path: root/zap/src/mem/fndbyte.S

/*
	Copyright 2022 Gabriel Jensen.
	This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
	If a copy of the MPL was not distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/.
*/

#include <zap/priv.h>

.globl zap_fndbyte

zap_fndbyte:

	/*
		void const *  ptr
		zap_sz        num
		unsigned char byte
	*/

#if defined(__amd64__)

	# rax: Address of the current element.
	# rdi: Address of the first element.
	# rsi: Address of the element after the last element.
	# rdx: Byte value.
	# rcx: Current byte.

	movq %rdi,%rax

	addq %rdi,%rsi

	# Iterate over the array:
.loop:

	# Check if we have reached the end of the array:
	cmpq %rax,%rsi
	je .nfnd
	
	# Check if we have found the byte value:
	movb (%rax),%cl
	cmpb %cl,%dl
	je .fnd

	# Continue to the next byte:
	incq %rax
	jmp .loop

	# Found:
.fnd:

	subq %rdi,%rax
	ret

	# Not found:
.nfnd:

	movq $0xFFFFFFFFFFFFFFFF,%rax
	ret

#endif