unsigned char bytes[TCLFLEXARRAY];	/* The array of bytes. The actual size of this
				 * field depends on the 'allocated' field
				 * above. */
} ByteArray;

#define BYTEARRAY_MAX_LEN (TCL_SIZE_MAX - (Tcl_Size)offsetof(ByteArray, bytes))
#define BYTEARRAY_SIZE(len) \
        ( (len < 0 || BYTEARRAY_MAX_LEN < (len)) \
	? (Tcl_Panic("negative length specified or max size of a Tcl value exceeded"), 0) \
	: (offsetof(ByteArray, bytes) + (len)) )
#define GET_BYTEARRAY(irPtr) ((ByteArray *) (irPtr)->twoPtrValue.ptr1)
#define SET_BYTEARRAY(irPtr, baPtr) \
		(irPtr)->twoPtrValue.ptr1 = (baPtr)

int

 *----------------------------------------------------------------------
 */

unsigned char *
Tcl_SetByteArrayLength(
    Tcl_Obj *objPtr,		/* The ByteArray object. */
    Tcl_Size numBytes)		/* Number of bytes in resized array
                                 * Must be >= 0 */
{
    ByteArray *byteArrayPtr;
    Tcl_ObjInternalRep *irPtr;

    assert(numBytes >= 0);
    if (Tcl_IsShared(objPtr)) {
	Tcl_Panic("%s called with shared object", "Tcl_SetByteArrayLength");

    if ((BYTEARRAY_MAX_LEN - byteArrayPtr->used) < len) {
	/* Will wrap around !! */
	Tcl_Panic("max size of a byte array exceeded");
    }
    needed = byteArrayPtr->used + len;
    if (needed > byteArrayPtr->allocated) {
	Tcl_Size newCapacity;

	byteArrayPtr =
	    (ByteArray *)TclReallocElemsEx(byteArrayPtr,
					   needed,
					   1,
					   offsetof(ByteArray, bytes),
					   &newCapacity);
	byteArrayPtr->allocated = newCapacity;
	SET_BYTEARRAY(irPtr, byteArrayPtr);
    }

    if (bytes) {
	memcpy(byteArrayPtr->bytes + byteArrayPtr->used, bytes, len);
    }