[PATCH 4/8] git-repack --max-pack-size: add fixup_header_footer()

[Dana How <danahow@gmail.com>]

Add our own version of the one in fast-import.c here.
Needed later to correct bad object count in header for split pack.

Signed-off-by: Dana L. How <danahow@gmail.com>
---
 builtin-pack-objects.c |   36 ++++++++++++++++++++++++++++++++++++
 1 files changed, 36 insertions(+), 0 deletions(-)

diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
index bc45ca6..98066bf 100644
--- a/builtin-pack-objects.c
+++ b/builtin-pack-objects.c
@@ -562,6 +562,42 @@ static off_t write_one(struct sha1file *f,
 	return offset + size;
 }
 
+static void fixup_header_footer(int pack_fd, unsigned char *pack_file_sha1,
+				char *pack_name, uint32_t object_count)
+{
+	static const int buf_sz = 128 * 1024;
+	SHA_CTX c;
+	struct pack_header hdr;
+	char *buf;
+
+	if (lseek(pack_fd, 0, SEEK_SET) != 0)
+		die("Failed seeking to start: %s", strerror(errno));
+	if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
+		die("Unable to reread header of %s", pack_name);
+	if (lseek(pack_fd, 0, SEEK_SET) != 0)
+		die("Failed seeking to start: %s", strerror(errno));
+	hdr.hdr_entries = htonl(object_count);
+	write_or_die(pack_fd, &hdr, sizeof(hdr));
+
+	SHA1_Init(&c);
+	SHA1_Update(&c, &hdr, sizeof(hdr));
+
+	buf = xmalloc(buf_sz);
+	for (;;) {
+		size_t n = xread(pack_fd, buf, buf_sz);
+		if (!n)
+			break;
+		if (n < 0)
+			die("Failed to checksum %s", pack_name);
+		SHA1_Update(&c, buf, n);
+	}
+	free(buf);
+
+	SHA1_Final(pack_file_sha1, &c);
+	write_or_die(pack_fd, pack_file_sha1, 20);
+	close(pack_fd);
+}
+
 /* forward declarations for write_pack_file */
 static void write_index_file(off_t last_obj_offset, unsigned char *sha1);
 static int adjust_perm(const char *path, mode_t mode);
-- 
1.5.2.rc0.766.gba60-dirty