path: root/zap/src/mem/strfill.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_strfill

zap_strfill:

	/*
		char * str
		char   chr
	*/

#if defined(__amd64__)

	# rdi: Address of the first character of the string.
	# rsi: Fill character.
	# rax: Address of the current character.

	movq %rdi,%rax

	# Iterate over string:
.loop:

	# Check if we have reached the null-terminator:
	cmpb $0x0,(%rax)
	je .done # Exit loop if we have.

	# Set the value of the current element:
	movb %sil,(%rax)

	# Continue to next character:
	incq %rax
	jmp .loop

	# Finish:
.done:

	# Get the length of the string:
	subq %rdi,%rax

	ret

#endif