wizapp-stdlib/src/core/mem/arena/mem_arena.c

// vim:fileencoding=utf-8:foldmethod=marker

#include "mem_arena.h"
#include "../utils/mem_utils.h"
#include "../../../common/aliases/aliases.h"
#include "../../../common/assert/assert.h"
#include "../../../common/misc/misc_utils.h"
#include "../../os/mem/mem_os.h"
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>

#ifndef DEFAULT_ALIGNMENT
// Why 2 * sizeof(void *) instead of sizeof(void *)
// https://handmade.network/forums/t/6860-alignment_arena_allocator
#define DEFAULT_ALIGNMENT (2 * sizeof(void *))
#endif /* ifndef DEFAULT_ALIGNMENT */

#define ARENA_MINIMUM_CAPACITY KB(16) // Allocate minimum of 4 pages

struct arena {
  u8 *buf;
  u8 *offset;
  u64 capacity;
  bool committed;

#ifdef WAPP_PLATFORM_WINDOWS
  wapp_misc_utils_padding_size(sizeof(u8 *) * 2 + sizeof(u64) + sizeof(bool));
#endif // ifdef WAPP_PLATFORM_WINDOWS
};

bool wapp_mem_arena_init_custom(Arena **arena, u64 base_capacity, MemAllocFlags flags, bool zero_buffer) {
  if (!arena || *arena || base_capacity == 0) {
    return false;
  }

  *arena = (Arena *)calloc(1, sizeof(Arena));
  Arena *arena_ptr = *arena;
  if (!arena_ptr) {
    return false;
  }

  u64 arena_capacity = wapp_misc_utils_u64_round_up_pow2(
      base_capacity >= ARENA_MINIMUM_CAPACITY ?
      base_capacity :
      ARENA_MINIMUM_CAPACITY
  );

  arena_ptr->buf = (u8 *)wapp_mem_util_alloc(NULL, arena_capacity, WAPP_MEM_ACCESS_READ_WRITE, flags,
                                             zero_buffer ? WAPP_MEM_INIT_INITIALISED : WAPP_MEM_INIT_UNINITIALISED);

  if (!(arena_ptr->buf)) {
    wapp_mem_arena_destroy(arena);
    return false;
  }

  arena_ptr->capacity  = arena_capacity;
  arena_ptr->offset    = arena_ptr->buf;
  arena_ptr->committed = (flags & WAPP_MEM_ALLOC_COMMIT) == WAPP_MEM_ALLOC_COMMIT;

  return true;
}

void *wapp_mem_arena_alloc(Arena *arena, u64 size) {
  return wapp_mem_arena_alloc_aligned(arena, size, DEFAULT_ALIGNMENT);
}

void *wapp_mem_arena_alloc_aligned(Arena *arena, u64 size, u64 alignment) {
  wapp_debug_assert(arena != NULL, "`arena` should not be NULL");

  u8 *alloc_start = arena->offset;

  u8 *output = wapp_mem_util_align_forward((void *)alloc_start, alignment);
  if (output + size >= arena->buf + arena->capacity) {
    return NULL;
  }

  arena->offset = output + size;

#ifdef WAPP_PLATFORM_WINDOWS
  if (!(arena->committed)) {
    wapp_mem_util_alloc(alloc_start, (uptr)(arena->offset) - (uptr)(alloc_start),
                        WAPP_MEM_ACCESS_READ_WRITE, WAPP_MEM_ALLOC_COMMIT,
                        WAPP_MEM_INIT_UNINITIALISED);
  }
#endif // ifdef WAPP_PLATFORM_WINDOWS

  memset(output, 0, size);

  return (void *)output;
}

void *wapp_mem_arena_realloc(Arena *arena, void *ptr, u64 old_size, u64 new_size) {
  if ((u8*)ptr < arena->buf || (u8*)ptr > arena->offset ||
      arena->offset + new_size >= arena->buf + arena->capacity) {
    return NULL;
  }

  void *new_ptr = wapp_mem_arena_alloc(arena, new_size);
  if (!new_ptr) {
    return NULL;
  }

  u64 copy_size = new_size <= old_size ? new_size : old_size;
  memcpy(new_ptr, ptr, copy_size);

  return new_ptr;
}

void *wapp_mem_arena_realloc_aligned(Arena *arena, void *ptr, u64 old_size, u64 new_size, u64 alignment) {
  if ((u8*)ptr < arena->buf || (u8*)ptr > arena->offset ||
      arena->offset + new_size >= arena->buf + arena->capacity) {
    return NULL;
  }

  void *new_ptr = wapp_mem_arena_alloc_aligned(arena, new_size, alignment);
  if (!new_ptr) {
    return NULL;
  }

  u64 copy_size = new_size <= old_size ? new_size : old_size;
  memcpy(new_ptr, ptr, copy_size);

  return new_ptr;
}

void wapp_mem_arena_clear(Arena *arena) {
  wapp_debug_assert(arena != NULL, "`arena` should not be NULL");

  memset(arena->buf, 0, arena->offset - arena->buf);
  arena->offset = arena->buf;
}

void wapp_mem_arena_destroy(Arena **arena) {
  wapp_debug_assert(arena != NULL && (*arena) != NULL, "`arena` double pointer is not valid");

  Arena *arena_ptr = *arena;
  if (arena_ptr->buf) {
    wapp_mem_util_free(arena_ptr->buf, arena_ptr->capacity);
  }

  arena_ptr->buf = arena_ptr->offset = NULL;
  arena_ptr->capacity = 0;

  free(*arena);
  *arena = NULL;
}