validate reused pack data with CRC when possible

This replaces the inflate validation with a CRC validation when reusing
data from a pack which uses index version 2.  That makes repacking much
safer against corruptions, and it should be a bit faster too.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
index 099dea0e1eea0165f9acd5fb37764249aea033c6..687b4b5a9944ace5fde99e6275adc2bd3ca7ef9a 100644 (file)
--- a/builtin-pack-objects.c
+++ b/builtin-pack-objects.c
@@ -233,12 +233,6 @@ static struct revindex_entry * find_packed_object(struct packed_git *p,
        die("internal error: pack revindex corrupt");
 }
 
-static off_t find_packed_object_size(struct packed_git *p, off_t ofs)
-{
-       struct revindex_entry *entry = find_packed_object(p, ofs);
-       return entry[1].offset - ofs;
-}
-
 static const unsigned char *find_packed_object_name(struct packed_git *p,
                                                    off_t ofs)
 {
@@ -321,6 +315,28 @@ static int check_pack_inflate(struct packed_git *p,
                stream.total_in == len) ? 0 : -1;
 }
 
+static int check_pack_crc(struct packed_git *p, struct pack_window **w_curs,
+                         off_t offset, off_t len, unsigned int nr)
+{
+       const uint32_t *index_crc;
+       uint32_t data_crc = crc32(0, Z_NULL, 0);
+
+       do {
+               unsigned int avail;
+               void *data = use_pack(p, w_curs, offset, &avail);
+               if (avail > len)
+                       avail = len;
+               data_crc = crc32(data_crc, data, avail);
+               offset += avail;
+               len -= avail;
+       } while (len);
+
+       index_crc = p->index_data;
+       index_crc += 2 + 256 + p->num_objects * (20/4) + nr;
+
+       return data_crc != ntohl(*index_crc);
+}
+
 static void copy_pack_data(struct sha1file *f,
                struct packed_git *p,
                struct pack_window **w_curs,
@@ -485,6 +501,7 @@ static unsigned long write_object(struct sha1file *f,
        else {
                struct packed_git *p = entry->in_pack;
                struct pack_window *w_curs = NULL;
+               struct revindex_entry *revidx;
                off_t offset;
 
                if (entry->delta) {
@@ -507,12 +524,17 @@ static unsigned long write_object(struct sha1file *f,
                        hdrlen += 20;
                }
 
-               offset = entry->in_pack_offset + entry->in_pack_header_size;
-               datalen = find_packed_object_size(p, entry->in_pack_offset)
-                               - entry->in_pack_header_size;
-               if (!pack_to_stdout && check_pack_inflate(p, &w_curs,
-                               offset, datalen, entry->size))
-                       die("corrupt delta in pack %s", sha1_to_hex(entry->sha1));
+               offset = entry->in_pack_offset;
+               revidx = find_packed_object(p, offset);
+               datalen = revidx[1].offset - offset;
+               if (!pack_to_stdout && p->index_version > 1 &&
+                   check_pack_crc(p, &w_curs, offset, datalen, revidx->nr))
+                       die("bad packed object CRC for %s", sha1_to_hex(entry->sha1));
+               offset += entry->in_pack_header_size;
+               datalen -= entry->in_pack_header_size;
+               if (!pack_to_stdout && p->index_version == 1 &&
+                   check_pack_inflate(p, &w_curs, offset, datalen, entry->size))
+                       die("corrupt packed object for %s", sha1_to_hex(entry->sha1));
                copy_pack_data(f, p, &w_curs, offset, datalen);
                unuse_pack(&w_curs);
                reused++;