php-src/Zend/zend_smart_str.h
Arnaud Le Blanc 4df3dd7679
Reduce memory allocated by var_export, json_encode, serialize, and other (#8902)
smart_str uses an over-allocated string to optimize for append operations. Functions that use smart_str tend to return the over-allocated string directly. This results in unnecessary memory usage, especially for small strings.

The overhead can be up to 231 bytes for strings smaller than that, and 4095 for other strings. This can be avoided for strings smaller than `4096 - zend_string header size - 1` by reallocating the string.

This change introduces `smart_str_trim_to_size()`, and calls it in `smart_str_extract()`. Functions that use `smart_str` are updated to use `smart_str_extract()`.

Fixes GH-8896
2022-07-08 14:47:46 +02:00

169 lines
6.1 KiB
C

/*
+----------------------------------------------------------------------+
| Copyright (c) The PHP Group |
+----------------------------------------------------------------------+
| This source file is subject to version 3.01 of the PHP license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| https://www.php.net/license/3_01.txt |
| If you did not receive a copy of the PHP license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@php.net so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Author: Sascha Schumann <sascha@schumann.cx> |
+----------------------------------------------------------------------+
*/
#ifndef ZEND_SMART_STR_H
#define ZEND_SMART_STR_H
#include <zend.h>
#include "zend_globals.h"
#include "zend_smart_str_public.h"
#define smart_str_appends_ex(dest, src, what) \
smart_str_appendl_ex((dest), (src), strlen(src), (what))
#define smart_str_appends(dest, src) \
smart_str_appendl((dest), (src), strlen(src))
#define smart_str_extract(dest) \
smart_str_extract_ex((dest), 0)
#define smart_str_trim_to_size(dest) \
smart_str_trim_to_size_ex((dest), 0)
#define smart_str_extend(dest, len) \
smart_str_extend_ex((dest), (len), 0)
#define smart_str_appendc(dest, c) \
smart_str_appendc_ex((dest), (c), 0)
#define smart_str_appendl(dest, src, len) \
smart_str_appendl_ex((dest), (src), (len), 0)
#define smart_str_append(dest, src) \
smart_str_append_ex((dest), (src), 0)
#define smart_str_append_smart_str(dest, src) \
smart_str_append_smart_str_ex((dest), (src), 0)
#define smart_str_sets(dest, src) \
smart_str_setl((dest), (src), strlen(src));
#define smart_str_append_long(dest, val) \
smart_str_append_long_ex((dest), (val), 0)
#define smart_str_append_unsigned(dest, val) \
smart_str_append_unsigned_ex((dest), (val), 0)
#define smart_str_free(dest) \
smart_str_free_ex((dest), 0)
BEGIN_EXTERN_C()
ZEND_API void ZEND_FASTCALL smart_str_erealloc(smart_str *str, size_t len);
ZEND_API void ZEND_FASTCALL smart_str_realloc(smart_str *str, size_t len);
ZEND_API void ZEND_FASTCALL smart_str_append_escaped(smart_str *str, const char *s, size_t l);
/* If zero_fraction is true, then a ".0" will be added to numbers that would not otherwise
* have a fractional part and look like integers. */
ZEND_API void ZEND_FASTCALL smart_str_append_double(
smart_str *str, double num, int precision, bool zero_fraction);
ZEND_API void smart_str_append_printf(smart_str *dest, const char *format, ...)
ZEND_ATTRIBUTE_FORMAT(printf, 2, 3);
ZEND_API void ZEND_FASTCALL smart_str_append_escaped_truncated(smart_str *str, zend_string *value, size_t length);
ZEND_API void ZEND_FASTCALL smart_str_append_scalar(smart_str *str, zval *value, size_t truncate);
END_EXTERN_C()
static zend_always_inline size_t smart_str_alloc(smart_str *str, size_t len, bool persistent) {
if (UNEXPECTED(!str->s)) {
goto do_smart_str_realloc;
} else {
len += ZSTR_LEN(str->s);
if (UNEXPECTED(len >= str->a)) {
do_smart_str_realloc:
if (persistent) {
smart_str_realloc(str, len);
} else {
smart_str_erealloc(str, len);
}
}
}
return len;
}
static zend_always_inline char* smart_str_extend_ex(smart_str *dest, size_t len, bool persistent) {
size_t new_len = smart_str_alloc(dest, len, persistent);
char *ret = ZSTR_VAL(dest->s) + ZSTR_LEN(dest->s);
ZSTR_LEN(dest->s) = new_len;
return ret;
}
static zend_always_inline void smart_str_free_ex(smart_str *str, bool persistent) {
if (str->s) {
zend_string_release_ex(str->s, persistent);
str->s = NULL;
}
str->a = 0;
}
static zend_always_inline void smart_str_0(smart_str *str) {
if (str->s) {
ZSTR_VAL(str->s)[ZSTR_LEN(str->s)] = '\0';
}
}
static zend_always_inline size_t smart_str_get_len(smart_str *str) {
return str->s ? ZSTR_LEN(str->s) : 0;
}
static zend_always_inline void smart_str_trim_to_size_ex(smart_str *str, bool persistent)
{
if (str->s && str->a > ZSTR_LEN(str->s)) {
str->s = zend_string_realloc(str->s, ZSTR_LEN(str->s), persistent);
str->a = ZSTR_LEN(str->s);
}
}
static zend_always_inline zend_string *smart_str_extract_ex(smart_str *str, bool persistent) {
if (str->s) {
zend_string *res;
smart_str_0(str);
smart_str_trim_to_size_ex(str, persistent);
res = str->s;
str->s = NULL;
return res;
} else {
return ZSTR_EMPTY_ALLOC();
}
}
static zend_always_inline void smart_str_appendc_ex(smart_str *dest, char ch, bool persistent) {
size_t new_len = smart_str_alloc(dest, 1, persistent);
ZSTR_VAL(dest->s)[new_len - 1] = ch;
ZSTR_LEN(dest->s) = new_len;
}
static zend_always_inline void smart_str_appendl_ex(smart_str *dest, const char *str, size_t len, bool persistent) {
size_t new_len = smart_str_alloc(dest, len, persistent);
memcpy(ZSTR_VAL(dest->s) + ZSTR_LEN(dest->s), str, len);
ZSTR_LEN(dest->s) = new_len;
}
static zend_always_inline void smart_str_append_ex(smart_str *dest, const zend_string *src, bool persistent) {
smart_str_appendl_ex(dest, ZSTR_VAL(src), ZSTR_LEN(src), persistent);
}
static zend_always_inline void smart_str_append_smart_str_ex(smart_str *dest, const smart_str *src, bool persistent) {
if (src->s && ZSTR_LEN(src->s)) {
smart_str_append_ex(dest, src->s, persistent);
}
}
static zend_always_inline void smart_str_append_long_ex(smart_str *dest, zend_long num, bool persistent) {
char buf[32];
char *result = zend_print_long_to_buf(buf + sizeof(buf) - 1, num);
smart_str_appendl_ex(dest, result, buf + sizeof(buf) - 1 - result, persistent);
}
static zend_always_inline void smart_str_append_unsigned_ex(smart_str *dest, zend_ulong num, bool persistent) {
char buf[32];
char *result = zend_print_ulong_to_buf(buf + sizeof(buf) - 1, num);
smart_str_appendl_ex(dest, result, buf + sizeof(buf) - 1 - result, persistent);
}
static zend_always_inline void smart_str_setl(smart_str *dest, const char *src, size_t len) {
smart_str_free(dest);
smart_str_appendl(dest, src, len);
}
#endif