Speed up unquoting of quoted double quotes and backslashes.

diff --git a/WHATS_NEW b/WHATS_NEW
index 51959eb56dab9e9b2f5f2c9ea07c031b3ca096b9..a97379110e30a1daf49662967faf2a7d3c3d415f 100644 (file)
--- a/WHATS_NEW
+++ b/WHATS_NEW
@@ -1,5 +1,6 @@
 Version 2.02.75 - 
 =====================================
+  Speed up unquoting of quoted double quotes and backslashes.
   Speed up CRC32 calculations by using a larger lookup table.
 
 Version 2.02.74 - 24th September 2010

diff --git a/lib/misc/lvm-string.c b/lib/misc/lvm-string.c
index 960157e9618853cf4c71febc11e68fa2be31a4e2..675fb8229eb16faea218188c5035b26292b89a3e 100644 (file)
--- a/lib/misc/lvm-string.c
+++ b/lib/misc/lvm-string.c
@@ -108,33 +108,64 @@ static void _quote_characters(char **out, const char *src,
        }
 }
 
+static void _unquote_one_character(char *src, const char orig_char,
+                                  const char quote_char)
+{
+       char *out;
+       char s, n;
+
+       /* Optimise for the common case where no changes are needed. */
+       while ((s = *src++)) {
+               if (s == quote_char &&
+                   ((n = *src) == orig_char || n == quote_char)) {
+                       out = src++;
+                       *(out - 1) = n;
+
+                       while ((s = *src++)) {
+                               if (s == quote_char &&
+                                   ((n = *src) == orig_char || n == quote_char)) {
+                                       s = n;
+                                       src++;
+                               }
+                               *out = s;
+                               out++;
+                       }
+
+                       *out = '\0';
+                       return;
+               }
+       }
+}
+
 /*
  * Unquote each character given in orig_char array and unquote quote_char
- * as well. The array ends up with '\0' character. Also save the first
- * occurence of each character from orig_char that was found unquoted in
- * arr_substr_first_unquoted array. This way we can process several
- * characters in one go.
+ * as well. Also save the first occurrence of each character from orig_char
+ * that was found unquoted in arr_substr_first_unquoted array. This way we can
+ * process several characters in one go.
  */
-static void _unquote_characters(char *src, const int orig_chars[],
-                               const int quote_char,
+static void _unquote_characters(char *src, const char *orig_chars,
+                               const int num_orig_chars, 
+                               const char quote_char,
                                char *arr_substr_first_unquoted[])
 {
        char *out = src;
-       int c;
-       int i;
-
-       while (*src) {
-               for (i = 0; (c = orig_chars[i]); i++) {
-                       if (*src == quote_char &&
-                           (*(src + 1) == c || *(src + 1) == quote_char)) {
+       char c, s, n;
+       unsigned i;
+
+       while ((s = *src++)) {
+               for (i = 0; i < num_orig_chars; i++) {
+                       c = orig_chars[i];
+                       if (s == quote_char &&
+                           ((n = *src) == c || n == quote_char)) {
+                               s = n;
                                src++;
                                break;
                        }
-                       else if (arr_substr_first_unquoted && (*src == c) &&
-                                !arr_substr_first_unquoted[i])
+                       if (arr_substr_first_unquoted && (s == c) &&
+                           !arr_substr_first_unquoted[i])
                                arr_substr_first_unquoted[i] = out;
-               }
-               *out++ = *src++;
+               };
+               *out++ = s;
        }
 
        *out = '\0';
@@ -229,9 +260,7 @@ char *escape_double_quotes(char *out, const char *src)
  */
 void unescape_double_quotes(char *src)
 {
-       const int orig_chars[] = {'\"', '\0'};
-
-       _unquote_characters(src, orig_chars, '\\', NULL);
+       _unquote_one_character(src, '\"', '\\');
 }
 
 /*
@@ -244,10 +273,10 @@ void unescape_colons_and_at_signs(char *src,
                                  char **substr_first_unquoted_colon,
                                  char **substr_first_unquoted_at_sign)
 {
-       const int orig_chars[] = {':', '@', '\0'};
+       const char *orig_chars = ":@";
        char *arr_substr_first_unquoted[] = {NULL, NULL, NULL};
 
-       _unquote_characters(src, orig_chars, '\\', arr_substr_first_unquoted);
+       _unquote_characters(src, orig_chars, 2, '\\', arr_substr_first_unquoted);
 
        if (substr_first_unquoted_colon)
                *substr_first_unquoted_colon = arr_substr_first_unquoted[0];