_HashEntry *hPtr;

    if (dictPtr->typePtr != &tclDictType) {
        int result = SetDictFromAny(interp, dictPtr);
        if (result != TCL_OK) {
            return result;
        }
    }

    dict = dictPtr->internalRep.otherValuePtr;
    hPtr = Tcl_FindHashEntry(&dict->table, (char *) keyPtr);
    if (hPtr == NULL) {
        *valuePtrPtr = NULL;
    } else {
        *valuePtrPtr = Tcl_GetHashValue(hPtr);
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DictObjRemove --
 *
 *      Remove the key,value pair with the given key from the dictionary; the
 *      key does not need to be present in the dictionary.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      The object pointed to by dictPtr is converted to a dictionary if it is
 *      not already one, and any string representation that it has is
 *      invalidated.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_DictObjRemove(
    Tcl_Interp *interp,
    Tcl_Obj *dictPtr,
    Tcl_Obj *keyPtr)
{
    Dict *dict;

    if (Tcl_IsShared(dictPtr)) {
        Tcl_Panic("%s called with shared object", "Tcl_DictObjRemove");
    }

    if (dictPtr->typePtr != &tclDictType) {
        int result = SetDictFromAny(interp, dictPtr);
        if (result != TCL_OK) {
            return result;
        }
    }

    if (dictPtr->bytes != NULL) {
        Tcl_InvalidateStringRep(dictPtr);
    }
    dict = dictPtr->internalRep.otherValuePtr;
    if (DeleteChainEntry(dict, keyPtr)) {
        dict->epoch++;
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DictObjSize --
 *
 *      How many key,value pairs are there in the dictionary?
 *
 * Results:
 *      A standard Tcl result. Updates the variable pointed to by sizePtr with
 *      the number of key,value pairs in the dictionary.
 *
 * Side effects:
 *      The dictPtr object is converted to a dictionary type if it is not a
 *      dictionary already.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_DictObjSize(
    Tcl_Interp *interp,
    Tcl_Obj *dictPtr,
    int *sizePtr)
{
    Dict *dict;

    if (dictPtr->typePtr != &tclDictType) {
        int result = SetDictFromAny(interp, dictPtr);
        if (result != TCL_OK) {
            return result;
        }
    }

    dict = dictPtr->internalRep.otherValuePtr;
    *sizePtr = dict->table.numEntries;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DictObjFirst --
 *
 *      Start a traversal of the dictionary. Caller must supply the search
 *      context, pointers for returning key and value, and a pointer to allow
 *      indication of whether the dictionary has been traversed (i.e. the
 *      dictionary is empty). The order of traversal is undefined.
 *
 * Results:
 *      A standard Tcl result. Updates the variables pointed to by keyPtrPtr,
 *      valuePtrPtr and donePtr. Either of keyPtrPtr and valuePtrPtr may be
 *      NULL, in which case the key/value is not made available to the caller.
 *
 * Side effects:
 *      The dictPtr object is converted to a dictionary type if it is not a
 *      dictionary already. The search context is initialised if the search
 *      has not finished. The dictionary's internal rep is Tcl_Preserve()d if
 *      the dictionary has at least one element.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_DictObjFirst(
    Tcl_Interp *interp,         /* For error messages, or NULL if no error
                                 * messages desired. */
    Tcl_Obj *dictPtr,           /* Dictionary to traverse. */
    Tcl_DictSearch *searchPtr,  /* Pointer to a dict search context. */
    Tcl_Obj **keyPtrPtr,        /* Pointer to a variable to have the first key
                                 * written into, or NULL. */
    Tcl_Obj **valuePtrPtr,      /* Pointer to a variable to have the first
                                 * value written into, or NULL.*/
    int *donePtr)               /* Pointer to a variable which will have a 1
                                 * written into when there are no further
                                 * values in the dictionary, or a 0
                                 * otherwise. */
{
    Dict *dict;
    ChainEntry *cPtr;

    if (dictPtr->typePtr != &tclDictType) {
        int result = SetDictFromAny(interp, dictPtr);

        if (result != TCL_OK) {
            return result;
        }
    }

    dict = dictPtr->internalRep.otherValuePtr;
    cPtr = dict->entryChainHead;
    if (cPtr == NULL) {
        searchPtr->epoch = -1;
        *donePtr = 1;
    } else {
        *donePtr = 0;
        searchPtr->dictionaryPtr = (Tcl_Dict) dict;
        searchPtr->epoch = dict->epoch;
        searchPtr->next = cPtr->nextPtr;
        dict->refcount++;
        if (keyPtrPtr != NULL) {
            *keyPtrPtr = (Tcl_Obj *) Tcl_GetHashKey(&dict->table,
                    &cPtr->entry);
        }
        if (valuePtrPtr != NULL) {
            *valuePtrPtr = Tcl_GetHashValue(&cPtr->entry);
        }
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DictObjNext --
 *
 *      Continue a traversal of a dictionary previously started with
 *      Tcl_DictObjFirst. This function is safe against concurrent
 *      modification of the underlying object (including type shimmering),
 *      treating such situations as if the search has terminated, though it is
 *      up to the caller to ensure that the object itself is not disposed
 *      until the search has finished. It is _not_ safe against modifications
 *      from other threads.
 *
 * Results:
 *      Updates the variables pointed to by keyPtrPtr, valuePtrPtr and
 *      donePtr. Either of keyPtrPtr and valuePtrPtr may be NULL, in which
 *      case the key/value is not made available to the caller.
 *
 * Side effects:
 *      Removes a reference to the dictionary's internal rep if the search
 *      terminates.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DictObjNext(
    Tcl_DictSearch *searchPtr,  /* Pointer to a hash search context. */
    Tcl_Obj **keyPtrPtr,        /* Pointer to a variable to have the first key
                                 * written into, or NULL. */
    Tcl_Obj **valuePtrPtr,      /* Pointer to a variable to have the first
                                 * value written into, or NULL.*/
    int *donePtr)               /* Pointer to a variable which will have a 1
                                 * written into when there are no further
                                 * values in the dictionary, or a 0
                                 * otherwise. */
{
    ChainEntry *cPtr;

    /*
     * If the searh is done; we do no work.
     */

    if (searchPtr->epoch == -1) {
        *donePtr = 1;
        return;
    }

    /*
     * Bail out if the dictionary has had any elements added, modified or
     * removed. This *shouldn't* happen, but...
     */

    if (((Dict *)searchPtr->dictionaryPtr)->epoch != searchPtr->epoch) {
        Tcl_Panic("concurrent dictionary modification and search");
    }

    cPtr = searchPtr->next;
    if (cPtr == NULL) {
        Tcl_DictObjDone(searchPtr);
        *donePtr = 1;
        return;
    }

    searchPtr->next = cPtr->nextPtr;
    *donePtr = 0;
    if (keyPtrPtr != NULL) {
        *keyPtrPtr = (Tcl_Obj *) Tcl_GetHashKey(
                &((Dict *)searchPtr->dictionaryPtr)->table, &cPtr->entry);
    }
    if (valuePtrPtr != NULL) {
        *valuePtrPtr = Tcl_GetHashValue(&cPtr->entry);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DictObjDone --
 *
 *      Call this if you want to stop a search before you reach the end of the
 *      dictionary (e.g. because of abnormal termination of the search). It
 *      need not be used if the search reaches its natural end (i.e. if either
 *      Tcl_DictObjFirst or Tcl_DictObjNext sets its donePtr variable to 1).
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Removes a reference to the dictionary's internal rep.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DictObjDone(
    Tcl_DictSearch *searchPtr)          /* Pointer to a hash search context. */
{
    Dict *dict;

    if (searchPtr->epoch != -1) {
        searchPtr->epoch = -1;
        dict = (Dict *) searchPtr->dictionaryPtr;
        dict->refcount--;
        if (dict->refcount <= 0) {
            DeleteDict(dict);
        }
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DictObjPutKeyList --
 *
 *      Add a key...key,value pair to a dictionary tree. The main dictionary
 *      value must not be shared, though sub-dictionaries may be. All
 *      intermediate dictionaries on the path must exist.
 *
 * Results:
 *      A standard Tcl result. Note that in the error case, a message is left
 *      in interp unless that is NULL.
 *
 * Side effects:
 *      If the dictionary and any of its sub-dictionaries on the path have
 *      string representations, these are invalidated.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_DictObjPutKeyList(
    Tcl_Interp *interp,
    Tcl_Obj *dictPtr,
    int keyc,
    Tcl_Obj *const keyv[],
    Tcl_Obj *valuePtr)
{
    Dict *dict;
    Tcl_HashEntry *hPtr;
    int isNew;

    if (Tcl_IsShared(dictPtr)) {
        Tcl_Panic("%s called with shared object", "Tcl_DictObjPutKeyList");
    }
    if (keyc < 1) {
        Tcl_Panic("%s called with empty key list", "Tcl_DictObjPutKeyList");
    }

    dictPtr = TclTraceDictPath(interp, dictPtr, keyc-1,keyv, DICT_PATH_CREATE);
    if (dictPtr == NULL) {
        return TCL_ERROR;
    }

    dict = dictPtr->internalRep.otherValuePtr;
    hPtr = CreateChainEntry(dict, keyv[keyc-1], &isNew);
    Tcl_IncrRefCount(valuePtr);
    if (!isNew) {
        Tcl_Obj *oldValuePtr = Tcl_GetHashValue(hPtr);
        TclDecrRefCount(oldValuePtr);
    }
    Tcl_SetHashValue(hPtr, valuePtr);
    InvalidateDictChain(dictPtr);

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DictObjRemoveKeyList --
 *
 *      Remove a key...key,value pair from a dictionary tree (the value
 *      removed is implicit in the key path). The main dictionary value must
 *      not be shared, though sub-dictionaries may be. It is not an error if
 *      there is no value associated with the given key list, but all
 *      intermediate dictionaries on the key path must exist.
 *
 * Results:
 *      A standard Tcl result. Note that in the error case, a message is left
 *      in interp unless that is NULL.
 *
 * Side effects:
 *      If the dictionary and any of its sub-dictionaries on the key path have
 *      string representations, these are invalidated.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_DictObjRemoveKeyList(
    Tcl_Interp *interp,
    Tcl_Obj *dictPtr,
    int keyc,
    Tcl_Obj *const keyv[])
{
    Dict *dict;

    if (Tcl_IsShared(dictPtr)) {
        Tcl_Panic("%s called with shared object", "Tcl_DictObjRemoveKeyList");
    }
    if (keyc < 1) {
        Tcl_Panic("%s called with empty key list", "Tcl_DictObjRemoveKeyList");
    }

    dictPtr = TclTraceDictPath(interp, dictPtr, keyc-1,keyv, DICT_PATH_UPDATE);
    if (dictPtr == NULL) {
        return TCL_ERROR;
    }

    dict = dictPtr->internalRep.otherValuePtr;
    DeleteChainEntry(dict, keyv[keyc-1]);
    InvalidateDictChain(dictPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_NewDictObj --
 *
 *      This function is normally called when not debugging: i.e., when
 *      TCL_MEM_DEBUG is not defined. It creates a new dict object without any
 *      content.
 *
 *      When TCL_MEM_DEBUG is defined, this function just returns the result
 *      of calling the debugging version Tcl_DbNewDictObj.
 *
 * Results:
 *      A new dict object is returned; it has no keys defined in it. The new
 *      object's string representation is left NULL, and the ref count of the
 *      object is 0.
 *
 * Side Effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
Tcl_NewDictObj(void)
{
#ifdef TCL_MEM_DEBUG
    return Tcl_DbNewDictObj("unknown", 0);
#else /* !TCL_MEM_DEBUG */

    Tcl_Obj *dictPtr;
    Dict *dict;

    TclNewObj(dictPtr);
    Tcl_InvalidateStringRep(dictPtr);
    dict = (Dict *) ckalloc(sizeof(Dict));
    InitChainTable(dict);
    dict->epoch = 0;
    dict->chain = NULL;
    dict->refcount = 1;
    dictPtr->internalRep.otherValuePtr = dict;
    dictPtr->typePtr = &tclDictType;
    return dictPtr;
#endif
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DbNewDictObj --
 *
 *      This function is normally called when debugging: i.e., when
 *      TCL_MEM_DEBUG is defined. It creates new dict objects. It is the same
 *      as the Tcl_NewDictObj function above except that it calls
 *      Tcl_DbCkalloc directly with the file name and line number from its
 *      caller. This simplifies debugging since then the [memory active]
 *      command will report the correct file name and line number when
 *      reporting objects that haven't been freed.
 *
 *      When TCL_MEM_DEBUG is not defined, this function just returns the
 *      result of calling Tcl_NewDictObj.
 *
 * Results:
 *      A new dict object is returned; it has no keys defined in it. The new
 *      object's string representation is left NULL, and the ref count of the
 *      object is 0.
 *
 * Side Effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
Tcl_DbNewDictObj(
    const char *file,
    int line)
{
#ifdef TCL_MEM_DEBUG
    Tcl_Obj *dictPtr;
    Dict *dict;

    TclDbNewObj(dictPtr, file, line);
    Tcl_InvalidateStringRep(dictPtr);
    dict = (Dict *) ckalloc(sizeof(Dict));
    InitChainTable(dict);
    dict->epoch = 0;
    dict->chain = NULL;
    dict->refcount = 1;
    dictPtr->internalRep.otherValuePtr = dict;
    dictPtr->typePtr = &tclDictType;
    return dictPtr;
#else /* !TCL_MEM_DEBUG */
    return Tcl_NewDictObj();
#endif
}

/***** START OF FUNCTIONS IMPLEMENTING TCL COMMANDS *****/

/*
 *----------------------------------------------------------------------
 *
 * DictCreateCmd --
 *
 *      This function implements the "dict create" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictCreateCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *dictObj;
    int i;

    /*
     * Must have an even number of arguments; note that number of preceding
     * arguments (i.e. "dict create" is also even, which makes this much
     * easier.)
     */

    if ((objc & 1) == 0) {
        Tcl_WrongNumArgs(interp, 1, objv, "?key value ...?");
        return TCL_ERROR;
    }

    dictObj = Tcl_NewDictObj();
    for (i=1 ; i<objc ; i+=2) {
        /*
         * The next command is assumed to never fail...
         */
        Tcl_DictObjPut(interp, dictObj, objv[i], objv[i+1]);
    }
    Tcl_SetObjResult(interp, dictObj);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictGetCmd --
 *
 *      This function implements the "dict get" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictGetCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *dictPtr, *valuePtr = NULL;
    int result;

    if (objc < 2) {
        Tcl_WrongNumArgs(interp, 1, objv, "dictionary ?key key ...?");
        return TCL_ERROR;
    }

    /*
     * Test for the special case of no keys, which returns a *list* of all
     * key,value pairs. We produce a copy here because that makes subsequent
     * list handling more efficient.
     */

    if (objc == 2) {
        Tcl_Obj *keyPtr, *listPtr;
        Tcl_DictSearch search;
        int done;

        result = Tcl_DictObjFirst(interp, objv[1], &search,
                &keyPtr, &valuePtr, &done);
        if (result != TCL_OK) {
            return result;
        }
        listPtr = Tcl_NewListObj(0, NULL);
        while (!done) {
            /*
             * Assume these won't fail as we have complete control over the
             * types of things here.
             */

            Tcl_ListObjAppendElement(interp, listPtr, keyPtr);
            Tcl_ListObjAppendElement(interp, listPtr, valuePtr);

            Tcl_DictObjNext(&search, &keyPtr, &valuePtr, &done);
        }
        Tcl_SetObjResult(interp, listPtr);
        return TCL_OK;
    }

    /*
     * Loop through the list of keys, looking up the key at the current index
     * in the current dictionary each time. Once we've done the lookup, we set
     * the current dictionary to be the value we looked up (in case the value
     * was not the last one and we are going through a chain of searches.)
     * Note that this loop always executes at least once.
     */

    dictPtr = TclTraceDictPath(interp, objv[1], objc-3,objv+2, DICT_PATH_READ);
    if (dictPtr == NULL) {
        return TCL_ERROR;
    }
    result = Tcl_DictObjGet(interp, dictPtr, objv[objc-1], &valuePtr);
    if (result != TCL_OK) {
        return result;
    }
    if (valuePtr == NULL) {
        Tcl_ResetResult(interp);
        Tcl_AppendResult(interp, "key \"", TclGetString(objv[objc-1]),
                "\" not known in dictionary", NULL);
        return TCL_ERROR;
    }
    Tcl_SetObjResult(interp, valuePtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictReplaceCmd --
 *
 *      This function implements the "dict replace" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictReplaceCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *dictPtr;
    int i, result;
    int allocatedDict = 0;

    if ((objc < 2) || (objc & 1)) {
        Tcl_WrongNumArgs(interp, 1, objv, "dictionary ?key value ...?");
        return TCL_ERROR;
    }

    dictPtr = objv[1];
    if (Tcl_IsShared(dictPtr)) {
        dictPtr = Tcl_DuplicateObj(dictPtr);
        allocatedDict = 1;
    }
    for (i=2 ; i<objc ; i+=2) {
        result = Tcl_DictObjPut(interp, dictPtr, objv[i], objv[i+1]);
        if (result != TCL_OK) {
            if (allocatedDict) {
                TclDecrRefCount(dictPtr);
            }
            return TCL_ERROR;
        }
    }
    Tcl_SetObjResult(interp, dictPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictRemoveCmd --
 *
 *      This function implements the "dict remove" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictRemoveCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *dictPtr;
    int i, result;
    int allocatedDict = 0;

    if (objc < 2) {
        Tcl_WrongNumArgs(interp, 1, objv, "dictionary ?key ...?");
        return TCL_ERROR;
    }

    dictPtr = objv[1];
    if (Tcl_IsShared(dictPtr)) {
        dictPtr = Tcl_DuplicateObj(dictPtr);
        allocatedDict = 1;
    }
    for (i=2 ; i<objc ; i++) {
        result = Tcl_DictObjRemove(interp, dictPtr, objv[i]);
        if (result != TCL_OK) {
            if (allocatedDict) {
                TclDecrRefCount(dictPtr);
            }
            return TCL_ERROR;
        }
    }
    Tcl_SetObjResult(interp, dictPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictMergeCmd --
 *
 *      This function implements the "dict merge" Tcl command. See the user
 *      documentation for details on what it does, and TIP#163 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictMergeCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *targetObj, *keyObj, *valueObj;
    int allocatedDict = 0;
    int i, done;
    Tcl_DictSearch search;

    if (objc == 1) {
        /*
         * No dictionary arguments; return default (empty value).
         */

        return TCL_OK;
    }

    /*
     * Make sure first argument is a dictionary.
     */

    targetObj = objv[1];
    if (targetObj->typePtr != &tclDictType) {
        if (SetDictFromAny(interp, targetObj) != TCL_OK) {
            return TCL_ERROR;
        }
    }

    if (objc == 2) {
        /*
         * Single argument, return it.
         */

        Tcl_SetObjResult(interp, objv[1]);
        return TCL_OK;
    }

    /*
     * Normal behaviour: combining two (or more) dictionaries.
     */

    if (Tcl_IsShared(targetObj)) {
        targetObj = Tcl_DuplicateObj(targetObj);
        allocatedDict = 1;
    }
    for (i=2 ; i<objc ; i++) {
        if (Tcl_DictObjFirst(interp, objv[i], &search, &keyObj, &valueObj,
                &done) != TCL_OK) {
            if (allocatedDict) {
                TclDecrRefCount(targetObj);
            }
            return TCL_ERROR;
        }
        while (!done) {
            /*
             * Next line can't fail; already know we have a dictionary in
             * targetObj.
             */

            Tcl_DictObjPut(NULL, targetObj, keyObj, valueObj);
            Tcl_DictObjNext(&search, &keyObj, &valueObj, &done);
        }
        Tcl_DictObjDone(&search);
    }
    Tcl_SetObjResult(interp, targetObj);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictKeysCmd --
 *
 *      This function implements the "dict keys" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictKeysCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *listPtr;
    char *pattern = NULL;

    if (objc!=2 && objc!=3) {
        Tcl_WrongNumArgs(interp, 1, objv, "dictionary ?pattern?");
        return TCL_ERROR;
    }

    /*
     * A direct check that we have a dictionary. We don't start the iteration
     * yet because that might allocate memory or set locks that we do not
     * need. [Bug 1705778, leak K04]
     */

    if (objv[1]->typePtr != &tclDictType) {
        int result = SetDictFromAny(interp, objv[1]);

        if (result != TCL_OK) {
            return result;
        }
    }

    if (objc == 3) {
        pattern = TclGetString(objv[2]);
    }
    listPtr = Tcl_NewListObj(0, NULL);
    if ((pattern != NULL) && TclMatchIsTrivial(pattern)) {
        Tcl_Obj *valuePtr = NULL;

        Tcl_DictObjGet(interp, objv[1], objv[2], &valuePtr);
        if (valuePtr != NULL) {
            Tcl_ListObjAppendElement(NULL, listPtr, objv[2]);
        }
    } else {
        Tcl_DictSearch search;
        Tcl_Obj *keyPtr;
        int done;

        /*
         * At this point, we know we have a dictionary (or at least something
         * that can be represented; it could theoretically have shimmered away
         * when the pattern was fetched, but that shouldn't be damaging) so we
         * can start the iteration process without checking for failures.
         */

        Tcl_DictObjFirst(NULL, objv[1], &search, &keyPtr, NULL, &done);
        for (; !done ; Tcl_DictObjNext(&search, &keyPtr, NULL, &done)) {
            if (!pattern || Tcl_StringMatch(TclGetString(keyPtr), pattern)) {
                Tcl_ListObjAppendElement(NULL, listPtr, keyPtr);
            }
        }
        Tcl_DictObjDone(&search);
    }

    Tcl_SetObjResult(interp, listPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictValuesCmd --
 *
 *      This function implements the "dict values" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictValuesCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *valuePtr, *listPtr;
    Tcl_DictSearch search;
    int done;
    char *pattern;

    if (objc!=2 && objc!=3) {
        Tcl_WrongNumArgs(interp, 1, objv, "dictionary ?pattern?");
        return TCL_ERROR;
    }

    if (Tcl_DictObjFirst(interp, objv[1], &search, NULL, &valuePtr,
            &done) != TCL_OK) {
        return TCL_ERROR;
    }
    if (objc == 3) {
        pattern = TclGetString(objv[2]);
    } else {
        pattern = NULL;
    }
    listPtr = Tcl_NewListObj(0, NULL);
    for (; !done ; Tcl_DictObjNext(&search, NULL, &valuePtr, &done)) {
        if (pattern==NULL || Tcl_StringMatch(TclGetString(valuePtr),pattern)) {
            /*
             * Assume this operation always succeeds.
             */

            Tcl_ListObjAppendElement(interp, listPtr, valuePtr);
        }
    }
    Tcl_DictObjDone(&search);

    Tcl_SetObjResult(interp, listPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictSizeCmd --
 *
 *      This function implements the "dict size" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictSizeCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    int result, size;

    if (objc != 2) {
        Tcl_WrongNumArgs(interp, 1, objv, "dictionary");
        return TCL_ERROR;
    }
    result = Tcl_DictObjSize(interp, objv[1], &size);
    if (result == TCL_OK) {
        Tcl_SetObjResult(interp, Tcl_NewIntObj(size));
    }
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * DictExistsCmd --
 *
 *      This function implements the "dict exists" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictExistsCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *dictPtr, *valuePtr;
    int result;

    if (objc < 3) {
        Tcl_WrongNumArgs(interp, 1, objv, "dictionary key ?key ...?");
        return TCL_ERROR;
    }

    dictPtr = TclTraceDictPath(interp, objv[1], objc-3, objv+2,
            DICT_PATH_EXISTS);
    if (dictPtr == NULL) {
        return TCL_ERROR;
    }
    if (dictPtr == DICT_PATH_NON_EXISTENT) {
        Tcl_SetObjResult(interp, Tcl_NewBooleanObj(0));
        return TCL_OK;
    }
    result = Tcl_DictObjGet(interp, dictPtr, objv[objc-1], &valuePtr);
    if (result != TCL_OK) {
        return result;
    }
    Tcl_SetObjResult(interp, Tcl_NewBooleanObj(valuePtr != NULL));
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictInfoCmd --
 *
 *      This function implements the "dict info" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictInfoCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *dictPtr;
    Dict *dict;

    if (objc != 2) {
        Tcl_WrongNumArgs(interp, 1, objv, "dictionary");
        return TCL_ERROR;
    }

    dictPtr = objv[1];
    if (dictPtr->typePtr != &tclDictType) {
        int result = SetDictFromAny(interp, dictPtr);
        if (result != TCL_OK) {
            return result;
        }
    }
    dict = dictPtr->internalRep.otherValuePtr;

    /*
     * This next cast is actually OK.
     */

    Tcl_SetResult(interp, (char *) Tcl_HashStats(&dict->table), TCL_DYNAMIC);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictIncrCmd --
 *
 *      This function implements the "dict incr" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictIncrCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    int code = TCL_OK;
    Tcl_Obj *dictPtr, *valuePtr = NULL;

    if (objc < 3 || objc > 4) {
        Tcl_WrongNumArgs(interp, 1, objv, "varName key ?increment?");
        return TCL_ERROR;
    }

    dictPtr = Tcl_ObjGetVar2(interp, objv[1], NULL, 0);
    if (dictPtr == NULL) {
        /*
         * Variable didn't yet exist. Create new dictionary value.
         */

        dictPtr = Tcl_NewDictObj();
    } else if (Tcl_DictObjGet(interp, dictPtr, objv[2], &valuePtr) != TCL_OK) {
        /*
         * Variable contents are not a dict, report error.
         */

        return TCL_ERROR;
    }
    if (Tcl_IsShared(dictPtr)) {
        /*
         * A little internals surgery to avoid copying a string rep that will
         * soon be no good.
         */

        char *saved = dictPtr->bytes;

        dictPtr->bytes = NULL;
        dictPtr = Tcl_DuplicateObj(dictPtr);
        dictPtr->bytes = saved;
    }
    if (valuePtr == NULL) {
        /*
         * Key not in dictionary. Create new key with increment as value.
         */

        if (objc == 4) {
            /*
             * Verify increment is an integer.
             */

            mp_int increment;

            code = Tcl_GetBignumFromObj(interp, objv[3], &increment);
            if (code != TCL_OK) {
                Tcl_AddErrorInfo(interp, "\n    (reading increment)");
            } else {
                Tcl_DictObjPut(interp, dictPtr, objv[2], objv[3]);
            }
        } else {
            Tcl_DictObjPut(interp, dictPtr, objv[2], Tcl_NewIntObj(1));
        }
    } else {
        /*
         * Key in dictionary. Increment its value with minimum dup.
         */

        if (Tcl_IsShared(valuePtr)) {
            valuePtr = Tcl_DuplicateObj(valuePtr);
            Tcl_DictObjPut(interp, dictPtr, objv[2], valuePtr);
        }
        if (objc == 4) {
            code = TclIncrObj(interp, valuePtr, objv[3]);
        } else {
            Tcl_Obj *incrPtr = Tcl_NewIntObj(1);

            Tcl_IncrRefCount(incrPtr);
            code = TclIncrObj(interp, valuePtr, incrPtr);
            Tcl_DecrRefCount(incrPtr);
        }
    }
    if (code == TCL_OK) {
        Tcl_InvalidateStringRep(dictPtr);
        valuePtr = Tcl_ObjSetVar2(interp, objv[1], NULL,
                dictPtr, TCL_LEAVE_ERR_MSG);
        if (valuePtr == NULL) {
            code = TCL_ERROR;
        } else {
            Tcl_SetObjResult(interp, valuePtr);
        }
    } else if (dictPtr->refCount == 0) {
        Tcl_DecrRefCount(dictPtr);
    }
    return code;
}

/*
 *----------------------------------------------------------------------
 *
 * DictLappendCmd --
 *
 *      This function implements the "dict lappend" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictLappendCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *dictPtr, *valuePtr, *resultPtr;
    int i, allocatedDict = 0, allocatedValue = 0;

    if (objc < 3) {
        Tcl_WrongNumArgs(interp, 1, objv, "varName key ?value ...?");
        return TCL_ERROR;
    }

    dictPtr = Tcl_ObjGetVar2(interp, objv[1], NULL, 0);
    if (dictPtr == NULL) {
        allocatedDict = 1;
        dictPtr = Tcl_NewDictObj();
    } else if (Tcl_IsShared(dictPtr)) {
        allocatedDict = 1;
        dictPtr = Tcl_DuplicateObj(dictPtr);
    }

    if (Tcl_DictObjGet(interp, dictPtr, objv[2], &valuePtr) != TCL_OK) {
        if (allocatedDict) {
            TclDecrRefCount(dictPtr);
        }
        return TCL_ERROR;
    }

    if (valuePtr == NULL) {
        valuePtr = Tcl_NewListObj(objc-3, objv+3);
        allocatedValue = 1;
    } else {
        if (Tcl_IsShared(valuePtr)) {
            allocatedValue = 1;
            valuePtr = Tcl_DuplicateObj(valuePtr);
        }

        for (i=3 ; i<objc ; i++) {
            if (Tcl_ListObjAppendElement(interp, valuePtr,
                    objv[i]) != TCL_OK) {
                if (allocatedValue) {
                    TclDecrRefCount(valuePtr);
                }
                if (allocatedDict) {
                    TclDecrRefCount(dictPtr);
                }
                return TCL_ERROR;
            }
        }
    }

    if (allocatedValue) {
        Tcl_DictObjPut(interp, dictPtr, objv[2], valuePtr);
    } else if (dictPtr->bytes != NULL) {
        Tcl_InvalidateStringRep(dictPtr);
    }

    resultPtr = Tcl_ObjSetVar2(interp, objv[1], NULL, dictPtr,
            TCL_LEAVE_ERR_MSG);
    if (resultPtr == NULL) {
        return TCL_ERROR;
    }
    Tcl_SetObjResult(interp, resultPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictAppendCmd --
 *
 *      This function implements the "dict append" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictAppendCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *dictPtr, *valuePtr, *resultPtr;
    int i, allocatedDict = 0;

    if (objc < 3) {
        Tcl_WrongNumArgs(interp, 1, objv, "varName key ?value ...?");
        return TCL_ERROR;
    }

    dictPtr = Tcl_ObjGetVar2(interp, objv[1], NULL, 0);
    if (dictPtr == NULL) {
        allocatedDict = 1;
        dictPtr = Tcl_NewDictObj();
    } else if (Tcl_IsShared(dictPtr)) {
        allocatedDict = 1;
        dictPtr = Tcl_DuplicateObj(dictPtr);
    }

    if (Tcl_DictObjGet(interp, dictPtr, objv[2], &valuePtr) != TCL_OK) {
        if (allocatedDict) {
            TclDecrRefCount(dictPtr);
        }
        return TCL_ERROR;
    }

    if (valuePtr == NULL) {
        TclNewObj(valuePtr);
    } else {
        if (Tcl_IsShared(valuePtr)) {
            valuePtr = Tcl_DuplicateObj(valuePtr);
        }
    }

    for (i=3 ; i<objc ; i++) {
        Tcl_AppendObjToObj(valuePtr, objv[i]);
    }

    Tcl_DictObjPut(interp, dictPtr, objv[2], valuePtr);

    resultPtr = Tcl_ObjSetVar2(interp, objv[1], NULL, dictPtr,
            TCL_LEAVE_ERR_MSG);
    if (resultPtr == NULL) {
        return TCL_ERROR;
    }
    Tcl_SetObjResult(interp, resultPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictForCmd --
 *
 *      This function implements the "dict for" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictForCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Interp *iPtr = (Interp *) interp;
    Tcl_Obj *scriptObj, *keyVarObj, *valueVarObj;
    Tcl_Obj **varv, *keyObj, *valueObj;
    Tcl_DictSearch search;
    int varc, done, result;

    if (objc != 4) {
        Tcl_WrongNumArgs(interp, 1, objv,
                "{keyVar valueVar} dictionary script");
        return TCL_ERROR;
    }

    if (TclListObjGetElements(interp, objv[1], &varc, &varv) != TCL_OK) {
        return TCL_ERROR;
    }
    if (varc != 2) {
        Tcl_SetResult(interp, "must have exactly two variable names",
                TCL_STATIC);
        return TCL_ERROR;
    }
    keyVarObj = varv[0];
    valueVarObj = varv[1];
    scriptObj = objv[3];

    if (Tcl_DictObjFirst(interp, objv[2], &search, &keyObj, &valueObj,
            &done) != TCL_OK) {
        return TCL_ERROR;
    }

    /*
     * Make sure that these objects (which we need throughout the body of the
     * loop) don't vanish. Note that the dictionary internal rep is locked
     * internally so that updates, shimmering, etc are not a problem.
     */

    Tcl_IncrRefCount(keyVarObj);
    Tcl_IncrRefCount(valueVarObj);
    Tcl_IncrRefCount(scriptObj);

    result = TCL_OK;
    while (!done) {
        /*
         * Stop the value from getting hit in any way by any traces on the key
         * variable.
         */

        Tcl_IncrRefCount(valueObj);
        if (Tcl_ObjSetVar2(interp, keyVarObj, NULL, keyObj, 0) == NULL) {
            Tcl_ResetResult(interp);
            Tcl_AppendResult(interp, "couldn't set key variable: \"",
                    TclGetString(keyVarObj), "\"", NULL);
            TclDecrRefCount(valueObj);
            result = TCL_ERROR;
            break;
        }
        TclDecrRefCount(valueObj);
        if (Tcl_ObjSetVar2(interp, valueVarObj, NULL, valueObj, 0) == NULL) {
            Tcl_ResetResult(interp);
            Tcl_AppendResult(interp, "couldn't set value variable: \"",
                    TclGetString(valueVarObj), "\"", NULL);
            result = TCL_ERROR;
            break;
        }

        /*
         * TIP #280. Make invoking context available to loop body.
         */

        result = TclEvalObjEx(interp, scriptObj, 0, iPtr->cmdFramePtr, 3);
        if (result == TCL_CONTINUE) {
            result = TCL_OK;
        } else if (result != TCL_OK) {
            if (result == TCL_BREAK) {
                result = TCL_OK;
            } else if (result == TCL_ERROR) {
                Tcl_AppendObjToErrorInfo(interp, Tcl_ObjPrintf(
                        "\n    (\"dict for\" body line %d)",
                        interp->errorLine));
            }
            break;
        }

        Tcl_DictObjNext(&search, &keyObj, &valueObj, &done);
    }

    /*
     * Stop holding a reference to these objects.
     */

    TclDecrRefCount(keyVarObj);
    TclDecrRefCount(valueVarObj);
    TclDecrRefCount(scriptObj);

    Tcl_DictObjDone(&search);
    if (result == TCL_OK) {
        Tcl_ResetResult(interp);
    }
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * DictSetCmd --
 *
 *      This function implements the "dict set" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictSetCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *dictPtr, *resultPtr;
    int result, allocatedDict = 0;

    if (objc < 4) {
        Tcl_WrongNumArgs(interp, 1, objv, "varName key ?key ...? value");
        return TCL_ERROR;
    }

    dictPtr = Tcl_ObjGetVar2(interp, objv[1], NULL, 0);
    if (dictPtr == NULL) {
        allocatedDict = 1;
        dictPtr = Tcl_NewDictObj();
    } else if (Tcl_IsShared(dictPtr)) {
        allocatedDict = 1;
        dictPtr = Tcl_DuplicateObj(dictPtr);
    }

    result = Tcl_DictObjPutKeyList(interp, dictPtr, objc-3, objv+2,
            objv[objc-1]);
    if (result != TCL_OK) {
        if (allocatedDict) {
            TclDecrRefCount(dictPtr);
        }
        return TCL_ERROR;
    }

    resultPtr = Tcl_ObjSetVar2(interp, objv[1], NULL, dictPtr,
            TCL_LEAVE_ERR_MSG);
    if (resultPtr == NULL) {
        return TCL_ERROR;
    }
    Tcl_SetObjResult(interp, resultPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictUnsetCmd --
 *
 *      This function implements the "dict unset" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictUnsetCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Tcl_Obj *dictPtr, *resultPtr;
    int result, allocatedDict = 0;

    if (objc < 3) {
        Tcl_WrongNumArgs(interp, 1, objv, "varName key ?key ...?");
        return TCL_ERROR;
    }

    dictPtr = Tcl_ObjGetVar2(interp, objv[1], NULL, 0);
    if (dictPtr == NULL) {
        allocatedDict = 1;
        dictPtr = Tcl_NewDictObj();
    } else if (Tcl_IsShared(dictPtr)) {
        allocatedDict = 1;
        dictPtr = Tcl_DuplicateObj(dictPtr);
    }

    result = Tcl_DictObjRemoveKeyList(interp, dictPtr, objc-2, objv+2);
    if (result != TCL_OK) {
        if (allocatedDict) {
            TclDecrRefCount(dictPtr);
        }
        return TCL_ERROR;
    }

    resultPtr = Tcl_ObjSetVar2(interp, objv[1], NULL, dictPtr,
            TCL_LEAVE_ERR_MSG);
    if (resultPtr == NULL) {
        return TCL_ERROR;
    }
    Tcl_SetObjResult(interp, resultPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * DictFilterCmd --
 *
 *      This function implements the "dict filter" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictFilterCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Interp *iPtr = (Interp *) interp;
    static const char *filters[] = {
        "key", "script", "value", NULL
    };
    enum FilterTypes {
        FILTER_KEYS, FILTER_SCRIPT, FILTER_VALUES
    };
    Tcl_Obj *scriptObj, *keyVarObj, *valueVarObj;
    Tcl_Obj **varv, *keyObj, *valueObj, *resultObj, *boolObj;
    Tcl_DictSearch search;
    int index, varc, done, result, satisfied;
    char *pattern;

    if (objc < 3) {
        Tcl_WrongNumArgs(interp, 1, objv, "dictionary filterType ...");
        return TCL_ERROR;
    }
    if (Tcl_GetIndexFromObj(interp, objv[2], filters, "filterType",
             0, &index) != TCL_OK) {
        return TCL_ERROR;
    }

    switch ((enum FilterTypes) index) {
    case FILTER_KEYS:
        if (objc != 4) {
            Tcl_WrongNumArgs(interp, 1, objv, "dictionary key globPattern");
            return TCL_ERROR;
        }

        /*
         * Create a dictionary whose keys all match a certain pattern.
         */

        if (Tcl_DictObjFirst(interp, objv[1], &search,
                &keyObj, &valueObj, &done) != TCL_OK) {
            return TCL_ERROR;
        }
        pattern = TclGetString(objv[3]);
        resultObj = Tcl_NewDictObj();
        if (TclMatchIsTrivial(pattern)) {
            /*
             * Must release the search lock here to prevent a memory leak
             * since we are not exhausing the search. [Bug 1705778, leak K05]
             */

            Tcl_DictObjDone(&search);
            Tcl_DictObjGet(interp, objv[1], objv[3], &valueObj);
            if (valueObj != NULL) {
                Tcl_DictObjPut(interp, resultObj, objv[3], valueObj);
            }
        } else {
            while (!done) {
                if (Tcl_StringMatch(TclGetString(keyObj), pattern)) {
                    Tcl_DictObjPut(interp, resultObj, keyObj, valueObj);
                }
                Tcl_DictObjNext(&search, &keyObj, &valueObj, &done);
            }
        }
        Tcl_SetObjResult(interp, resultObj);
        return TCL_OK;

    case FILTER_VALUES:
        if (objc != 4) {
            Tcl_WrongNumArgs(interp, 1, objv, "dictionary value globPattern");
            return TCL_ERROR;
        }

        /*
         * Create a dictionary whose values all match a certain pattern.
         */

        if (Tcl_DictObjFirst(interp, objv[1], &search,
                &keyObj, &valueObj, &done) != TCL_OK) {
            return TCL_ERROR;
        }
        pattern = TclGetString(objv[3]);
        resultObj = Tcl_NewDictObj();
        while (!done) {
            if (Tcl_StringMatch(TclGetString(valueObj), pattern)) {
                Tcl_DictObjPut(interp, resultObj, keyObj, valueObj);
            }
            Tcl_DictObjNext(&search, &keyObj, &valueObj, &done);
        }
        Tcl_SetObjResult(interp, resultObj);
        return TCL_OK;

    case FILTER_SCRIPT:
        if (objc != 5) {
            Tcl_WrongNumArgs(interp, 1, objv,
                    "dictionary script {keyVar valueVar} filterScript");
            return TCL_ERROR;
        }

        /*
         * Create a dictionary whose key,value pairs all satisfy a script
         * (i.e. get a true boolean result from its evaluation). Massive
         * copying from the "dict for" implementation has occurred!
         */

        if (TclListObjGetElements(interp, objv[3], &varc, &varv) != TCL_OK) {
            return TCL_ERROR;
        }
        if (varc != 2) {
            Tcl_SetResult(interp, "must have exactly two variable names",
                    TCL_STATIC);
            return TCL_ERROR;
        }
        keyVarObj = varv[0];
        valueVarObj = varv[1];
        scriptObj = objv[4];

        /*
         * Make sure that these objects (which we need throughout the body of
         * the loop) don't vanish. Note that the dictionary internal rep is
         * locked internally so that updates, shimmering, etc are not a
         * problem.
         */

        Tcl_IncrRefCount(keyVarObj);
        Tcl_IncrRefCount(valueVarObj);
        Tcl_IncrRefCount(scriptObj);

        result = Tcl_DictObjFirst(interp, objv[1],
                &search, &keyObj, &valueObj, &done);
        if (result != TCL_OK) {
            TclDecrRefCount(keyVarObj);
            TclDecrRefCount(valueVarObj);
            TclDecrRefCount(scriptObj);
            return TCL_ERROR;
        }

        resultObj = Tcl_NewDictObj();

        while (!done) {
            /*
             * Stop the value from getting hit in any way by any traces on the
             * key variable.
             */

            Tcl_IncrRefCount(keyObj);
            Tcl_IncrRefCount(valueObj);
            if (Tcl_ObjSetVar2(interp, keyVarObj, NULL, keyObj,
                    TCL_LEAVE_ERR_MSG) == NULL) {
                Tcl_ResetResult(interp);
                Tcl_AppendResult(interp, "couldn't set key variable: \"",
                        TclGetString(keyVarObj), "\"", NULL);
                result = TCL_ERROR;
                goto abnormalResult;
            }
            if (Tcl_ObjSetVar2(interp, valueVarObj, NULL, valueObj,
                    TCL_LEAVE_ERR_MSG) == NULL) {
                Tcl_ResetResult(interp);
                Tcl_AppendResult(interp, "couldn't set value variable: \"",
                        TclGetString(valueVarObj), "\"", NULL);
                goto abnormalResult;
            }

            /*
             * TIP #280. Make invoking context available to loop body.
             */

            result = TclEvalObjEx(interp, scriptObj, 0, iPtr->cmdFramePtr, 4);
            switch (result) {
            case TCL_OK:
                boolObj = Tcl_GetObjResult(interp);
                Tcl_IncrRefCount(boolObj);
                Tcl_ResetResult(interp);
                if (Tcl_GetBooleanFromObj(interp, boolObj,
                        &satisfied) != TCL_OK) {
                    TclDecrRefCount(boolObj);
                    result = TCL_ERROR;
                    goto abnormalResult;
                }
                TclDecrRefCount(boolObj);
                if (satisfied) {
                    Tcl_DictObjPut(interp, resultObj, keyObj, valueObj);
                }
                break;
            case TCL_BREAK:
                /*
                 * Force loop termination by calling Tcl_DictObjDone; this
                 * makes the next Tcl_DictObjNext say there is nothing more to
                 * do.
                 */

                Tcl_ResetResult(interp);
                Tcl_DictObjDone(&search);
            case TCL_CONTINUE:
                result = TCL_OK;
                break;
            case TCL_ERROR:
                Tcl_AppendObjToErrorInfo(interp, Tcl_ObjPrintf(
                        "\n    (\"dict filter\" script line %d)",
                        interp->errorLine));
            default:
                goto abnormalResult;
            }

            TclDecrRefCount(keyObj);
            TclDecrRefCount(valueObj);

            Tcl_DictObjNext(&search, &keyObj, &valueObj, &done);
        }

        /*
         * Stop holding a reference to these objects.
         */

        TclDecrRefCount(keyVarObj);
        TclDecrRefCount(valueVarObj);
        TclDecrRefCount(scriptObj);
        Tcl_DictObjDone(&search);

        if (result == TCL_OK) {
            Tcl_SetObjResult(interp, resultObj);
        } else {
            TclDecrRefCount(resultObj);
        }
        return result;

    abnormalResult:
        Tcl_DictObjDone(&search);
        TclDecrRefCount(keyObj);
        TclDecrRefCount(valueObj);
        TclDecrRefCount(keyVarObj);
        TclDecrRefCount(valueVarObj);
        TclDecrRefCount(scriptObj);
        TclDecrRefCount(resultObj);
        return result;
    }
    Tcl_Panic("unexpected fallthrough");
    /* Control never reaches this point. */
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * DictUpdateCmd --
 *
 *      This function implements the "dict update" Tcl command. See the user
 *      documentation for details on what it does, and TIP#212 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictUpdateCmd(
    ClientData clientData,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Interp *iPtr = (Interp *) interp;
    Tcl_Obj *dictPtr, *objPtr;
    int i, result, dummy;
    Tcl_InterpState state;

    if (objc < 5 || !(objc & 1)) {
        Tcl_WrongNumArgs(interp, 1, objv,
                "varName key varName ?key varName ...? script");
        return TCL_ERROR;
    }

    dictPtr = Tcl_ObjGetVar2(interp, objv[1], NULL, TCL_LEAVE_ERR_MSG);
    if (dictPtr == NULL) {
        return TCL_ERROR;
    }
    if (Tcl_DictObjSize(interp, dictPtr, &dummy) != TCL_OK) {
        return TCL_ERROR;
    }
    Tcl_IncrRefCount(dictPtr);
    for (i=2 ; i+2<objc ; i+=2) {
        if (Tcl_DictObjGet(interp, dictPtr, objv[i], &objPtr) != TCL_OK) {
            TclDecrRefCount(dictPtr);
            return TCL_ERROR;
        }
        if (objPtr == NULL) {
            /* ??? */
            Tcl_UnsetVar(interp, Tcl_GetString(objv[i+1]), 0);
        } else if (Tcl_ObjSetVar2(interp, objv[i+1], NULL, objPtr,
                TCL_LEAVE_ERR_MSG) == NULL) {
            TclDecrRefCount(dictPtr);
            return TCL_ERROR;
        }
    }
    TclDecrRefCount(dictPtr);

    /*
     * Execute the body.
     */

    result = TclEvalObjEx(interp, objv[objc-1], 0, iPtr->cmdFramePtr, objc-1);
    if (result == TCL_ERROR) {
        Tcl_AddErrorInfo(interp, "\n    (body of \"dict update\")");
    }

    /*
     * If the dictionary variable doesn't exist, drop everything silently.
     */

    dictPtr = Tcl_ObjGetVar2(interp, objv[1], NULL, 0);
    if (dictPtr == NULL) {
        return result;
    }

    /*
     * Double-check that it is still a dictionary.
     */

    state = Tcl_SaveInterpState(interp, result);
    if (Tcl_DictObjSize(interp, dictPtr, &dummy) != TCL_OK) {
        Tcl_DiscardInterpState(state);
        return TCL_ERROR;
    }

    if (Tcl_IsShared(dictPtr)) {
        dictPtr = Tcl_DuplicateObj(dictPtr);
    }

    /*
     * Write back the values from the variables, treating failure to read as
     * an instruction to remove the key.
     */

    for (i=2 ; i+2<objc ; i+=2) {
        objPtr = Tcl_ObjGetVar2(interp, objv[i+1], NULL, 0);
        if (objPtr == NULL) {
            Tcl_DictObjRemove(interp, dictPtr, objv[i]);
        } else if (objPtr == dictPtr) {
            /*
             * Someone is messing us around, trying to build a recursive
             * structure. [Bug 1786481]
             */

            Tcl_DictObjPut(interp, dictPtr, objv[i],
                    Tcl_DuplicateObj(objPtr));
        } else {
            /* Shouldn't fail */
            Tcl_DictObjPut(interp, dictPtr, objv[i], objPtr);
        }
    }

    /*
     * Write the dictionary back to its variable.
     */

    if (Tcl_ObjSetVar2(interp, objv[1], NULL, dictPtr,
            TCL_LEAVE_ERR_MSG) == NULL) {
        Tcl_DiscardInterpState(state);
        return TCL_ERROR;
    }

    return Tcl_RestoreInterpState(interp, state);
}

/*
 *----------------------------------------------------------------------
 *
 * DictWithCmd --
 *
 *      This function implements the "dict with" Tcl command. See the user
 *      documentation for details on what it does, and TIP#212 for the formal
 *      specification.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

static int
DictWithCmd(
    ClientData dummy,
    Tcl_Interp *interp,
    int objc,
    Tcl_Obj *const *objv)
{
    Interp *iPtr = (Interp *) interp;
    Tcl_Obj *dictPtr, *keysPtr, *keyPtr, *valPtr, **keyv, *leafPtr;
    Tcl_DictSearch s;
    Tcl_InterpState state;
    int done, result, keyc, i, allocdict = 0;

    if (objc < 3) {
        Tcl_WrongNumArgs(interp, 1, objv, "dictVar ?key ...? script");
        return TCL_ERROR;
    }

    /*
     * Get the dictionary to open out.
     */

    dictPtr = Tcl_ObjGetVar2(interp, objv[1], NULL, TCL_LEAVE_ERR_MSG);
    if (dictPtr == NULL) {
        return TCL_ERROR;
    }
    if (objc > 3) {
        dictPtr = TclTraceDictPath(interp, dictPtr, objc-3, objv+2,
                DICT_PATH_READ);
        if (dictPtr == NULL) {
            return TCL_ERROR;
        }
    }

    /*
     * Go over the list of keys and write each corresponding value to a
     * variable in the current context with the same name. Also keep a copy of
     * the keys so we can write back properly later on even if the dictionary
     * has been structurally modified.
     */

    if (Tcl_DictObjFirst(interp, dictPtr, &s, &keyPtr, &valPtr,
            &done) != TCL_OK) {
        return TCL_ERROR;
    }

    TclNewObj(keysPtr);
    Tcl_IncrRefCount(keysPtr);

    for (; !done ; Tcl_DictObjNext(&s, &keyPtr, &valPtr, &done)) {
        Tcl_ListObjAppendElement(NULL, keysPtr, keyPtr);
        if (Tcl_ObjSetVar2(interp, keyPtr, NULL, valPtr,
                TCL_LEAVE_ERR_MSG) == NULL) {
            TclDecrRefCount(keysPtr);
            Tcl_DictObjDone(&s);
            return TCL_ERROR;
        }
    }

    /*
     * Execute the body, while making the invoking context available to the
     * loop body (TIP#280).
     */

    result = TclEvalObjEx(interp, objv[objc-1], 0, iPtr->cmdFramePtr, objc-1);
    if (result == TCL_ERROR) {
        Tcl_AddErrorInfo(interp, "\n    (body of \"dict with\")");
    }

    /*
     * If the dictionary variable doesn't exist, drop everything silently.
     */

    dictPtr = Tcl_ObjGetVar2(interp, objv[1], NULL, 0);
    if (dictPtr == NULL) {
        TclDecrRefCount(keysPtr);
        return result;
    }

    /*
     * Double-check that it is still a dictionary.
     */

    state = Tcl_SaveInterpState(interp, result);
    if (Tcl_DictObjSize(interp, dictPtr, &i) != TCL_OK) {
        TclDecrRefCount(keysPtr);
        Tcl_DiscardInterpState(state);
        return TCL_ERROR;
    }

    if (Tcl_IsShared(dictPtr)) {
        dictPtr = Tcl_DuplicateObj(dictPtr);
        allocdict = 1;
    }

    if (objc > 3) {
        /*
         * Want to get to the dictionary which we will update; need to do
         * prepare-for-update de-sharing along the path *but* avoid generating
         * an error on a non-existant path (we'll treat that the same as a
         * non-existant variable. Luckily, the de-sharing operation isn't
         * deeply damaging if we don't go on to update; it's just less than
         * perfectly efficient (but no memory should be leaked).
         */

        leafPtr = TclTraceDictPath(interp, dictPtr, objc-3, objv+2,
                DICT_PATH_EXISTS | DICT_PATH_UPDATE);
        if (leafPtr == NULL) {
            TclDecrRefCount(keysPtr);
            if (allocdict) {
                TclDecrRefCount(dictPtr);
            }
            Tcl_DiscardInterpState(state);
            return TCL_ERROR;
        }
        if (leafPtr == DICT_PATH_NON_EXISTENT) {
            TclDecrRefCount(keysPtr);
            if (allocdict) {
                TclDecrRefCount(dictPtr);
            }
            return Tcl_RestoreInterpState(interp, state);
        }
    } else {
        leafPtr = dictPtr;
    }

    /*
     * Now process our updates on the leaf dictionary.
     */

    TclListObjGetElements(NULL, keysPtr, &keyc, &keyv);
    for (i=0 ; i<keyc ; i++) {
        valPtr = Tcl_ObjGetVar2(interp, keyv[i], NULL, 0);
        if (valPtr == NULL) {
            Tcl_DictObjRemove(NULL, leafPtr, keyv[i]);
        } else if (leafPtr == valPtr) {
            /*
             * Someone is messing us around, trying to build a recursive
             * structure. [Bug 1786481]
             */

            Tcl_DictObjPut(NULL, leafPtr, keyv[i], Tcl_DuplicateObj(valPtr));
        } else {
            Tcl_DictObjPut(NULL, leafPtr, keyv[i], valPtr);
        }
    }
    TclDecrRefCount(keysPtr);

    /*
     * Ensure that none of the dictionaries in the chain still have a string
     * rep.
     */

    if (objc > 3) {
        InvalidateDictChain(leafPtr);
    }

    /*
     * Write back the outermost dictionary to the variable.
     */

    if (Tcl_ObjSetVar2(interp, objv[1], NULL, dictPtr,
            TCL_LEAVE_ERR_MSG) == NULL) {
        Tcl_DiscardInterpState(state);
        return TCL_ERROR;
    }
    return Tcl_RestoreInterpState(interp, state);
}

/*
 *----------------------------------------------------------------------
 *
 * TclInitDictCmd --
 *
 *      This function is create the "dict" Tcl command. See the user
 *      documentation for details on what it does, and TIP#111 for the formal
 *      specification.
 *
 * Results:
 *      A Tcl command handle.
 *
 * Side effects:
 *      May advance compilation epoch.
 *
 *----------------------------------------------------------------------
 */

Tcl_Command
TclInitDictCmd(
    Tcl_Interp *interp)
{
    return TclMakeEnsemble(interp, "dict", implementationMap);
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */