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# 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
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