[PATCH] diff.c: locate_size_cache() fix.

[git.git] / sha1_file.c

diff --git a/sha1_file.c b/sha1_file.c
index af39e88..a2ba4c8 100644 (file)
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -401,6 +401,97 @@ void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned l
        return unpack_sha1_rest(&stream, hdr, *size);
 }
 
+int sha1_delta_base(const unsigned char *sha1, unsigned char *base_sha1)
+{
+       int ret;
+       unsigned long mapsize, size;
+       void *map;
+       z_stream stream;
+       char hdr[64], type[20];
+       void *delta_data_head;
+
+       map = map_sha1_file(sha1, &mapsize);
+       if (!map)
+               return -1;
+       ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
+       if (ret < Z_OK || parse_sha1_header(hdr, type, &size) < 0) {
+               ret = -1;
+               goto out;
+       }
+       if (strcmp(type, "delta")) {
+               ret = 0;
+               goto out;
+       }
+
+       delta_data_head = hdr + strlen(hdr) + 1;
+       ret = 1;
+       memcpy(base_sha1, delta_data_head, 20);
+ out:
+       inflateEnd(&stream);
+       munmap(map, mapsize);
+       return ret;
+}
+
+int sha1_file_size(const unsigned char *sha1, unsigned long *sizep)
+{
+       int ret, status;
+       unsigned long mapsize, size;
+       void *map;
+       z_stream stream;
+       char hdr[64], type[20];
+       const unsigned char *data;
+       unsigned char cmd;
+       int i;
+
+       map = map_sha1_file(sha1, &mapsize);
+       if (!map)
+               return -1;
+       ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
+       status = -1;
+       if (ret < Z_OK || parse_sha1_header(hdr, type, &size) < 0)
+               goto out;
+       if (strcmp(type, "delta")) {
+               *sizep = size;
+               status = 0;
+               goto out;
+       }
+
+       /* We are dealing with a delta object.  Inflated, the first
+        * 20 bytes hold the base object SHA1, and delta data follows
+        * immediately after it.
+        *
+        * The initial part of the delta starts at delta_data_head +
+        * 20.  Borrow code from patch-delta to read the result size.
+        */
+       data = hdr + strlen(hdr) + 1 + 20;
+
+       /* Skip over the source size; we are not interested in
+        * it and we cannot verify it because we do not want
+        * to read the base object.
+        */
+       cmd = *data++;
+       while (cmd) {
+               if (cmd & 1)
+                       data++;
+               cmd >>= 1;
+       }
+       /* Read the result size */
+       size = i = 0;
+       cmd = *data++;
+       while (cmd) {
+               if (cmd & 1)
+                       size |= *data++ << i;
+               i += 8;
+               cmd >>= 1;
+       }
+       *sizep = size;
+       status = 0;
+ out:
+       inflateEnd(&stream);
+       munmap(map, mapsize);
+       return status;
+}
+
 void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
 {
        unsigned long mapsize;