Arena stack

memory.c

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "common.h"
#include "memory.h"

#define ALIGNMENT 8
#define DEFAULT_REGION_SIZE 8096

static struct Arena {
  size_t total;
  size_t used;
  struct Arena *next;
  char mem[];
} *main_arena = NULL;

Arena *new_region(size_t size) {
  Arena *arena = (Arena *)calloc(1, size);
  arena->total = size - (sizeof(uintptr_t) * 3);
  arena->used = 0;
  arena->next = NULL;
  return arena;
}

Arena *push_region(size_t size) {
  Arena *new_arena = new_region(size);
  new_arena->next = main_arena;
  main_arena = new_arena;
  return new_arena;
}

void *allocate_space(size_t size) {
  if (main_arena == NULL || (main_arena->total - main_arena->used) < size)
    push_region(DEFAULT_REGION_SIZE);

  void *mem_space = (void *)&main_arena->mem[main_arena->used];
  main_arena->used += size + (ALIGNMENT % size);

  return mem_space;
}

void free_regions(void) {
  Arena **current = &main_arena;
  while (*current) {
    Arena *to_free = *current;
    *current = to_free->next;
    free(to_free);
  }

  fprintf(stderr, "The arena stack has been freed.\n");
}

char *gc_strndup(const char *str, size_t length) {
  char *mem = (char *)allocate_space(length + 1);
  return memmove(&mem[0], &str[0], length);
}

void *gc_memdup(const void *mem, size_t size) {
  void *memdup = allocate_space(size);
  return memmove(memdup, mem, size);
}