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Simplify Arena allocator

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This commit is contained in:
Abdelrahman Said
2024-04-24 23:10:55 +01:00
parent 92db9206cc
commit d4313fb8e4
2 changed files with 3 additions and 179 deletions
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5
mem/include/arena/mem_arena.h
View File

@@ -2,7 +2,6 @@
#define MEM_ARENA_H #define MEM_ARENA_H
#include "aliases.h" #include "aliases.h"
#include "mem_allocator.h"
#include <stdbool.h> #include <stdbool.h>
#ifdef __cplusplus #ifdef __cplusplus
@@ -11,13 +10,9 @@ extern "C" {
typedef struct growing_arena Arena; typedef struct growing_arena Arena;
Allocator wapp_mem_arena_allocator(const Arena *arena);
bool wapp_mem_arena_init(Arena **arena, u64 base_capacity); bool wapp_mem_arena_init(Arena **arena, u64 base_capacity);
void *wapp_mem_arena_alloc(Arena *arena, u64 size); void *wapp_mem_arena_alloc(Arena *arena, u64 size);
void *wapp_mem_arena_alloc_aligned(Arena *arena, u64 size, u64 alignment); void *wapp_mem_arena_alloc_aligned(Arena *arena, u64 size, u64 alignment);
void *wapp_mem_arena_realloc(Arena *arena, void *ptr, u64 size);
void *wapp_mem_arena_realloc_aligned(Arena *arena, void *ptr, u64 size,
u64 alignment);
void wapp_mem_arena_clear(Arena *arena); void wapp_mem_arena_clear(Arena *arena);
void wapp_mem_arena_free(Arena **arena); void wapp_mem_arena_free(Arena **arena);

177
mem/src/arena/mem_arena.c
View File

@@ -1,8 +1,6 @@
#include "mem_arena.h" #include "mem_arena.h"
#include "aliases.h" #include "aliases.h"
#include "mem_allocator.h"
#include "mem_utils.h" #include "mem_utils.h"
#include <math.h>
#include <stdbool.h> #include <stdbool.h>
#include <stdlib.h> #include <stdlib.h>
#include <string.h> #include <string.h>
@@ -13,24 +11,12 @@
#define DEFAULT_ALIGNMENT (2 * sizeof(void *)) #define DEFAULT_ALIGNMENT (2 * sizeof(void *))
#endif /* ifndef DEFAULT_ALIGNMENT */ #endif /* ifndef DEFAULT_ALIGNMENT */
#define HDR_MAGIC_BYTE_COUNT 8
#define HDR_MAGIC \
{ 0x57, 0x41, 0x41, 0x52, 0x4e, 0x48, 0x44, 0x52 }
#define MAX_HDR_SEARCH_LENGTH 256
#define ARENA_MINIMUM_CAPACITY 1024 #define ARENA_MINIMUM_CAPACITY 1024
typedef struct arena_alloc_hdr ArenaAllocHDR;
struct arena_alloc_hdr {
u8 magic[HDR_MAGIC_BYTE_COUNT];
u64 alloc_size;
u64 alignment;
u8 *alloc_start;
};
typedef struct base_arena BaseArena; typedef struct base_arena BaseArena;
struct base_arena { struct base_arena {
u8 *buf; u8 *buf;
u8 *last;
u8 *offset; u8 *offset;
u64 capacity; u64 capacity;
BaseArena *prev; BaseArena *prev;
@@ -43,35 +29,14 @@ struct growing_arena {
u64 initial_capacity; u64 initial_capacity;
}; };
internal BaseArena *find_arena_from_pointer(const Arena *arena, void *ptr);
internal bool base_arena_init(BaseArena *arena, u64 capacity); internal bool base_arena_init(BaseArena *arena, u64 capacity);
internal void *base_arena_alloc_aligned(BaseArena *arena, u64 size, internal void *base_arena_alloc_aligned(BaseArena *arena, u64 size,
u64 alignment); u64 alignment);
internal void base_arena_clear(BaseArena *arena); internal void base_arena_clear(BaseArena *arena);
internal void base_arena_free(BaseArena *arena); internal void base_arena_free(BaseArena *arena);
internal ArenaAllocHDR *find_alloc_header(BaseArena *arena, void *alloc_ptr);
internal void *mem_arena_alloc(u64 size, void *alloc_obj);
internal void *mem_arena_alloc_aligned(u64 size, u64 alignment,
void *alloc_obj);
internal void *mem_arena_realloc(void *ptr, u64 size, void *alloc_obj);
internal void *mem_arena_realloc_aligned(void *ptr, u64 size, u64 alignment,
void *alloc_obj);
// PUBLIC API // PUBLIC API
Allocator wapp_mem_arena_allocator(const Arena *arena) {
return (Allocator){
.obj = (void *)arena,
.alloc = mem_arena_alloc,
.alloc_aligned = mem_arena_alloc_aligned,
.realloc = mem_arena_realloc,
.realloc_aligned = mem_arena_realloc_aligned,
.free = NULL,
};
}
bool wapp_mem_arena_init(Arena **arena, u64 base_capacity) { bool wapp_mem_arena_init(Arena **arena, u64 base_capacity) {
if (!arena || *arena || base_capacity == 0) { if (!arena || *arena || base_capacity == 0) {
return false; return false;
@@ -142,54 +107,6 @@ void *wapp_mem_arena_alloc_aligned(Arena *arena, u64 size, u64 alignment) {
return output; return output;
} }
void *wapp_mem_arena_realloc(Arena *arena, void *ptr, u64 size) {
return wapp_mem_arena_realloc_aligned(arena, ptr, size, DEFAULT_ALIGNMENT);
}
void *wapp_mem_arena_realloc_aligned(Arena *arena, void *ptr, u64 size,
u64 alignment) {
if (!arena) {
return NULL;
}
BaseArena *base_arena = find_arena_from_pointer(arena, ptr);
if (!base_arena) {
return NULL;
}
ArenaAllocHDR *header = find_alloc_header(base_arena, ptr);
if (!header) {
return NULL;
}
if (header->alloc_start + header->alloc_size == base_arena->offset) {
// Avoid allocating new pointer and copying memory if pointer is at the end
// of the arena
i64 diff = size - header->alloc_size;
u8 *new_offset = base_arena->offset + diff;
u8 *clear_start = diff < 0 ? new_offset : base_arena->offset;
memset(clear_start, 0, llabs(diff));
header->alloc_size = size;
base_arena->offset = new_offset;
return header->alloc_start;
}
void *new_alloc = wapp_mem_arena_alloc_aligned(arena, size, alignment);
if (!new_alloc) {
return NULL;
}
u64 to_copy = size < header->alloc_size ? size : header->alloc_size;
memcpy(new_alloc, ptr, to_copy);
return new_alloc;
}
void wapp_mem_arena_clear(Arena *arena) { void wapp_mem_arena_clear(Arena *arena) {
if (!arena) { if (!arena) {
return; return;
@@ -255,30 +172,6 @@ void wapp_mem_arena_free(Arena **arena) {
// INTERNAL FUNCTIONS // INTERNAL FUNCTIONS
internal BaseArena *find_arena_from_pointer(const Arena *arena, void *ptr) {
if (!arena || !ptr) {
return NULL;
}
// Ensure pointer is not out of bounds
u8 *alloc = (u8 *)ptr;
BaseArena *active = arena->active_arena;
if (alloc > active->buf + arena->initial_capacity) {
return NULL;
}
for (u64 i = 0; i < arena->count; ++i) {
if (alloc >= active->buf && alloc < active->buf + arena->initial_capacity) {
return (BaseArena *)active;
}
active = active->prev;
}
return NULL;
}
internal bool base_arena_init(BaseArena *arena, u64 capacity) { internal bool base_arena_init(BaseArena *arena, u64 capacity) {
if (!arena || arena->buf || capacity == 0) { if (!arena || arena->buf || capacity == 0) {
return false; return false;
@@ -305,23 +198,15 @@ internal void *base_arena_alloc_aligned(BaseArena *arena, u64 size,
return NULL; return NULL;
} }
u8 *start_offset = arena->offset; u8 *alloc_start = arena->offset;
u8 *alloc_start = arena->offset + sizeof(ArenaAllocHDR);
u8 *output = wapp_mem_util_align_forward((void *)alloc_start, alignment); u8 *output = wapp_mem_util_align_forward((void *)alloc_start, alignment);
if (output + size >= arena->buf + arena->capacity) { if (output + size >= arena->buf + arena->capacity) {
return NULL; return NULL;
} }
ArenaAllocHDR *header = (ArenaAllocHDR *)start_offset;
*header = (ArenaAllocHDR){
.magic = HDR_MAGIC,
.alloc_size = size,
.alignment = alignment,
.alloc_start = output,
};
arena->offset = output + size; arena->offset = output + size;
arena->last = output;
return (void *)output; return (void *)output;
} }
@@ -348,59 +233,3 @@ internal void base_arena_free(BaseArena *arena) {
arena->capacity = 0; arena->capacity = 0;
arena->prev = arena->next = NULL; arena->prev = arena->next = NULL;
} }
internal ArenaAllocHDR *find_alloc_header(BaseArena *arena, void *alloc_ptr) {
persistent const u8 magic[HDR_MAGIC_BYTE_COUNT] = HDR_MAGIC;
u8 *current = (u8 *)alloc_ptr;
u8 *max_search_end = current - MAX_HDR_SEARCH_LENGTH;
u8 *arena_buf_start = arena->buf;
u8 *search_end =
max_search_end > arena_buf_start ? max_search_end : arena_buf_start;
bool match;
for (; current >= search_end; --current) {
match = true;
for (u64 i = 0; i < HDR_MAGIC_BYTE_COUNT; ++i) {
if (current[i] != magic[i]) {
match = false;
break;
}
}
if (match) {
return (ArenaAllocHDR *)current;
}
}
return NULL;
}
internal void *mem_arena_alloc(u64 size, void *alloc_obj) {
Arena *arena = (Arena *)alloc_obj;
return wapp_mem_arena_alloc(arena, size);
}
internal void *mem_arena_alloc_aligned(u64 size, u64 alignment,
void *alloc_obj) {
Arena *arena = (Arena *)alloc_obj;
return wapp_mem_arena_alloc_aligned(arena, size, alignment);
}
internal void *mem_arena_realloc(void *ptr, u64 size, void *alloc_obj) {
Arena *arena = (Arena *)alloc_obj;
return wapp_mem_arena_realloc(arena, ptr, size);
}
internal void *mem_arena_realloc_aligned(void *ptr, u64 size, u64 alignment,
void *alloc_obj) {
Arena *arena = (Arena *)alloc_obj;
return wapp_mem_arena_realloc_aligned(arena, ptr, size, alignment);
}