The pack-file format is slightly different from the traditional git
object format, in that it has a much denser binary header encoding.
The traditional format uses an ASCII string with type and length
information, which is somewhat wasteful.
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxx>
---
This should probably be applied to the main tree asap if we think
this is at all a worthwhile exercise. But somebody should verify that I
got the format right first!
sha1_file.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++--------
1 files changed, 57 insertions(+), 9 deletions(-)
diff --git a/sha1_file.c b/sha1_file.c
index 8734d50..ca5f0c0 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -697,9 +697,9 @@ static int unpack_sha1_header(z_stream *
return inflate(stream, 0);
}
-static void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size)
+static void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size, unsigned int hdrlen)
{
- int bytes = strlen(buffer) + 1;
+ int bytes = hdrlen;
unsigned char *buf = xmalloc(1+size);
memcpy(buf, (char *) buffer + bytes, stream->total_out - bytes);
@@ -720,9 +720,9 @@ static void *unpack_sha1_rest(z_stream *
* too permissive for what we want to check. So do an anal
* object header parse by hand.
*/
-static int parse_sha1_header(char *hdr, char *type, unsigned long *sizep)
+static int parse_ascii_sha1_header(char *hdr, char *type, unsigned long *sizep)
{
- int i;
+ int i, bytes = 0;
unsigned long size;
/*
@@ -733,6 +733,7 @@ static int parse_sha1_header(char *hdr,
i = 10;
for (;;) {
char c = *hdr++;
+ bytes++;
if (c == ' ')
break;
if (!--i)
@@ -746,6 +747,7 @@ static int parse_sha1_header(char *hdr,
* decimal format (ie "010" is not valid).
*/
size = *hdr++ - '0';
+ bytes++;
if (size > 9)
return -1;
if (size) {
@@ -754,6 +756,7 @@ static int parse_sha1_header(char *hdr,
if (c > 9)
break;
hdr++;
+ bytes++;
size = size * 10 + c;
}
}
@@ -762,20 +765,65 @@ static int parse_sha1_header(char *hdr,
/*
* The length must be followed by a zero byte
*/
- return *hdr ? -1 : 0;
+ bytes++;
+ if (*hdr)
+ bytes = -1;
+ return bytes;
+}
+
+static int parse_binary_sha1_header(char *hdr, char *type, unsigned long *sizep)
+{
+ unsigned char c;
+ int bytes = 1;
+ unsigned long size;
+ unsigned object_type, bits;
+ static const char *typename[8] = {
+ NULL, /* OBJ_EXT */
+ "commit", "tree", "blob", "tag",
+ NULL, NULL, NULL
+ };
+
+ c = *hdr++;
+ object_type = (c >> 4) & 7;
+ if (!typename[object_type])
+ return -1;
+ strcpy(type, typename[object_type]);
+ size = c & 15;
+ bits = 4;
+ while (!(c & 0x80)) {
+ if (bits >= 8*sizeof(unsigned long))
+ return -1;
+ c = *hdr++;
+ size += (unsigned long) (c & 0x7f) << bits;
+ bytes++;
+ bits += 7;
+ }
+ *sizep = size;
+ return bytes;
+}
+
+static int parse_sha1_header(char *hdr, char *type, unsigned long *sizep)
+{
+ int retval = parse_ascii_sha1_header(hdr, type, sizep);
+ if (retval < 0)
+ retval = parse_binary_sha1_header(hdr, type, sizep);
+ return retval;
}
void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
{
- int ret;
+ int ret, hdrlen;
z_stream stream;
char hdr[8192];
ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
- if (ret < Z_OK || parse_sha1_header(hdr, type, size) < 0)
+ if (ret < Z_OK)
+ return NULL;
+ hdrlen = parse_sha1_header(hdr, type, size);
+ if (hdrlen < 0)
return NULL;
- return unpack_sha1_rest(&stream, hdr, *size);
+ return unpack_sha1_rest(&stream, hdr, *size, hdrlen);
}
/* forward declaration for a mutually recursive function */
@@ -1192,7 +1240,7 @@ struct packed_git *find_sha1_pack(const
int sha1_object_info(const unsigned char *sha1, char *type, unsigned long *sizep)
{
- int status;
+ int status, hdrlen;
unsigned long mapsize, size;
void *map;
z_stream stream;
-
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