/*
* tclLink.c --
*
* This file implements linked variables (a C variable that is tied to a
* Tcl variable). The idea of linked variables was first suggested by
* Andreas Stolcke and this implementation is based heavily on a
* prototype implementation provided by him.
*
* Copyright (c) 1993 The Regents of the University of California.
* Copyright (c) 1994-1997 Sun Microsystems, Inc.
*
* See the file "license.terms" for information on usage and redistribution of
* this file, and for a DISCLAIMER OF ALL WARRANTIES.
*
* RCS: @(#) $Id: tclLink.c,v 1.24 2007/12/13 15:23:18 dgp Exp $
*/
#include "tclInt.h"
/*
* For each linked variable there is a data structure of the following type,
* which describes the link and is the clientData for the trace set on the Tcl
* variable.
*/
typedef struct Link {
Tcl_Interp *interp; /* Interpreter containing Tcl variable. */
Tcl_Obj *varName; /* Name of variable (must be global). This is
* needed during trace callbacks, since the
* actual variable may be aliased at that time
* via upvar. */
char *addr; /* Location of C variable. */
int type; /* Type of link (TCL_LINK_INT, etc.). */
union {
char c;
unsigned char uc;
int i;
unsigned int ui;
short s;
unsigned short us;
long l;
unsigned long ul;
Tcl_WideInt w;
Tcl_WideUInt uw;
float f;
double d;
} lastValue; /* Last known value of C variable; used to
* avoid string conversions. */
int flags; /* Miscellaneous one-bit values; see below for
* definitions. */
} Link;
/*
* Definitions for flag bits:
* LINK_READ_ONLY - 1 means errors should be generated if Tcl
* script attempts to write variable.
* LINK_BEING_UPDATED - 1 means that a call to Tcl_UpdateLinkedVar is
* in progress for this variable, so trace
* callbacks on the variable should be ignored.
*/
#define LINK_READ_ONLY 1
#define LINK_BEING_UPDATED 2
/*
* Forward references to functions defined later in this file:
*/
static char * LinkTraceProc(ClientData clientData,Tcl_Interp *interp,
CONST char *name1, CONST char *name2, int flags);
static Tcl_Obj * ObjValue(Link *linkPtr);
/*
* Convenience macro for accessing the value of the C variable pointed to by a
* link. Note that this macro produces something that may be regarded as an
* lvalue or rvalue; it may be assigned to as well as read. Also note that
* this macro assumes the name of the variable being accessed (linkPtr); this
* is not strictly a good thing, but it keeps the code much shorter and
* cleaner.
*/
#define LinkedVar(type) (*(type *) linkPtr->addr)
/*
*----------------------------------------------------------------------
*
* Tcl_LinkVar --
*
* Link a C variable to a Tcl variable so that changes to either one
* causes the other to change.
*
* Results:
* The return value is TCL_OK if everything went well or TCL_ERROR if an
* error occurred (the interp's result is also set after errors).
*
* Side effects:
* The value at *addr is linked to the Tcl variable "varName", using
* "type" to convert between string values for Tcl and binary values for
* *addr.
*
*----------------------------------------------------------------------
*/
int
Tcl_LinkVar(
Tcl_Interp *interp, /* Interpreter in which varName exists. */
CONST char *varName, /* Name of a global variable in interp. */
char *addr, /* Address of a C variable to be linked to
* varName. */
int type) /* Type of C variable: TCL_LINK_INT, etc. Also
* may have TCL_LINK_READ_ONLY OR'ed in. */
{
Tcl_Obj *objPtr;
Link *linkPtr;
int code;
linkPtr = (Link *) ckalloc(sizeof(Link));
linkPtr->interp = interp;
linkPtr->varName = Tcl_NewStringObj(varName, -1);
Tcl_IncrRefCount(linkPtr->varName);
linkPtr->addr = addr;
linkPtr->type = type & ~TCL_LINK_READ_ONLY;
if (type & TCL_LINK_READ_ONLY) {
linkPtr->flags = LINK_READ_ONLY;
} else {
linkPtr->flags = 0;
}
objPtr = ObjValue(linkPtr);
if (Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, objPtr,
TCL_GLOBAL_ONLY|TCL_LEAVE_ERR_MSG) == NULL) {
Tcl_DecrRefCount(linkPtr->varName);
ckfree((char *) linkPtr);
return TCL_ERROR;
}
code = Tcl_TraceVar(interp, varName, TCL_GLOBAL_ONLY|TCL_TRACE_READS
|TCL_TRACE_WRITES|TCL_TRACE_UNSETS, LinkTraceProc,
(ClientData) linkPtr);
if (code != TCL_OK) {
Tcl_DecrRefCount(linkPtr->varName);
ckfree((char *) linkPtr);
}
return code;
}
/*
*----------------------------------------------------------------------
*
* Tcl_UnlinkVar --
*
* Destroy the link between a Tcl variable and a C variable.
*
* Results:
* None.
*
* Side effects:
* If "varName" was previously linked to a C variable, the link is broken
* to make the variable independent. If there was no previous link for
* "varName" then nothing happens.
*
*----------------------------------------------------------------------
*/
void
Tcl_UnlinkVar(
Tcl_Interp *interp, /* Interpreter containing variable to unlink */
CONST char *varName) /* Global variable in interp to unlink. */
{
Link *linkPtr;
linkPtr = (Link *) Tcl_VarTraceInfo(interp, varName, TCL_GLOBAL_ONLY,
LinkTraceProc, (ClientData) NULL);
if (linkPtr == NULL) {
return;
}
Tcl_UntraceVar(interp, varName,
TCL_GLOBAL_ONLY|TCL_TRACE_READS|TCL_TRACE_WRITES|TCL_TRACE_UNSETS,
LinkTraceProc, (ClientData) linkPtr);
Tcl_DecrRefCount(linkPtr->varName);
ckfree((char *) linkPtr);
}
/*
*----------------------------------------------------------------------
*
* Tcl_UpdateLinkedVar --
*
* This function is invoked after a linked variable has been changed by C
* code. It updates the Tcl variable so that traces on the variable will
* trigger.
*
* Results:
* None.
*
* Side effects:
* The Tcl variable "varName" is updated from its C value, causing traces
* on the variable to trigger.
*
*----------------------------------------------------------------------
*/
void
Tcl_UpdateLinkedVar(
Tcl_Interp *interp, /* Interpreter containing variable. */
CONST char *varName) /* Name of global variable that is linked. */
{
Link *linkPtr;
int savedFlag;
linkPtr = (Link *) Tcl_VarTraceInfo(interp, varName, TCL_GLOBAL_ONLY,
LinkTraceProc, (ClientData) NULL);
if (linkPtr == NULL) {
return;
}
savedFlag = linkPtr->flags & LINK_BEING_UPDATED;
linkPtr->flags |= LINK_BEING_UPDATED;
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
/*
* Callback may have unlinked the variable. [Bug 1740631]
*/
linkPtr = (Link *) Tcl_VarTraceInfo(interp, varName, TCL_GLOBAL_ONLY,
LinkTraceProc, (ClientData) NULL);
if (linkPtr != NULL) {
linkPtr->flags = (linkPtr->flags & ~LINK_BEING_UPDATED) | savedFlag;
}
}
/*
*----------------------------------------------------------------------
*
* LinkTraceProc --
*
* This function is invoked when a linked Tcl variable is read, written,
* or unset from Tcl. It's responsible for keeping the C variable in sync
* with the Tcl variable.
*
* Results:
* If all goes well, NULL is returned; otherwise an error message is
* returned.
*
* Side effects:
* The C variable may be updated to make it consistent with the Tcl
* variable, or the Tcl variable may be overwritten to reject a
* modification.
*
*----------------------------------------------------------------------
*/
static char *
LinkTraceProc(
ClientData clientData, /* Contains information about the link. */
Tcl_Interp *interp, /* Interpreter containing Tcl variable. */
CONST char *name1, /* First part of variable name. */
CONST char *name2, /* Second part of variable name. */
int flags) /* Miscellaneous additional information. */
{
Link *linkPtr = (Link *) clientData;
int changed, valueLength;
CONST char *value;
char **pp;
Tcl_Obj *valueObj;
int valueInt;
Tcl_WideInt valueWide;
double valueDouble;
/*
* If the variable is being unset, then just re-create it (with a trace)
* unless the whole interpreter is going away.
*/
if (flags & TCL_TRACE_UNSETS) {
if (Tcl_InterpDeleted(interp)) {
Tcl_DecrRefCount(linkPtr->varName);
ckfree((char *) linkPtr);
} else if (flags & TCL_TRACE_DESTROYED) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
Tcl_TraceVar(interp, Tcl_GetString(linkPtr->varName),
TCL_GLOBAL_ONLY|TCL_TRACE_READS|TCL_TRACE_WRITES
|TCL_TRACE_UNSETS, LinkTraceProc, (ClientData) linkPtr);
}
return NULL;
}
/*
* If we were invoked because of a call to Tcl_UpdateLinkedVar, then don't
* do anything at all. In particular, we don't want to get upset that the
* variable is being modified, even if it is supposed to be read-only.
*/
if (linkPtr->flags & LINK_BEING_UPDATED) {
return NULL;
}
/*
* For read accesses, update the Tcl variable if the C variable has
* changed since the last time we updated the Tcl variable.
*/
if (flags & TCL_TRACE_READS) {
switch (linkPtr->type) {
case TCL_LINK_INT:
case TCL_LINK_BOOLEAN:
changed = (LinkedVar(int) != linkPtr->lastValue.i);
break;
case TCL_LINK_DOUBLE:
changed = (LinkedVar(double) != linkPtr->lastValue.d);
break;
case TCL_LINK_WIDE_INT:
changed = (LinkedVar(Tcl_WideInt) != linkPtr->lastValue.w);
break;
case TCL_LINK_WIDE_UINT:
changed = (LinkedVar(Tcl_WideUInt) != linkPtr->lastValue.uw);
break;
case TCL_LINK_CHAR:
changed = (LinkedVar(char) != linkPtr->lastValue.c);
break;
case TCL_LINK_UCHAR:
changed = (LinkedVar(unsigned char) != linkPtr->lastValue.uc);
break;
case TCL_LINK_SHORT:
changed = (LinkedVar(short) != linkPtr->lastValue.s);
break;
case TCL_LINK_USHORT:
changed = (LinkedVar(unsigned short) != linkPtr->lastValue.us);
break;
case TCL_LINK_UINT:
changed = (LinkedVar(unsigned int) != linkPtr->lastValue.ui);
break;
case TCL_LINK_LONG:
changed = (LinkedVar(long) != linkPtr->lastValue.l);
break;
case TCL_LINK_ULONG:
changed = (LinkedVar(unsigned long) != linkPtr->lastValue.ul);
break;
case TCL_LINK_FLOAT:
changed = (LinkedVar(float) != linkPtr->lastValue.f);
break;
case TCL_LINK_STRING:
changed = 1;
break;
default:
return "internal error: bad linked variable type";
}
if (changed) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
}
return NULL;
}
/*
* For writes, first make sure that the variable is writable. Then convert
* the Tcl value to C if possible. If the variable isn't writable or can't
* be converted, then restore the varaible's old value and return an
* error. Another tricky thing: we have to save and restore the interp's
* result, since the variable access could occur when the result has been
* partially set.
*/
if (linkPtr->flags & LINK_READ_ONLY) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "linked variable is read-only";
}
valueObj = Tcl_ObjGetVar2(interp, linkPtr->varName,NULL, TCL_GLOBAL_ONLY);
if (valueObj == NULL) {
/*
* This shouldn't ever happen.
*/
return "internal error: linked variable couldn't be read";
}
switch (linkPtr->type) {
case TCL_LINK_INT:
if (Tcl_GetIntFromObj(NULL, valueObj, &linkPtr->lastValue.i)
!= TCL_OK) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "variable must have integer value";
}
LinkedVar(int) = linkPtr->lastValue.i;
break;
case TCL_LINK_WIDE_INT:
if (Tcl_GetWideIntFromObj(NULL, valueObj, &linkPtr->lastValue.w)
!= TCL_OK) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "variable must have integer value";
}
LinkedVar(Tcl_WideInt) = linkPtr->lastValue.w;
break;
case TCL_LINK_DOUBLE:
if (Tcl_GetDoubleFromObj(NULL, valueObj, &linkPtr->lastValue.d)
!= TCL_OK) {
#ifdef ACCEPT_NAN
if (valueObj->typePtr != &tclDoubleType) {
#endif
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL,
ObjValue(linkPtr), TCL_GLOBAL_ONLY);
return "variable must have real value";
#ifdef ACCEPT_NAN
}
linkPtr->lastValue.d = valueObj->internalRep.doubleValue;
#endif
}
LinkedVar(double) = linkPtr->lastValue.d;
break;
case TCL_LINK_BOOLEAN:
if (Tcl_GetBooleanFromObj(NULL, valueObj, &linkPtr->lastValue.i)
!= TCL_OK) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "variable must have boolean value";
}
LinkedVar(int) = linkPtr->lastValue.i;
break;
case TCL_LINK_CHAR:
if (Tcl_GetIntFromObj(interp, valueObj, &valueInt) != TCL_OK
|| valueInt < SCHAR_MIN || valueInt > SCHAR_MAX) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "variable must have char value";
}
linkPtr->lastValue.c = (char)valueInt;
LinkedVar(char) = linkPtr->lastValue.c;
break;
case TCL_LINK_UCHAR:
if (Tcl_GetIntFromObj(interp, valueObj, &valueInt) != TCL_OK
|| valueInt < 0 || valueInt > UCHAR_MAX) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "variable must have unsigned char value";
}
linkPtr->lastValue.uc = (unsigned char) valueInt;
LinkedVar(unsigned char) = linkPtr->lastValue.uc;
break;
case TCL_LINK_SHORT:
if (Tcl_GetIntFromObj(interp, valueObj, &valueInt) != TCL_OK
|| valueInt < SHRT_MIN || valueInt > SHRT_MAX) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "variable must have short value";
}
linkPtr->lastValue.s = (short)valueInt;
LinkedVar(short) = linkPtr->lastValue.s;
break;
case TCL_LINK_USHORT:
if (Tcl_GetIntFromObj(interp, valueObj, &valueInt) != TCL_OK
|| valueInt < 0 || valueInt > USHRT_MAX) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "variable must have unsigned short value";
}
linkPtr->lastValue.us = (unsigned short)valueInt;
LinkedVar(unsigned short) = linkPtr->lastValue.us;
break;
case TCL_LINK_UINT:
if (Tcl_GetWideIntFromObj(interp, valueObj, &valueWide) != TCL_OK
|| valueWide < 0 || valueWide > UINT_MAX) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "variable must have unsigned int value";
}
linkPtr->lastValue.ui = (unsigned int)valueWide;
LinkedVar(unsigned int) = linkPtr->lastValue.ui;
break;
case TCL_LINK_LONG:
if (Tcl_GetWideIntFromObj(interp, valueObj, &valueWide) != TCL_OK
|| valueWide < LONG_MIN || valueWide > LONG_MAX) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "variable must have long value";
}
linkPtr->lastValue.l = (long)valueWide;
LinkedVar(long) = linkPtr->lastValue.l;
break;
case TCL_LINK_ULONG:
if (Tcl_GetWideIntFromObj(interp, valueObj, &valueWide) != TCL_OK
|| valueWide < 0 || (Tcl_WideUInt) valueWide > ULONG_MAX) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "variable must have unsigned long value";
}
linkPtr->lastValue.ul = (unsigned long)valueWide;
LinkedVar(unsigned long) = linkPtr->lastValue.ul;
break;
case TCL_LINK_WIDE_UINT:
/*
* FIXME: represent as a bignum.
*/
if (Tcl_GetWideIntFromObj(interp, valueObj, &valueWide) != TCL_OK) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "variable must have unsigned wide int value";
}
linkPtr->lastValue.uw = (Tcl_WideUInt)valueWide;
LinkedVar(Tcl_WideUInt) = linkPtr->lastValue.uw;
break;
case TCL_LINK_FLOAT:
if (Tcl_GetDoubleFromObj(interp, valueObj, &valueDouble) != TCL_OK
|| valueDouble < -FLT_MAX || valueDouble > FLT_MAX) {
Tcl_ObjSetVar2(interp, linkPtr->varName, NULL, ObjValue(linkPtr),
TCL_GLOBAL_ONLY);
return "variable must have float value";
}
linkPtr->lastValue.f = (float)valueDouble;
LinkedVar(float) = linkPtr->lastValue.f;
break;
case TCL_LINK_STRING:
value = Tcl_GetStringFromObj(valueObj, &valueLength);
valueLength++;
pp = (char **) linkPtr->addr;
*pp = ckrealloc(*pp, valueLength);
memcpy(*pp, value, (unsigned) valueLength);
break;
default:
return "internal error: bad linked variable type";
}
return NULL;
}
/*
*----------------------------------------------------------------------
*
* ObjValue --
*
* Converts the value of a C variable to a Tcl_Obj* for use in a Tcl
* variable to which it is linked.
*
* Results:
* The return value is a pointer to a Tcl_Obj that represents the value
* of the C variable given by linkPtr.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
static Tcl_Obj *
ObjValue(
Link *linkPtr) /* Structure describing linked variable. */
{
char *p;
Tcl_Obj *resultObj;
switch (linkPtr->type) {
case TCL_LINK_INT:
linkPtr->lastValue.i = LinkedVar(int);
return Tcl_NewIntObj(linkPtr->lastValue.i);
case TCL_LINK_WIDE_INT:
linkPtr->lastValue.w = LinkedVar(Tcl_WideInt);
return Tcl_NewWideIntObj(linkPtr->lastValue.w);
case TCL_LINK_DOUBLE:
linkPtr->lastValue.d = LinkedVar(double);
return Tcl_NewDoubleObj(linkPtr->lastValue.d);
case TCL_LINK_BOOLEAN:
linkPtr->lastValue.i = LinkedVar(int);
return Tcl_NewBooleanObj(linkPtr->lastValue.i != 0);
case TCL_LINK_CHAR:
linkPtr->lastValue.c = LinkedVar(char);
return Tcl_NewIntObj(linkPtr->lastValue.c);
case TCL_LINK_UCHAR:
linkPtr->lastValue.uc = LinkedVar(unsigned char);
return Tcl_NewIntObj(linkPtr->lastValue.uc);
case TCL_LINK_SHORT:
linkPtr->lastValue.s = LinkedVar(short);
return Tcl_NewIntObj(linkPtr->lastValue.s);
case TCL_LINK_USHORT:
linkPtr->lastValue.us = LinkedVar(unsigned short);
return Tcl_NewIntObj(linkPtr->lastValue.us);
case TCL_LINK_UINT:
linkPtr->lastValue.ui = LinkedVar(unsigned int);
return Tcl_NewWideIntObj((Tcl_WideInt) linkPtr->lastValue.ui);
case TCL_LINK_LONG:
linkPtr->lastValue.l = LinkedVar(long);
return Tcl_NewWideIntObj((Tcl_WideInt) linkPtr->lastValue.l);
case TCL_LINK_ULONG:
linkPtr->lastValue.ul = LinkedVar(unsigned long);
return Tcl_NewWideIntObj((Tcl_WideInt) linkPtr->lastValue.ul);
case TCL_LINK_FLOAT:
linkPtr->lastValue.f = LinkedVar(float);
return Tcl_NewDoubleObj(linkPtr->lastValue.f);
case TCL_LINK_WIDE_UINT:
linkPtr->lastValue.uw = LinkedVar(Tcl_WideUInt);
/*
* FIXME: represent as a bignum.
*/
return Tcl_NewWideIntObj((Tcl_WideInt) linkPtr->lastValue.uw);
case TCL_LINK_STRING:
p = LinkedVar(char *);
if (p == NULL) {
TclNewLiteralStringObj(resultObj, "NULL");
return resultObj;
}
return Tcl_NewStringObj(p, -1);
/*
* This code only gets executed if the link type is unknown (shouldn't
* ever happen).
*/
default:
TclNewLiteralStringObj(resultObj, "??");
return resultObj;
}
}
/*
* Local Variables:
* mode: c
* c-basic-offset: 4
* fill-column: 78
* End:
*/
|
