# 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_strcp

zap_strcp:
# Address of the current input character:
#define iaddr %rax
# Address of the first input character:
#define start %rdi
# Address of the current output character:
#define oaddr %rsi
# Current character:
#define chr   %dl

	movq start,iaddr

	# Iterate over the strings:
.loop:

	# Copy character:
	movb (iaddr),chr # chr = *iaddr
	movb chr,(oaddr) # *oaddr = chr

	# Check if we have reached the null-terminator:
	testb chr,chr # if (chr == 0x0)
	jz .done      # goto done

	# Continue to the next character:

	incq iaddr # ++iaddr
	incq oaddr # ++oaddr
	jmp .loop  # goto loop

	# Finish:
.done:

	# Get the length of the (input) string:
	subq start,iaddr # iaddr -= start
	decq iaddr       # --iaddr        // We do not count the null-terminator in the string length.

	ret # return iaddr