tclenv.c

linux系统下的音频通信

 *	Interpreters are updated, as is environ.
 *
 *----------------------------------------------------------------------
 */

void
TclUnsetEnv(name)
    CONST char *name;			/* Name of variable to remove. */
{
    EnvInterp *eiPtr;
    char *oldValue;
    int length, index;
#ifdef USE_PUTENV
    char *string;
#else
    char **envPtr;
#endif

#ifdef MAC_TCL
    if (environ == NULL) {
	environSize = TclMacCreateEnv();
    }
#endif

    index = FindVariable(name, &length);

    /*
     * First make sure that the environment variable exists to avoid
     * doing needless work and to avoid recursion on the unset.
     */
    
    if (index == -1) {
	return;
    }
    /*
     * Remember the old value so we can free it if Tcl created the string.
     */

    oldValue = environ[index];

    /*
     * Update the system environment.  This must be done before we 
     * update the interpreters or we will recurse.
     */

#ifdef USE_PUTENV
    string = ckalloc(length+2);
    memcpy((VOID *) string, (VOID *) name, (size_t) length);
    string[length] = '=';
    string[length+1] = '\0';
    putenv(string);
    ckfree(string);
#else
    for (envPtr = environ+index+1; ; envPtr++) {
	envPtr[-1] = *envPtr;
	if (*envPtr == NULL) {
	    break;
	}
    }
#endif

    /*
     * Replace the old value in the cache.
     */

    ReplaceString(oldValue, NULL);

    /*
     * Update all of the interpreters.
     */

    for (eiPtr = firstInterpPtr; eiPtr != NULL; eiPtr = eiPtr->nextPtr) {
	(void) Tcl_UnsetVar2(eiPtr->interp, "env", (char *) name,
		TCL_GLOBAL_ONLY);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclGetEnv --
 *
 *	Retrieve the value of an environment variable.
 *
 * Results:
 *	Returns a pointer to a static string in the environment,
 *	or NULL if the value was not found.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

char *
TclGetEnv(name)
    CONST char *name;		/* Name of variable to find. */
{
    int length, index;

#ifdef MAC_TCL
    if (environ == NULL) {
	environSize = TclMacCreateEnv();
    }
#endif

    index = FindVariable(name, &length);
    if ((index != -1) &&  (*(environ[index]+length) == '=')) {
	return environ[index]+length+1;
    } else {
	return NULL;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * EnvTraceProc --
 *
 *	This procedure is invoked whenever an environment variable
 *	is modified or deleted.  It propagates the change to the
 *	"environ" array and to any other interpreters for whom
 *	we're managing an "env" array.
 *
 * Results:
 *	Always returns NULL to indicate success.
 *
 * Side effects:
 *	Environment variable changes get propagated.  If the whole
 *	"env" array is deleted, then we stop managing things for
 *	this interpreter (usually this happens because the whole
 *	interpreter is being deleted).
 *
 *----------------------------------------------------------------------
 */

	/* ARGSUSED */
static char *
EnvTraceProc(clientData, interp, name1, name2, flags)
    ClientData clientData;	/* Not used. */
    Tcl_Interp *interp;		/* Interpreter whose "env" variable is
				 * being modified. */
    char *name1;		/* Better be "env". */
    char *name2;		/* Name of variable being modified, or
				 * NULL if whole array is being deleted. */
    int flags;			/* Indicates what's happening. */
{
    /*
     * First see if the whole "env" variable is being deleted.  If
     * so, just forget about this interpreter.
     */

    if (name2 == NULL) {
	register EnvInterp *eiPtr, *prevPtr;

	if ((flags & (TCL_TRACE_UNSETS|TCL_TRACE_DESTROYED))
		!= (TCL_TRACE_UNSETS|TCL_TRACE_DESTROYED)) {
	    panic("EnvTraceProc called with confusing arguments");
	}
	eiPtr = firstInterpPtr;
	if (eiPtr->interp == interp) {
	    firstInterpPtr = eiPtr->nextPtr;
	} else {
	    for (prevPtr = eiPtr, eiPtr = eiPtr->nextPtr; ;
		    prevPtr = eiPtr, eiPtr = eiPtr->nextPtr) {
		if (eiPtr == NULL) {
		    panic("EnvTraceProc couldn't find interpreter");
		}
		if (eiPtr->interp == interp) {
		    prevPtr->nextPtr = eiPtr->nextPtr;
		    break;
		}
	    }
	}
	ckfree((char *) eiPtr);
	return NULL;
    }

    /*
     * If a value is being set, call TclSetEnv to do all of the work.
     */

    if (flags & TCL_TRACE_WRITES) {
	TclSetEnv(name2, Tcl_GetVar2(interp, "env", name2, TCL_GLOBAL_ONLY));
    }

    if (flags & TCL_TRACE_UNSETS) {
	TclUnsetEnv(name2);
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * ReplaceString --
 *
 *	Replace one string with another in the environment variable
 *	cache.  The cache keeps track of all of the environment
 *	variables that Tcl has modified so they can be freed later.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May free the old string.
 *
 *----------------------------------------------------------------------
 */

static void
ReplaceString(oldStr, newStr)
    CONST char *oldStr;		/* Old environment string. */
    char *newStr;		/* New environment string. */
{
    int i;
    char **newCache;

    /*
     * Check to see if the old value was allocated by Tcl.  If so,
     * it needs to be deallocated to avoid memory leaks.  Note that this
     * algorithm is O(n), not O(1).  This will result in n-squared behavior
     * if lots of environment changes are being made.
     */

    for (i = 0; i < cacheSize; i++) {
	if ((environCache[i] == oldStr) || (environCache[i] == NULL)) {
	    break;
	}
    }
    if (i < cacheSize) {
	/*
	 * Replace or delete the old value.
	 */

	if (environCache[i]) {
	    ckfree(environCache[i]);
	}
	    
	if (newStr) {
	    environCache[i] = newStr;
	} else {
	    for (; i < cacheSize-1; i++) {
		environCache[i] = environCache[i+1];
	    }
	    environCache[cacheSize-1] = NULL;
	}
    } else {	
        int allocatedSize = (cacheSize + 5) * sizeof(char *);

	/*
	 * We need to grow the cache in order to hold the new string.
	 */

	newCache = (char **) ckalloc((size_t) allocatedSize);
        (VOID *) memset(newCache, (int) 0, (size_t) allocatedSize);
        
	if (environCache) {
	    memcpy((VOID *) newCache, (VOID *) environCache,
		    (size_t) (cacheSize * sizeof(char*)));
	    ckfree((char *) environCache);
	}
	environCache = newCache;
	environCache[cacheSize] = (char *) newStr;
	environCache[cacheSize+1] = NULL;
	cacheSize += 5;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * FindVariable --
 *
 *	Locate the entry in environ for a given name.
 *
 * Results:
 *	The return value is the index in environ of an entry with the
 *	name "name", or -1 if there is no such entry.   The integer at
 *	*lengthPtr is filled in with the length of name (if a matching
 *	entry is found) or the length of the environ array (if no matching
 *	entry is found).
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static int
FindVariable(name, lengthPtr)
    CONST char *name;		/* Name of desired environment variable. */
    int *lengthPtr;		/* Used to return length of name (for
				 * successful searches) or number of non-NULL
				 * entries in environ (for unsuccessful
				 * searches). */
{
    int i;
    register CONST char *p1, *p2;

    for (i = 0, p1 = environ[i]; p1 != NULL; i++, p1 = environ[i]) {
	for (p2 = name; *p2 == *p1; p1++, p2++) {
	    /* NULL loop body. */
	}
	if ((*p1 == '=') && (*p2 == '\0')) {
	    *lengthPtr = p2-name;
	    return i;
	}
    }
    *lengthPtr = i;
    return -1;
}

/*
 *----------------------------------------------------------------------
 *
 * TclFinalizeEnvironment --
 *
 *	This function releases any storage allocated by this module
 *	that isn't still in use by the global environment.  Any
 *	strings that are still in the environment will be leaked.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	May deallocate storage.
 *
 *----------------------------------------------------------------------
 */

void
TclFinalizeEnvironment()
{
    /*
     * For now we just deallocate the cache array and none of the environment
     * strings.  This may leak more memory that strictly necessary, since some
     * of the strings may no longer be in the environment.  However,
     * determining which ones are ok to delete is n-squared, and is pretty
     * unlikely, so we don't bother.
     */

    if (environCache) {
	ckfree((char *) environCache);
	environCache = NULL;
	cacheSize    = 0;
#ifndef USE_PUTENV
	environSize  = 0;
#endif
    }
}