#ifndef UNDAR_H
#define UNDAR_H

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

typedef struct arena_s Arena;
struct arena_s {
	unsigned char *tape;
	unsigned int count;
	unsigned int capacity;
};

static void *aalloc(Arena *arena, unsigned int size){
    unsigned int pos;
	if(arena == NULL) return NULL;
	if(arena->count + size > arena->capacity) return NULL;

	pos = arena->count;
	arena->count += size;
	return (void *)&arena->tape[pos];
}

static void *
areturn(Arena *arena, unsigned int checkpoint, const void *src, unsigned int size)
{
    void *dest;
    if(arena == NULL || src == NULL) return NULL;
    
    dest = (void *)&arena->tape[checkpoint];
    if (src == dest) return dest;

    memmove(dest, src, size);
    arena->count = checkpoint + size;
    
    return dest;
}

#define ARENA_RETURN(arena, ckpt, src_ptr, type) \
    return (type *)areturn((arena), (ckpt), (src_ptr), sizeof(type))

#define ARENA_RETURN_ARRAY(arena, ckpt, src_ptr, type, count) \
    return (type *)areturn((arena), (ckpt), (src_ptr), sizeof(type) * (count))

#endif