From 154bf6f53529e88dfa03d6ff5034b575f92cdbb5 Mon Sep 17 00:00:00 2001
From: nasr <nsrddyn@gmail.com>
Date: Tue, 14 Apr 2026 23:11:49 +0200
Subject: feature(setup): base implementation

---
 source/base/base_stack.h | 210 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 210 insertions(+)
 create mode 100755 source/base/base_stack.h

(limited to 'source/base/base_stack.h')

diff --git a/source/base/base_stack.h b/source/base/base_stack.h
new file mode 100755
index 0000000..43a7230
--- /dev/null
+++ b/source/base/base_stack.h
@@ -0,0 +1,210 @@
+#ifndef STACK_H
+#define STACK_H
+
+typedef struct mem_stack_header mem_stack_header;
+struct mem_stack_header
+{
+    u8 padding;
+    u8 previous_offset;
+};
+
+
+typedef struct mem_stack mem_stack;
+struct mem_stack
+{
+    mem_stack_header *header;
+
+    u64 current_offset;
+    u64 capacity;
+    u8 *base_position;
+};
+
+internal mem_stack *
+stack_create(u64 capacity)
+{
+    mem_stack *stack = (mem_stack *)mmap(
+    0,
+    capacity + sizeof(mem_stack),
+    PROT_READ | PROT_WRITE,
+    MAP_SHARED | MAP_ANONYMOUS,
+    -1,
+    0);
+
+    if (stack == MAP_FAILED)
+    {
+        return NULL;
+    }
+
+    stack->capacity       = capacity;
+    stack->base_position  = (u8 *)stack + sizeof(mem_stack);
+    stack->current_offset = 0;
+
+    return stack;
+}
+
+internal u8
+calculate_padding(u64 pointer, u8 alignment, u64 header_size)
+{
+    u8 modulo, padding;
+
+    if (!is_pow(alignment))
+    {
+        return 0;
+    }
+
+    modulo = pointer & (u8)(alignment - 1);
+
+    padding = 0;
+
+    if (0 == modulo)
+    {
+        padding = alignment - modulo;
+    }
+
+    if (padding < header_size)
+    {
+        header_size -= padding;
+
+        if ((header_size & (alignment - 1)) != 0)
+        {
+            padding += alignment * (1 + (header_size / alignment));
+        }
+        else
+        {
+            padding += alignment * (header_size / alignment);
+        }
+    }
+
+    return padding;
+}
+
+internal mem_stack *
+stack_push_align(mem_stack *stack, u64 size, u8 alignment)
+{
+    u8 padding = 0;
+
+    if (!is_pow(alignment))
+    {
+        return (0);
+    }
+
+    if (alignment > 128)
+    {
+        alignment = 128;
+    }
+
+    u64 current_address = (u64)stack->base_position + stack->current_offset;
+    padding             = calculate_padding(current_address, alignment, sizeof(mem_stack_header));
+
+    if (stack->current_offset + padding + size > stack->capacity)
+    {
+        return 0;
+    }
+
+    stack->current_offset += padding;
+
+    u64               next_address = current_address + (u64)padding;
+    mem_stack_header *header       = (mem_stack_header *)(next_address - sizeof(mem_stack_header));
+    header->padding                = padding;
+
+    stack->current_offset += size;
+
+    return MemSet((void *)next_address, size);
+}
+internal void *
+stack_push(mem_stack *stack, u64 size)
+{
+    return stack_push_align(stack, size, ARENA_ALIGN);
+}
+
+internal void
+stack_pop(mem_stack *stack, void *pointer)
+{
+    if (pointer != NULL)
+    {
+        u64               start, end, current_address;
+        mem_stack_header *header;
+        u64               prev_offset;
+
+        start           = (u64)stack->base_position;
+        end             = start + (u64)stack->capacity;
+        current_address = (u64)pointer;
+
+        if (!(start <= current_address && current_address < end))
+        {
+            if (0 && "Out of bounds memory address passed to stack allocator (free)")
+            {
+                return;
+            }
+            return;
+        }
+
+        if (current_address >= start + (u64)stack->base_position)
+        {
+            return;
+        }
+
+        header                = (mem_stack_header *)(current_address - sizeof(mem_stack_header));
+        prev_offset           = (size_t)(current_address - (u64)header->padding - start);
+        stack->current_offset = prev_offset;
+    }
+}
+
+internal mem_stack *
+stack_resize_align(mem_stack *stack, void *pointer, u64 old_size, u64 new_size, u8 alignment)
+{
+    if (pointer == NULL)
+    {
+        return stack_push_align(stack, new_size, alignment);
+    }
+    else if (new_size == 0)
+    {
+        stack_pop(stack, pointer);
+        return NULL;
+    }
+
+    u64   start, end, current_address;
+    u64   min_size = old_size < new_size ? old_size : new_size;
+    void *new_pointer;
+
+    start           = (u64)stack->base_position;
+    end             = start + (u64)stack->capacity;
+    current_address = (u64)pointer;
+    if (!(start <= current_address && current_address < end))
+    {
+        return NULL;
+    }
+
+    if (current_address >= start + (u64)stack->current_offset)
+    {
+        return NULL;
+    }
+
+    if (old_size == new_size)
+    {
+        return pointer;
+    }
+
+    new_pointer = stack_push_align(stack, new_size, alignment);
+    memmove(new_pointer, pointer, min_size);
+    return new_pointer;
+}
+
+internal void
+stack_pop_all(mem_stack *stack)
+{
+    stack->current_offset = 0;
+}
+
+internal void
+stack_destroy(mem_stack *stack)
+{
+    if (!stack)
+    {
+        return;
+    }
+
+    munmap(stack, stack->capacity + sizeof(mem_stack));
+}
+
+#endif
-- 
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