Arena Allocator

A lightweight, single-header C++ arena allocator. Simply drop arena.hpp into your project's include directory.

Usage

For a detailed demonstration see example.cpp

#include <cstdint>
#define ARENA_IMPLEMENTATION

#include "arena.hpp"
#include <cstdlib>
#include <print>

struct app {
  char name[16];
  uint16_t id;
};

int main(int argc, char *argv[]) {

  void *mem = malloc(6500);
  Arena a = {0};
  arena_init(&a, mem, 6500);

  int *x;
  app *info;

  x = (int *)arena_alloc(&a, sizeof(int));
  info = (app *)arena_alloc(&a, sizeof(app));

  *x = 5;
  *info = {.name = "some text\0", .id = 1235};

  std::println("{:p}: {:d}", static_cast<const void *>(x), (int)a.buffer[0]);

  std::println("{:p}: {:s}\t{:d}", static_cast<const void *>(info), info->name,
               info->id);

  std::println("{}", a.offset);

  arena_reset(&a);
  //do something else with the memory

  arena_free(&a);
  free(mem);
  return 0;
}

Acknowledgements

This arena allocator implementation is based on the concepts and implementation described in Ginger Bill's article "Memory Allocation Strategies - Part 2: Linear (Arena) Allocators."

Original article: https://www.gingerbill.org/article/2019/02/08/memory-allocation-strategies-002/