sha1: Add new notmuch_sha1_of_string function

We'll be using this for storing really long terms in the database
and when we just need to look them up, (and never read back the
original data directly from the database). For example, storing
arbitrarily long directory paths in the database along with
mtime timestamps.

Note that if we did want to store arbitrarily long terms and also
be able to read them back, the Xapian folks recommending splitting
the term off with multiple prefixes. See the note near the end
of this page:

http://trac.xapian.org/wiki/FAQ/UniqueIds

notmuch-private.h

@@ -217,15 +217,9 @@ notmuch_parse_date (const char *str, int *tz_offset);
 
 /* sha1.c */
 
-/* Create a hexadecimal string version of the SHA-1 digest of the
+char *
- * named file.
+notmuch_sha1_of_string (const char *str);
- *
+
- * 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);
 

sha1.c

@@ -25,6 +25,54 @@
 /* Just some simple interfaces on top of libsha1 so that we can leave
  * libsha1 as untouched as possible. */
 
+static char *
+_hex_of_sha1_digest (const unsigned char digest[SHA1_DIGEST_SIZE])
+{
+    char *result, *r;
+    int i;
+
+    result = xcalloc (SHA1_DIGEST_SIZE * 2 + 1, 1);
+
+    for (r = result, i = 0;
+	 i < SHA1_DIGEST_SIZE;
+	 r += 2, i++)
+    {
+	sprintf (r, "%02x", digest[i]);
+    }
+
+    return result;
+}
+
+/* Create a hexadcimal string version of the SHA-1 digest of 'str'
+ * (including its null terminating character).
+ *
+ * This function returns a newly allocated string which the caller
+ * should free() when finished.
+ */
+char *
+notmuch_sha1_of_string (const char *str)
+{
+    sha1_ctx sha1;
+    unsigned char digest[SHA1_DIGEST_SIZE];
+
+    sha1_begin (&sha1);
+
+    sha1_hash ((unsigned char *) str, strlen (str) + 1, &sha1);
+
+    sha1_end (digest, &sha1);
+
+    return _hex_of_sha1_digest (digest);
+}
+
+/* Create a hexadecimal string version of the SHA-1 digest of the
+ * contents 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)
 {
@@ -34,8 +82,7 @@ notmuch_sha1_of_file (const char *filename)
     size_t bytes_read;
     sha1_ctx sha1;
     unsigned char digest[SHA1_DIGEST_SIZE];
-    char *result, *r;
+    char *result;
-    int i;
 
     file = fopen (filename, "r");
     if (file == NULL)
@@ -59,16 +106,7 @@ notmuch_sha1_of_file (const char *filename)
 
     sha1_end (digest, &sha1);
 
-    result = calloc (SHA1_DIGEST_SIZE * 2 + 1, 1);
+    result = _hex_of_sha1_digest (digest);
-    if (result == NULL)
-	return NULL;
-
-    for (r = result, i = 0;
-	 i < SHA1_DIGEST_SIZE;
-	 r += 2, i++)
-    {
-	sprintf (r, "%02x", digest[i]);
-    }
 
     fclose (file);