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// TODO: the previous position of the stack header never get's set
// TODO: renmae current_position in arena.cpp and arena.h to current_address or vice versa
#if PLATFORM_LINUX
internal MemStack *unix_stack_create(u64 capacity)
{
MemStack *stack = (MemStack *)mmap(0, capacity + sizeof(MemStack), 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(MemStack);
stack->current_offset = 0;
return stack;
}
internal void unix_stack_destroy(MemStack *stack)
{
if (!stack) {
return;
}
munmap(stack, stack->capacity + sizeof(MemStack));
}
#endif // PLATFORM_LINUX
#if PLATFORM_WINDOWS
// request a page from the operating system
internal MemStack *win32_stack_create(u64 capacity)
{
MemStack *stack = (MemStack *)VirtualAlloc(NULL, capacity + sizeof(MemStack),
MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
if (!stack) {
Log("Failed to receive a memory address from the operating system");
return NULL;
}
stack->capacity = capacity;
stack->base_position = (u8 *)stack + sizeof(MemStack);
stack->current_offset = 0;
return stack;
}
internal void win32_stack_destroy(MemStack *stack)
{
b32 result = VirtualFree(stack,
0, // stands for the byte of committed pages
MEM_RELEASE);
if (!result) {
Log("Failed to receive a memory address from the operating system");
}
}
#endif // PLATFORM_WINDOWS
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 + (u8)(header_size / alignment));
} else {
padding += alignment * ((u8)(header_size / alignment));
}
}
return padding;
}
internal MemStack *stack_push_align(MemStack *stack, u64 size, u8 alignment)
{
// NOTE: satifisying static analyzer
AssertLog((stack != NULL), "STACK IS NULL");
u8 padding = 0;
// NOTE: this shouln't be possible because we have the allignment predefined
// so it's bassically a useless check
if (!is_pow(alignment)) {
breakpoint();
return (0);
}
if (alignment > 128) { // NOTE: where does the 128 come from?
alignment = 128;
}
u64 current_address;
current_address = (u64)stack->base_position + stack->current_offset; // NOTE: we already we're checking if the stack existed
padding = calculate_padding(current_address, alignment, sizeof(MemStackHeader));
if (stack->current_offset + padding + size > stack->capacity) {
breakpoint();
return 0;
}
stack->current_offset += padding;
u64 next_address = current_address + (u64)padding;
MemStackHeader *header = (MemStackHeader *)(next_address - sizeof(MemStackHeader));
header->padding = padding;
stack->current_offset += size;
return (MemStack *)MemSet((MemStack *)next_address, size);
}
internal void *stack_push(MemStack *stack, u64 size)
{
return stack_push_align(stack, size, arena_align);
}
internal void stack_pop(MemStack *stack, void *pointer)
{
if (pointer != NULL) {
u64 start, end, current_address;
MemStackHeader *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->current_offset) {
return;
}
header = (MemStackHeader *)(current_address - sizeof(MemStackHeader));
prev_offset = (size_t)(current_address - (u64)header->padding - start);
stack->current_offset = prev_offset;
}
}
internal MemStack *stack_resize_align(MemStack *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 (MemStack *)pointer;
}
new_pointer = stack_push_align(stack, new_size, alignment);
AssertLog((new_pointer != NULL), "stack_push_align failed in stack_resize_align");
memmove(new_pointer, pointer, min_size);
return (MemStack *)new_pointer;
}
internal MemStack *arena_to_stack(MemArena *arena, u64 requested_size)
{
Assert(arena);
MemStack *stack = PushStruct(arena, MemStack);
u8 *buffer = PushArray(arena, u8, requested_size);
stack->header = 0;
stack->base_position = buffer;
stack->capacity = requested_size;
stack->current_offset = 0;
return stack;
}
#if 0
#if MEM_DEBUG
global_variable String8List *stack_log; // TODO: initialize this in the mem stack callback
#endif
internal void
stack_debug_view(MemArena *global_arena, MemStack *stack)
{
if(!stack_log)
{
stack_log = PushStruct(global_arena, String8List);
}
}
#endif
internal void stack_clear(MemStack *stack) { stack->current_offset = 0; }
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