First complete iteration of stack allocator
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@ -1,18 +1,23 @@
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package sectr
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Stack :: struct ( $ Type : typeid, $ Size : i32 ) {
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idx : i32,
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import "core:mem"
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import "core:slice"
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//region Fixed Stack
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StackFixed :: struct ( $ Type : typeid, $ Size : u32 ) {
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idx : u32,
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items : [ Size ] Type,
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}
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stack_push :: proc( using stack : ^ Stack( $ Type, $ Size ), value : Type ) {
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stack_push :: proc( using stack : ^ StackFixed( $ Type, $ Size ), value : Type ) {
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verify( idx < len( items ), "Attempted to push on a full stack" )
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items[ idx ] = value
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idx += 1
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}
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stack_pop :: proc( using stack : ^ Stack( $ Type, $ Size ) ) {
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stack_pop :: proc( using stack : ^StackFixed( $ Type, $ Size ) ) {
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verify( idx > 0, "Attempted to pop an empty stack" )
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idx -= 1
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@ -21,12 +26,244 @@ stack_pop :: proc( using stack : ^ Stack( $ Type, $ Size ) ) {
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}
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}
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stack_peek_ref :: proc( using stack : ^ Stack( $ Type, $ Size ) ) -> ^ Type {
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stack_peek_ref :: proc( using stack : ^StackFixed( $ Type, $ Size ) ) -> ( ^Type) {
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last := max( 0, idx - 1 )
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return & items[last]
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}
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stack_peek :: proc ( using stack : ^ Stack( $ Type, $ Size ) ) -> Type {
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stack_peek :: proc ( using stack : ^StackFixed( $ Type, $ Size ) ) -> Type {
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last := max( 0, idx - 1 )
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return items[last]
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}
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//endregion Fixed Stack
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//region Stack Allocator
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/* Growing Stack allocator
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This implementation can support growing if the backing allocator supports
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it without fragmenting the back allocator.
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Each block in the stack is tracked with a doubly-linked list to have debug stats.
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(It could be removed for non-debug builds)
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*/
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StackAllocatorBase :: struct {
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backing : Allocator,
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using links : DLL_NodeFL(StackAllocatorHeader),
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peak_used : int,
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size : int,
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data : [^]byte,
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}
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StackAllocator :: struct {
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using base : ^StackAllocatorBase,
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}
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StackAllocatorHeader :: struct {
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using links : DLL_NodePN(StackAllocatorHeader),
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block_size : int,
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padding : int,
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}
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stack_allocator :: proc( using self : StackAllocator ) -> ( allocator : Allocator ) {
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allocator.procedure = stack_allocator_proc
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allocator.data = self.base
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return
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}
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stack_allocator_init :: proc( size : int, allocator := context.allocator ) -> ( stack : StackAllocator, alloc_error : AllocatorError )
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{
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header_size := size_of(StackAllocatorBase)
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raw_mem : rawptr
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raw_mem, alloc_error = alloc( header_size + size, mem.DEFAULT_ALIGNMENT )
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if alloc_error != AllocatorError.None do return
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stack.base = cast( ^StackAllocatorBase) raw_mem
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stack.size = size
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stack.data = cast( [^]byte) (cast( [^]StackAllocatorBase) stack.base)[ 1:]
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stack.top = cast(^StackAllocatorHeader) stack.data
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stack.bottom = stack.first
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return
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}
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stack_allocator_init_via_memory :: proc( memory : []byte ) -> ( stack : StackAllocator )
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{
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header_size := size_of(StackAllocatorBase)
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if len(memory) < (header_size + Kilobyte) {
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verify(false, "Assigning a stack allocator less than a kilobyte of space")
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return
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}
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stack.base = cast( ^StackAllocatorBase) & memory[0]
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stack.size = len(memory) - header_size
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stack.data = cast( [^]byte ) (cast( [^]StackAllocatorBase) stack.base)[ 1:]
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stack.top = cast( ^StackAllocatorHeader) stack.data
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stack.bottom = stack.first
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return
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}
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stack_allocator_push :: proc( using self : StackAllocator, block_size, alignment : int, zero_memory : bool ) -> ( []byte, AllocatorError )
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{
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// TODO(Ed): Make sure first push is fine.
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verify( block_size > Kilobyte, "Attempted to push onto the stack less than a Kilobyte")
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top_block_ptr := memory_after_header( top )
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theoretical_size := cast(int) (uintptr(top_block_ptr) + uintptr(block_size) - uintptr(bottom))
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if theoretical_size > size {
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// TODO(Ed) : Check if backing allocator supports resize, if it does attempt to grow.
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return nil, .Out_Of_Memory
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}
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top_block_slice := slice_ptr( top_block_ptr, top.block_size )
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next_spot := uintptr( top_block_ptr) + uintptr(top.block_size)
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header_offset_pad := calc_padding_with_header( uintptr(next_spot), uintptr(alignment), size_of(StackAllocatorHeader) )
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header := cast( ^StackAllocatorHeader) (next_spot + uintptr(header_offset_pad) - uintptr(size_of( StackAllocatorHeader)))
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header.padding = header_offset_pad
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header.prev = last
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header.block_size = block_size
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curr_block_ptr := memory_after_header( header )
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curr_block := slice_ptr( curr_block_ptr, block_size )
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curr_used := cast(int) (uintptr(curr_block_ptr) + uintptr(block_size) - uintptr(self.top))
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self.peak_used += max( peak_used, curr_used )
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dll_push_back( & base.links.last, header )
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if zero_memory {
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slice.zero( curr_block )
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}
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return curr_block, .None
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}
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stack_allocator_resize_top :: proc( using self : StackAllocator, new_block_size, alignment : int, zero_memory : bool ) -> AllocatorError
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{
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verify( new_block_size > Kilobyte, "Attempted to resize the last pushed on the stack to less than a Kilobyte")
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top_block_ptr := memory_after_header( top )
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theoretical_size := cast(int) (uintptr(top_block_ptr) + uintptr(top.block_size) - uintptr(bottom))
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if theoretical_size > size {
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// TODO(Ed) : Check if backing allocator supports resize, if it does attempt to grow.
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return .Out_Of_Memory
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}
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if zero_memory && new_block_size > top.block_size {
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added_ptr := top_block_ptr[ top.block_size:]
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added_slice := slice_ptr( added_ptr, new_block_size - top.block_size )
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slice.zero( added_slice )
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}
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top.block_size = new_block_size
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return .None
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}
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stack_allocator_pop :: proc( using self : StackAllocator ) {
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base.links.top = top.prev
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base.links.top.next = nil
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}
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stack_allocator_proc :: proc(
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allocator_data : rawptr,
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mode : AllocatorMode,
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block_size : int,
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alignment : int,
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old_memory : rawptr,
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old_size : int,
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location : SourceCodeLocation = #caller_location
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) -> ([]byte, AllocatorError)
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{
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stack := StackAllocator { cast( ^StackAllocatorBase) allocator_data }
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if stack.data == nil {
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return nil, AllocatorError.Invalid_Argument
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}
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switch mode
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{
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case .Alloc, .Alloc_Non_Zeroed:
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{
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return stack_allocator_push( stack, block_size, alignment, mode == .Alloc )
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}
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case .Free:
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{
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if old_memory == nil {
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return nil, .None
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}
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start := uintptr(stack.data)
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end := start + uintptr(block_size)
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curr_addr := uintptr(old_memory)
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verify( start <= curr_addr && curr_addr < end, "Out of bounds memory address passed to stack allocator (free)" )
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block_ptr := memory_after_header( stack.last )
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if curr_addr >= start + uintptr(block_ptr) {
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return nil, .None
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}
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dll_pop_back( & stack.last, stack.last )
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}
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case .Free_All:
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{
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// TODO(Ed) : Review that we don't have any header issues with the reset.
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stack.last = stack.first
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stack.first.next = nil
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stack.first.block_size = 0
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}
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case .Resize, .Resize_Non_Zeroed:
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{
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// Check if old_memory is at the first on the stack, if it is, just grow its size
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// Otherwise, log that the user cannot resize stack items that are not at the top of the stack allocated.
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if old_memory == nil {
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return stack_allocator_push(stack, block_size, alignment, mode == .Resize )
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}
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if block_size == 0 {
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return nil, .None
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}
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start := uintptr(stack.data)
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end := start + uintptr(block_size)
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curr_addr := uintptr(old_memory)
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verify( start <= curr_addr && curr_addr < end, "Out of bounds memory address passed to stack allocator (resize)" )
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block_ptr := memory_after_header( stack.top )
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if block_ptr != old_memory {
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ensure( false, "Attempted to reszie a block of memory on the stack other than top most" )
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return nil, .None
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}
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if old_size == block_size {
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return byte_slice( old_memory, block_size ), .None
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}
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stack_allocator_resize_top( stack, block_size, alignment, mode == .Resize )
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return byte_slice( block_ptr, block_size ), .None
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}
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case .Query_Features:
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{
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feature_flags := ( ^AllocatorModeSet)(old_memory)
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if feature_flags != nil {
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(feature_flags ^) = {.Alloc, .Alloc_Non_Zeroed, .Free, .Free_All, .Resize, .Resize_Non_Zeroed, .Query_Features}
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}
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return nil, .None
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}
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case .Query_Info:
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{
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return nil, .Mode_Not_Implemented
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}
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}
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return nil, .None
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}
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//endregion Stack Allocator
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