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-rw-r--r--patch-delta.c94
1 files changed, 94 insertions, 0 deletions
diff --git a/patch-delta.c b/patch-delta.c
new file mode 100644
index 0000000..b5c8594
--- /dev/null
+++ b/patch-delta.c
@@ -0,0 +1,94 @@
+/*
+ * 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;
+#define PARSE_CP_PARAM(bit, var, shift) do { \
+ if (cmd & (bit)) { \
+ if (data >= top) \
+ goto bad_length; \
+ var |= ((unsigned) *data++ << (shift)); \
+ } } while (0)
+ PARSE_CP_PARAM(0x01, cp_off, 0);
+ PARSE_CP_PARAM(0x02, cp_off, 8);
+ PARSE_CP_PARAM(0x04, cp_off, 16);
+ PARSE_CP_PARAM(0x08, cp_off, 24);
+ PARSE_CP_PARAM(0x10, cp_size, 0);
+ PARSE_CP_PARAM(0x20, cp_size, 8);
+ PARSE_CP_PARAM(0x40, cp_size, 16);
+#undef PARSE_CP_PARAM
+ if (cp_size == 0) cp_size = 0x10000;
+ if (unsigned_add_overflows(cp_off, cp_size) ||
+ cp_off + cp_size > src_size ||
+ cp_size > size)
+ goto bad_length;
+ memcpy(out, (char *) src_buf + cp_off, cp_size);
+ out += cp_size;
+ size -= cp_size;
+ } else if (cmd) {
+ if (cmd > size || cmd > top - data)
+ goto bad_length;
+ 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) {
+ bad_length:
+ error("delta replay has gone wild");
+ bad:
+ free(dst_buf);
+ return NULL;
+ }
+
+ *dst_size = out - dst_buf;
+ return dst_buf;
+}