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#include <assert.h>
#include <dirent.h>
#include <fcntl.h>
#include <stdint.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include "arena.h"
mem_arena *
arena_create(u64 capacity)
{
mem_arena *arena = mmap(0, capacity, PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_SHARED | MAP_ANONYMOUS, -1, 0);
if (arena == MAP_FAILED)
{
assert(0);
}
arena->capacity = capacity;
arena->pos = ARENA_BASE_POS;
return arena;
}
// make it a void pointer to allow implicit conversion
void
arena_destroy(mem_arena *arena)
{
munmap(arena, arena->capacity);
}
void *
arena_push(mem_arena *arena, u64 size, b32 non_zero)
{
u64 pos_aligned = ALIGN_UP_POW2(arena->pos, ARENA_ALIGN);
u64 new_pos = pos_aligned + size;
if (new_pos > arena->capacity)
{
assert(0);
return NULL;
}
arena->pos = new_pos;
// cast to u8 to be able to do pointer arithemtic
u8 *out = (u8 *)arena + pos_aligned;
if (!non_zero)
{
memset(out, 0, size);
}
return out;
}
void
arena_pop(mem_arena *arena, u64 size)
{
size = MIN(size, arena->pos - ARENA_BASE_POS);
arena->pos -= size;
}
void
arena_pop_to(mem_arena *arena, u64 pos)
{
u64 size = pos < arena->pos ? arena->pos - pos : 0;
arena_pop(arena, size);
}
void
arena_clear(mem_arena *arena)
{
arena_pop_to(arena, ARENA_BASE_POS);
}
#define PUSH_STRUCT(arena, T) (T *)arena_push((arena), sizeof(T), 0)
#define PUSH_STRUCT_NZ(arena, T) (T *)arena_push((arena), sizeof(T), 1)
#define PUSH_ARRAY(arena, T, n) (T *)arena_push((arena), sizeof(T) * (n), 0)
#define PUSH_ARRAY_NZ(arena, T, n) (T *)arena_push((arena), sizeof(T) * (n), 1)
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