117 lines
4.0 KiB
C++
117 lines
4.0 KiB
C++
constexpr size_t ARENA_BLOCK_SIZE = mib(4);
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constexpr size_t ARENA_ALIGNMENT = 8;
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struct Scratch_Arena : Allocator {
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int cap, len;
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uint8_t memory[];
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};
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struct Scratch_Scope {
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Scratch_Arena *arena;
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int pos;
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Scratch_Scope(Scratch_Arena *arena) { this->arena = arena; this->pos = arena->len; }
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~Scratch_Scope() { this->arena->len = this->pos; }
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};
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static void *scratch_arena_push_size(Scratch_Arena *arena, size_t size) {
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size_t generous_size = size + ARENA_ALIGNMENT;
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if (arena->len + generous_size > arena->cap) {
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assert(size < arena->cap);
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assert_message(0, "Scratch arena is too small, failed to handle a request, capacity: %d, occupied: %d, allocation: %d", generous_size);
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return 0;
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}
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size_t aligned_fill = align_up((size_t)arena->memory + arena->len, ARENA_ALIGNMENT) - (size_t)arena->memory;
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assert(((int64_t)aligned_fill - (int64_t)arena->len) >= 0);
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assert(((int64_t)aligned_fill - (int64_t)arena->len) <= ARENA_ALIGNMENT);
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arena->len = aligned_fill;
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uint8_t *result = arena->memory + arena->len;
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arena->len += size;
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return (void *)result;
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}
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static Scratch_Arena *make_scratch_arena(void *buff, size_t size) {
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Scratch_Arena *scratch = (Scratch_Arena *)buff;
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scratch->len = 0;
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scratch->cap = size - sizeof(Scratch_Arena);
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scratch->allocate = (Allocator::Allocate *)scratch_arena_push_size;
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scratch->deallocate = deallocate_stub;
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return scratch;
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}
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static Scratch_Arena *allocate_scratch_arena(Allocator *allocator, size_t size_without_members) {
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Scratch_Arena *scratch = (Scratch_Arena *)allocate_size(allocator, size_without_members + sizeof(Scratch_Arena), false);
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scratch->cap = size_without_members;
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scratch->len = 0;
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scratch->allocate = (Allocator::Allocate *)scratch_arena_push_size;
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scratch->deallocate = deallocate_stub;
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return scratch;
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}
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struct Push_Arena_Block {
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Push_Arena_Block *next;
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uint8_t memory[];
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};
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struct Push_Arena : Allocator {
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Allocator *block_allocator;
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Push_Arena_Block *blocks;
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size_t allocated_block_count;
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size_t block_fill;
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size_t wasted_memory;
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};
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static void push_arena_add_block(Push_Arena *arena) {
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Push_Arena_Block *block = (Push_Arena_Block *)allocate_size(arena->block_allocator, sizeof(Push_Arena_Block) + ARENA_BLOCK_SIZE, false);
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memory_zero(block, sizeof(Push_Arena_Block));
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SLL_STACK_ADD(arena->blocks, block);
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if (arena->allocated_block_count) arena->wasted_memory += ARENA_BLOCK_SIZE - arena->block_fill;
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arena->allocated_block_count += 1;
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arena->block_fill = 0;
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}
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static void push_arena_deallocate(Push_Arena *arena) {
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for(Push_Arena_Block *it = arena->blocks; it; it = it->next) {
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deallocate(arena->block_allocator, it);
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}
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memory_zero(arena, sizeof(*arena));
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}
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static void *push_arena_push_size(Push_Arena *arena, size_t size) {
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assert(arena->block_allocator);
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assert(size < ARENA_BLOCK_SIZE / 2);
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size_t generous_size = size + ARENA_ALIGNMENT;
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if (arena->blocks == 0 || (arena->block_fill + generous_size > ARENA_BLOCK_SIZE)) {
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push_arena_add_block(arena);
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}
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Push_Arena_Block *L = arena->blocks;
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size_t aligned_fill = align_up((size_t)L->memory + arena->block_fill, ARENA_ALIGNMENT) - (size_t)L->memory;
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assert(((int64_t)aligned_fill - (int64_t)arena->block_fill) >= 0);
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assert(((int64_t)aligned_fill - (int64_t)arena->block_fill) <= ARENA_ALIGNMENT);
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arena->block_fill = aligned_fill;
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uint8_t *result = L->memory + arena->block_fill;
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arena->block_fill += size;
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return (void *)result;
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}
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static Push_Arena make_push_arena(Allocator *allocator) {
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Push_Arena result = {};
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result.block_allocator = allocator;
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result.allocate = (Allocator::Allocate *)push_arena_push_size;
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result.deallocate = (Allocator::Deallocate *)deallocate_stub;
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return result;
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}
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struct CRT_Heap : Allocator {};
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static void *crt_allocate(Allocator *allocator, size_t size) { return malloc(size); }
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static void crt_deallocate(Allocator *allocator, void *p) { return free(p); }
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static CRT_Heap make_crt_heap() {
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CRT_Heap result = {};
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result.allocate = crt_allocate;
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result.deallocate = crt_deallocate;
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return result;
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}
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