[PATCH] Deltification library work by Nicolas Pitre.

This patch adds the basic library functions to create and replay delta
information.  Also included is a test-delta utility to validate the
code.

diff-delta was based on LibXDiff written by Davide Libenzi

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

patch-delta.c

@@ -0,0 +1,88 @@
+/*
+ * patch-delta.c:
+ * recreate a buffer from a source and the delta produced by diff-delta.c
+ *
+ * (C) 2005 Nicolas Pitre <nico@cam.org>
+ *
+ * This code is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include "delta.h"
+
+void *patch_delta(void *src_buf, unsigned long src_size,
+		  void *delta_buf, unsigned long delta_size,
+		  unsigned long *dst_size)
+{
+	const unsigned char *data, *top;
+	unsigned char *dst_buf, *out, cmd;
+	unsigned long size;
+	int i;
+
+	/* the smallest delta size possible is 6 bytes */
+	if (delta_size < 6)
+		return NULL;
+
+	data = delta_buf;
+	top = delta_buf + delta_size;
+
+	/* make sure the orig file size matches what we expect */
+	size = i = 0;
+	cmd = *data++;
+	while (cmd) {
+		if (cmd & 1)
+			size |= *data++ << i;
+		i += 8;
+		cmd >>= 1;
+	}
+	if (size != src_size)
+		return NULL;
+
+	/* now the result size */
+	size = i = 0;
+	cmd = *data++;
+	while (cmd) {
+		if (cmd & 1)
+			size |= *data++ << i;
+		i += 8;
+		cmd >>= 1;
+	}
+	dst_buf = malloc(size);
+	if (!dst_buf)
+		return NULL;
+
+	out = dst_buf;
+	while (data < top) {
+		cmd = *data++;
+		if (cmd & 0x80) {
+			unsigned long cp_off = 0, cp_size = 0;
+			const unsigned char *buf;
+			if (cmd & 0x01) cp_off = *data++;
+			if (cmd & 0x02) cp_off |= (*data++ << 8);
+			if (cmd & 0x04) cp_off |= (*data++ << 16);
+			if (cmd & 0x08) cp_off |= (*data++ << 24);
+			if (cmd & 0x10) cp_size = *data++;
+			if (cmd & 0x20) cp_size |= (*data++ << 8);
+			if (cp_size == 0) cp_size = 0x10000;
+			buf = (cmd & 0x40) ? dst_buf : src_buf;
+			memcpy(out, buf + cp_off, cp_size);
+			out += cp_size;
+		} else {
+			memcpy(out, data, cmd);
+			out += cmd;
+			data += cmd;
+		}
+	}
+
+	/* sanity check */
+	if (data != top || out - dst_buf != size) {
+		free(dst_buf);
+		return NULL;
+	}
+
+	*dst_size = size;
+	return dst_buf;
+}