1 files changed, 86 insertions, 0 deletions
diff --git a/patch-delta.c b/patch-delta.c
new file mode 100644
index 0000000000..56e0a5ede2
--- /dev/null
+++ b/patch-delta.c
@@ -0,0 +1,86 @@
+/*
+ * patch-delta.c:
+ * recreate a buffer from a source and the delta produced by diff-delta.c
+ *
+ * (C) 2005 Nicolas Pitre <nico@fluxnic.net>
+ *
+ * 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 "git-compat-util.h"
+#include "delta.h"
+
+void *patch_delta(const void *src_buf, unsigned long src_size,
+		  const 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;
+
+	if (delta_size < DELTA_SIZE_MIN)
+		return NULL;
+
+	data = delta_buf;
+	top = (const unsigned char *) delta_buf + delta_size;
+
+	/* make sure the orig file size matches what we expect */
+	size = get_delta_hdr_size(&data, top);
+	if (size != src_size)
+		return NULL;
+
+	/* now the result size */
+	size = get_delta_hdr_size(&data, top);
+	dst_buf = xmallocz(size);
+
+	out = dst_buf;
+	while (data < top) {
+		cmd = *data++;
+		if (cmd & 0x80) {
+			unsigned long cp_off = 0, cp_size = 0;
+			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 |= ((unsigned) *data++ << 24);
+			if (cmd & 0x10) cp_size = *data++;
+			if (cmd & 0x20) cp_size |= (*data++ << 8);
+			if (cmd & 0x40) cp_size |= (*data++ << 16);
+			if (cp_size == 0) cp_size = 0x10000;
+			if (unsigned_add_overflows(cp_off, cp_size) ||
+			    cp_off + cp_size > src_size ||
+			    cp_size > size)
+				break;
+			memcpy(out, (char *) src_buf + cp_off, cp_size);
+			out += cp_size;
+			size -= cp_size;
+		} else if (cmd) {
+			if (cmd > size)
+				break;
+			memcpy(out, data, cmd);
+			out += cmd;
+			data += cmd;
+			size -= cmd;
+		} else {
+			/*
+			 * cmd == 0 is reserved for future encoding
+			 * extensions. In the mean time we must fail when
+			 * encountering them (might be data corruption).
+			 */
+			error("unexpected delta opcode 0");
+			goto bad;
+		}
+	}
+
+	/* sanity check */
+	if (data != top || size != 0) {
+		error("delta replay has gone wild");
+		bad:
+		free(dst_buf);
+		return NULL;
+	}
+
+	*dst_size = out - dst_buf;
+	return dst_buf;
+}