1 files changed, 19 insertions, 0 deletions
diff --git a/src/odb.h b/src/odb.h
new file mode 100644
index 000000000..2f205b20f
--- /dev/null
+++ b/src/odb.h
@@ -0,0 +1,19 @@
+#ifndef INCLUDE_odb_h__
+#define INCLUDE_odb_h__
+
+/** First 4 bytes of a pack-*.idx file header.
+ *
+ * Note this header exists only in idx v2 and later.  The idx v1
+ * file format does not have a magic sequence at the front, and
+ * must be detected by the first four bytes *not* being this value
+ * and the first 8 bytes matching the following expression:
+ *
+ *   uint32_t *fanout = ... the file data at offset 0 ...
+ *   ntohl(fanout[0]) < ntohl(fanout[1])
+ *
+ * The value chosen here for PACK_TOC is such that the above
+ * cannot be true for an idx v1 file.
+ */
+#define PACK_TOC 0xff744f63 /* -1tOc */
+
+#endif