1 | '\" |
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2 | '\" Copyright (c) 1996-1997 Sun Microsystems, Inc. |
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3 | '\" |
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4 | '\" See the file "license.terms" for information on usage and redistribution |
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5 | '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. |
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6 | '\" |
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7 | '\" RCS: @(#) $Id: ObjectType.3,v 1.16 2007/12/13 15:22:31 dgp Exp $ |
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8 | '\" |
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9 | .so man.macros |
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10 | .TH Tcl_ObjType 3 8.0 Tcl "Tcl Library Procedures" |
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11 | .BS |
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12 | .SH NAME |
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13 | Tcl_RegisterObjType, Tcl_GetObjType, Tcl_AppendAllObjTypes, Tcl_ConvertToType \- manipulate Tcl object types |
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14 | .SH SYNOPSIS |
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15 | .nf |
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16 | \fB#include <tcl.h>\fR |
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17 | .sp |
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18 | \fBTcl_RegisterObjType\fR(\fItypePtr\fR) |
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19 | .sp |
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20 | Tcl_ObjType * |
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21 | \fBTcl_GetObjType\fR(\fItypeName\fR) |
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22 | .sp |
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23 | int |
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24 | \fBTcl_AppendAllObjTypes\fR(\fIinterp, objPtr\fR) |
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25 | .sp |
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26 | int |
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27 | \fBTcl_ConvertToType\fR(\fIinterp, objPtr, typePtr\fR) |
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28 | .SH ARGUMENTS |
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29 | .AS "const char" *typeName |
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30 | .AP Tcl_ObjType *typePtr in |
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31 | Points to the structure containing information about the Tcl object type. |
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32 | This storage must live forever, |
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33 | typically by being statically allocated. |
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34 | .AP "const char" *typeName in |
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35 | The name of a Tcl object type that \fBTcl_GetObjType\fR should look up. |
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36 | .AP Tcl_Interp *interp in |
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37 | Interpreter to use for error reporting. |
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38 | .AP Tcl_Obj *objPtr in |
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39 | For \fBTcl_AppendAllObjTypes\fR, this points to the object onto which |
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40 | it appends the name of each object type as a list element. |
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41 | For \fBTcl_ConvertToType\fR, this points to an object that |
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42 | must have been the result of a previous call to \fBTcl_NewObj\fR. |
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43 | .BE |
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44 | |
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45 | .SH DESCRIPTION |
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46 | .PP |
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47 | The procedures in this man page manage Tcl object types. |
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48 | They are used to register new object types, look up types, |
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49 | and force conversions from one type to another. |
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50 | .PP |
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51 | \fBTcl_RegisterObjType\fR registers a new Tcl object type |
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52 | in the table of all object types supported by Tcl. |
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53 | The argument \fItypePtr\fR points to a Tcl_ObjType structure that |
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54 | describes the new type by giving its name |
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55 | and by supplying pointers to four procedures |
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56 | that implement the type. |
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57 | If the type table already contains a type |
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58 | with the same name as in \fItypePtr\fR, |
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59 | it is replaced with the new type. |
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60 | The Tcl_ObjType structure is described |
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61 | in the section \fBTHE TCL_OBJTYPE STRUCTURE\fR below. |
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62 | .PP |
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63 | \fBTcl_GetObjType\fR returns a pointer to the Tcl_ObjType |
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64 | with name \fItypeName\fR. |
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65 | It returns NULL if no type with that name is registered. |
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66 | .PP |
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67 | \fBTcl_AppendAllObjTypes\fR appends the name of each object type |
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68 | as a list element onto the Tcl object referenced by \fIobjPtr\fR. |
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69 | The return value is \fBTCL_OK\fR unless there was an error |
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70 | converting \fIobjPtr\fR to a list object; |
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71 | in that case \fBTCL_ERROR\fR is returned. |
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72 | .PP |
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73 | \fBTcl_ConvertToType\fR converts an object from one type to another |
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74 | if possible. |
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75 | It creates a new internal representation for \fIobjPtr\fR |
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76 | appropriate for the target type \fItypePtr\fR |
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77 | and sets its \fItypePtr\fR member to that type. |
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78 | Any internal representation for \fIobjPtr\fR's old type is freed. |
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79 | If an error occurs during conversion, it returns \fBTCL_ERROR\fR |
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80 | and leaves an error message in the result object for \fIinterp\fR |
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81 | unless \fIinterp\fR is NULL. |
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82 | Otherwise, it returns \fBTCL_OK\fR. |
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83 | Passing a NULL \fIinterp\fR allows this procedure to be used |
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84 | as a test whether the conversion can be done (and in fact was done). |
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85 | .SH "THE TCL_OBJTYPE STRUCTURE" |
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86 | .PP |
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87 | Extension writers can define new object types by defining four |
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88 | procedures, |
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89 | initializing a Tcl_ObjType structure to describe the type, |
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90 | and calling \fBTcl_RegisterObjType\fR. |
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91 | The \fBTcl_ObjType\fR structure is defined as follows: |
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92 | .PP |
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93 | .CS |
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94 | typedef struct Tcl_ObjType { |
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95 | char *\fIname\fR; |
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96 | Tcl_FreeInternalRepProc *\fIfreeIntRepProc\fR; |
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97 | Tcl_DupInternalRepProc *\fIdupIntRepProc\fR; |
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98 | Tcl_UpdateStringProc *\fIupdateStringProc\fR; |
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99 | Tcl_SetFromAnyProc *\fIsetFromAnyProc\fR; |
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100 | } Tcl_ObjType; |
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101 | .CE |
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102 | .SS "THE NAME FIELD" |
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103 | .PP |
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104 | The \fIname\fR member describes the name of the type, e.g. \fBint\fR. |
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105 | Extension writers can look up an object type using its name |
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106 | with the \fBTcl_GetObjType\fR procedure. |
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107 | The remaining four members are pointers to procedures |
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108 | called by the generic Tcl object code: |
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109 | .SS "THE SETFROMANYPROC FIELD" |
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110 | .PP |
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111 | The \fIsetFromAnyProc\fR member contains the address of a function |
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112 | called to create a valid internal representation |
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113 | from an object's string representation. |
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114 | .PP |
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115 | .CS |
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116 | typedef int (Tcl_SetFromAnyProc) (Tcl_Interp *\fIinterp\fR, |
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117 | Tcl_Obj *\fIobjPtr\fR); |
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118 | .CE |
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119 | .PP |
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120 | If an internal representation cannot be created from the string, |
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121 | it returns \fBTCL_ERROR\fR and puts a message |
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122 | describing the error in the result object for \fIinterp\fR |
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123 | unless \fIinterp\fR is NULL. |
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124 | If \fIsetFromAnyProc\fR is successful, |
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125 | it stores the new internal representation, |
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126 | sets \fIobjPtr\fR's \fItypePtr\fR member to point to |
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127 | \fIsetFromAnyProc\fR's \fBTcl_ObjType\fR, and returns \fBTCL_OK\fR. |
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128 | Before setting the new internal representation, |
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129 | the \fIsetFromAnyProc\fR must free any internal representation |
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130 | of \fIobjPtr\fR's old type; |
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131 | it does this by calling the old type's \fIfreeIntRepProc\fR |
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132 | if it is not NULL. |
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133 | As an example, the \fIsetFromAnyProc\fR for the built-in Tcl integer type |
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134 | gets an up-to-date string representation for \fIobjPtr\fR |
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135 | by calling \fBTcl_GetStringFromObj\fR. |
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136 | It parses the string to obtain an integer and, |
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137 | if this succeeds, |
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138 | stores the integer in \fIobjPtr\fR's internal representation |
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139 | and sets \fIobjPtr\fR's \fItypePtr\fR member to point to the integer type's |
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140 | Tcl_ObjType structure. |
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141 | Do not release \fIobjPtr\fR's old internal representation unless you |
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142 | replace it with a new one or reset the \fItypePtr\fR member to NULL. |
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143 | .SS "THE UPDATESTRINGPROC FIELD" |
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144 | .PP |
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145 | The \fIupdateStringProc\fR member contains the address of a function |
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146 | called to create a valid string representation |
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147 | from an object's internal representation. |
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148 | .PP |
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149 | .CS |
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150 | typedef void (Tcl_UpdateStringProc) (Tcl_Obj *\fIobjPtr\fR); |
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151 | .CE |
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152 | .PP |
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153 | \fIobjPtr\fR's \fIbytes\fR member is always NULL when it is called. |
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154 | It must always set \fIbytes\fR non-NULL before returning. |
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155 | We require the string representation's byte array |
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156 | to have a null after the last byte, at offset \fIlength\fR; |
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157 | this allows string representations that do not contain null bytes |
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158 | to be treated as conventional null character-terminated C strings. |
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159 | Storage for the byte array must be allocated in the heap by \fBTcl_Alloc\fR |
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160 | or \fBckalloc\fR. Note that \fIupdateStringProc\fRs must allocate |
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161 | enough storage for the string's bytes and the terminating null byte. |
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162 | The \fIupdateStringProc\fR for Tcl's built-in list type, for example, |
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163 | builds an array of strings for each element object |
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164 | and then calls \fBTcl_Merge\fR |
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165 | to construct a string with proper Tcl list structure. |
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166 | It stores this string as the list object's string representation. |
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167 | .SS "THE DUPINTREPPROC FIELD" |
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168 | .PP |
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169 | The \fIdupIntRepProc\fR member contains the address of a function |
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170 | called to copy an internal representation from one object to another. |
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171 | .PP |
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172 | .CS |
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173 | typedef void (Tcl_DupInternalRepProc) (Tcl_Obj *\fIsrcPtr\fR, |
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174 | Tcl_Obj *\fIdupPtr\fR); |
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175 | .CE |
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176 | .PP |
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177 | \fIdupPtr\fR's internal representation is made a copy of \fIsrcPtr\fR's |
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178 | internal representation. |
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179 | Before the call, |
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180 | \fIsrcPtr\fR's internal representation is valid and \fIdupPtr\fR's is not. |
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181 | \fIsrcPtr\fR's object type determines what |
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182 | copying its internal representation means. |
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183 | For example, the \fIdupIntRepProc\fR for the Tcl integer type |
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184 | simply copies an integer. |
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185 | The built-in list type's \fIdupIntRepProc\fR |
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186 | allocates a new array that points at the original element objects; |
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187 | the elements are shared between the two lists |
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188 | (and their reference counts are incremented to reflect the new references). |
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189 | .SS "THE FREEINTREPPROC FIELD" |
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190 | .PP |
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191 | The \fIfreeIntRepProc\fR member contains the address of a function |
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192 | that is called when an object is freed. |
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193 | .PP |
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194 | .CS |
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195 | typedef void (Tcl_FreeInternalRepProc) (Tcl_Obj *\fIobjPtr\fR); |
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196 | .CE |
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197 | .PP |
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198 | The \fIfreeIntRepProc\fR function can deallocate the storage |
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199 | for the object's internal representation |
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200 | and do other type-specific processing necessary when an object is freed. |
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201 | For example, Tcl list objects have an \fIinternalRep.otherValuePtr\fR |
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202 | that points to an array of pointers to each element in the list. |
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203 | The list type's \fIfreeIntRepProc\fR decrements |
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204 | the reference count for each element object |
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205 | (since the list will no longer refer to those objects), |
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206 | then deallocates the storage for the array of pointers. |
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207 | The \fIfreeIntRepProc\fR member can be set to NULL |
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208 | to indicate that the internal representation does not require freeing. |
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209 | The \fIfreeIntRepProc\fR implementation should not access the |
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210 | \fIbytes\fR member of the object, as this may potentially have already |
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211 | been deleted. |
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212 | .SH "SEE ALSO" |
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213 | Tcl_NewObj, Tcl_DecrRefCount, Tcl_IncrRefCount |
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214 | .SH KEYWORDS |
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215 | internal representation, object, object type, string representation, type conversion |
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