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#ifndef BASE_ARENA_H
#define BASE_ARENA_H
#include "base_io.h"
typedef struct MemArena MemArena;
typedef struct ScratchArena ScratchArena;
internal b32 is_pow(umm x);
internal u64 align(u64 pointer, umm alignment);
//-
struct MemArena
{
u64 current_position;
u64 previous_position;
u64 capacity;
u8 *base_position;
};
struct ScratchArena
{
MemArena *arena;
u64 start_position;
};
#if defined(PLATFORM_WINDOWS)
#include "base_arena_windows.h"
#elif defined(PLATFORM_LINUX)
#include "base_arena_unix.h"
#endif
#if defined(PLATFORM_LINUX)
#define ArenaCreate(capacity) unix_arena_create(capacity)
#define ArenaDestroy(arena) unix_arena_destroy(arena)
#elif defined(PLATFORM_WINDOWS)
#define ArenaCreate(capacity) win32_arena_create(capacity)
#define ArenaDestroy(arena) win32_arena_destroy(arena)
#endif
internal void *arena_alloc(MemArena *arena, u64 size, b32 zero);
internal void arena_pop(MemArena *arena, u64 size);
internal void arena_pop_to(MemArena *arena, u64 pos);
internal void arena_clear(MemArena *arena);
internal void scratch_end(ScratchArena *temp);
internal ScratchArena scratch_start(MemArena *arena);
internal MemArena *arena_resize_align(MemArena *arena, void *old_memory, u64 new_size, u64 old_size, umm alignment);
internal MemArena *arena_resize(MemArena *arena, void *old_memory, u64 new_size, u64 old_size);
#define Align(pointer, alignment) align((u64)(pointer), (umm)(alignment))
#define PushStruct(arena, type) (type *)arena_alloc((arena), sizeof(type), 0)
#define PushStructZero(arena, type) (type *)arena_alloc((arena), sizeof(type), 1)
#define PushArray(arena, type, len) (type *)arena_alloc((arena), sizeof(type) * (len), 0)
#define PushArrayZero(arena, type, len) (type *)arena_alloc((arena), sizeof(type) * (len), 1)
#define KiB(n) (((u64)(n)) << 10)
#define MiB(n) (((u64)(n)) << 20)
#define GiB(n) (((u64)(n)) << 30)
internal void *
arena_alloc(MemArena *arena, u64 size, b32 zero)
{
if(!arena)
{
return NULL;
}
u64 aligned = Align(arena->current_position, arena_align);
u64 new_pos = aligned + size;
if(new_pos > arena->capacity)
{
return NULL;
}
void *out = arena->base_position + aligned;
arena->previous_position = arena->current_position;
arena->current_position = aligned + size;
if(zero)
{
MemSet(out, size);
}
return out;
}
internal void
arena_pop(MemArena *arena, u64 size)
{
size = Min(size, arena->current_position);
arena->current_position -= size;
}
internal void
arena_pop_to(MemArena *arena, u64 pos)
{
u64 size = pos < arena->current_position ? arena->current_position - pos : 0;
arena_pop(arena, size);
}
internal void
arena_clear(MemArena *arena)
{
arena->current_position = 0;
}
internal MemArena *
arena_resize_align(MemArena *arena, void *old_memory, u64 new_size, u64 old_size, umm alignment)
{
u8 *old_mem = (u8 *)old_memory;
if(!is_pow(alignment))
{
Align(arena->current_position, alignment);
}
if(old_memory == NULL || old_size == 0)
{
return (MemArena *)arena_alloc(arena, new_size, 0);
}
else if((old_mem >= arena->base_position && old_mem < arena->base_position + arena->capacity))
{
if((arena->base_position + arena->previous_position) == old_memory)
{
arena->current_position = arena->previous_position + new_size;
if(new_size > old_size)
{
MemSet(&arena->current_position, new_size - old_size);
}
return (MemArena *)old_memory;
}
else
{
void *new_memory = arena_alloc(arena, new_size, 0);
umm copy_size = old_size < new_size ? old_size : new_size;
memmove(new_memory, old_mem, copy_size);
}
}
else
{
Log("yeah something in the mem allocater failed i guess");
}
return NULL;
}
internal MemArena *
arena_resize(MemArena *arena, void *old_memory, u64 new_size, u64 old_size)
{
return arena_resize_align(arena, old_memory, new_size, old_size, arena_align);
}
internal ScratchArena
scratch_start(MemArena *arena)
{
ScratchArena sa;
sa.arena = arena;
sa.start_position = arena->current_position;
return sa;
}
internal void
scratch_end(ScratchArena *sa)
{
sa.arena->current_position = sa->start_position;
}
//-
internal b32
is_pow(umm x)
{
return (x & (x - 1)) == 0;
}
internal u64
align(u64 pointer, umm alignment)
{
if((alignment & (alignment - 1)) == 0)
{
return pointer;
}
return (pointer + alignment - 1) & ~(alignment - 1);
}
#endif /* BASE_ARENA_H */
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