diff options
Diffstat (limited to 'generic/tclLink.c')
| -rw-r--r-- | generic/tclLink.c | 423 |
1 files changed, 423 insertions, 0 deletions
diff --git a/generic/tclLink.c b/generic/tclLink.c new file mode 100644 index 0000000..bd6191d --- /dev/null +++ b/generic/tclLink.c @@ -0,0 +1,423 @@ +/* + * 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) 1994-1996 Sun Microsystems, Inc. + * + * See the file "license.terms" for information on usage and redistribution + * of this file, and for a DISCLAIMER OF ALL WARRANTIES. + * + * SCCS: @(#) tclLink.c 1.15 97/01/21 21:51:42 + */ + +#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. */ + char *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 { + int i; + 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 procedures defined later in this file: + */ + +static char * LinkTraceProc _ANSI_ARGS_((ClientData clientData, + Tcl_Interp *interp, char *name1, char *name2, + int flags)); +static char * StringValue _ANSI_ARGS_((Link *linkPtr, + char *buffer)); + +/* + *---------------------------------------------------------------------- + * + * 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 (interp->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(interp, varName, addr, type) + Tcl_Interp *interp; /* Interpreter in which varName exists. */ + 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. */ +{ + Link *linkPtr; + char buffer[TCL_DOUBLE_SPACE]; + int code; + + linkPtr = (Link *) ckalloc(sizeof(Link)); + linkPtr->interp = interp; + linkPtr->varName = (char *) ckalloc((unsigned) (strlen(varName) + 1)); + strcpy(linkPtr->varName, 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; + } + if (Tcl_SetVar(interp, varName, StringValue(linkPtr, buffer), + TCL_GLOBAL_ONLY|TCL_LEAVE_ERR_MSG) == NULL) { + ckfree(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) { + ckfree(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(interp, varName) + Tcl_Interp *interp; /* Interpreter containing variable to unlink. */ + 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); + ckfree(linkPtr->varName); + ckfree((char *) linkPtr); +} + +/* + *---------------------------------------------------------------------- + * + * Tcl_UpdateLinkedVar -- + * + * This procedure 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(interp, varName) + Tcl_Interp *interp; /* Interpreter containing variable. */ + char *varName; /* Name of global variable that is linked. */ +{ + Link *linkPtr; + char buffer[TCL_DOUBLE_SPACE]; + 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_SetVar(interp, linkPtr->varName, StringValue(linkPtr, buffer), + TCL_GLOBAL_ONLY); + linkPtr->flags = (linkPtr->flags & ~LINK_BEING_UPDATED) | savedFlag; +} + +/* + *---------------------------------------------------------------------- + * + * LinkTraceProc -- + * + * This procedure 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, interp, name1, name2, flags) + ClientData clientData; /* Contains information about the link. */ + Tcl_Interp *interp; /* Interpreter containing Tcl variable. */ + char *name1; /* First part of variable name. */ + char *name2; /* Second part of variable name. */ + int flags; /* Miscellaneous additional information. */ +{ + Link *linkPtr = (Link *) clientData; + int changed; + char buffer[TCL_DOUBLE_SPACE]; + char *value, **pp; + Tcl_DString savedResult; + + /* + * 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 (flags & TCL_INTERP_DESTROYED) { + ckfree(linkPtr->varName); + ckfree((char *) linkPtr); + } else if (flags & TCL_TRACE_DESTROYED) { + Tcl_SetVar(interp, linkPtr->varName, StringValue(linkPtr, buffer), + TCL_GLOBAL_ONLY); + Tcl_TraceVar(interp, 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 = *(int *)(linkPtr->addr) != linkPtr->lastValue.i; + break; + case TCL_LINK_DOUBLE: + changed = *(double *)(linkPtr->addr) != linkPtr->lastValue.d; + break; + case TCL_LINK_STRING: + changed = 1; + break; + default: + return "internal error: bad linked variable type"; + } + if (changed) { + Tcl_SetVar(interp, linkPtr->varName, StringValue(linkPtr, buffer), + 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 interpreter's result, since the variable access + * could occur when the result has been partially set. + */ + + if (linkPtr->flags & LINK_READ_ONLY) { + Tcl_SetVar(interp, linkPtr->varName, StringValue(linkPtr, buffer), + TCL_GLOBAL_ONLY); + return "linked variable is read-only"; + } + value = Tcl_GetVar(interp, linkPtr->varName, TCL_GLOBAL_ONLY); + if (value == NULL) { + /* + * This shouldn't ever happen. + */ + return "internal error: linked variable couldn't be read"; + } + Tcl_DStringInit(&savedResult); + Tcl_DStringAppend(&savedResult, interp->result, -1); + Tcl_ResetResult(interp); + switch (linkPtr->type) { + case TCL_LINK_INT: + if (Tcl_GetInt(interp, value, &linkPtr->lastValue.i) != TCL_OK) { + Tcl_DStringResult(interp, &savedResult); + Tcl_SetVar(interp, linkPtr->varName, + StringValue(linkPtr, buffer), TCL_GLOBAL_ONLY); + return "variable must have integer value"; + } + *(int *)(linkPtr->addr) = linkPtr->lastValue.i; + break; + case TCL_LINK_DOUBLE: + if (Tcl_GetDouble(interp, value, &linkPtr->lastValue.d) + != TCL_OK) { + Tcl_DStringResult(interp, &savedResult); + Tcl_SetVar(interp, linkPtr->varName, + StringValue(linkPtr, buffer), TCL_GLOBAL_ONLY); + return "variable must have real value"; + } + *(double *)(linkPtr->addr) = linkPtr->lastValue.d; + break; + case TCL_LINK_BOOLEAN: + if (Tcl_GetBoolean(interp, value, &linkPtr->lastValue.i) + != TCL_OK) { + Tcl_DStringResult(interp, &savedResult); + Tcl_SetVar(interp, linkPtr->varName, + StringValue(linkPtr, buffer), TCL_GLOBAL_ONLY); + return "variable must have boolean value"; + } + *(int *)(linkPtr->addr) = linkPtr->lastValue.i; + break; + case TCL_LINK_STRING: + pp = (char **)(linkPtr->addr); + if (*pp != NULL) { + ckfree(*pp); + } + *pp = (char *) ckalloc((unsigned) (strlen(value) + 1)); + strcpy(*pp, value); + break; + default: + return "internal error: bad linked variable type"; + } + Tcl_DStringResult(interp, &savedResult); + return NULL; +} + +/* + *---------------------------------------------------------------------- + * + * StringValue -- + * + * Converts the value of a C variable to a string for use in a + * Tcl variable to which it is linked. + * + * Results: + * The return value is a pointer + to a string that represents + * the value of the C variable given by linkPtr. + * + * Side effects: + * None. + * + *---------------------------------------------------------------------- + */ + +static char * +StringValue(linkPtr, buffer) + Link *linkPtr; /* Structure describing linked variable. */ + char *buffer; /* Small buffer to use for converting + * values. Must have TCL_DOUBLE_SPACE + * bytes or more. */ +{ + char *p; + + switch (linkPtr->type) { + case TCL_LINK_INT: + linkPtr->lastValue.i = *(int *)(linkPtr->addr); + TclFormatInt(buffer, linkPtr->lastValue.i); + return buffer; + case TCL_LINK_DOUBLE: + linkPtr->lastValue.d = *(double *)(linkPtr->addr); + Tcl_PrintDouble((Tcl_Interp *) NULL, linkPtr->lastValue.d, buffer); + return buffer; + case TCL_LINK_BOOLEAN: + linkPtr->lastValue.i = *(int *)(linkPtr->addr); + if (linkPtr->lastValue.i != 0) { + return "1"; + } + return "0"; + case TCL_LINK_STRING: + p = *(char **)(linkPtr->addr); + if (p == NULL) { + return "NULL"; + } + return p; + } + + /* + * This code only gets executed if the link type is unknown + * (shouldn't ever happen). + */ + + return "??"; +} |