/src/php-src/Zend/zend_arena.h

Source
/*
   +----------------------------------------------------------------------+
   | Zend Engine                                                          |
   +----------------------------------------------------------------------+
   | Copyright © Zend Technologies Ltd., a subsidiary company of          |
   |     Perforce Software, Inc., and Contributors.                       |
   +----------------------------------------------------------------------+
   | This source file is subject to the Modified BSD License that is      |
   | bundled with this package in the file LICENSE, and is available      |
   | through the World Wide Web at <https://www.php.net/license/>.        |
   |                                                                      |
   | SPDX-License-Identifier: BSD-3-Clause                                |
   +----------------------------------------------------------------------+
   | Authors: Dmitry Stogov <dmitry@php.net>                              |
   +----------------------------------------------------------------------+
*/

#ifndef _ZEND_ARENA_H_
#define _ZEND_ARENA_H_

#include "zend.h"

#ifndef ZEND_TRACK_ARENA_ALLOC

typedef struct _zend_arena zend_arena;

struct _zend_arena {
  char    *ptr;
  char    *end;
  zend_arena  *prev;
};

static zend_always_inline zend_arena* zend_arena_create(size_t size)
{
  zend_arena *arena = (zend_arena*)emalloc(size);

  arena->ptr = (char*) arena + ZEND_MM_ALIGNED_SIZE(sizeof(zend_arena));
  arena->end = (char*) arena + size;
  arena->prev = NULL;
  return arena;
}

static zend_always_inline void zend_arena_destroy(zend_arena *arena)
{
  do {
    zend_arena *prev = arena->prev;
    efree(arena);
    arena = prev;
  } while (arena);
}

static zend_always_inline void* zend_arena_alloc(zend_arena **arena_ptr, size_t size)
{
  zend_arena *arena = *arena_ptr;
  char *ptr = arena->ptr;

  size = ZEND_MM_ALIGNED_SIZE(size);

  if (EXPECTED(size <= (size_t)(arena->end - ptr))) {
    arena->ptr = ptr + size;
  } else {
    size_t arena_size =
      UNEXPECTED((size + ZEND_MM_ALIGNED_SIZE(sizeof(zend_arena))) > (size_t)(arena->end - (char*) arena)) ?
        (size + ZEND_MM_ALIGNED_SIZE(sizeof(zend_arena))) :
        (size_t)(arena->end - (char*) arena);
    zend_arena *new_arena = (zend_arena*)emalloc(arena_size);

    ptr = (char*) new_arena + ZEND_MM_ALIGNED_SIZE(sizeof(zend_arena));
    new_arena->ptr = (char*) new_arena + ZEND_MM_ALIGNED_SIZE(sizeof(zend_arena)) + size;
    new_arena->end = (char*) new_arena + arena_size;
    new_arena->prev = arena;
    *arena_ptr = new_arena;
  }

  return (void*) ptr;
}

static zend_always_inline void* zend_arena_calloc(zend_arena **arena_ptr, size_t count, size_t unit_size)
{
  bool overflow;
  size_t size;
  void *ret;

  size = zend_safe_address(unit_size, count, 0, &overflow);
  if (UNEXPECTED(overflow)) {
    zend_error_noreturn(E_ERROR, "Possible integer overflow in zend_arena_calloc() (%zu * %zu)", unit_size, count);
  }
  ret = zend_arena_alloc(arena_ptr, size);
  memset(ret, 0, size);
  return ret;
}

static zend_always_inline void* zend_arena_checkpoint(zend_arena *arena)
{
  return arena->ptr;
}

static zend_always_inline void zend_arena_release(zend_arena **arena_ptr, void *checkpoint)
{
  zend_arena *arena = *arena_ptr;

  while (UNEXPECTED((char*)checkpoint > arena->end) ||
         UNEXPECTED((char*)checkpoint <= (char*)arena)) {
    zend_arena *prev = arena->prev;
    efree(arena);
    *arena_ptr = arena = prev;
  }
  ZEND_ASSERT((char*)checkpoint > (char*)arena && (char*)checkpoint <= arena->end);
  arena->ptr = (char*)checkpoint;
}

static zend_always_inline bool zend_arena_contains(zend_arena *arena, void *ptr)
{
  while (arena) {
    if ((char*)ptr > (char*)arena && (char*)ptr <= arena->ptr) {
      return 1;
    }
    arena = arena->prev;
  }
  return 0;
}

#else

/* Use normal allocations and keep track of them for mass-freeing.
 * This is intended for use with asan/valgrind. */

typedef struct _zend_arena zend_arena;

struct _zend_arena {
  void **ptr;
  void **end;
  struct _zend_arena *prev;
  void *ptrs[0];
};

#define ZEND_TRACKED_ARENA_SIZE 1000

static zend_always_inline zend_arena *zend_arena_create(size_t _size)
{
  zend_arena *arena = (zend_arena*) emalloc(
    sizeof(zend_arena) + sizeof(void *) * ZEND_TRACKED_ARENA_SIZE);
  arena->ptr = &arena->ptrs[0];
  arena->end = &arena->ptrs[ZEND_TRACKED_ARENA_SIZE];
  arena->prev = NULL;
  return arena;
}

static zend_always_inline void zend_arena_destroy(zend_arena *arena)
{
  do {
    zend_arena *prev = arena->prev;
    void **ptr;
    for (ptr = arena->ptrs; ptr < arena->ptr; ptr++) {
      efree(*ptr);
    }
    efree(arena);
    arena = prev;
  } while (arena);
}

static zend_always_inline void *zend_arena_alloc(zend_arena **arena_ptr, size_t size)
{
  zend_arena *arena = *arena_ptr;
  if (arena->ptr == arena->end) {
    *arena_ptr = zend_arena_create(0);
    (*arena_ptr)->prev = arena;
    arena = *arena_ptr;
  }

  return *arena->ptr++ = emalloc(size);
}

static zend_always_inline void* zend_arena_calloc(zend_arena **arena_ptr, size_t count, size_t unit_size)
{
  bool overflow;
  size_t size;
  void *ret;

  size = zend_safe_address(unit_size, count, 0, &overflow);
  if (UNEXPECTED(overflow)) {
    zend_error_noreturn(E_ERROR, "Possible integer overflow in zend_arena_calloc() (%zu * %zu)", unit_size, count);
  }
  ret = zend_arena_alloc(arena_ptr, size);
  memset(ret, 0, size);
  return ret;
}

static zend_always_inline void* zend_arena_checkpoint(zend_arena *arena)
{
  return arena->ptr;
}

static zend_always_inline void zend_arena_release(zend_arena **arena_ptr, void *checkpoint)
{
  while (1) {
    zend_arena *arena = *arena_ptr;
    zend_arena *prev = arena->prev;
    while (1) {
      if (arena->ptr == (void **) checkpoint) {
        return;
      }
      if (arena->ptr == arena->ptrs) {
        break;
      }
      arena->ptr--;
      efree(*arena->ptr);
    }
    efree(arena);
    *arena_ptr = prev;
    ZEND_ASSERT(*arena_ptr);
  }
}

static zend_always_inline bool zend_arena_contains(zend_arena *arena, void *ptr)
{
  /* TODO: Dummy */
  return 1;
}

#endif

#endif /* _ZEND_ARENA_H_ */

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Created: 2026-06-13 07:01