mu: optimize indexing (get_uid_term)

Some users were report seeing get_uid_term high in the profiles; so
optimize this:

- make mu_util_get_hash a static inline function (used by get_uid_term)
- don't use 'realpath' in get_uid_term, seem that's the main culprit
- some slight faster string handling there too.

lib/mu-store-priv.hh

@@ -177,7 +177,8 @@ public:
 			mu_contacts_clear (_contacts);
 	}
 
-	std::string get_uid_term (const char *path) const;
+	// not re-entrant; stays valid until called again
+	const char *get_uid_term (const char *path) const;
 
 	MuContacts* contacts() { return _contacts; }
 

lib/mu-store-read.cc

@@ -44,24 +44,16 @@
 
 
 // note: not re-entrant
-std::string
+const char*
 _MuStore::get_uid_term (const char* path) const
 {
-	char real_path[PATH_MAX + 1];
+	static char uid_term[64] = { '\0' };
+	if (G_UNLIKELY(uid_term[0] == '\0'))
+		uid_term[0] = mu_msg_field_xapian_prefix(MU_MSG_FIELD_ID_UID);
 
-	static const std::string uid_prefix (
-		1, mu_msg_field_xapian_prefix(MU_MSG_FIELD_ID_UID));
+	strncpy (uid_term + 1, mu_util_get_hash (path), sizeof(uid_term) - 1);
 
-	/* check profile to see if realpath is expensive; we need
-	 * realpath here (and in mu-msg-file) to ensure that the same
-	 * messages are only considered ones (ignore e.g. symlinks and
-	 * '//' in paths) */
-
-	// note: realpath fails when there's no file at path
-	if (!realpath (path, real_path))
-		strcpy (real_path, path);
-
-	return std::string (uid_prefix + mu_util_get_hash (real_path));
+	return uid_term;
 }
 
 
@@ -72,7 +64,6 @@ mu_store_new_read_only (const char* xpath, GError **err)
 
 	try {
 		return new _MuStore (xpath);
-
 	} catch (const MuStoreError& merr) {
 		mu_util_g_set_error (err, merr.mu_error(), "%s",
 				     merr.what().c_str());

lib/mu-util.c

@@ -559,25 +559,3 @@ mu_util_read_password (const char *prompt)
 }
 
 
-const char*
-mu_util_get_hash (const char* str)
-{
-	unsigned	djbhash, bkdrhash, bkdrseed;
-	unsigned	u;
-	static char	hex[18];
-
-	g_return_val_if_fail (str, NULL);
-
-	djbhash  = 5381;
-	bkdrhash = 0;
-	bkdrseed = 1313;
-
-	for(u = 0; str[u]; ++u) {
-		djbhash  = ((djbhash << 5) + djbhash) + str[u];
-		bkdrhash = bkdrhash * bkdrseed + str[u];
-	}
-
-	snprintf (hex, sizeof(hex), "%08x%08x", djbhash, bkdrhash);
-
-	return hex;
-}

lib/mu-util.h

@@ -513,9 +513,26 @@ gboolean mu_util_g_set_error (GError **err, MuError errcode, const char *frm, ..
  * @return the hash as a static string, which stays valid until this
  * function is called again.
  */
-const char* mu_util_get_hash (const char* str);
+static inline const char*
+mu_util_get_hash (const char* str)
+{
+	unsigned	djbhash, bkdrhash, bkdrseed;
+	unsigned	u;
+	static char	hex[18];
 
+	djbhash  = 5381;
+	bkdrhash = 0;
+	bkdrseed = 1313;
 
+	for(u = 0; str[u]; ++u) {
+		djbhash  = ((djbhash << 5) + djbhash) + str[u];
+		bkdrhash = bkdrhash * bkdrseed + str[u];
+	}
+
+	snprintf (hex, sizeof(hex), "%08x%08x", djbhash, bkdrhash);
+
+	return hex;
+}
 
 
 #define MU_COLOR_RED		"\x1b[31m"