Change pack file format. Hopefully for the last time.
This also adds a header with a signature, version info, and the number
of objects to the pack file. It also encodes the file length and type
more efficiently.
diff --git a/pack-objects.c b/pack-objects.c
index e976460..d1e62dc 100644
--- a/pack-objects.c
+++ b/pack-objects.c
@@ -2,25 +2,18 @@
#include "cache.h"
#include "object.h"
#include "delta.h"
+#include "pack.h"
#include "csum-file.h"
static const char pack_usage[] = "git-pack-objects [--window=N] [--depth=N] {--stdout | base-name} < object-list";
-/*
- * The object type is a single-character shorthand:
- * - 'C' for "Commit"
- * - 'T' for "Tree"
- * - 'B' for "Blob"
- * - 'G' for "taG"
- * - 'D' for "Delta"
- */
struct object_entry {
unsigned char sha1[20];
unsigned long size;
unsigned long offset;
unsigned int depth;
unsigned int hash;
- unsigned char type;
+ enum object_type type;
unsigned long delta_size;
struct object_entry *delta;
};
@@ -49,13 +42,54 @@
return delta_buf;
}
+/*
+ * The per-object header is a pretty dense thing, which is
+ * - first byte: low four bits are "size", then three bits of "type",
+ * and the high bit is "size continues".
+ * - each byte afterwards: low seven bits are size continuation,
+ * with the high bit being "size continues"
+ */
+static int encode_header(enum object_type type, unsigned long size, unsigned char *hdr)
+{
+ int n = 1, i;
+ unsigned char c;
+
+ if (type < OBJ_COMMIT || type > OBJ_DELTA)
+ die("bad type %d", type);
+
+ /*
+ * Shift the size up by 7 bits at a time,
+ * until you get bits in the "high four".
+ * That will be our beginning. We'll have
+ * four size bits in 28..31, then groups
+ * of seven in 21..27, 14..20, 7..13 and
+ * finally 0..6.
+ */
+ if (size) {
+ n = 5;
+ while (!(size & 0xfe000000)) {
+ size <<= 7;
+ n--;
+ }
+ }
+ c = (type << 4) | (size >> 28);
+ for (i = 1; i < n; i++) {
+ *hdr++ = c | 0x80;
+ c = (size >> 21) & 0x7f;
+ size <<= 7;
+ }
+ *hdr = c;
+ return n;
+}
+
static unsigned long write_object(struct sha1file *f, struct object_entry *entry)
{
unsigned long size;
char type[10];
void *buf = read_sha1_file(entry->sha1, type, &size);
- char header[25];
+ unsigned char header[10];
unsigned hdrlen, datalen;
+ enum object_type obj_type;
if (!buf)
die("unable to read %s", sha1_to_hex(entry->sha1));
@@ -67,18 +101,18 @@
* length, except for deltas that has the 20 bytes of delta sha
* instead.
*/
- header[0] = entry->type;
- hdrlen = 5;
+ obj_type = entry->type;
if (entry->delta) {
- header[0] = 'D';
- memcpy(header+5, entry->delta, 20);
buf = delta_against(buf, size, entry);
size = entry->delta_size;
- hdrlen = 25;
+ obj_type = OBJ_DELTA;
}
- datalen = htonl(size);
- memcpy(header+1, &datalen, 4);
+ hdrlen = encode_header(obj_type, size, header);
sha1write(f, header, hdrlen);
+ if (entry->delta) {
+ sha1write(f, entry->delta, 20);
+ hdrlen += 20;
+ }
datalen = sha1write_compressed(f, buf, size);
free(buf);
return hdrlen + datalen;
@@ -88,13 +122,19 @@
{
int i;
struct sha1file *f;
- unsigned long offset = 0;
+ unsigned long offset;
unsigned long mb;
+ struct pack_header hdr;
if (!base_name)
f = sha1fd(1, "<stdout>");
else
f = sha1create("%s.%s", base_name, "pack");
+ hdr.hdr_signature = htonl(PACK_SIGNATURE);
+ hdr.hdr_version = htonl(1);
+ hdr.hdr_entries = htonl(nr_objects);
+ sha1write(f, &hdr, sizeof(hdr));
+ offset = sizeof(hdr);
for (i = 0; i < nr_objects; i++) {
struct object_entry *entry = objects + i;
entry->offset = offset;
@@ -168,13 +208,13 @@
if (!sha1_object_info(entry->sha1, type, &entry->size)) {
if (!strcmp(type, "commit")) {
- entry->type = 'C';
+ entry->type = OBJ_COMMIT;
} else if (!strcmp(type, "tree")) {
- entry->type = 'T';
+ entry->type = OBJ_TREE;
} else if (!strcmp(type, "blob")) {
- entry->type = 'B';
+ entry->type = OBJ_BLOB;
} else if (!strcmp(type, "tag")) {
- entry->type = 'G';
+ entry->type = OBJ_TAG;
} else
die("unable to pack object %s of type %s",
sha1_to_hex(entry->sha1), type);
