fasmg-include/interface/allocator.inc

; vim:ft=fasm:

; TODO: add arena allocator
; TODO: add general purpose allocator
interface Allocator
	; u8* alloc(usize)
	alloc size

	; u8* realloc(u8*, usize)
	realloc ptr, new_size

	; void realloc(u8*)
	free ptr
end interface

struct FixedBufferAllocator.data
	memory dq ?
	size dq ?
	capacity dq ?
	alignment db 8
ends
macro FixedBufferAllocator.data.new _data*, _memory*, _capacity*, _size:0, _alignment:8
	mov qword [_data + FixedBufferAllocator.data.memory], _memory
	mov qword [_data + FixedBufferAllocator.data.size], _size
	mov qword [_data + FixedBufferAllocator.data.capacity], _capacity
	mov byte  [_data + FixedBufferAllocator.data.alignment], _alignment

end macro

proc FixedBufferAllocator.reset
	using_regs rax
		interface.self_data rax
		mov [rax + FixedBufferAllocator.data.size], 0
	end using_regs
end proc

proc FixedBufferAllocator.alloc
	.self_data = r15
	.new_size = r14
	.old_size = r13
	.size = rdi
	;.alignment = 8

	using_regs .self_data, .new_size, .old_size
		interface.self_data rax, .self_data

		.check_size:
			mov .old_size, [.self_data + FixedBufferAllocator.data.size]
			lea .new_size, [.old_size + .size]
			movzx rsi, byte [.self_data + FixedBufferAllocator.data.alignment]
			align_to .new_size, rsi
			mov .new_size, rax
			xor rax, rax
			cmp [.self_data + FixedBufferAllocator.data.capacity], .new_size
			jl .capcity_exceeded

		.capacity_ok:
			mov [.self_data + FixedBufferAllocator.data.size], .new_size
			mov rax, [.self_data + FixedBufferAllocator.data.memory]
			lea rax, [rax + .old_size]
		.capcity_exceeded:
	end using_regs
end proc

proc Allocator.realloc_default
	xor rax, rax
end proc

proc Allocator.free_default
	xor rax, rax
end proc