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// Arena allocation
// Michal Vlasák, FIT CTU, 2023
#include "arena.h"
#include "stdlib.h"
#include "stdint.h"
#include "string.h"
static size_t
align(size_t pos, size_t alignment)
{
return (pos + (alignment - 1)) & ~(alignment - 1);
}
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void
arena_init(Arena *arena)
{
ArenaChunk *chunk = &sentinel;
arena->current = chunk;
arena->prev_size_sum = 0;
}
void *
arena_alloc(Arena *arena, size_t size)
{
size_t pos = align(arena->current->pos, 8);
size_t current_size = arena->current->size;
if (pos + size > current_size) {
arena->prev_size_sum += current_size;
size_t new_size = size + (current_size ? current_size * 2 : 1024);
ArenaChunk *new = malloc(new_size);
new->size = new_size;
new->prev = arena->current;
arena->current = new;
pos = align(sizeof(ArenaChunk), 8);
}
arena->current->pos = pos + size;
return ((unsigned char *) arena->current) + pos;
}
size_t
arena_save(Arena *arena)
{
return arena->prev_size_sum + arena->current->pos;
}
void
arena_restore(Arena *arena, size_t pos)
{
ArenaChunk *chunk = arena->current;
while (pos < arena->prev_size_sum) {
ArenaChunk *prev = chunk->prev;
free(chunk);
chunk = prev;
arena->prev_size_sum -= chunk->size;
}
chunk->pos = pos - arena->prev_size_sum;
arena->current = chunk;
}
void
arena_destroy(Arena *arena)
{
arena_restore(arena, 0);
if (arena->current != &sentinel) {
free(arena->current);
arena->current = &sentinel;
}
}
void
garena_init(GArena *arena)
{
arena->mem = NULL;
arena->pos = 0;
arena->capacity = 0;
}
void
garena_destroy(GArena *arena)
{
free(arena->mem);
}
void *
garena_alloc(GArena *arena, size_t size, size_t alignment)
{
size_t pos = align(arena->pos, alignment);
if (pos + size > arena->capacity) {
arena->capacity = arena->capacity ? arena->capacity * 2 : size * 8;
arena->mem = realloc(arena->mem, arena->capacity);
}
arena->pos = pos + size;
return &arena->mem[pos];
}
size_t
garena_save(GArena *arena)
{
return arena->pos;
}
void *
garena_restore(GArena *arena, size_t pos)
{
arena->pos = pos;
return &arena->mem[pos];
}
void *
garena_mem(GArena *arena)
{
return arena->mem;
}
size_t
garena_cnt_from_(GArena *arena, size_t start, size_t elem_size)
{
return (arena->pos - start) / elem_size;
}
void *
garena_from(GArena *arena, size_t start, size_t alignment)
{
size_t pos = align(start, alignment);
return &arena->mem[pos];
}
void *
move_to_arena_(Arena *arena, GArena *garena, size_t start, size_t alignment)
{
size_t size = garena->pos - start;
if (size == 0) {
return NULL;
}
garena_restore(garena, start);
void *old = garena_from(garena, start, alignment);
return memcpy(arena_alloc(arena, size), old, size);
}