1 |
/* $Header$ */
|
2 |
/*
|
3 |
* tclLink.c --
|
4 |
*
|
5 |
* This file implements linked variables (a C variable that is
|
6 |
* tied to a Tcl variable). The idea of linked variables was
|
7 |
* first suggested by Andreas Stolcke and this implementation is
|
8 |
* based heavily on a prototype implementation provided by
|
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* him.
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10 |
*
|
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* Copyright (c) 1993 The Regents of the University of California.
|
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* Copyright (c) 1994-1997 Sun Microsystems, Inc.
|
13 |
*
|
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* See the file "license.terms" for information on usage and redistribution
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* of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
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*
|
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* RCS: @(#) $Id: tcllink.c,v 1.1.1.1 2001/06/13 04:42:27 dtashley Exp $
|
18 |
*/
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19 |
|
20 |
#include "tclInt.h"
|
21 |
|
22 |
/*
|
23 |
* For each linked variable there is a data structure of the following
|
24 |
* type, which describes the link and is the clientData for the trace
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25 |
* set on the Tcl variable.
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26 |
*/
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27 |
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28 |
typedef struct Link {
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29 |
Tcl_Interp *interp; /* Interpreter containing Tcl variable. */
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30 |
char *varName; /* Name of variable (must be global). This
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31 |
* is needed during trace callbacks, since
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32 |
* the actual variable may be aliased at
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33 |
* that time via upvar. */
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34 |
char *addr; /* Location of C variable. */
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35 |
int type; /* Type of link (TCL_LINK_INT, etc.). */
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36 |
union {
|
37 |
int i;
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38 |
double d;
|
39 |
} lastValue; /* Last known value of C variable; used to
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* avoid string conversions. */
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int flags; /* Miscellaneous one-bit values; see below
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* for definitions. */
|
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} Link;
|
44 |
|
45 |
/*
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* Definitions for flag bits:
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* LINK_READ_ONLY - 1 means errors should be generated if Tcl
|
48 |
* script attempts to write variable.
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49 |
* LINK_BEING_UPDATED - 1 means that a call to Tcl_UpdateLinkedVar
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* is in progress for this variable, so
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* trace callbacks on the variable should
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* be ignored.
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*/
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54 |
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55 |
#define LINK_READ_ONLY 1
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#define LINK_BEING_UPDATED 2
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/*
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* Forward references to procedures defined later in this file:
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*/
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61 |
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62 |
static char * LinkTraceProc _ANSI_ARGS_((ClientData clientData,
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63 |
Tcl_Interp *interp, char *name1, char *name2,
|
64 |
int flags));
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65 |
static char * StringValue _ANSI_ARGS_((Link *linkPtr,
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66 |
char *buffer));
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67 |
|
68 |
/*
|
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*----------------------------------------------------------------------
|
70 |
*
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* Tcl_LinkVar --
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72 |
*
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* Link a C variable to a Tcl variable so that changes to either
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* one causes the other to change.
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*
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* Results:
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* The return value is TCL_OK if everything went well or TCL_ERROR
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78 |
* if an error occurred (the interp's result is also set after
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* errors).
|
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*
|
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* Side effects:
|
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* The value at *addr is linked to the Tcl variable "varName",
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* using "type" to convert between string values for Tcl and
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* binary values for *addr.
|
85 |
*
|
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*----------------------------------------------------------------------
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*/
|
88 |
|
89 |
int
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90 |
Tcl_LinkVar(interp, varName, addr, type)
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91 |
Tcl_Interp *interp; /* Interpreter in which varName exists. */
|
92 |
char *varName; /* Name of a global variable in interp. */
|
93 |
char *addr; /* Address of a C variable to be linked
|
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* to varName. */
|
95 |
int type; /* Type of C variable: TCL_LINK_INT, etc.
|
96 |
* Also may have TCL_LINK_READ_ONLY
|
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* OR'ed in. */
|
98 |
{
|
99 |
Link *linkPtr;
|
100 |
char buffer[TCL_DOUBLE_SPACE];
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101 |
int code;
|
102 |
|
103 |
linkPtr = (Link *) ckalloc(sizeof(Link));
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104 |
linkPtr->interp = interp;
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105 |
linkPtr->varName = (char *) ckalloc((unsigned) (strlen(varName) + 1));
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106 |
strcpy(linkPtr->varName, varName);
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107 |
linkPtr->addr = addr;
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108 |
linkPtr->type = type & ~TCL_LINK_READ_ONLY;
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109 |
if (type & TCL_LINK_READ_ONLY) {
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110 |
linkPtr->flags = LINK_READ_ONLY;
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111 |
} else {
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112 |
linkPtr->flags = 0;
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113 |
}
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114 |
if (Tcl_SetVar(interp, varName, StringValue(linkPtr, buffer),
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115 |
TCL_GLOBAL_ONLY|TCL_LEAVE_ERR_MSG) == NULL) {
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116 |
ckfree(linkPtr->varName);
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117 |
ckfree((char *) linkPtr);
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118 |
return TCL_ERROR;
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119 |
}
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120 |
code = Tcl_TraceVar(interp, varName, TCL_GLOBAL_ONLY|TCL_TRACE_READS
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121 |
|TCL_TRACE_WRITES|TCL_TRACE_UNSETS, LinkTraceProc,
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122 |
(ClientData) linkPtr);
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123 |
if (code != TCL_OK) {
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124 |
ckfree(linkPtr->varName);
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125 |
ckfree((char *) linkPtr);
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126 |
}
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127 |
return code;
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128 |
}
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129 |
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130 |
/*
|
131 |
*----------------------------------------------------------------------
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132 |
*
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133 |
* Tcl_UnlinkVar --
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*
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* Destroy the link between a Tcl variable and a C variable.
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136 |
*
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* Results:
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* None.
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*
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* Side effects:
|
141 |
* If "varName" was previously linked to a C variable, the link
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142 |
* is broken to make the variable independent. If there was no
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* previous link for "varName" then nothing happens.
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144 |
*
|
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*----------------------------------------------------------------------
|
146 |
*/
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void
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Tcl_UnlinkVar(interp, varName)
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Tcl_Interp *interp; /* Interpreter containing variable to unlink. */
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char *varName; /* Global variable in interp to unlink. */
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{
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153 |
Link *linkPtr;
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154 |
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155 |
linkPtr = (Link *) Tcl_VarTraceInfo(interp, varName, TCL_GLOBAL_ONLY,
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LinkTraceProc, (ClientData) NULL);
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if (linkPtr == NULL) {
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return;
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}
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160 |
Tcl_UntraceVar(interp, varName,
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TCL_GLOBAL_ONLY|TCL_TRACE_READS|TCL_TRACE_WRITES|TCL_TRACE_UNSETS,
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162 |
LinkTraceProc, (ClientData) linkPtr);
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ckfree(linkPtr->varName);
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ckfree((char *) linkPtr);
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}
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/*
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*----------------------------------------------------------------------
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*
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* Tcl_UpdateLinkedVar --
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*
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* This procedure is invoked after a linked variable has been
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* changed by C code. It updates the Tcl variable so that
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* traces on the variable will trigger.
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*
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* Results:
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177 |
* None.
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*
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179 |
* Side effects:
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180 |
* The Tcl variable "varName" is updated from its C value,
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181 |
* causing traces on the variable to trigger.
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182 |
*
|
183 |
*----------------------------------------------------------------------
|
184 |
*/
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185 |
|
186 |
void
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187 |
Tcl_UpdateLinkedVar(interp, varName)
|
188 |
Tcl_Interp *interp; /* Interpreter containing variable. */
|
189 |
char *varName; /* Name of global variable that is linked. */
|
190 |
{
|
191 |
Link *linkPtr;
|
192 |
char buffer[TCL_DOUBLE_SPACE];
|
193 |
int savedFlag;
|
194 |
|
195 |
linkPtr = (Link *) Tcl_VarTraceInfo(interp, varName, TCL_GLOBAL_ONLY,
|
196 |
LinkTraceProc, (ClientData) NULL);
|
197 |
if (linkPtr == NULL) {
|
198 |
return;
|
199 |
}
|
200 |
savedFlag = linkPtr->flags & LINK_BEING_UPDATED;
|
201 |
linkPtr->flags |= LINK_BEING_UPDATED;
|
202 |
Tcl_SetVar(interp, linkPtr->varName, StringValue(linkPtr, buffer),
|
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TCL_GLOBAL_ONLY);
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linkPtr->flags = (linkPtr->flags & ~LINK_BEING_UPDATED) | savedFlag;
|
205 |
}
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206 |
|
207 |
/*
|
208 |
*----------------------------------------------------------------------
|
209 |
*
|
210 |
* LinkTraceProc --
|
211 |
*
|
212 |
* This procedure is invoked when a linked Tcl variable is read,
|
213 |
* written, or unset from Tcl. It's responsible for keeping the
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* C variable in sync with the Tcl variable.
|
215 |
*
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216 |
* Results:
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217 |
* If all goes well, NULL is returned; otherwise an error message
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* is returned.
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219 |
*
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220 |
* Side effects:
|
221 |
* The C variable may be updated to make it consistent with the
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* Tcl variable, or the Tcl variable may be overwritten to reject
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223 |
* a modification.
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224 |
*
|
225 |
*----------------------------------------------------------------------
|
226 |
*/
|
227 |
|
228 |
static char *
|
229 |
LinkTraceProc(clientData, interp, name1, name2, flags)
|
230 |
ClientData clientData; /* Contains information about the link. */
|
231 |
Tcl_Interp *interp; /* Interpreter containing Tcl variable. */
|
232 |
char *name1; /* First part of variable name. */
|
233 |
char *name2; /* Second part of variable name. */
|
234 |
int flags; /* Miscellaneous additional information. */
|
235 |
{
|
236 |
Link *linkPtr = (Link *) clientData;
|
237 |
int changed;
|
238 |
char buffer[TCL_DOUBLE_SPACE];
|
239 |
char *value, **pp, *result;
|
240 |
Tcl_Obj *objPtr;
|
241 |
|
242 |
/*
|
243 |
* If the variable is being unset, then just re-create it (with a
|
244 |
* trace) unless the whole interpreter is going away.
|
245 |
*/
|
246 |
|
247 |
if (flags & TCL_TRACE_UNSETS) {
|
248 |
if (flags & TCL_INTERP_DESTROYED) {
|
249 |
ckfree(linkPtr->varName);
|
250 |
ckfree((char *) linkPtr);
|
251 |
} else if (flags & TCL_TRACE_DESTROYED) {
|
252 |
Tcl_SetVar(interp, linkPtr->varName, StringValue(linkPtr, buffer),
|
253 |
TCL_GLOBAL_ONLY);
|
254 |
Tcl_TraceVar(interp, linkPtr->varName, TCL_GLOBAL_ONLY
|
255 |
|TCL_TRACE_READS|TCL_TRACE_WRITES|TCL_TRACE_UNSETS,
|
256 |
LinkTraceProc, (ClientData) linkPtr);
|
257 |
}
|
258 |
return NULL;
|
259 |
}
|
260 |
|
261 |
/*
|
262 |
* If we were invoked because of a call to Tcl_UpdateLinkedVar, then
|
263 |
* don't do anything at all. In particular, we don't want to get
|
264 |
* upset that the variable is being modified, even if it is
|
265 |
* supposed to be read-only.
|
266 |
*/
|
267 |
|
268 |
if (linkPtr->flags & LINK_BEING_UPDATED) {
|
269 |
return NULL;
|
270 |
}
|
271 |
|
272 |
/*
|
273 |
* For read accesses, update the Tcl variable if the C variable
|
274 |
* has changed since the last time we updated the Tcl variable.
|
275 |
*/
|
276 |
|
277 |
if (flags & TCL_TRACE_READS) {
|
278 |
switch (linkPtr->type) {
|
279 |
case TCL_LINK_INT:
|
280 |
case TCL_LINK_BOOLEAN:
|
281 |
changed = *(int *)(linkPtr->addr) != linkPtr->lastValue.i;
|
282 |
break;
|
283 |
case TCL_LINK_DOUBLE:
|
284 |
changed = *(double *)(linkPtr->addr) != linkPtr->lastValue.d;
|
285 |
break;
|
286 |
case TCL_LINK_STRING:
|
287 |
changed = 1;
|
288 |
break;
|
289 |
default:
|
290 |
return "internal error: bad linked variable type";
|
291 |
}
|
292 |
if (changed) {
|
293 |
Tcl_SetVar(interp, linkPtr->varName, StringValue(linkPtr, buffer),
|
294 |
TCL_GLOBAL_ONLY);
|
295 |
}
|
296 |
return NULL;
|
297 |
}
|
298 |
|
299 |
/*
|
300 |
* For writes, first make sure that the variable is writable. Then
|
301 |
* convert the Tcl value to C if possible. If the variable isn't
|
302 |
* writable or can't be converted, then restore the varaible's old
|
303 |
* value and return an error. Another tricky thing: we have to save
|
304 |
* and restore the interpreter's result, since the variable access
|
305 |
* could occur when the result has been partially set.
|
306 |
*/
|
307 |
|
308 |
if (linkPtr->flags & LINK_READ_ONLY) {
|
309 |
Tcl_SetVar(interp, linkPtr->varName, StringValue(linkPtr, buffer),
|
310 |
TCL_GLOBAL_ONLY);
|
311 |
return "linked variable is read-only";
|
312 |
}
|
313 |
value = Tcl_GetVar(interp, linkPtr->varName, TCL_GLOBAL_ONLY);
|
314 |
if (value == NULL) {
|
315 |
/*
|
316 |
* This shouldn't ever happen.
|
317 |
*/
|
318 |
return "internal error: linked variable couldn't be read";
|
319 |
}
|
320 |
|
321 |
objPtr = Tcl_GetObjResult(interp);
|
322 |
Tcl_IncrRefCount(objPtr);
|
323 |
Tcl_ResetResult(interp);
|
324 |
result = NULL;
|
325 |
|
326 |
switch (linkPtr->type) {
|
327 |
case TCL_LINK_INT:
|
328 |
if (Tcl_GetInt(interp, value, &linkPtr->lastValue.i) != TCL_OK) {
|
329 |
Tcl_SetObjResult(interp, objPtr);
|
330 |
Tcl_SetVar(interp, linkPtr->varName,
|
331 |
StringValue(linkPtr, buffer), TCL_GLOBAL_ONLY);
|
332 |
result = "variable must have integer value";
|
333 |
goto end;
|
334 |
}
|
335 |
*(int *)(linkPtr->addr) = linkPtr->lastValue.i;
|
336 |
break;
|
337 |
case TCL_LINK_DOUBLE:
|
338 |
if (Tcl_GetDouble(interp, value, &linkPtr->lastValue.d)
|
339 |
!= TCL_OK) {
|
340 |
Tcl_SetObjResult(interp, objPtr);
|
341 |
Tcl_SetVar(interp, linkPtr->varName,
|
342 |
StringValue(linkPtr, buffer), TCL_GLOBAL_ONLY);
|
343 |
result = "variable must have real value";
|
344 |
goto end;
|
345 |
}
|
346 |
*(double *)(linkPtr->addr) = linkPtr->lastValue.d;
|
347 |
break;
|
348 |
case TCL_LINK_BOOLEAN:
|
349 |
if (Tcl_GetBoolean(interp, value, &linkPtr->lastValue.i)
|
350 |
!= TCL_OK) {
|
351 |
Tcl_SetObjResult(interp, objPtr);
|
352 |
Tcl_SetVar(interp, linkPtr->varName,
|
353 |
StringValue(linkPtr, buffer), TCL_GLOBAL_ONLY);
|
354 |
result = "variable must have boolean value";
|
355 |
goto end;
|
356 |
}
|
357 |
*(int *)(linkPtr->addr) = linkPtr->lastValue.i;
|
358 |
break;
|
359 |
case TCL_LINK_STRING:
|
360 |
pp = (char **)(linkPtr->addr);
|
361 |
if (*pp != NULL) {
|
362 |
ckfree(*pp);
|
363 |
}
|
364 |
*pp = (char *) ckalloc((unsigned) (strlen(value) + 1));
|
365 |
strcpy(*pp, value);
|
366 |
break;
|
367 |
default:
|
368 |
return "internal error: bad linked variable type";
|
369 |
}
|
370 |
end:
|
371 |
Tcl_DecrRefCount(objPtr);
|
372 |
return result;
|
373 |
}
|
374 |
|
375 |
/*
|
376 |
*----------------------------------------------------------------------
|
377 |
*
|
378 |
* StringValue --
|
379 |
*
|
380 |
* Converts the value of a C variable to a string for use in a
|
381 |
* Tcl variable to which it is linked.
|
382 |
*
|
383 |
* Results:
|
384 |
* The return value is a pointer to a string that represents
|
385 |
* the value of the C variable given by linkPtr.
|
386 |
*
|
387 |
* Side effects:
|
388 |
* None.
|
389 |
*
|
390 |
*----------------------------------------------------------------------
|
391 |
*/
|
392 |
|
393 |
static char *
|
394 |
StringValue(linkPtr, buffer)
|
395 |
Link *linkPtr; /* Structure describing linked variable. */
|
396 |
char *buffer; /* Small buffer to use for converting
|
397 |
* values. Must have TCL_DOUBLE_SPACE
|
398 |
* bytes or more. */
|
399 |
{
|
400 |
char *p;
|
401 |
|
402 |
switch (linkPtr->type) {
|
403 |
case TCL_LINK_INT:
|
404 |
linkPtr->lastValue.i = *(int *)(linkPtr->addr);
|
405 |
TclFormatInt(buffer, linkPtr->lastValue.i);
|
406 |
return buffer;
|
407 |
case TCL_LINK_DOUBLE:
|
408 |
linkPtr->lastValue.d = *(double *)(linkPtr->addr);
|
409 |
Tcl_PrintDouble((Tcl_Interp *) NULL, linkPtr->lastValue.d, buffer);
|
410 |
return buffer;
|
411 |
case TCL_LINK_BOOLEAN:
|
412 |
linkPtr->lastValue.i = *(int *)(linkPtr->addr);
|
413 |
if (linkPtr->lastValue.i != 0) {
|
414 |
return "1";
|
415 |
}
|
416 |
return "0";
|
417 |
case TCL_LINK_STRING:
|
418 |
p = *(char **)(linkPtr->addr);
|
419 |
if (p == NULL) {
|
420 |
return "NULL";
|
421 |
}
|
422 |
return p;
|
423 |
}
|
424 |
|
425 |
/*
|
426 |
* This code only gets executed if the link type is unknown
|
427 |
* (shouldn't ever happen).
|
428 |
*/
|
429 |
|
430 |
return "??";
|
431 |
}
|
432 |
|
433 |
/* End of tcllink.c */
|