path: root/zap/src/mem/streq.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_streq

zap_streq:

	/*
		char const * lstr
		char const * rstr
	*/

#if defined(__amd64__)

	# rdi: Address of the current left character.
	# rsi: Address of the current right character.
	# rax: Current left character.
	# rdx: Current right character.

	# Iterate over the strings:
.loop:

	# Copy the characters into registers:
	movb (%rdi),%al
	movb (%rsi),%dl

	# Check if the characters are equal:
	cmpb %al,%dl
	jne .neq # If not, the strings also aren't equal.

	# Check if we have reached the null-terminator:
	testb %al,%al
	jz .eq # If so, all previous characters have compared equal, and the strings are equal.

	# Continue to the next characters:
	incq %rdi
	incq %rsi
	jmp .loop

	# The strings have compared equal:
.eq:

	movb $0xFF,%al
	ret

	/* The strings have compared unequal: */
.neq:

	movb $0x0,%al
	ret

#endif