+/* sha1.c */
+
+/* Create a hexadecimal string version of the SHA-1 digest of the
+ * named file.
+ *
+ * This function returns a newly allocated string which the caller
+ * should free() when finished.
+ *
+ * If any error occurs while reading the file, (permission denied,
+ * file not found, etc.), this function returns NULL.
+ */
+char *
+notmuch_sha1_of_file (const char *filename);
+