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 e9764604f6f17f4eb018b4fd7247550e90583f8c..d1e62dc019b46afb4eab076be430381d8fe07c64 100644 (file)
--- 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 @@ static void *delta_against(void *buf, unsigned long size, struct object_entry *e
        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 @@ static unsigned long write_object(struct sha1file *f, struct object_entry *entry
         * 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 @@ static void write_pack_file(void)
 {
        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 @@ static void check_object(struct object_entry *entry)
 
        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);

diff --git a/pack.h b/pack.h
new file mode 100644 (file)
index 0000000..08e120d
--- /dev/null
+++ b/pack.h
@@ -0,0 +1,23 @@
+#ifndef PACK_H
+#define PACK_H
+
+enum object_type {
+       OBJ_NONE,
+       OBJ_COMMIT,
+       OBJ_TREE,
+       OBJ_BLOB,
+       OBJ_TAG,
+       OBJ_DELTA,
+};
+
+/*
+ * Packed object header
+ */
+#define PACK_SIGNATURE 0x5041434b      /* "PACK" */
+struct pack_header {
+       unsigned int hdr_signature;
+       unsigned int hdr_version;
+       unsigned int hdr_entries;
+};
+
+#endif

diff --git a/sha1_file.c b/sha1_file.c
index e27affb2885717974b5612d4a41a91ed390d7ff7..6e3fd180f90bb6edf36095978baa2d35b772d21c 100644 (file)
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -10,6 +10,7 @@
 #include <dirent.h>
 #include "cache.h"
 #include "delta.h"
+#include "pack.h"
 
 #ifndef O_NOATIME
 #if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
@@ -665,37 +666,60 @@ static int packed_delta_info(unsigned char *base_sha1,
        return 0;
 }
 
+static unsigned long unpack_object_header(struct packed_git *p, unsigned long offset,
+       enum object_type *type, unsigned long *sizep)
+{
+       unsigned char *pack, c;
+       unsigned long size;
+
+       if (offset >= p->pack_size)
+               die("object offset outside of pack file");
+
+       pack =  p->pack_base + offset;
+       c = *pack++;
+       offset++;
+       *type = (c >> 4) & 7;
+       size = c & 15;
+       while (c & 0x80) {
+               if (offset >= p->pack_size)
+                       die("object offset outside of pack file");
+               c = *pack++;
+               offset++;
+               size = (size << 7) | (c & 0x7f);
+       }
+       *sizep = size;
+       return offset;
+}
+
 static int packed_object_info(struct pack_entry *entry,
                              char *type, unsigned long *sizep)
 {
        struct packed_git *p = entry->p;
        unsigned long offset, size, left;
        unsigned char *pack;
-
-       offset = entry->offset;
-       if (p->pack_size - 5 < offset)
-               die("object offset outside of pack file");
+       enum object_type kind;
 
        if (use_packed_git(p))
                die("cannot map packed file");
 
+       offset = unpack_object_header(p, entry->offset, &kind, &size);
        pack = p->pack_base + offset;
-       size = (pack[1] << 24) + (pack[2] << 16) + (pack[3] << 8) + pack[4];
-       left = p->pack_size - offset - 5;
-       switch (*pack) {
-       case 'D':
-               return packed_delta_info(pack+5, size, left, type, sizep);
+       left = p->pack_size - offset;
+
+       switch (kind) {
+       case OBJ_DELTA:
+               return packed_delta_info(pack, size, left, type, sizep);
                break;
-       case 'C':
+       case OBJ_COMMIT:
                strcpy(type, "commit");
                break;
-       case 'T':
+       case OBJ_TREE:
                strcpy(type, "tree");
                break;
-       case 'B':
+       case OBJ_BLOB:
                strcpy(type, "blob");
                break;
-       case 'G':
+       case OBJ_TAG:
                strcpy(type, "tag");
                break;
        default:
@@ -787,37 +811,34 @@ static void *unpack_entry(struct pack_entry *entry,
        struct packed_git *p = entry->p;
        unsigned long offset, size, left;
        unsigned char *pack;
-
-       offset = entry->offset;
-       if (p->pack_size - 5 < offset)
-               die("object offset outside of pack file");
+       enum object_type kind;
 
        if (use_packed_git(p))
                die("cannot map packed file");
 
+       offset = unpack_object_header(p, entry->offset, &kind, &size);
        pack = p->pack_base + offset;
-       size = (pack[1] << 24) + (pack[2] << 16) + (pack[3] << 8) + pack[4];
-       left = p->pack_size - offset - 5;
-       switch (*pack) {
-       case 'D':
-               return unpack_delta_entry(pack+5, size, left, type, sizep);
-       case 'C':
+       left = p->pack_size - offset;
+       switch (kind) {
+       case OBJ_DELTA:
+               return unpack_delta_entry(pack, size, left, type, sizep);
+       case OBJ_COMMIT:
                strcpy(type, "commit");
                break;
-       case 'T':
+       case OBJ_TREE:
                strcpy(type, "tree");
                break;
-       case 'B':
+       case OBJ_BLOB:
                strcpy(type, "blob");
                break;
-       case 'G':
+       case OBJ_TAG:
                strcpy(type, "tag");
                break;
        default:
                die("corrupted pack file");
        }
        *sizep = size;
-       return unpack_non_delta_entry(pack+5, size, left);
+       return unpack_non_delta_entry(pack, size, left);
 }
 
 static int find_pack_entry_1(const unsigned char *sha1,

diff --git a/unpack-objects.c b/unpack-objects.c
index 57f3c9b6bb4790149a50f3855f42b5eb479b09d8..98b696cf2cb88cc85a887c677718231fe8cf065f 100644 (file)
--- a/unpack-objects.c
+++ b/unpack-objects.c
@@ -1,6 +1,7 @@
 #include "cache.h"
 #include "object.h"
 #include "delta.h"
+#include "pack.h"
 
 static int dry_run;
 static int nr_entries;
@@ -92,7 +93,7 @@ static int check_index(void)
 }
 
 static int unpack_non_delta_entry(struct pack_entry *entry,
-                                 int kind,
+                                 enum object_type kind,
                                  unsigned char *data,
                                  unsigned long size,
                                  unsigned long left)
@@ -101,9 +102,9 @@ static int unpack_non_delta_entry(struct pack_entry *entry,
        z_stream stream;
        char *buffer;
        unsigned char sha1[20];
-       char *type_s;
+       char *type;
 
-       printf("%s %c %lu\n", sha1_to_hex(entry->sha1), kind, size);
+       printf("%s %c %lu\n", sha1_to_hex(entry->sha1), ".CTBGD"[kind], size);
        if (dry_run)
                return 0;
 
@@ -121,18 +122,18 @@ static int unpack_non_delta_entry(struct pack_entry *entry,
        if ((st != Z_STREAM_END) || stream.total_out != size)
                goto err_finish;
        switch (kind) {
-       case 'C': type_s = "commit"; break;
-       case 'T': type_s = "tree"; break;
-       case 'B': type_s = "blob"; break;
-       case 'G': type_s = "tag"; break;
+       case OBJ_COMMIT: type = "commit"; break;
+       case OBJ_TREE:   type = "tree"; break;
+       case OBJ_BLOB:   type = "blob"; break;
+       case OBJ_TAG:    type = "tag"; break;
        default: goto err_finish;
        }
-       if (write_sha1_file(buffer, size, type_s, sha1) < 0)
+       if (write_sha1_file(buffer, size, type, sha1) < 0)
                die("failed to write %s (%s)",
-                   sha1_to_hex(entry->sha1), type_s);
-       printf("%s %s\n", sha1_to_hex(sha1), type_s);
+                   sha1_to_hex(entry->sha1), type);
+       printf("%s %s\n", sha1_to_hex(sha1), type);
        if (memcmp(sha1, entry->sha1, 20))
-               die("resulting %s have wrong SHA1", type_s);
+               die("resulting %s have wrong SHA1", type);
 
  finish:
        st = 0;
@@ -237,28 +238,44 @@ static int unpack_delta_entry(struct pack_entry *entry,
 static void unpack_entry(struct pack_entry *entry)
 {
        unsigned long offset, size, left;
-       unsigned char *pack;
+       unsigned char *pack, c;
+       int type;
 
        /* Have we done this one already due to deltas based on it? */
        if (lookup_object(entry->sha1))
                return;
 
        offset = ntohl(entry->offset);
-       if (offset > pack_size - 5)
-               die("object offset outside of pack file");
+       if (offset >= pack_size)
+               goto bad;
+
        pack = pack_base + offset;
-       size = (pack[1] << 24) + (pack[2] << 16) + (pack[3] << 8) + pack[4];
-       left = pack_size - offset - 5;
-       switch (*pack) {
-       case 'C': case 'T': case 'B': case 'G':
-               unpack_non_delta_entry(entry, *pack, pack+5, size, left);
-               break;
-       case 'D':
+       c = *pack++;
+       offset++;
+       type = (c >> 4) & 7;
+       size = (c & 15);
+       while (c & 0x80) {
+               if (offset >= pack_size)
+                       goto bad;
+               offset++;
+               c = *pack++;
+               size = (size << 7) + (c & 0x7f);
+               
+       }
+       left = pack_size - offset;
+       switch (type) {
+       case OBJ_COMMIT:
+       case OBJ_TREE:
+       case OBJ_BLOB:
+       case OBJ_TAG:
+               unpack_non_delta_entry(entry, type, pack, size, left);
+               return;
+       case OBJ_DELTA:
                unpack_delta_entry(entry, pack+5, size, left);
-               break;
-       default:
-               die("corrupted pack file");
+               return;
        }
+bad:
+       die("corrupted pack file");
 }
 
 /*