Tcl Source Code

 *
 * Side effects:
 *	May allocate a new Tcl_Obj.
 *
 *---------------------------------------------------------------------------
 */

void
ReverseBytes(
    unsigned char *to,		/* Copy bytes into here... */
    unsigned char *from,	/* ...from here... */
    int count)		/* Until this many are copied, */
				/* reversing as you go. */
{
    unsigned char *src = from + count - 1;
    if (to == from) {
	/* Reversing in place */
	while (to < src) {
	    unsigned char c = *src;
	    *src-- = *to;
	    *to++ = c;
	}
    }  else {
	while (src >= from) {
	    *to++ = *src--;
	}
    }
}

void
ReverseUniChars(
    Tcl_UniChar *to,		/* Copy Tcl_UniChars into here... */
    Tcl_UniChar *from,		/* ...from here... */
    unsigned int count)		/* Until this many are copied, */
				/* reversing as you go. */
{
    Tcl_UniChar *src = from + count - 1;
    if (to == from) {
	/* Reversing in place */
	from += count - 1;
	while (to < src) {
	    Tcl_UniChar c = *src;
	    *src-- = *to;
	    *to++ = c;
	}
    }  else {
	while (src >= from) {
	    *to++ = *src--;
	}
    }
}

Tcl_Obj *
TclStringObjReverse(
    Tcl_Obj *objPtr)
{
    String *stringPtr;


    if (TclIsPureByteArray(objPtr)) {
	int numBytes;
	unsigned char *from = Tcl_GetByteArrayFromObj(objPtr, &numBytes);

	if (Tcl_IsShared(objPtr)) {
	    objPtr = Tcl_NewByteArrayObj(NULL, numBytes);
	}
	ReverseBytes(Tcl_GetByteArrayFromObj(objPtr, NULL), from, numBytes);
	return objPtr;
    }

    SetStringFromAny(NULL, objPtr);
    stringPtr = GET_STRING(objPtr);

    if (stringPtr->hasUnicode) {
	Tcl_UniChar *from = Tcl_GetUnicode(objPtr);


	if (Tcl_IsShared(objPtr)) {


	    /*
	     * Create a non-empty, pure unicode value, so we can coax
	     * Tcl_SetObjLength into growing the unicode rep buffer.
	     */

	    Tcl_UniChar ch = 0;
	    objPtr = Tcl_NewUnicodeObj(&ch, 1);
	    Tcl_SetObjLength(objPtr, stringPtr->numChars);



	}

	ReverseUniChars(Tcl_GetUnicode(objPtr), from, stringPtr->numChars);






    }

    if (objPtr->bytes) {
	int numChars = stringPtr->numChars;
	int numBytes = objPtr->length;
	char *to, *from = objPtr->bytes;

	    while (bytesLeft) {
		/*
		 * NOTE: We know that the from buffer is NUL-terminated.
		 * It's part of the contract for objPtr->bytes values.
		 * Thus, we can skip calling Tcl_UtfCharComplete() here.
		 */
		Tcl_UniChar ch = 0;
		int bytesInChar = Tcl_UtfToUniChar(from, &ch);

		ReverseBytes((unsigned char *)to, (unsigned char *)from,
			bytesInChar);
		to += bytesInChar;
		from += bytesInChar;
		bytesLeft -= bytesInChar;