/*
	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/.
*/

#include <zap/priv.h>

#include <stdbool.h>
#include <stdint.h>

#if defined(zap_priv_fastimpl)
__asm__ (
	".globl zap_streq\n"

	"zap_streq:\n"
		/*
			char const * lstr
			char const * rstr
		*/
#if defined(sus_arch_amd64)
		/* rax: Address of the current input character. */
		"movq %rdi,%rax\n"
		/* rsi: Address of the current output character. */
		"movq %rsi,%rsi\n"
		/* rdx: Current input character. */
		/* rcx: Current output character. */
	".loop:\n"
		"movb (%rax),%dl\n" /* Move the characters into registers. */
		"movb (%rsi),%cl\n"
		"cmpb %dl,%cl\n" /* Check if the characters are equal... */
		"jne .neq\n" /* ... indicate inequality if they are not. */
		"testb %dl,%dl\n" /* Check if we have reached the null-terminator... */
		"jz .eq\n" /* ... indicate equality if we have. */
		"incq %rax\n" /* Increment positions. */
		"incq %rsi\n"
		"jmp .loop\n" /* Restart loop. */
	".eq:\n" /* Indicate equality. */
		"movb $0x1,%al\n"
		"ret\n"
	".neq:\n" /* Indicate inequality. */
		"movb $0x0,%al\n"
		"ret\n"
#elif defined(sus_arch_ia32)
	/* eax: Address of the current input character. */
	"movl 0x4(%esp),%eax\n"
	/* ecx: Address of the current output character. */
	"movl 0x8(%esp),%ecx\n"
	/* edx: Current input character. */
	/* edx: Current output character. */
	".loop:\n"
		"movb (%eax),%dl\n" /* Move the characters into registers. */
		"movb (%ecx),%dh\n"
		"cmpb %dl,%dh\n" /* Check if the characters are equal... */
		"jne .neq\n" /* ... indicate inequality if they are not. */
		"testb %dl,%dl\n" /* Check if we have reached the null-terminator... */
		"jz .eq\n" /* ... indicate equality if we have. */
		"incl %eax\n" /* Increment positions. */
		"incl %ecx\n"
		"jmp .loop\n" /* Restart loop. */
	".eq:\n" /* Indicate equality. */
		"movb $0x1,%al\n"
		"ret\n"
	".neq:\n" /* Indicate inequality. */
		"movb $0x0,%al\n"
		"ret\n"
#endif
);
#else
bool zap_streq(char const * const _lstr,char const * const _rstr) {
	char const * lpos = _lstr;
	char const * rpos = _rstr;
	for (;;++lpos,++rpos) {
		char const lchr = *lpos;
		char const rchr = *rpos;
		sus_likely (lchr != rchr) {return false;}
		if (lchr == '\x0') {return true;}
	}
	sus_unreach();
}
#endif