Tcl Source Code

/*
 *----------------------------------------------------------------------
 *
 * TclAppendBytesToByteArray --
 *
 *	This function appends an array of bytes to a byte array object. Note
 *	that the object *must* be unshared, and the array of bytes *must not*
 *	refer to the object being appended to.


 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Allocates enough memory for an array of bytes of the requested total
 *	size, or possibly larger. [Bug 2992970]
 *
 *----------------------------------------------------------------------
 */

void
TclAppendBytesToByteArray(
    Tcl_Obj *objPtr,
    const unsigned char *bytes,
    int len)
{
    ByteArray *byteArrayPtr;
    int needed;

    if (Tcl_IsShared(objPtr)) {
	Tcl_Panic("%s called with shared object","TclAppendBytesToByteArray");
    }
    if (len < 0) {
	Tcl_Panic("%s must be called with definite number of bytes to append",
		"TclAppendBytesToByteArray");
    }
    if (len == 0) {
	/* Append zero bytes is a no-op. */
	return;
    }
    if (objPtr->typePtr != &tclByteArrayType) {
	SetByteArrayFromAny(NULL, objPtr);
    }
    byteArrayPtr = GET_BYTEARRAY(objPtr);

    if (len > INT_MAX - byteArrayPtr->used) {
	Tcl_Panic("max size for a Tcl value (%d bytes) exceeded", INT_MAX);
    }

    needed = byteArrayPtr->used + len;
    /*
     * If we need to, resize the allocated space in the byte array.
     */

    if (needed > byteArrayPtr->allocated) {

	ByteArray *ptr = NULL;
	int attempt;


	if (needed <= INT_MAX/2) {






	    /* Try to allocate double the total space that is needed. */
	    attempt = 2 * needed;


	    ptr = attemptckrealloc(byteArrayPtr, BYTEARRAY_SIZE(attempt));

	}
	if (ptr == NULL) {
	    /* Try to allocate double the increment that is needed (plus). */
	    unsigned int limit = INT_MAX - needed;
	    unsigned int extra = len + TCL_MIN_GROWTH;
	    int growth = (int) ((extra > limit) ? limit : extra);

	    attempt = needed + growth;
	    ptr = attemptckrealloc(byteArrayPtr, BYTEARRAY_SIZE(attempt));

	}

	if (ptr == NULL) {
	    /* Last chance: Try to allocate exactly what is needed. */
	    attempt = needed;




	    ptr = ckrealloc(byteArrayPtr, BYTEARRAY_SIZE(attempt));
	}

	byteArrayPtr = ptr;
	byteArrayPtr->allocated = attempt;

	SET_BYTEARRAY(objPtr, byteArrayPtr);
    }




    if (bytes) {

	memcpy(byteArrayPtr->bytes + byteArrayPtr->used, bytes, len);
    }
    byteArrayPtr->used += len;
    TclInvalidateStringRep(objPtr);

}

/*
 *----------------------------------------------------------------------
 *
 * TclInitBinaryCmd --
 *

     * Note that we only do this when the objects don't have string reps; if
     * it did, then appending the byte arrays together could well lose
     * information; this is a special-case optimization only.
     */

    if ((TclIsPureByteArray(objPtr) || objPtr->bytes == tclEmptyStringRep)
	    && TclIsPureByteArray(appendObjPtr)) {



	/*
	 * You might expect the code here to be
	 *
	 *  bytes = Tcl_GetByteArrayFromObj(appendObjPtr, &length);
	 *  TclAppendBytesToByteArray(objPtr, bytes, length);
	 *
	 * and essentially all of the time that would be fine.  However,
	 * it would run into trouble in the case where objPtr and
	 * appendObjPtr point to the same thing.  That may never be a
	 * good idea.  It seems to violate Copy On Write, and we don't
	 * have any tests for the situation, since making any Tcl commands
	 * that call Tcl_AppendObjToObj() do that appears impossible
	 * (They honor Copy On Write!).  For the sake of extensions that
	 * go off into that realm, though, here's a more complex approach

	 * that can handle all the cases.
	 */

	/* Get lengths */
	int lengthSrc;

	(void) Tcl_GetByteArrayFromObj(objPtr, &length);
	(void) Tcl_GetByteArrayFromObj(appendObjPtr, &lengthSrc);

	/* Grow buffer enough for the append */
	TclAppendBytesToByteArray(objPtr, NULL, lengthSrc);

	/* Reset objPtr back to the original value */
	Tcl_SetByteArrayLength(objPtr, length);

	/*
	 * Now do the append knowing that buffer growth cannot cause
	 * any trouble.
	 */

	TclAppendBytesToByteArray(objPtr,
		Tcl_GetByteArrayFromObj(appendObjPtr, NULL), lengthSrc);
	return;
    }

    /*
     * Must append as strings.
     */