[PATCH] assorted delta code cleanup

This is a wrap-up patch including all the cleanups I've done to the
delta code and its usage.  The most important change is the
factorization of the delta header handling code.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

delta.h

@@ -9,4 +9,26 @@ extern void *patch_delta(void *src_buf, unsigned long src_size,
 			 void *delta_buf, unsigned long delta_size,
 			 unsigned long *dst_size);
 
+/* the smallest possible delta size is 4 bytes */
+#define DELTA_SIZE_MIN	4
+
+/*
+ * This must be called twice on the delta data buffer, first to get the
+ * expected reference buffer size, and again to get the result buffer size.
+ */
+static inline unsigned long get_delta_hdr_size(const unsigned char **datap)
+{
+	const unsigned char *data = *datap;
+	unsigned char cmd = *data++;
+	unsigned long size = cmd & ~0x80;
+	int i = 7;
+	while (cmd & 0x80) {
+		cmd = *data++;
+		size |= (cmd & ~0x80) << i;
+		i += 7;
+	}
+	*datap = data;
+	return size;
+}
+
 #endif