Optimize stripos/stristr

Closes GH-7847
Closes GH-7852

Previously stripos/stristr would lowercase both the haystack and the
needle to reuse strpos. The approach in this PR is similar to strpos.
memchr is highly optimized so we're using it to search for the first
character of the needle in the haystack. If we find it we compare the
remaining characters of the needle manually.

The new implementation seems to perform about half as well as strpos (as
two memchr calls are necessary to find the next candidate).

NEWS

@@ -20,6 +20,8 @@ PHP                                                                        NEWS
   . net_get_interfaces() also reports wireless network interfaces on Windows.
     (Yurun)
   . Finished AVIF support in getimagesize(). (Yannis Guyon)
+  . Fixed bug GH-7847 (stripos with large haystack has bad performance).
+    (ilutov)
 
 - Zip:
   . add ZipArchive::clearError() method

UPGRADING.INTERNALS

@@ -17,6 +17,9 @@ PHP 8.2 INTERNALS UPGRADE NOTES
   zend_binary_str(n)casecmp() as one would expect. Call the appropriate
   wrapped function directly instead.
 * Removed the (ZEND_)WRONG_PARAM_COUNT_WITH_RETVAL() macros.
+* php_stristr() no longer lowercases the haystack and needle as a side effect.
+  Call zend_str_tolower() yourself if necessary. You no longer need to copy
+  the haystack and needle before passing them to php_stristr().
 
 ========================
 2. Build system changes

Zend/zend_operators.h

@@ -919,6 +919,67 @@ static zend_always_inline void zend_unwrap_reference(zval *op) /* {{{ */
 }
 /* }}} */
 
+static zend_always_inline bool zend_strnieq(const char *ptr1, const char *ptr2, size_t num)
+{
+	const char *end = ptr1 + num;
+	while (ptr1 < end) {
+		if (zend_tolower_ascii(*ptr1++) != zend_tolower_ascii(*ptr2++)) {
+			return 0;
+		}
+	}
+	return 1;
+}
+
+static zend_always_inline const char *
+zend_memnistr(const char *haystack, const char *needle, size_t needle_len, const char *end)
+{
+	ZEND_ASSERT(end >= haystack);
+
+	if (UNEXPECTED(needle_len == 0)) {
+		return haystack;
+	}
+
+	if (UNEXPECTED(needle_len > (end - haystack))) {
+		return NULL;
+	}
+
+	const char first_lower = zend_tolower_ascii(*needle);
+	const char first_upper = zend_toupper_ascii(*needle);
+	const char *p_lower = (const char *)memchr(haystack, first_lower, end - haystack);
+	const char *p_upper = NULL;
+	if (first_lower != first_upper) { 
+		// If the needle length is 1 we don't need to look beyond p_lower as it is a guaranteed match
+		size_t upper_search_length = end - (needle_len == 1 && p_lower != NULL ? p_lower : haystack);
+		p_upper = (const char *)memchr(haystack, first_upper, upper_search_length);
+	}
+	const char *p = !p_upper || (p_lower && p_lower < p_upper) ? p_lower : p_upper;
+
+	if (needle_len == 1) {
+		return p;
+	}
+
+	const char needle_end_lower = zend_tolower_ascii(needle[needle_len - 1]);
+	const char needle_end_upper = zend_toupper_ascii(needle[needle_len - 1]);
+	end -= needle_len;
+
+	while (p && p <= end) {
+		if (needle_end_lower == p[needle_len - 1] || needle_end_upper == p[needle_len - 1]) {
+			if (zend_strnieq(needle + 1, p + 1, needle_len - 2)) {
+				return p;
+			}
+		}
+		if (p_lower == p) {
+			p_lower = (const char *)memchr(p_lower + 1, first_lower, end - p_lower);
+		}
+		if (p_upper == p) {
+			p_upper = (const char *)memchr(p_upper + 1, first_upper, end - p_upper);
+		}
+		p = !p_upper || (p_lower && p_lower < p_upper) ? p_lower : p_upper;
+	}
+
+	return NULL;
+}
+
 
 END_EXTERN_C()
 

ext/libxml/libxml.c

@@ -378,9 +378,9 @@ php_libxml_input_buffer_create_filename(const char *URI, xmlCharEncoding enc)
 				const char buf[] = "Content-Type:";
 				if (Z_TYPE_P(header) == IS_STRING &&
 						!zend_binary_strncasecmp(Z_STRVAL_P(header), Z_STRLEN_P(header), buf, sizeof(buf)-1, sizeof(buf)-1)) {
-					char *needle = estrdup("charset=");
+					char needle[] = "charset=";
 					char *haystack = estrndup(Z_STRVAL_P(header), Z_STRLEN_P(header));
-					char *encoding = php_stristr(haystack, needle, Z_STRLEN_P(header), sizeof("charset=")-1);
+					char *encoding = php_stristr(haystack, needle, Z_STRLEN_P(header), strlen(needle));
 
 					if (encoding) {
 						char *end;
@@ -408,7 +408,6 @@ php_libxml_input_buffer_create_filename(const char *URI, xmlCharEncoding enc)
 						}
 					}
 					efree(haystack);
-					efree(needle);
 					break; /* found content-type */
 				}
 			} ZEND_HASH_FOREACH_END();

ext/phar/phar.c

@@ -2531,7 +2531,6 @@ int phar_flush(phar_archive_data *phar, char *user_stub, zend_long len, int conv
 {
 	char halt_stub[] = "__HALT_COMPILER();";
 	zend_string *newstub;
-	char *tmp;
 	phar_entry_info *entry, *newentry;
 	size_t halt_offset;
 	int restore_alias_len, global_flags = 0, closeoldfile;
@@ -2635,9 +2634,7 @@ int phar_flush(phar_archive_data *phar, char *user_stub, zend_long len, int conv
 		} else {
 			free_user_stub = 0;
 		}
-		tmp = estrndup(user_stub, len);
-		if ((pos = php_stristr(tmp, halt_stub, len, sizeof(halt_stub) - 1)) == NULL) {
-			efree(tmp);
+		if ((pos = php_stristr(user_stub, halt_stub, len, sizeof(halt_stub) - 1)) == NULL) {
 			if (closeoldfile) {
 				php_stream_close(oldfile);
 			}
@@ -2650,8 +2647,6 @@ int phar_flush(phar_archive_data *phar, char *user_stub, zend_long len, int conv
 			}
 			return EOF;
 		}
-		pos = user_stub + (pos - tmp);
-		efree(tmp);
 		len = pos - user_stub + 18;
 		if ((size_t)len != php_stream_write(newfile, user_stub, len)
 		||			  5 != php_stream_write(newfile, " ?>\r\n", 5)) {

ext/phar/tar.c

@@ -967,7 +967,7 @@ int phar_tar_flush(phar_archive_data *phar, char *user_stub, zend_long len, int
 	int closeoldfile, free_user_stub;
 	size_t signature_length;
 	struct _phar_pass_tar_info pass;
-	char *buf, *signature, *tmp, sigbuf[8];
+	char *buf, *signature, sigbuf[8];
 	char halt_stub[] = "__HALT_COMPILER();";
 
 	entry.flags = PHAR_ENT_PERM_DEF_FILE;
@@ -1063,9 +1063,7 @@ int phar_tar_flush(phar_archive_data *phar, char *user_stub, zend_long len, int
 			free_user_stub = 0;
 		}
 
-		tmp = estrndup(user_stub, len);
-		if ((pos = php_stristr(tmp, halt_stub, len, sizeof(halt_stub) - 1)) == NULL) {
-			efree(tmp);
+		if ((pos = php_stristr(user_stub, halt_stub, len, sizeof(halt_stub) - 1)) == NULL) {
 			if (error) {
 				spprintf(error, 0, "illegal stub for tar-based phar \"%s\"", phar->fname);
 			}
@@ -1074,8 +1072,6 @@ int phar_tar_flush(phar_archive_data *phar, char *user_stub, zend_long len, int
 			}
 			return EOF;
 		}
-		pos = user_stub + (pos - tmp);
-		efree(tmp);
 
 		len = pos - user_stub + 18;
 		entry.fp = php_stream_fopen_tmpfile();

ext/phar/zip.c

@@ -1202,7 +1202,6 @@ int phar_zip_flush(phar_archive_data *phar, char *user_stub, zend_long len, int
 	char *pos;
 	static const char newstub[] = "<?php // zip-based phar archive stub file\n__HALT_COMPILER();";
 	char halt_stub[] = "__HALT_COMPILER();";
-	char *tmp;
 
 	php_stream *stubfile, *oldfile;
 	int free_user_stub, closeoldfile = 0;
@@ -1305,9 +1304,7 @@ int phar_zip_flush(phar_archive_data *phar, char *user_stub, zend_long len, int
 			free_user_stub = 0;
 		}
 
-		tmp = estrndup(user_stub, len);
-		if ((pos = php_stristr(tmp, halt_stub, len, sizeof(halt_stub) - 1)) == NULL) {
-			efree(tmp);
+		if ((pos = php_stristr(user_stub, halt_stub, len, sizeof(halt_stub) - 1)) == NULL) {
 			if (error) {
 				spprintf(error, 0, "illegal stub for zip-based phar \"%s\"", phar->fname);
 			}
@@ -1316,8 +1313,6 @@ int phar_zip_flush(phar_archive_data *phar, char *user_stub, zend_long len, int
 			}
 			return EOF;
 		}
-		pos = user_stub + (pos - tmp);
-		efree(tmp);
 
 		len = pos - user_stub + 18;
 		entry.fp = php_stream_fopen_tmpfile();

ext/standard/string.c

@@ -1687,9 +1687,7 @@ PHP_FUNCTION(pathinfo)
    case insensitive strstr */
 PHPAPI char *php_stristr(char *s, char *t, size_t s_len, size_t t_len)
 {
-	zend_str_tolower(s, s_len);
-	zend_str_tolower(t, t_len);
-	return (char*)php_memnstr(s, t, t_len, s + s_len);
+	return (char*)php_memnistr(s, t, t_len, s + s_len);
 }
 /* }}} */
 
@@ -1735,8 +1733,6 @@ PHP_FUNCTION(stristr)
 	zend_string *haystack, *needle;
 	const char *found = NULL;
 	size_t  found_offset;
-	char *haystack_dup;
-	char *orig_needle;
 	bool part = 0;
 
 	ZEND_PARSE_PARAMETERS_START(2, 3)
@@ -1746,13 +1742,10 @@ PHP_FUNCTION(stristr)
 		Z_PARAM_BOOL(part)
 	ZEND_PARSE_PARAMETERS_END();
 
-	haystack_dup = estrndup(ZSTR_VAL(haystack), ZSTR_LEN(haystack));
-	orig_needle = estrndup(ZSTR_VAL(needle), ZSTR_LEN(needle));
-	found = php_stristr(haystack_dup, orig_needle, ZSTR_LEN(haystack), ZSTR_LEN(needle));
-	efree(orig_needle);
+	found = php_stristr(ZSTR_VAL(haystack), ZSTR_VAL(needle), ZSTR_LEN(haystack), ZSTR_LEN(needle));
 
 	if (found) {
-		found_offset = found - haystack_dup;
+		found_offset = found - ZSTR_VAL(haystack);
 		if (part) {
 			RETVAL_STRINGL(ZSTR_VAL(haystack), found_offset);
 		} else {
@@ -1761,8 +1754,6 @@ PHP_FUNCTION(stristr)
 	} else {
 		RETVAL_FALSE;
 	}
-
-	efree(haystack_dup);
 }
 /* }}} */
 
@@ -1890,7 +1881,6 @@ PHP_FUNCTION(stripos)
 	const char *found = NULL;
 	zend_string *haystack, *needle;
 	zend_long offset = 0;
-	zend_string *needle_dup = NULL, *haystack_dup;
 
 	ZEND_PARSE_PARAMETERS_START(2, 3)
 		Z_PARAM_STR(haystack)
@@ -1907,23 +1897,14 @@ PHP_FUNCTION(stripos)
 		RETURN_THROWS();
 	}
 
-	if (ZSTR_LEN(needle) > ZSTR_LEN(haystack)) {
-		RETURN_FALSE;
-	}
-
-	haystack_dup = zend_string_tolower(haystack);
-	needle_dup = zend_string_tolower(needle);
-	found = (char*)php_memnstr(ZSTR_VAL(haystack_dup) + offset,
-			ZSTR_VAL(needle_dup), ZSTR_LEN(needle_dup), ZSTR_VAL(haystack_dup) + ZSTR_LEN(haystack));
+	found = (char*)php_memnistr(ZSTR_VAL(haystack) + offset,
+			ZSTR_VAL(needle), ZSTR_LEN(needle), ZSTR_VAL(haystack) + ZSTR_LEN(haystack));
 
 	if (found) {
-		RETVAL_LONG(found - ZSTR_VAL(haystack_dup));
+		RETVAL_LONG(found - ZSTR_VAL(haystack));
 	} else {
 		RETVAL_FALSE;
 	}
-
-	zend_string_release_ex(haystack_dup, 0);
-	zend_string_release_ex(needle_dup, 0);
 }
 /* }}} */
 

main/php.h

@@ -344,6 +344,7 @@ END_EXTERN_C()
 #define phpin zendin
 
 #define php_memnstr zend_memnstr
+#define php_memnistr zend_memnistr
 
 /* functions */
 BEGIN_EXTERN_C()