Merge branch 'ds/fsck-pack-revindex'

"git fsck" learned to validate the on-disk pack reverse index files.

* ds/fsck-pack-revindex:
  fsck: validate .rev file header
  fsck: check rev-index position values
  fsck: check rev-index checksums
  fsck: create scaffolding for rev-index checks

1 files changed, 41 insertions, 2 deletions

diff --git a/pack-revindex.c b/pack-revindex.c
index db282dac8d..1f51b712e8 100644
--- a/pack-revindex.c
+++ b/pack-revindex.c
@@ -7,6 +7,7 @@
 #include "trace2.h"
 #include "config.h"
 #include "midx.h"
+#include "csum-file.h"
 
 struct revindex_entry {
 	off_t offset;
@@ -213,7 +214,8 @@ static int load_revindex_from_disk(char *revindex_name,
 	fd = git_open(revindex_name);
 
 	if (fd < 0) {
-		ret = -1;
+		/* "No file" means return 1. */
+		ret = 1;
 		goto cleanup;
 	}
 	if (fstat(fd, &st)) {
@@ -265,7 +267,7 @@ cleanup:
 	return ret;
 }
 
-static int load_pack_revindex_from_disk(struct packed_git *p)
+int load_pack_revindex_from_disk(struct packed_git *p)
 {
 	char *revindex_name;
 	int ret;
@@ -303,6 +305,43 @@ int load_pack_revindex(struct repository *r, struct packed_git *p)
 	return -1;
 }
 
+/*
+ * verify_pack_revindex verifies that the on-disk rev-index for the given
+ * pack-file is the same that would be created if written from scratch.
+ *
+ * A negative number is returned on error.
+ */
+int verify_pack_revindex(struct packed_git *p)
+{
+	int res = 0;
+
+	/* Do not bother checking if not initialized. */
+	if (!p->revindex_map || !p->revindex_data)
+		return res;
+
+	if (!hashfile_checksum_valid((const unsigned char *)p->revindex_map, p->revindex_size)) {
+		error(_("invalid checksum"));
+		res = -1;
+	}
+
+	/* This may fail due to a broken .idx. */
+	if (create_pack_revindex_in_memory(p))
+		return res;
+
+	for (size_t i = 0; i < p->num_objects; i++) {
+		uint32_t nr = p->revindex[i].nr;
+		uint32_t rev_val = get_be32(p->revindex_data + i);
+
+		if (nr != rev_val) {
+			error(_("invalid rev-index position at %"PRIu64": %"PRIu32" != %"PRIu32""),
+			      (uint64_t)i, nr, rev_val);
+			res = -1;
+		}
+	}
+
+	return res;
+}
+
 int load_midx_revindex(struct multi_pack_index *m)
 {
 	struct strbuf revindex_name = STRBUF_INIT;