Improve similar_text(), reduce recursive call to php_similar_char()

If the longest common substring is the leftmost common substring, there
is no need to check the string prefixes for further common substrings,
since there are none.

diff --git a/ext/standard/string.c b/ext/standard/string.c
index 42e58ca498304f9280453df8cb255cb272048ca1..12e91dc11234c14146a6ac49fde1e7b4feea9fd2 100644 (file)
--- a/ext/standard/string.c
+++ b/ext/standard/string.c
@@ -3557,7 +3557,7 @@ PHP_FUNCTION(strrev)
 
 /* {{{ php_similar_str
  */
-static void php_similar_str(const char *txt1, size_t len1, const char *txt2, size_t len2, size_t *pos1, size_t *pos2, size_t *max)
+static void php_similar_str(const char *txt1, size_t len1, const char *txt2, size_t len2, size_t *pos1, size_t *pos2, size_t *max, size_t *count)
 {
        char *p, *q;
        char *end1 = (char *) txt1 + len1;
@@ -3565,11 +3565,13 @@ static void php_similar_str(const char *txt1, size_t len1, const char *txt2, siz
        size_t l;
 
        *max = 0;
+       *count = 0;
        for (p = (char *) txt1; p < end1; p++) {
                for (q = (char *) txt2; q < end2; q++) {
                        for (l = 0; (p + l < end1) && (q + l < end2) && (p[l] == q[l]); l++);
                        if (l > *max) {
                                *max = l;
+                               *count += 1;
                                *pos1 = p - txt1;
                                *pos2 = q - txt2;
                        }
@@ -3583,11 +3585,11 @@ static void php_similar_str(const char *txt1, size_t len1, const char *txt2, siz
 static size_t php_similar_char(const char *txt1, size_t len1, const char *txt2, size_t len2)
 {
        size_t sum;
-       size_t pos1 = 0, pos2 = 0, max;
+       size_t pos1 = 0, pos2 = 0, max, count;
 
-       php_similar_str(txt1, len1, txt2, len2, &pos1, &pos2, &max);
+       php_similar_str(txt1, len1, txt2, len2, &pos1, &pos2, &max, &count);
        if ((sum = max)) {
-               if (pos1 && pos2) {
+               if (pos1 && pos2 && count > 1) {
                        sum += php_similar_char(txt1, pos1,
                                                                        txt2, pos2);
                }