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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_strlen
zap_strlen:
# Address of the current character:
#define addr %rax
# Address of the first character:
#define start %rdi
# Current character:
#define chr %dl
movq start,addr
# Iterate over the string:
.loop:
# Move the character into a register:
movb (addr),chr # chr = *addr
# Check if we have reached the null-terminator:
testb chr,chr # if (chr == 0x0)
jz .done # goto done
# Continue to the next character:
incq addr # ++addr
jmp .loop # goto loop
# Done:
.done:
# Get the length:
subq start,addr # addr -= start
ret # return addr
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