push from SNAPKITTYWEST/snapkitty-twin-mars-asm

42fb483 verified about 2 months ago

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; strings.asm — string primitives: strlen, str_eq, str_copy
%include "include/syscall.inc"

section .text
global str_len
global str_eq
global str_copy

; size_t str_len(const char *s)
str_len:
    xor rax, rax
.loop:
    cmp byte [rdi+rax], 0
    je .done
    inc rax
    jmp .loop
.done:
    ret

; int str_eq(const char *a, const char *b) — returns 1 if equal, 0 if not
str_eq:
    push rbx
.loop:
    movzx rax, byte [rdi]
    movzx rbx, byte [rsi]
    cmp rax, rbx
    jne .not_eq
    test rax, rax
    je .equal
    inc rdi
    inc rsi
    jmp .loop
.equal:
    mov rax, 1
    pop rbx
    ret
.not_eq:
    xor rax, rax
    pop rbx
    ret

; void str_copy(char *dst, const char *src)
str_copy:
.loop:
    movzx rax, byte [rsi]
    mov [rdi], al
    test rax, rax
    je .done
    inc rdi
    inc rsi
    jmp .loop
.done:
    ret

	; strings.asm — string primitives: strlen, str_eq, str_copy
	%include "include/syscall.inc"

	section .text
	global str_len
	global str_eq
	global str_copy

	; size_t str_len(const char *s)
	str_len:
	xor rax, rax
	.loop:
	cmp byte [rdi+rax], 0
	je .done
	inc rax
	jmp .loop
	.done:
	ret

	; int str_eq(const char a, const char b) — returns 1 if equal, 0 if not
	str_eq:
	push rbx
	.loop:
	movzx rax, byte [rdi]
	movzx rbx, byte [rsi]
	cmp rax, rbx
	jne .not_eq
	test rax, rax
	je .equal
	inc rdi
	inc rsi
	jmp .loop
	.equal:
	mov rax, 1
	pop rbx
	ret
	.not_eq:
	xor rax, rax
	pop rbx
	ret

	; void str_copy(char dst, const char src)
	str_copy:
	.loop:
	movzx rax, byte [rsi]
	mov [rdi], al
	test rax, rax
	je .done
	inc rdi
	inc rsi
	jmp .loop
	.done:
	ret