Start mini arena

2026-06-10 11:59:42 +02:00
parent 627c6d16ca
commit bc78e4150b
1 changed files with 96 additions and 0 deletions
@@ -0,0 +1,96 @@
+#pragma once
+#include "base_core.h"
+
+typedef struct MiniArena MiniArena;
+struct MiniArena {
+    U8 *start;  // start of user buffer
+    U8 *curr;   // next alloc point
+    U8 *end;    // one past end of user buffer
+    int checkpoint_level;  // level of miniarenatmp_begin stacks
+};
+
+typedef struct MiniArenaCheckpoint MiniArenaCheckpoint;
+struct MiniArenaCheckpoint {
+    U8 *alloc_point;
+    MiniArena *arena;
+};
+
+#define LARENA_STATIC_INITIALIZER(data) LARENA_INITIALIZER((data), sizeof(data))
+#define LARENA_INITIALIZER(data, sz) {.start = (data), .curr = (data), .end = (data) + sz, .checkpoint_level = 0}
+#define LARENA_DEFINE(var_name, size_, alignment_)  \
+    struct {                                        \
+        _Alignas(alignment_) U8 memory[size_]; \
+    } var_name##_arena_memory;                      \
+    MiniArena var_name = LARENA_STATIC_INITIALIZER(var_name##_arena_memory.memory)
+#define LARENA_ALLOC_TYPE(allocator, type_) miniarenaalloc_aligned((allocator), sizeof(type_), _Alignof(type_))
+#define LARENA_ALLOC_ARRAY(allocator, type_, nr_elements_) miniarenaalloc_aligned((allocator), (nr_elements_) * sizeof(type_), _Alignof(type_))
+static INLINE size_t miniarena_size(const MiniArena *arena)
+{
+    return (size_t)(arena->end - arena->start);
+}
+
+static INLINE size_t miniarena_used(const MiniArena *arena)
+{
+    return (size_t)(arena->curr - arena->start);
+}
+static INLINE size_t miniarena_available(const MiniArena *arena)
+{
+    return miniarena_size(arena) - miniarena_used(arena);
+}
+
+static INLINE void miniarena_init(MiniArena *arena, void *memory, size_t sz)
+{
+    arena->start = arena->curr = (U8 *)memory;
+    arena->end = arena->start + sz;
+}
+
+static INLINE MiniArenaCheckpoint miniarenatmp_begin(MiniArena *arena)
+{
+    MiniArenaCheckpoint checkpoint = {};
+
+    checkpoint.arena = arena;
+    checkpoint.alloc_point = arena->curr;
+    arena->checkpoint_level++;
+
+    return checkpoint;
+}
+
+static INLINE void miniarenatmp_end(MiniArenaCheckpoint *state)
+{
+    MiniArena *arena = state->arena;
+    Assert(arena->checkpoint_level > 0);
+    arena->curr = state->alloc_point;
+    arena->checkpoint_level--;
+}
+static INLINE void *miniarena_push(MiniArena *arena, size_t sz)
+{
+    if (sz > miniarena_available(arena)) {
+        return NULL;
+    }
+    void *start = arena->curr;
+    arena->curr += sz;
+    return start;
+}
+
+[[gnu::alloc_align(3)]]
+static INLINE void *miniaren_push_aligned(MiniArena *arena, size_t sz, unsigned int align)
+{
+    Assert(IsPow2(align));
+
+    uintptr_t curr = (uintptr_t)arena->curr;
+    uintptr_t aligned = AlignUp(curr, align);
+    U8 *start = (U8 *)aligned;
+
+    if (sz > (size_t)(arena->end - start)) {
+        return NULL;
+    }
+
+    arena->curr = start + sz;
+
+    return start;
+}
+
+static INLINE void miniarena_reset(MiniArena *arena)
+{
+    arena->curr = arena->start;
+}