Using arena as token array, remove arenas idea

base_arena.cpp

@@ -1,110 +1,6 @@
 constexpr size_t ARENA_BLOCK_SIZE = mib(4);
 constexpr size_t ARENA_ALIGNMENT = 8;
 
-struct Scratch_Arena : Allocator {
-  int cap, len;
-  uint8_t memory[];
-};
-
-struct Scratch_Scope {
-  Scratch_Arena *arena;
-  int pos;
-  Scratch_Scope(Scratch_Arena *arena) { this->arena = arena; this->pos = arena->len; }
-  ~Scratch_Scope() { this->arena->len = this->pos; }
-};
-
-static void *scratch_arena_push_size(Scratch_Arena *arena, size_t size) {
-  size_t generous_size = size + ARENA_ALIGNMENT;
-  if (arena->len + generous_size > arena->cap) {
-    assert(size < arena->cap);
-    assert_message(0, "Scratch arena is too small, failed to handle a request, capacity: %d, occupied: %d, allocation: %d", generous_size);
-    return 0;
-  }
-  
-  size_t aligned_fill = align_up((size_t)arena->memory + arena->len, ARENA_ALIGNMENT) - (size_t)arena->memory;
-  assert(((int64_t)aligned_fill - (int64_t)arena->len) >= 0);
-  assert(((int64_t)aligned_fill - (int64_t)arena->len) <= ARENA_ALIGNMENT);
-  arena->len = aligned_fill;
-
-  uint8_t *result = arena->memory + arena->len;
-  arena->len += size;
-  return (void *)result;
-}
-
-static Scratch_Arena *make_scratch_arena(void *buff, size_t size) {
-  Scratch_Arena *scratch = (Scratch_Arena *)buff;
-  scratch->len = 0;
-  scratch->cap = size - sizeof(Scratch_Arena);
-  scratch->allocate = (Allocator::Allocate *)scratch_arena_push_size;
-  scratch->deallocate = deallocate_stub;
-  return scratch;
-}
-
-static Scratch_Arena *allocate_scratch_arena(Allocator *allocator, size_t size_without_members) {
-  Scratch_Arena *scratch = (Scratch_Arena *)allocate_size(allocator, size_without_members + sizeof(Scratch_Arena), false);
-  scratch->cap = size_without_members;
-  scratch->len = 0;
-  scratch->allocate = (Allocator::Allocate *)scratch_arena_push_size;
-  scratch->deallocate = deallocate_stub;
-  return scratch;
-}
-
-struct Push_Arena_Block {
-  Push_Arena_Block *next;
-  uint8_t memory[];
-};
-
-struct Push_Arena : Allocator {
-  Allocator *block_allocator;
-  Push_Arena_Block *blocks;
-  size_t allocated_block_count;
-  size_t block_fill;
-  size_t wasted_memory;
-};
-
-static void push_arena_add_block(Push_Arena *arena) {
-  Push_Arena_Block *block = (Push_Arena_Block *)allocate_size(arena->block_allocator, sizeof(Push_Arena_Block) + ARENA_BLOCK_SIZE, false);
-  memory_zero(block, sizeof(Push_Arena_Block));
-  SLL_STACK_ADD(arena->blocks, block);
-  if (arena->allocated_block_count) arena->wasted_memory += ARENA_BLOCK_SIZE - arena->block_fill;
-  arena->allocated_block_count += 1;
-  arena->block_fill = 0;
-}
-
-static void push_arena_deallocate(Push_Arena *arena) {
-  for(Push_Arena_Block *it = arena->blocks; it; it = it->next) {
-    deallocate(arena->block_allocator, it);
-  }
-  memory_zero(arena, sizeof(*arena));
-}
-
-static void *push_arena_push_size(Push_Arena *arena, size_t size) {
-  assert(arena->block_allocator);
-  assert(size < ARENA_BLOCK_SIZE / 2);
-  size_t generous_size = size + ARENA_ALIGNMENT;
-  if (arena->blocks == 0 || (arena->block_fill + generous_size > ARENA_BLOCK_SIZE)) {
-    push_arena_add_block(arena);
-  }
-
-  Push_Arena_Block *L = arena->blocks;
-  size_t aligned_fill = align_up((size_t)L->memory + arena->block_fill, ARENA_ALIGNMENT) - (size_t)L->memory;
-  assert(((int64_t)aligned_fill - (int64_t)arena->block_fill) >= 0);
-  assert(((int64_t)aligned_fill - (int64_t)arena->block_fill) <= ARENA_ALIGNMENT);
-  arena->block_fill = aligned_fill;
-
-  uint8_t *result = L->memory + arena->block_fill;
-  arena->block_fill += size;
-  return (void *)result;
-}
-
-static Push_Arena make_push_arena(Allocator *allocator) {
-  Push_Arena result = {};
-  result.block_allocator = allocator;
-  result.allocate = (Allocator::Allocate *)push_arena_push_size;
-  result.deallocate = (Allocator::Deallocate *)deallocate_stub;
-  return result;
-}
-
 struct CRT_Heap : Allocator {};
 static void *crt_allocate(Allocator *allocator, size_t size) { return malloc(size); }
 static void crt_deallocate(Allocator *allocator, void *p) { return free(p); }
@@ -208,6 +104,26 @@ CORE_Static Arena
   result.memory.commit = size;
   result.memory.reserve = size;
   result.alignment = default_alignment;
-  result.len = 0;
+  result.allocate  = (Allocator::Allocate *)arena_push_size;
+  result.deallocate= (Allocator::Deallocate *)deallocate_stub;
   return result;
 }
+
+CORE_Static Arena
+arena_from_buffer(void *buffer, size_t size) {
+  Arena result = {};
+  result.memory.data = (U8 *)buffer;
+  result.memory.commit = size;
+  result.memory.reserve = size;
+  result.alignment = default_alignment;
+  result.allocate  = (Allocator::Allocate *)arena_push_size;
+  result.deallocate= (Allocator::Deallocate *)deallocate_stub;
+  return result;
+}
+
+struct Scratch_Scope {
+  Arena *arena;
+  int pos;
+  Scratch_Scope(Arena *arena) { this->arena = arena; this->pos = arena->len; }
+  ~Scratch_Scope() { this->arena->len = this->pos; }
+};