# 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/.

.globl zap_utf20len

zap_utf20len:
	# rax: Address of the current character.
	# rdi: Address of the first character.
	# rdx: Current character.

	movq %rdi,%rax

	# Iterate over the string:
.loop:

	# Move the character into a register:
	movl (%rax),%edx

	# Check if we have reached the null-terminator:
	testl %edx,%edx
	jz .done # If so, we are done.

	# Continue to the next character:
	addq $0x4,%rax
	jmp .loop

	# Done:
.done:

	# Get the length:
	subq %rdi,%rax
	shrq $0x2,%rax # Divide by four to get the number of doublewords rather than bytes.

	ret