From d10b72057e1738a0c59af1f92ab5ab0b6efa65b0 Mon Sep 17 00:00:00 2001
From: Krzosa Karol <krzosa.karol@gmail.com>
Date: Sun, 1 Jan 2023 00:38:19 +0100
Subject: [PATCH] Block based arena

---
 build.bat          |  6 +++-
 core_arena.cpp     | 83 ++++++++++++++++++++++++++++++++++++++++++++++
 core_generated.cpp |  2 --
 3 files changed, 88 insertions(+), 3 deletions(-)
 create mode 100644 core_arena.cpp

diff --git a/build.bat b/build.bat
index 8de3cfc..5eeb352 100644
--- a/build.bat
+++ b/build.bat
@@ -1,10 +1,14 @@
 @echo off
 
+set clang-flags=-O0 -Wall -Wno-unused-function -fno-exceptions -fdiagnostics-absolute-paths -g -o main.exe -Wl,user32.lib
+
 pushd %~dp0
 rem cl main.cpp -I.. user32.lib
-clang core_main.cpp -O0 -Wall -Wno-unused-function -fno-exceptions -fdiagnostics-absolute-paths -g -o main.exe -Wl,user32.lib
+rem clang core_main.cpp %clang-flags%
 rem ubuntu run clang core_main.cpp -O0 -Wall -Wno-unused-function -fno-exceptions -fdiagnostics-absolute-paths -g -o core.out
 
+clang core_arena.cpp %clang-flags%
+
 rem clang test.cpp
 
 rem main.exe -testing
diff --git a/core_arena.cpp b/core_arena.cpp
new file mode 100644
index 0000000..a06de78
--- /dev/null
+++ b/core_arena.cpp
@@ -0,0 +1,83 @@
+#include "base.cpp"
+
+struct Arena_Block {
+  Arena_Block *next;
+  Arena_Block *prev;
+  size_t cap;
+  size_t len;
+  uint8_t memory[];
+};
+
+constexpr size_t default_block_size = mib(1);
+struct Arena_Block_Based : Allocator {
+  Arena_Block *first;
+  Arena_Block *last;
+  Arena_Block *first_free;
+  Allocator *block_allocator;
+  size_t alignment;
+};
+
+static void arena_add_block(Arena_Block_Based *arena, size_t min_size) {
+  Arena_Block *block = 0;
+  for (Arena_Block *it = arena->first_free; it; it = it->next) {
+    if (it->cap > min_size) {
+      block = it;
+      DLL_STACK_REMOVE(arena->first_free, it);
+      break;
+    }
+  }
+  
+  if (!block) {
+    block = (Arena_Block *)allocate_size(arena->block_allocator, sizeof(Arena_Block) + min_size + default_alignment, false);
+    block->cap = min_size + default_alignment;
+  }
+
+  block->len = 0;
+  block->next = 0;
+  block->prev = 0;
+  DLL_QUEUE_ADD(arena->first, arena->last, block);
+}
+
+static void *block_arena_push_size(Arena_Block_Based *arena, size_t size) {
+  size_t generous_size = size + arena->alignment;
+  if (!arena->last || (arena->last->len + generous_size > arena->last->cap)) {
+    assert(arena->block_allocator);
+    size_t block_size = max(default_block_size, generous_size);
+    arena_add_block(arena, block_size);
+  }
+
+  Arena_Block *L = arena->last;
+  size_t adjusted_len = align_up((size_t)L->memory + L->len, arena->alignment) - (size_t)L->memory;
+  assert(((int64_t)adjusted_len - (int64_t)L->len) > 0);
+  assert(((int64_t)adjusted_len - (int64_t)L->len) <= arena->alignment);
+  L->len = adjusted_len;
+
+  uint8_t *result = L->memory + L->len;
+  L->len += size;
+  return (void *)result;
+}
+
+static Arena_Block_Based make_arena_block_based(Allocator *allocator) {
+  Arena_Block_Based result = {};
+  result.block_allocator = allocator;
+  result.alignment = default_alignment;
+  result.allocate = (Allocator::Allocate *)block_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); }
+static CRT_Heap make_crt_heap() {
+  CRT_Heap result = {};
+  result.allocate = crt_allocate;
+  result.deallocate = crt_deallocate;
+  return result;
+}
+
+int main() {
+  CRT_Heap heap = make_crt_heap();
+  Arena_Block_Based arena = make_arena_block_based(&heap);
+  void *result = allocate_size(&arena, 32);
+}
\ No newline at end of file
diff --git a/core_generated.cpp b/core_generated.cpp
index 5f657ba..6bc0372 100644
--- a/core_generated.cpp
+++ b/core_generated.cpp
@@ -1,6 +1,4 @@
 
-
-
 /*#import meta
 
 print("Operator_Info op_info_table[] = {")