arena pop

2 files changed, 18 insertions, 0 deletions

diff --git a/qstd/memory.c b/qstd/memory.c
index 7d669d2..87618f9 100644
--- a/qstd/memory.c
+++ b/qstd/memory.c
@@ -34,10 +34,12 @@ void init_arena(
 	a->buf = mem;
 	a->size = size;
 	a->ptr = 0;
+	a->last_push = 0;
 }
 
 void clear_arena(Arena* a) {
 	a->ptr = 0;
+	a->last_push = 0;
 }
 
 void* imp_arena_alloc(
@@ -75,6 +77,19 @@ void* arena_alloc_aligned(
 	return (void*)align_address((uintptr_t)p, align);
 }
 
+void arena_push(Arena* a) {
+	int last = a->last_push, * prev;
+	a->last_push = a->ptr;
+	prev = arena_alloc(a, sizeof *prev);
+	*prev = last;
+}
+
+void arena_pop(Arena* a) {
+	assert(a->last_push);
+	a->ptr -= a->last_push;
+	a->last_push = *(int*)&a->buf[a->ptr];
+}
+
 void init_heap(
 	Heap* h,
 	void* mem,
diff --git a/qstd/memory.h b/qstd/memory.h
index a0b819a..d87dce6 100644
--- a/qstd/memory.h
+++ b/qstd/memory.h
@@ -13,6 +13,7 @@ void zero(void* buf, int size);
 typedef struct Arena {
 	char* buf;
 	int size, ptr;
+	int last_push;
 } Arena;
 
 void init_arena(
@@ -30,6 +31,8 @@ void* arena_alloc_aligned(
 	int size,
 	int align
 );
+void arena_push(Arena* a);
+void arena_pop(Arena* a);
 
 typedef struct Heap {
 	char* buf;