391 lines
11 KiB
C
391 lines
11 KiB
C
/*
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* tclLink.c --
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*
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* This file implements linked variables (a C variable that is
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* tied to a Tcl variable). The idea of linked variables was
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* first suggested by Andreas Stolcke and this implementation is
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* based heavily on a prototype implementation provided by
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* him.
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*
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* Copyright (c) 1993 The Regents of the University of California.
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* Copyright (c) 1994 Sun Microsystems, Inc.
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*
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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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* SCCS: @(#) tclLink.c 1.12 96/02/15 11:50:26
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*/
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#include "tclInt.h"
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/*
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* For each linked variable there is a data structure of the following
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* type, which describes the link and is the clientData for the trace
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* set on the Tcl variable.
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*/
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typedef struct Link {
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Tcl_Interp *interp; /* Interpreter containing Tcl variable. */
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char *varName; /* Name of variable (must be global). This
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* is needed during trace callbacks, since
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* the actual variable may be aliased at
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* that time via upvar. */
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char *addr; /* Location of C variable. */
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int type; /* Type of link (TCL_LINK_INT, etc.). */
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int writable; /* Zero means Tcl variable is read-only. */
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union {
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int i;
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double d;
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} lastValue; /* Last known value of C variable; used to
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* avoid string conversions. */
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} Link;
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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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static char * LinkTraceProc _ANSI_ARGS_((ClientData clientData,
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Tcl_Interp *interp, char *name1, char *name2,
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int flags));
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static char * StringValue _ANSI_ARGS_((Link *linkPtr,
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char *buffer));
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/*
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*----------------------------------------------------------------------
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*
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* Tcl_LinkVar --
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*
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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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* if an error occurred (interp->result is also set after 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.
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*
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*----------------------------------------------------------------------
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*/
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int
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Tcl_LinkVar(interp, varName, addr, type)
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Tcl_Interp *interp; /* Interpreter in which varName exists. */
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char *varName; /* Name of a global variable in interp. */
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char *addr; /* Address of a C variable to be linked
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* to varName. */
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int type; /* Type of C variable: TCL_LINK_INT, etc.
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* Also may have TCL_LINK_READ_ONLY
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* OR'ed in. */
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{
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Link *linkPtr;
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char buffer[TCL_DOUBLE_SPACE];
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int code;
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linkPtr = (Link *) ckalloc(sizeof(Link));
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linkPtr->interp = interp;
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linkPtr->varName = (char *) ckalloc((unsigned) (strlen(varName) + 1));
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strcpy(linkPtr->varName, varName);
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linkPtr->addr = addr;
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linkPtr->type = type & ~TCL_LINK_READ_ONLY;
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linkPtr->writable = (type & TCL_LINK_READ_ONLY) == 0;
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if (Tcl_SetVar(interp, varName, StringValue(linkPtr, buffer),
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TCL_GLOBAL_ONLY|TCL_LEAVE_ERR_MSG) == NULL) {
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ckfree(linkPtr->varName);
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ckfree((char *) linkPtr);
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return TCL_ERROR;
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}
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code = Tcl_TraceVar(interp, varName, TCL_GLOBAL_ONLY|TCL_TRACE_READS
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|TCL_TRACE_WRITES|TCL_TRACE_UNSETS, LinkTraceProc,
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(ClientData) linkPtr);
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if (code != TCL_OK) {
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ckfree(linkPtr->varName);
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ckfree((char *) linkPtr);
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}
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return code;
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}
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/*
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*----------------------------------------------------------------------
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*
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* 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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*
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* Results:
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* None.
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*
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* Side effects:
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* If "varName" was previously linked to a C variable, the link
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* 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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*
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*----------------------------------------------------------------------
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*/
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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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Link *linkPtr;
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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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Tcl_UntraceVar(interp, varName,
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TCL_GLOBAL_ONLY|TCL_TRACE_READS|TCL_TRACE_WRITES|TCL_TRACE_UNSETS,
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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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* None.
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*
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* Side effects:
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* The Tcl variable "varName" is updated from its C value,
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* causing traces on the variable to trigger.
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*
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*----------------------------------------------------------------------
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*/
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void
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Tcl_UpdateLinkedVar(interp, varName)
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Tcl_Interp *interp; /* Interpreter containing variable. */
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char *varName; /* Name of global variable that is linked. */
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{
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Link *linkPtr;
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char buffer[TCL_DOUBLE_SPACE];
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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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Tcl_SetVar(interp, linkPtr->varName, StringValue(linkPtr, buffer),
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TCL_GLOBAL_ONLY);
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}
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/*
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*----------------------------------------------------------------------
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*
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* LinkTraceProc --
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*
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* This procedure is invoked when a linked Tcl variable is read,
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* written, or unset from Tcl. It's responsible for keeping the
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* C variable in sync with the Tcl variable.
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*
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* Results:
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* If all goes well, NULL is returned; otherwise an error message
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* is returned.
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*
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* Side effects:
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* 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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* a modification.
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*
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*----------------------------------------------------------------------
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*/
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static char *
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LinkTraceProc(clientData, interp, name1, name2, flags)
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ClientData clientData; /* Contains information about the link. */
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Tcl_Interp *interp; /* Interpreter containing Tcl variable. */
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char *name1; /* First part of variable name. */
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char *name2; /* Second part of variable name. */
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int flags; /* Miscellaneous additional information. */
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{
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Link *linkPtr = (Link *) clientData;
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int changed;
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char buffer[TCL_DOUBLE_SPACE];
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char *value, **pp;
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Tcl_DString savedResult;
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/*
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* If the variable is being unset, then just re-create it (with a
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* trace) unless the whole interpreter is going away.
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*/
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if (flags & TCL_TRACE_UNSETS) {
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if (flags & TCL_INTERP_DESTROYED) {
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ckfree(linkPtr->varName);
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ckfree((char *) linkPtr);
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} else if (flags & TCL_TRACE_DESTROYED) {
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Tcl_SetVar(interp, linkPtr->varName, StringValue(linkPtr, buffer),
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TCL_GLOBAL_ONLY);
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Tcl_TraceVar(interp, linkPtr->varName, TCL_GLOBAL_ONLY
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|TCL_TRACE_READS|TCL_TRACE_WRITES|TCL_TRACE_UNSETS,
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LinkTraceProc, (ClientData) linkPtr);
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}
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return NULL;
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}
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/*
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* For read accesses, update the Tcl variable if the C variable
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* has changed since the last time we updated the Tcl variable.
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*/
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if (flags & TCL_TRACE_READS) {
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switch (linkPtr->type) {
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case TCL_LINK_INT:
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case TCL_LINK_BOOLEAN:
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changed = *(int *)(linkPtr->addr) != linkPtr->lastValue.i;
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break;
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case TCL_LINK_DOUBLE:
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changed = *(double *)(linkPtr->addr) != linkPtr->lastValue.d;
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break;
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case TCL_LINK_STRING:
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changed = 1;
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break;
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default:
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return "internal error: bad linked variable type";
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}
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if (changed) {
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Tcl_SetVar(interp, linkPtr->varName, StringValue(linkPtr, buffer),
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TCL_GLOBAL_ONLY);
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}
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return NULL;
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}
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/*
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* For writes, first make sure that the variable is writable. Then
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* convert the Tcl value to C if possible. If the variable isn't
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* writable or can't be converted, then restore the varaible's old
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* value and return an error. Another tricky thing: we have to save
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* and restore the interpreter's result, since the variable access
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* could occur when the result has been partially set.
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*/
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if (!linkPtr->writable) {
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Tcl_SetVar(interp, linkPtr->varName, StringValue(linkPtr, buffer),
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TCL_GLOBAL_ONLY);
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return "linked variable is read-only";
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}
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value = Tcl_GetVar(interp, linkPtr->varName, TCL_GLOBAL_ONLY);
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if (value == NULL) {
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/*
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* This shouldn't ever happen.
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*/
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return "internal error: linked variable couldn't be read";
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}
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Tcl_DStringInit(&savedResult);
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Tcl_DStringAppend(&savedResult, interp->result, -1);
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Tcl_ResetResult(interp);
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switch (linkPtr->type) {
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case TCL_LINK_INT:
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if (Tcl_GetInt(interp, value, &linkPtr->lastValue.i) != TCL_OK) {
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Tcl_DStringResult(interp, &savedResult);
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Tcl_SetVar(interp, linkPtr->varName,
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StringValue(linkPtr, buffer), TCL_GLOBAL_ONLY);
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return "variable must have integer value";
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}
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*(int *)(linkPtr->addr) = linkPtr->lastValue.i;
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break;
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case TCL_LINK_DOUBLE:
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if (Tcl_GetDouble(interp, value, &linkPtr->lastValue.d)
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!= TCL_OK) {
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Tcl_DStringResult(interp, &savedResult);
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Tcl_SetVar(interp, linkPtr->varName,
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StringValue(linkPtr, buffer), TCL_GLOBAL_ONLY);
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return "variable must have real value";
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}
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*(double *)(linkPtr->addr) = linkPtr->lastValue.d;
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break;
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case TCL_LINK_BOOLEAN:
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if (Tcl_GetBoolean(interp, value, &linkPtr->lastValue.i)
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!= TCL_OK) {
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Tcl_DStringResult(interp, &savedResult);
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Tcl_SetVar(interp, linkPtr->varName,
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StringValue(linkPtr, buffer), TCL_GLOBAL_ONLY);
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return "variable must have boolean value";
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}
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*(int *)(linkPtr->addr) = linkPtr->lastValue.i;
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break;
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case TCL_LINK_STRING:
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pp = (char **)(linkPtr->addr);
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if (*pp != NULL) {
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ckfree(*pp);
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}
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*pp = (char *) ckalloc((unsigned) (strlen(value) + 1));
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strcpy(*pp, value);
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break;
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default:
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return "internal error: bad linked variable type";
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}
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Tcl_DStringResult(interp, &savedResult);
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return NULL;
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}
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/*
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*----------------------------------------------------------------------
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*
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* StringValue --
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*
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* Converts the value of a C variable to a string for use in a
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* Tcl variable to which it is linked.
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*
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* Results:
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* The return value is a pointer
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to a string that represents
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* the value of the C variable given by linkPtr.
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*
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* Side effects:
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* None.
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*
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*----------------------------------------------------------------------
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*/
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static char *
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StringValue(linkPtr, buffer)
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Link *linkPtr; /* Structure describing linked variable. */
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char *buffer; /* Small buffer to use for converting
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* values. Must have TCL_DOUBLE_SPACE
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* bytes or more. */
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{
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char *p;
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switch (linkPtr->type) {
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case TCL_LINK_INT:
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linkPtr->lastValue.i = *(int *)(linkPtr->addr);
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sprintf(buffer, "%d", linkPtr->lastValue.i);
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return buffer;
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case TCL_LINK_DOUBLE:
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linkPtr->lastValue.d = *(double *)(linkPtr->addr);
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Tcl_PrintDouble(linkPtr->interp, linkPtr->lastValue.d, buffer);
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return buffer;
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case TCL_LINK_BOOLEAN:
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linkPtr->lastValue.i = *(int *)(linkPtr->addr);
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if (linkPtr->lastValue.i != 0) {
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return "1";
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}
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return "0";
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case TCL_LINK_STRING:
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p = *(char **)(linkPtr->addr);
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if (p == NULL) {
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return "NULL";
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}
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return p;
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}
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/*
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* This code only gets executed if the link type is unknown
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* (shouldn't ever happen).
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*/
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return "??";
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}
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