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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_utf8enclen
zap_utf8enclen:
# rdi: Address of the current character.
# rax: Length of the string.
# rsi: Current character.
movq $0x0,%rax
# Iterate over the input:
.loop:
movl (%rdi),%esi
# Test if we have reached the null-terminator:
testl %esi,%esi
jz .done
cmpl $0xFFFF,%esi
jg .oct4
cmpl $0x7FF,%esi
jg .oct3
cmpl $0x7F,%esi
jg .oct2
# One octet:
.oct1:
incq %rax
jmp .cnt
# Two octets:
.oct2:
addq $0x2,%rax
jmp .cnt
# Three octets:
.oct3:
addq $0x3,%rax
jmp .cnt
# Four octets:
.oct4:
addq $0x4,%rax
# Continue to the next codepoint:
.cnt:
addq $0x4,%rdi
jmp .loop
# Done:
.done:
ret
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