
/*
 * Author:
 *      Guido Draheim <guidod@gmx.de>
 *      Tomi Ollila <Tomi.Ollila@iki.fi>
 *
 * Copyright (c) 1999,2000,2001,2002,2003 Guido Draheim
 *          All rights reserved,
 *          use under the restrictions of the
 *          Lesser GNU General Public License
 *          or alternatively the restrictions
 *          of the Mozilla Public License 1.1
 */

#include <zzip/lib.h>           /* exported... */
#include <zzip/file.h>

#include <string.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdlib.h>
#include <ctype.h>

#include <zzip/format.h>
#include <zzip/fetch.h>
#include <zzip/__debug.h>

#if 0
# if defined ZZIP_HAVE_IO_H
# include <io.h>                /* tell */
# else
# define tell(fd) lseek(fd,0,SEEK_CUR)
# endif
#else
#define tells(fd) seeks(fd,0,SEEK_CUR)
#endif

/**
 * the direct function of => zzip_close(fp). it will cleanup the
 * inflate-portion of => zlib and free the structure given.
 *
 * it is called quite from the error-cleanup parts
 * of the various => _open functions.
 *
 * the .refcount is decreased and if zero the fp->dir is closed just as well.
 */
int
zzip_file_close(ZZIP_FILE * fp)
{
    auto int self;
    ZZIP_DIR *dir = fp->dir;

    if (fp->method)
        inflateEnd(&fp->d_stream);      /* inflateEnd() can be called many times */

    if (dir->cache.locked == NULL)
        dir->cache.locked = &self;

    if (fp->buf32k)
    {
        if (dir->cache.locked == &self && dir->cache.buf32k == NULL)
            dir->cache.buf32k = fp->buf32k;
        else
            free(fp->buf32k);
    }

    if (dir->currentfp == fp)
        dir->currentfp = NULL;

    dir->refcount--;
    /* ease to notice possible dangling reference errors */
    memset(fp, 0, sizeof(*fp));

    if (dir->cache.locked == &self && dir->cache.fp == NULL)
        dir->cache.fp = fp;
    else
        free(fp);

    if (dir->cache.locked == &self)
        dir->cache.locked = NULL;

    if (! dir->refcount)
        return zzip_dir_close(dir);
    else
        return 0;
}


static int
zzip_file_saveoffset(ZZIP_FILE * fp)
{
    if (fp)
    {
        int fd = fp->dir->fd;
        zzip_off_t off = fp->io->fd.seeks(fd, 0, SEEK_CUR);

        if (off < 0)
            return -1;

        fp->offset = off;
    }
    return 0;
}

# ifndef ZZIP_CHECK_BACKSLASH_DIRSEPARATOR      /* NOTE: also default */
# define ZZIP_CHECK_BACKSLASH_DIRSEPARATOR 0    /* to "NO" on win32 ! */
# endif

# if ! defined strcasecmp && ! defined ZZIP_HAVE_STRCASECMP
# define ZZIP_CHECK_BACKSLASH_DIRSEPARATOR 1
# endif

#if ! ZZIP_CHECK_BACKSLASH_DIRSEPARATOR+0
#define dirsep_strrchr(N,C) strrchr(N,C)
#define dirsep_casecmp strcasecmp
#else
#define dirsep_strrchr(N,C) _dirsep_strrchr(N)
#define dirsep_casecmp _dirsep_casecmp
static zzip_char_t *
_dirsep_strrchr(zzip_char_t * name)
{
    char *n = strrchr(name, '/');
    char *m = strrchr(name, '\\');

    if (m && n && m > n)
        n = m;
    return n;
}
static int
_dirsep_casecmp(zzip_char_t * s1, zzip_char_t * s2)
{
    /* ASCII tolower - including mapping of backslash in normal slash */
    static const char mapping[] = "@abcdefghijklmnopqrstuvwxyz[/]^_";
    int c1, c2;

    while (*s1 && *s2)
    {
        c1 = (int) (unsigned char) *s1;
        c2 = (int) (unsigned char) *s2;
        if ((c1 & 0xE0) == 0x40)
            c1 = mapping[c1 & 0x1f];
        if ((c2 & 0xE0) == 0x40)
            c2 = mapping[c2 & 0x1f];
        if (c1 != c2)
            return (c1 - c2);
        s1++;
        s2++;
    }

    return (((int) (unsigned char) *s1) - ((int) (unsigned char) *s2));
}
#endif

static int zzip_inflate_init(ZZIP_FILE *, struct zzip_dir_hdr *);

/**
 * open an => ZZIP_FILE from an already open => ZZIP_DIR handle. Since
 * we have a chance to reuse a cached => buf32k and => ZZIP_FILE memchunk
 * this is the best choice to unpack multiple files.
 *
 * Note: the zlib supports 2..15 bit windowsize, hence we provide a 32k
 *       memchunk here... just to be safe.
 *
 * On error it returns null and sets errcode in the ZZIP_DIR.
 */
ZZIP_FILE *
zzip_file_open(ZZIP_DIR * dir, zzip_char_t * name, int o_mode)
{
    auto int self;
    zzip_error_t err = 0;
    struct zzip_file *fp = 0;
    struct zzip_dir_hdr *hdr = dir->hdr0;
    int (*cmp) (zzip_char_t *, zzip_char_t *);

    cmp = (o_mode & ZZIP_CASELESS) ? dirsep_casecmp : strcmp;

    if (! dir)
        return NULL;
    if (! dir->fd || dir->fd == -1)
        { dir->errcode = EBADF; return NULL; }
    if (! hdr)
        { dir->errcode = ENOENT; return NULL; }

    if (o_mode & ZZIP_NOPATHS)
    {
        register zzip_char_t *n = dirsep_strrchr(name, '/');

        if (n)
            name = n + 1;
    }

    while (1)
    {
        register zzip_char_t *hdr_name = hdr->d_name;

        if (o_mode & ZZIP_NOPATHS)
        {
            register zzip_char_t *n = dirsep_strrchr(hdr_name, '/');

            if (n)
                hdr_name = n + 1;
        }

        HINT4("name='%s', compr=%d, size=%d\n",
              hdr->d_name, hdr->d_compr, hdr->d_usize);

        if (! cmp(hdr_name, name))
        {
            switch (hdr->d_compr)
            {
            case 0:            /* store */
            case 8:            /* inflate */
                break;
            default:
                { err = ZZIP_UNSUPP_COMPR; goto error; }
            }

            if (dir->cache.locked == NULL)
                dir->cache.locked = &self;

            if (dir->cache.locked == &self && dir->cache.fp)
            {
                fp = dir->cache.fp;
                dir->cache.fp = NULL;
                /* memset(zfp, 0, sizeof *fp); cleared in zzip_file_close() */
            } else
            {
                if (! (fp = (ZZIP_FILE *) calloc(1, sizeof(*fp))))
                    { err =  ZZIP_OUTOFMEM; goto error; }
            }

            fp->dir = dir;
            fp->io = dir->io;
            dir->refcount++;

            if (dir->cache.locked == &self && dir->cache.buf32k)
            {
                fp->buf32k = dir->cache.buf32k;
                dir->cache.buf32k = NULL;
            } else
            {
                if (! (fp->buf32k = (char *) malloc(ZZIP_32K)))
                    { err = ZZIP_OUTOFMEM; goto error; }
            }

            if (dir->cache.locked == &self)
                dir->cache.locked = NULL;
            /*
             * In order to support simultaneous open files in one zip archive
             * we'll fix the fd offset when opening new file/changing which
             * file to read...
             */

            if (zzip_file_saveoffset(dir->currentfp) < 0)
                { err = ZZIP_DIR_SEEK; goto error; }

            fp->offset = hdr->d_off;
            dir->currentfp = fp;

            if (dir->io->fd.seeks(dir->fd, hdr->d_off, SEEK_SET) < 0)
                { err = ZZIP_DIR_SEEK; goto error; }

            {
                /* skip local header - should test tons of other info,
                 * but trust that those are correct */
                zzip_ssize_t dataoff;
                struct zzip_file_header *p = (void *) fp->buf32k;

                dataoff = dir->io->fd.read(dir->fd, (void *) p, sizeof(*p));
                if (dataoff < (zzip_ssize_t) sizeof(*p))
                    { err = ZZIP_DIR_READ;  goto error; }
                if (! zzip_file_header_check_magic(p))   /* PK\3\4 */
                    { err = ZZIP_CORRUPTED; goto error; }

                dataoff = zzip_file_header_sizeof_tail(p);

                if (dir->io->fd.seeks(dir->fd, dataoff, SEEK_CUR) < 0)
                    { err = ZZIP_DIR_SEEK; goto error; }

                fp->dataoffset = dir->io->fd.tells(dir->fd);
                fp->usize = hdr->d_usize;
                fp->csize = hdr->d_csize;
            }

            err = zzip_inflate_init(fp, hdr);
            if (err)
                goto error;

            return fp;
        } else
        {
            if (hdr->d_reclen == 0)
                break;
            hdr = (struct zzip_dir_hdr *) ((char *) hdr + hdr->d_reclen);
        }                       /*cmp name */
    }                           /*forever */
    dir->errcode = ZZIP_ENOENT;
    return NULL;
  error:
    if (fp)
        zzip_file_close(fp);
    dir->errcode = err;
    return NULL;
}

/**
 *  call => inflateInit and setup fp's iterator variables,
 *  used by lowlevel => _open functions.
 */
static int
zzip_inflate_init(ZZIP_FILE * fp, struct zzip_dir_hdr *hdr)
{
    int err;

    fp->method = hdr->d_compr;
    fp->restlen = hdr->d_usize;

    if (fp->method)
    {
        memset(&fp->d_stream, 0, sizeof(fp->d_stream));

        err = inflateInit2(&fp->d_stream, -MAX_WBITS);
        if (err != Z_OK)
            goto error;

        fp->crestlen = hdr->d_csize;
    }
    return 0;
  error:
    if (fp)
        zzip_file_close(fp);
    return err;
}

/**
 * This function closes the given ZZIP_FILE handle.
 *
 * If the ZZIP_FILE wraps a normal stat'fd then it is just that int'fd
 * that is being closed and the otherwise empty ZZIP_FILE gets freed.
 */
int
zzip_fclose(ZZIP_FILE * fp)
{
    if (! fp)
        return 0;
    if (! fp->dir)               /* stat fd */
        { int r = fp->io->fd.close(fp->fd); free(fp); return r; }
    else
        return zzip_file_close(fp);
}

/** => zzip_fclose
 */
int
zzip_close(ZZIP_FILE * fp)
{
    return zzip_fclose(fp);
}

/**
 * This functions read data from zip-contained file.
 *
 * It works like => read(2) and will fill the given buffer with bytes from
 * the opened file. It will return the number of bytes read, so if the => EOF
 * is encountered you will be prompted with the number of bytes actually read.
 *
 * This is the routines that needs the => buf32k buffer, and it would have
 * need for much more polishing but it does already work quite well.
 *
 * Note: the 32K buffer is rather big. The original inflate-algorithm
 *       required just that but the latest zlib would work just fine with
 *       a smaller buffer.
 */
zzip_ssize_t
zzip_file_read(ZZIP_FILE * fp, void *buf, zzip_size_t len)
{
    ZZIP_DIR *dir;
    zzip_size_t l;
    zzip_ssize_t rv;

    if (! fp || ! fp->dir)
        return 0;

    dir = fp->dir;
    l = fp->restlen > len ? len : fp->restlen;
    if (fp->restlen == 0)
        return 0;

    /*
     * If this is other handle than previous, save current seek pointer
     * and read the file position of `this' handle.
     */
    if (dir->currentfp != fp)
    {
        if (zzip_file_saveoffset(dir->currentfp) < 0
            || fp->io->fd.seeks(dir->fd, fp->offset, SEEK_SET) < 0)
            { dir->errcode = ZZIP_DIR_SEEK; return -1; }
        else
            { dir->currentfp = fp; }
    }

    /* if more methods is to be supported, change this to `switch ()' */
    if (fp->method)             /* method != 0   == 8, inflate */
    {
        fp->d_stream.avail_out = l;
        fp->d_stream.next_out = (unsigned char *) buf;

        do
        {
            int err;
            zzip_size_t startlen;

            if (fp->crestlen > 0 && fp->d_stream.avail_in == 0)
            {
                zzip_size_t cl = (fp->crestlen < ZZIP_32K ?
                                  fp->crestlen : ZZIP_32K);
                /*  zzip_size_t cl =
                 *      fp->crestlen > 128 ? 128 : fp->crestlen;
                 */
                zzip_ssize_t i = fp->io->fd.read(dir->fd, fp->buf32k, cl);

                if (i <= 0)
                {
                    dir->errcode = ZZIP_DIR_READ;
                    /* or ZZIP_DIR_READ_EOF ? */
                    return -1;
                }
                fp->crestlen -= i;
                fp->d_stream.avail_in = i;
                fp->d_stream.next_in = (unsigned char *) fp->buf32k;
            }

            startlen = fp->d_stream.total_out;
            err = inflate(&fp->d_stream, Z_NO_FLUSH);

            if (err == Z_STREAM_END)
                { fp->restlen = 0; }
            else if (err == Z_OK)
                { fp->restlen -= (fp->d_stream.total_out - startlen); }
            else
                { dir->errcode = err; return -1; }
        }
        while (fp->restlen && fp->d_stream.avail_out);

        return l - fp->d_stream.avail_out;
    } else
    {                           /* method == 0 -- unstore */
        rv = fp->io->fd.read(dir->fd, buf, l);
        if (rv > 0)
            { fp->restlen-= rv; }
        else if (rv < 0)
            { dir->errcode = ZZIP_DIR_READ; }
        return rv;
    }
}

/**
 * This function will read(2) data from a real/zipped file.
 *
 * the replacement for => read(2) will fill the given buffer with bytes from
 * the opened file. It will return the number of bytes read, so if the EOF
 * is encountered you will be prompted with the number of bytes actually read.
 *
 * If the file-handle is wrapping a stat'able file then it will actually just
 * perform a normal => read(2)-call, otherwise => zzip_file_read is called
 * to decompress the data stream and any error is mapped to => errno(3).
 */
zzip_ssize_t
zzip_read(ZZIP_FILE * fp, void *buf, zzip_size_t len)
{
    if (! fp)
        return 0;
    if (! fp->dir)
        { return fp->io->fd.read(fp->fd, buf, len); }    /* stat fd */
    else
    {
        register zzip_ssize_t v;

        v = zzip_file_read(fp, buf, len);
        if (v == -1)
            { errno = zzip_errno(fp->dir->errcode); }
        return v;
    }
}

/** => zzip_read
 */
zzip_size_t
zzip_fread(void *ptr, zzip_size_t size, zzip_size_t nmemb, ZZIP_FILE * file)
{
    if (! size)
        size = 1;
    return zzip_read(file, ptr, size * nmemb) / size;
}


#define ZZIP_WRONLY             O_WRONLY
#define ZZIP_EXCL               O_EXCL

#if     defined                 O_SYNC
#define ZZIP_SYNC               O_SYNC
#else
#define ZZIP_SYNC               0
#endif

#if     defined                 O_NONBLOCK
#define ZZIP_NONBLOCK           O_NONBLOCK
#elif   defined                 O_NDELAY
#define ZZIP_NOCTTY             O_NDELAY
#else
#define ZZIP_NOCTTY             0
#endif

/* ------------------------------------------------------------------- */

/**                                                          also: fopen(2)
 * This function will => fopen(3) a real/zipped file.
 *
 * It has some magic functionality builtin - it will first try to open
 * the given <em>filename</em> as a normal file. If it does not
 * exist, the given path to the filename (if any) is split into
 * its directory-part and the file-part. A ".zip" extension is
 * then added to the directory-part to create the name of a
 * zip-archive. That zip-archive (if it exists) is being searched
 * for the file-part, and if found a zzip-handle is returned.
 *
 * Note that if the file is found in the normal fs-directory the
 * returned structure is mostly empty and the => zzip_read call will
 * use the libc => read to obtain data. Otherwise a => zzip_file_open
 * is performed and any error mapped to => errno(3).
 *
 * unlike the posix-wrapper => zzip_open the mode-argument is
 * a string which allows for more freedom to support the extra
 * zzip modes called ZZIP_CASEINSENSITIVE and ZZIP_IGNOREPATH.
 * Currently, this => zzip_fopen call will convert the following
 * characters in the mode-string into their corrsponding mode-bits:
 * * <code> "r" : O_RDONLY : </code> read-only
 * * <code> "b" : O_BINARY : </code> binary (win32 specific)
 * * <code> "f" : O_NOCTTY : </code> no char device (unix)
 * * <code> "i" : ZZIP_CASELESS : </code> inside zip file
 * * <code> "*" : ZZIP_NOPATHS : </code> inside zip file only
 * all other modes will be ignored for zip-contained entries
 * but they are transferred for compatibility and portability,
 * including these extra sugar bits:
 * * <code> "x" : O_EXCL :</code> fail if file did exist
 * * <code> "s" : O_SYNC :</code> synchronized access
 * * <code> "n" : O_NONBLOCK :</code> nonblocking access
 * * <code> "z#" : compression level :</code> for zlib
 * * <code> "g#" : group access :</code> unix access bits
 * * <code> "u#" : owner access :</code> unix access bits
 * * <code> "o#" : world access :</code> unix access bits
 * ... the access bits are in traditional unix bit format
 * with 7 = read/write/execute, 6 = read/write, 4 = read-only.
 *
 * The default access mode is 0664, and the compression level
 * is ignored since the lib can not yet write zip files, otherwise
 * it would be the initialisation value for the zlib deflateInit
 * where 0 = no-compression, 1 = best-speed, 9 = best-compression.
 *
 * This function returns a new zzip-handle (use => zzip_close to return
 * it). On error this function will return null setting => errno(3).
 */
ZZIP_FILE *
zzip_fopen(zzip_char_t * filename, zzip_char_t * mode)
{
    return zzip_freopen(filename, mode, 0);
}

/** => zzip_fopen
 *
 * This function receives an additional argument pointing to
 * a ZZIP_FILE* being already in use. If this extra argument is
 * null then this function is identical with calling => zzip_fopen
 *
 * Per default, the old file stream is closed and only the internal
 * structures associated with it are kept. These internal structures
 * may be reused for the return value, and this is a lot quicker when
 * the filename matches a zipped file that is incidently in the very
 * same zip arch as the old filename wrapped in the stream struct.
 *
 * That's simply because the zip arch's central directory does not
 * need to be read again. As an extension for this function, if the
 * mode-string contains a "q" then the old stream is not closed but
 * left untouched, instead it is only given as a hint that a new
 * file handle may share/copy the zip arch structures of the old file
 * handle if that is possible, i.e when they are in the same zip arch.
 *
 * This function returns a new zzip-handle (use => zzip_close to return
 * it). On error this function will return null setting => errno(3).
 */
ZZIP_FILE *
zzip_freopen(zzip_char_t * filename, zzip_char_t * mode, ZZIP_FILE * stream)
{
    int o_flags = 0;
    int o_modes = 0664;

    if (! mode)
        mode = "rb";

#   ifndef O_BINARY
#   define O_BINARY 0
#   endif
#   ifndef O_NOCTTY
#   define O_NOCTTY 0
#   endif
#   ifndef O_SYNC
#   define O_SYNC 0
#   endif
#   ifndef O_NONBLOCK
#   define O_NONBLOCK 0
#   endif

    for (; *mode; mode++)
    {
        switch (*mode)
        {
	    /* *INDENT-OFF* */
	case '0': case '1': case '2': case '3': case '4':
	case '5': case '6': case '7': case '8': case '9':
	    continue; /* ignore if not attached to other info */
        case 'r': o_flags |= mode[1] == '+' ? O_RDWR : O_RDONLY; break;
        case 'w': o_flags |= mode[1] == '+' ? O_RDWR : O_WRONLY;
                  o_flags |= O_TRUNC; break;
        case 'b': o_flags |= O_BINARY; break;
        case 'f': o_flags |= O_NOCTTY; break;
        case 'i': o_modes |= ZZIP_CASELESS; break;
        case '*': o_modes |= ZZIP_NOPATHS; break;
        case 'x': o_flags |= O_EXCL; break;
        case 's': o_flags |= O_SYNC; break;
        case 'n': o_flags |= O_NONBLOCK; break;
	case 'o': o_modes &=~ 07;
                  o_modes |= ((mode[1] - '0')) & 07; continue;
	case 'g': o_modes &=~ 070;
                  o_modes |= ((mode[1] - '0') << 3) & 070; continue;
	case 'u': o_modes &=~ 0700;
                  o_modes |= ((mode[1] - '0') << 6) & 0700; continue;
	case 'q': o_modes |= ZZIP_FACTORY; break;
	case 'z': /* compression level */
	    continue; /* currently ignored, just for write mode */
	    /* *INDENT-ON* */
        }
    }

    {
        ZZIP_FILE *fp =
            zzip_open_shared_io(stream, filename, o_flags, o_modes, 0, 0);

        if (! (o_modes & ZZIP_FACTORY) && stream)
            zzip_file_close(stream);

        return fp;
    }
}

/**
 * This function will => open(2) a real/zipped file
 *
 * It has some magic functionality builtin - it will first try to open
 * the given <em>filename</em> as a normal file. If it does not
 * exist, the given path to the filename (if any) is split into
 * its directory-part and the file-part. A ".zip" extension is
 * then added to the directory-part to create the name of a
 * zip-archive. That zip-archive (if it exists) is being searched
 * for the file-part, and if found a zzip-handle is returned.
 *
 * Note that if the file is found in the normal fs-directory the
 * returned structure is mostly empty and the => zzip_read call will
 * use the libc => read to obtain data. Otherwise a => zzip_file_open
 * is performed and any error mapped to => errno(3).
 *
 * There was a possibility to transfer zziplib-specific openmodes
 * through o_flags but you should please not use them anymore and
 * look into => zzip_open_ext_io to submit them down. This function
 * is shallow in that it just extracts the zzipflags and calls
 * * <code>zzip_open_ext_io(filename, o_flags, zzipflags|0664, 0, 0) </code>
 * you must stop using this extra functionality (not well known anyway)
 * since zzip_open might be later usable to open files for writing
 * in which case the _EXTRAFLAGS will get in conflict.
 *
 * compare with  => open(2) and => zzip_fopen
 */
ZZIP_FILE *
zzip_open(zzip_char_t * filename, int o_flags)
{
    /* backward compatibility */
    int o_modes = 0664;

    if (o_flags & ZZIP_CASEINSENSITIVE)
        {  o_flags ^= ZZIP_CASEINSENSITIVE; o_modes |= ZZIP_CASELESS; }
    if (o_flags & ZZIP_IGNOREPATH)
        {  o_flags ^= ZZIP_IGNOREPATH;      o_modes |= ZZIP_NOPATHS; }
    return zzip_open_ext_io(filename, o_flags, o_modes, 0, 0);
}

/* ZZIP_ONLYZIP won't work on platforms with sizeof(int) == 16bit */
#if ZZIP_SIZEOF_INT+0 == 2
#undef ZZIP_ONLYZIP
#endif

/** => zzip_open
 *
 * This function uses explicit ext and io instead of the internal
 * defaults, setting them to zero is equivalent to => zzip_open
 *
 * note that the two flag types have been split into an o_flags
 * (for fcntl-like openflags) and o_modes where the latter shall
 * carry the zzip_flags and possibly accessmodes for unix filesystems.
 * Since this version of zziplib can not write zipfiles, it is not
 * yet used for anything else than zzip-specific modeflags.
 *
 * This function returns a new zzip-handle (use => zzip_close to return
 * it). On error this function will return null setting => errno(3).
 */
ZZIP_FILE *
zzip_open_ext_io(zzip_char_t * filename, int o_flags, int o_modes,
                 zzip_strings_t * ext, zzip_plugin_io_t io)
{
    return zzip_open_shared_io(0, filename, o_flags, o_modes, ext, io);
}

/** => zzip_open
 *
 * This function takes an extra stream argument - if a handle has been
 * then ext/io can be left null and the new stream handle will pick up
 * the ext/io. This should be used only in specific environment however
 * since => zzip_file_real does not store any ext-sequence.
 *
 * The benefit for this function comes in when the old file handle
 * was openened from a file within a zip archive. When the new file
 * is in the same zip archive then the internal zzip_dir structures
 * will be shared. It is even quicker, as no check needs to be done
 * anymore trying to guess the zip archive place in the filesystem,
 * here we just check whether the zip archive's filepath is a prefix
 * part of the filename to be opened.
 *
 * Note that this function is also used by => zzip_freopen that
 * will unshare the old handle, thereby possibly closing the handle.
 *
 * This function returns a new zzip-handle (use => zzip_close to return
 * it). On error this function will return null setting => errno(3).
 */
ZZIP_FILE *
zzip_open_shared_io(ZZIP_FILE * stream,
                    zzip_char_t * filename, int o_flags, int o_modes,
                    zzip_strings_t * ext, zzip_plugin_io_t io)
{
    if (stream && stream->dir)
    {
        if (! ext)
            ext = stream->dir->fileext;
        if (! io)
            io = stream->dir->io;
    }
    if (! io)
        io = zzip_get_default_io();

    if (o_modes & (ZZIP_PREFERZIP | ZZIP_ONLYZIP))
        goto try_zzip;
  try_real:
    /* prefer an existing real file */
    {
        zzip_plugin_io_t os = (o_modes & ZZIP_ALLOWREAL)
            ? zzip_get_default_io() : io;
        int fd = os->fd.open(filename, o_flags);        /* io->fd.open */

        if (fd != -1)
        {
            ZZIP_FILE *fp = calloc(1, sizeof(ZZIP_FILE));

            if (! fp)
                { os->fd.close(fd); return 0; }  /* io->fd.close */

            fp->fd = fd;
            fp->io = os;
            return fp;
        }
        if (o_modes & ZZIP_PREFERZIP)
            return 0;
    }
  try_zzip:

    /* if the user had it in place of a normal xopen, then
     * we better defend this lib against illegal usage */
    if (o_flags & (O_CREAT | O_WRONLY))
        { errno = EINVAL; return 0; }
    if (o_flags & (O_RDWR))
        { o_flags ^= O_RDWR; o_flags |= O_RDONLY; }

    /* this is just for backward compatibility -and strictly needed to
     * prepare ourselves for more options and more options later on... */
    /*# if (o_modes & ZZIP_CASELESS) { o_flags |= ZZIP_CASEINSENSITIVE; } */
    /*# if (o_modes & ZZIP_NOPATHS)  { o_flags |= ZZIP_IGNOREPATH; } */

    /* see if we can open a file that is a zip file */
    {
        char basename[PATH_MAX];
        char *p;
        int filename_len = strlen(filename);

        if (filename_len >= PATH_MAX)
            { errno = ENAMETOOLONG; return 0; }
        memcpy(basename, filename, filename_len + 1);

        /* see if we can share the same zip directory */
        if (stream && stream->dir && stream->dir->realname)
        {
            zzip_size_t len = strlen(stream->dir->realname);

            if (! memcmp(filename, stream->dir->realname, len) &&
                filename[len] == '/' && filename[len + 1])
            {
                ZZIP_FILE *fp =
                    zzip_file_open(stream->dir, filename + len + 1, o_modes);
                if (! fp)
                    { errno = zzip_errno (stream->dir->errcode); }
                return fp;
            }
        }

        /* per each slash in filename, check if it there is a zzip around */
        while ((p = strrchr(basename, '/')))
        {
            zzip_error_t e = 0;
            ZZIP_DIR *dir;
            ZZIP_FILE *fp;
            int fd;

            *p = '\0';
            /* i.e. cut at path separator == possible zipfile basename */
            fd = __zzip_try_open(basename, o_flags | O_RDONLY | O_BINARY,
                                 ext, io);
            if (fd == -1)
                { continue; }

            /* found zip-file ....  now try to parse it */
            dir = zzip_dir_fdopen_ext_io(fd, &e, ext, io);
            if (e)
                { errno = zzip_errno(e); io->fd.close(fd); return 0; }

            /* (p - basename) is the lenghtof zzip_dir part of the filename */
            fp = zzip_file_open(dir, filename + (p - basename) + 1, o_modes);
            if (! fp)
                { errno = zzip_errno(dir->errcode); }
            else
                { if (! dir->realname) dir->realname = strdup (basename); }

            zzip_dir_close(dir);
            /* note: since (fp) is attached that (dir) will survive */
            /* but (dir) is implicitly closed on next zzip_close(fp) */

            return fp;
        }

        if (o_modes & ZZIP_PREFERZIP)
            goto try_real;
        else
            { errno = ENOENT; return 0; }
    }
}

#if defined ZZIP_LARGEFILE_RENAME && defined EOVERFLOW && defined PIC
#undef zzip_open_shared_io      /* zzip_open_shared_io64 */
#undef zzip_open_ext_io         /* zzip_open_ext_io64 */
#undef zzip_opendir_ext_io      /* zzip_opendir_ext_io64 */

ZZIP_FILE *zzip_open_shared_io(ZZIP_FILE * stream,
                               zzip_char_t * name, int o_flags,
                               int o_modes, zzip_strings_t * ext,
                               zzip_plugin_io_t io);
ZZIP_FILE *zzip_open_ext_io(zzip_char_t * name, int o_flags,
                            int o_modes, zzip_strings_t * ext,
                            zzip_plugin_io_t io);
ZZIP_DIR *zzip_opendir_ext_io(zzip_char_t * name, int o_modes,
                              zzip_strings_t * ext, zzip_plugin_io_t io);

/* DLL compatibility layer - so that 32bit code can link with this lib too */

ZZIP_FILE *
zzip_open_shared_io(ZZIP_FILE * stream,
                    zzip_char_t * name, int o_flags,
                    int o_modes, zzip_strings_t * ext, zzip_plugin_io_t io)
{
    if (! io)
        return zzip_open_shared_io64(stream, name, o_flags, o_modes, ext, io);
    errno = EOVERFLOW;
    return NULL;
}

ZZIP_FILE *
zzip_open_ext_io(zzip_char_t * name, int o_flags, int o_modes,
                 zzip_strings_t * ext, zzip_plugin_io_t io)
{
    if (! io)
        return zzip_open_ext_io64(name, o_flags, o_modes, ext, io);
    errno = EOVERFLOW;
    return NULL;
}

ZZIP_DIR *
zzip_opendir_ext_io(zzip_char_t * name, int o_modes,
                    zzip_strings_t * ext, zzip_plugin_io_t io)
{
    if (! io)
        return zzip_opendir_ext_io64(name, o_modes, ext, io);
    else
        { errno = EOVERFLOW; return NULL; }
}

#endif /* ZZIP_LARGEFILE_RENAME && EOVERFLOW && PIC */

/* ------------------------------------------------------------------- */

/**
 * This function will rewind a real/zipped file.
 *
 * It seeks to the beginning of this file's data in the zip,
 * or the beginning of the file for a stat'fd.
 */
int
zzip_rewind(ZZIP_FILE * fp)
{
    ZZIP_DIR *dir;
    int err;

    if (! fp)
        return -1;

    if (! fp->dir)
    {                           /* stat fd */
        fp->io->fd.seeks(fp->fd, 0, SEEK_SET);
        return 0;
    }

    dir = fp->dir;
    /*
     * If this is other handle than previous, save current seek pointer
     */
    if (dir->currentfp != fp)
    {
        if (zzip_file_saveoffset(dir->currentfp) < 0)
            { dir->errcode = ZZIP_DIR_SEEK; return -1; }
        else
            { dir->currentfp = fp; }
    }

    /* seek to beginning of this file */
    if (fp->io->fd.seeks(dir->fd, fp->dataoffset, SEEK_SET) < 0)
        return -1;

    /* reset the inflate init stuff */
    fp->restlen = fp->usize;
    fp->offset = fp->dataoffset;

    if (fp->method)
    {                           /* method == 8, deflate */
        err = inflateReset(&fp->d_stream);
        if (err != Z_OK)
            goto error;

        /* start over at next inflate with a fresh read() */
        fp->d_stream.avail_in = 0;
        fp->crestlen = fp->csize;
    }

    return 0;

  error:
    if (fp)
        zzip_file_close(fp);
    return err;
}

/**
 * This function will perform a => lseek(2) operation on a real/zipped file
 *
 * It will try to seek to the offset specified by offset, relative to whence,
 * which is one of SEEK_SET, SEEK_CUR or SEEK_END.
 *
 * If the file-handle is wrapping a stat'able file then it will actually just
 * perform a normal => lseek(2)-call. Otherwise the relative offset
 * is calculated, negative offsets are transformed into positive ones
 * by rewinding the file, and then data is read until the offset is
 * reached.  This can make the function terribly slow, but this is
 * how gzio implements it, so I'm not sure there is a better way
 * without using the internals of the algorithm.
 */
zzip_off_t
zzip_seek(ZZIP_FILE * fp, zzip_off_t offset, int whence)
{
    zzip_off_t cur_pos, rel_ofs, read_size, ofs;
    ZZIP_DIR *dir;

    if (! fp)
        return -1;

    if (! fp->dir)
    {                           /* stat fd */
        return fp->io->fd.seeks(fp->fd, offset, whence);
    }

    cur_pos = zzip_tell(fp);

    /* calculate relative offset */
    switch (whence)
    {
    case SEEK_SET:             /* from beginning */
        rel_ofs = offset - cur_pos;
        break;
    case SEEK_CUR:             /* from current */
        rel_ofs = offset;
        break;
    case SEEK_END:             /* from end */
        rel_ofs = fp->usize + offset - cur_pos;
        break;
    default:                   /* something wrong */
        return -1;
    }

    if (rel_ofs == 0)
        return cur_pos;         /* don't have to move */

    if (rel_ofs < 0)
    {                           /* convert backward into forward */
        if (zzip_rewind(fp) == -1)
            return -1;

        read_size = cur_pos + rel_ofs;
        cur_pos = 0;
    } else
    {                           /* amount to read is positive relative offset */
        read_size = rel_ofs;
    }

    if (read_size < 0)          /* bad offset, before beginning of file */
        return -1;

    if (read_size + cur_pos > (zzip_off_t) fp->usize)   /* bad offset, past EOF */
        return -1;

    if (read_size == 0)         /* nothing to read */
        return cur_pos;

    dir = fp->dir;
    /*
     * If this is other handle than previous, save current seek pointer
     * and read the file position of `this' handle.
     */
    if (dir->currentfp != fp)
    {
        if (zzip_file_saveoffset(dir->currentfp) < 0
            || fp->io->fd.seeks(dir->fd, fp->offset, SEEK_SET) < 0)
            { dir->errcode = ZZIP_DIR_SEEK; return -1; }
        else
            { dir->currentfp = fp; }
    }

    if (fp->method == 0)
    {                           /* unstore, just lseek relatively */
        ofs = fp->io->fd.tells(dir->fd);
        ofs = fp->io->fd.seeks(dir->fd, read_size, SEEK_CUR);
        if (ofs > 0)
        {                       /* readjust from beginning of file */
            ofs -= fp->dataoffset;
            fp->restlen = fp->usize - ofs;
        }
        return ofs;
    } else
    {                           /* method == 8, inflate */
        char *buf;

        /*FIXME: use a static buffer! */
        buf = (char *) malloc(ZZIP_32K);
        if (! buf)
            return -1;

        while (read_size > 0)
        {
            zzip_off_t size = ZZIP_32K;

            if (read_size < size /*32K */ )
                size = read_size;

            size = zzip_file_read(fp, buf, (zzip_size_t) size);
            if (size <= 0)
                { free(buf); return -1; }

            read_size -= size;
        }

        free(buf);
    }

    return zzip_tell(fp);
}

/**
 * This function will => tell(2) the current position in a real/zipped file
 *
 * It will return the current offset within the real/zipped file,
 * measured in uncompressed bytes for the zipped-file case.
 *
 * If the file-handle is wrapping a stat'able file then it will actually just
 * perform a normal => tell(2)-call, otherwise the offset is
 * calculated from the amount of data left and the total uncompressed
 * size;
 */
zzip_off_t
zzip_tell(ZZIP_FILE * fp)
{
    if (! fp)
        return -1;

    if (! fp->dir)               /* stat fd */
        return fp->io->fd.tells(fp->fd);

    /* current uncompressed offset is uncompressed size - data left */
    return (fp->usize - fp->restlen);
}

/*
 * Local variables:
 * c-file-style: "stroustrup"
 * End:
 */
