From 47c8ae43bf83b73d16257784e8afc957175489c0 Mon Sep 17 00:00:00 2001
From: Magnus Ahltorp <map@kth.se>
Date: Wed, 30 Nov 2016 16:46:37 +0100
Subject: Recover from extra data at end of index file

---
 c_src/filebuffer.c |  6 ++++++
 c_src/filebuffer.h |  2 ++
 c_src/permdb.c     | 41 ++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 48 insertions(+), 1 deletion(-)

(limited to 'c_src')

diff --git a/c_src/filebuffer.c b/c_src/filebuffer.c
index 40b79ad..d35bfa7 100644
--- a/c_src/filebuffer.c
+++ b/c_src/filebuffer.c
@@ -63,6 +63,12 @@ bf_lastcommit(buffered_file *file)
         return file->lastcommit;
 }
 
+void
+bf_setlastcommit(buffered_file *file, uint64_t lastcommit)
+{
+        file->lastcommit = lastcommit;
+}
+
 const char *
 bf_name(buffered_file *file)
 {
diff --git a/c_src/filebuffer.h b/c_src/filebuffer.h
index b2fb7ef..f98d20d 100644
--- a/c_src/filebuffer.h
+++ b/c_src/filebuffer.h
@@ -27,6 +27,8 @@ uint64_t
 bf_total_length(buffered_file *file);
 uint64_t
 bf_lastcommit(buffered_file *file);
+void
+bf_setlastcommit(buffered_file *file, uint64_t lastcommit);
 const char *
 bf_name(buffered_file *file);
 
diff --git a/c_src/permdb.c b/c_src/permdb.c
index f92958d..0ce74b6 100644
--- a/c_src/permdb.c
+++ b/c_src/permdb.c
@@ -272,6 +272,27 @@ verify_index_commit(buffered_file *file, node_offset offset)
         return validate_checksum(&commit, file);
 }
 
+node_offset
+search_index_commit(buffered_file *file, node_offset startoffset)
+{
+        node_offset offset = startoffset;
+
+        offset -= INDEX_COMMIT_TRAILER_SIZE;
+
+        while (offset > 0) {
+                unsigned char *data =
+                        bf_read(file, offset, INDEX_COMMIT_TRAILER_SIZE, NULL);
+                uint64_t cookie =
+                        read_be64(data + sizeof(uint64_t) + SHA256_DIGEST_SIZE);
+                if (cookie == index_commit_cookie) {
+                        return offset + INDEX_COMMIT_TRAILER_SIZE;
+                }
+                offset -= 8;
+        }
+        
+        return 0;
+}
+
 int
 indexfile_verify_file(buffered_file *file)
 {
@@ -283,7 +304,23 @@ indexfile_verify_file(buffered_file *file)
                 return -1;
         }
         free(header);
-        if (verify_index_commit(file, bf_total_length(file)) < 0) {
+        
+        node_offset offset = bf_total_length(file);
+        while (offset) {
+                offset = search_index_commit(file, offset);
+                if (offset) {
+                        fprintf(stderr,
+                                "verifying index file: found potential commit at %lld\n", (unsigned long long) offset);
+                }
+                if (offset && verify_index_commit(file, offset) == 0) {
+                        bf_setlastcommit(file, offset);
+                        break;
+                }
+        }
+        fprintf(stderr,
+                "verifying index file: found commit at %lld\n", (unsigned long long) bf_lastcommit(file));
+
+        if (offset == 0) {
                 fprintf(stderr,
                         "verifying index file: commit verification failed\n");
                 return -1;
@@ -468,9 +505,11 @@ try_reload_database(permdb_object *state) {
         if (bf_total_length(state->indexfile) == oldindexsize) {
                 return 0;
         } else {
+#if 0
                 if (datafile_verify_file(state->datafile) < 0) {
                         warnx("data file verification failed");
                 }
+#endif
                 if (indexfile_verify_file(state->indexfile) < 0) {
                         warnx("cannot rebuild in readonly mode");
                 }
-- 
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