分析PHP的similar_text函數

//比較字串,返回兩個字串第一個相同字符的區域 static void php_similar_str(const char *txt1, int len1, const char *txt2, int len2, int *pos1, int *pos2, int *max) { char *p, *q; char *end1 = (char *) txt1 + len1; char *end2 = (char *) txt2 + len2; int l; *max = 0; //遍曆字串 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) { //保存相同區域信息 *max = l; *pos1 = p - txt1; *pos2 = q - txt2; } } } } //遞歸函數,比較txt1和txt2的相同字符數量 static int php_similar_char(const char *txt1, int len1, const char *txt2, int len2) { int sum; int pos1, pos2, max; php_similar_str(txt1, len1, txt2, len2, &pos1, &pos2, &max); if ((sum = max)) {//這樣寫有什麽意義?????!!!!! //遞歸上次不同部分的前部 if (pos1 && pos2) { sum += php_similar_char(txt1, pos1, txt2, pos2); } //遞歸上次不同部分的後部 if ((pos1 + max < len1) && (pos2 + max < len2)) { sum += php_similar_char(txt1 + pos1 + max, len1 - pos1 - max, txt2 + pos2 + max, len2 - pos2 - max); } } //返回本次比較後的相同字符數量 return sum; } //PHP函數本身，一堆宏，做了些串轉換和返回值換算,主功能由上面兩個函數做了。 PHP_FUNCTION(similar_text) { zval **t1, **t2, **percent; int ac = ZEND_NUM_ARGS(); int sim; if (ac < 2 || ac > 3 || zend_get_parameters_ex(ac, &t1, &t2, &percent) == FAILURE) { WRONG_PARAM_COUNT; } convert_to_string_ex(t1); convert_to_string_ex(t2); if (ac > 2) { convert_to_double_ex(percent); } if (Z_STRLEN_PP(t1) + Z_STRLEN_PP(t2) == 0) { if (ac > 2) { Z_DVAL_PP(percent) = 0; } RETURN_LONG(0); } sim = php_similar_char(Z_STRVAL_PP(t1), Z_STRLEN_PP(t1), Z_STRVAL_PP(t2), Z_STRLEN_PP(t2)); if (ac > 2) { Z_DVAL_PP(percent) = sim * 200.0 / (Z_STRLEN_PP(t1) + Z_STRLEN_PP(t2)); } RETURN_LONG(sim); } 所有看出similar_text是根據ASCII做比較的，是不考慮詞組問題的。 測試了一下，結果如下： int main(int argc, char *argv[]) { char *str1="weican wuxin"; char *str2="wuxin weican"; int pos1,pos2,max; php_similar_str(str1,strlen(str1),str2,strlen(str2),&pos1,&pos2,&max); printf("php_similar_str:%d,%d=%d\n",pos1,pos2,max); max=php_similar_char(str1,strlen(str1),str2,strlen(str2)); printf("php_similar_char:%d\n",max); system("PAUSE"); return 0; } php_similar_str:0,6=6 php_similar_char:6 char *str1="TCP協議通訊工作原a理"; char *str2="TCPa協議通訊工作原理"; php_similar_str:3,4=14 php_similar_char:19