path: root/zap/src/memfill.c

/*
	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 <stddef.h>
#include <stdint.h>

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

	"zap_memfill:\n"
		/*
			void const * ptr
			size_t       num
			uint_least8_t      val
		*/
#if defined(sus_arch_amd64)
		/* rdi: Address of the current element. */
		/* rsi: Address of the element after the last element. */
		"addq %rdi,%rsi\n"
	".loop:\n"
		"cmpq %rdi,%rsi\n"
		"je .done\n" /* Exit loop if we have reached the final element. */
		"movb %dl,(%rdi)\n"
		"incq %rdi\n"
		"jmp .loop\n" /* Continue to next element. */
	".done:\n"
		"ret\n"
#elif defined(sus_arch_ia32)
		/* eax: Address of the current element. */
		"movl 0x4(%esp),%eax\n"
		/* ecx: Address of the element after the last element. */
		"movl 0x4(%esp),%ecx\n"
		"addl 0x8(%esp),%ecx\n"
		/* edx: Byte value. */
		"movb 0xC(%esp),%dl\n"
	".loop:\n"
		"cmpl %eax,%ecx\n"
		"je .done\n" /* Exit loop if we have reached the final element. */
		"movb %dl,(%eax)\n"
		"incl %eax\n"
		"jmp .loop\n" /* Continue to next element. */
	".done:\n"
		"ret\n"
#endif
);
#else
void zap_memfill(void * const _ptr,size_t const _num,uint_least8_t const _byte) {
	uint_least8_t *       pos      = (uint_least8_t *)_ptr;
	uint_least8_t * const afterbuf = pos + _num;
	for (;pos != afterbuf;++pos) {*pos = _byte;}
}
#endif