exemplos da aula 6

curso/exemplos/06/print_utils.asm

@@ -0,0 +1,159 @@
+; ------------------------------------------------------------
+; print_utils.asm
+; Sub-rotinas:
+;   - print_char(rdi = caractere)
+;   - print_str(rdi = ptr string \0-terminated)
+;   - print_int(rax = inteiro, sem newline)
+; Macros:
+; - SAVE_REGS: salva registradores voláteis
+; - RESTORE_REGS: restaura registradores salvos
+; ------------------------------------------------------------
+
+%macro SAVE_REGS 0
+	push rax
+	push rbx
+	push rcx
+	push rdx
+	push rsi
+	push rdi
+	push r8
+	push r9
+	push r10
+	push r11
+%endmacro
+
+%macro RESTORE_REGS 0
+	pop r11
+	pop r10
+	pop r9
+	pop r8
+	pop rdi
+	pop rsi
+	pop rdx
+	pop rcx
+	pop rbx
+	pop rax
+%endmacro
+
+section .bss
+	int_buf resb 22      ; buffer para int e char
+
+section .text
+global print_char
+global print_str
+global print_int
+
+; ------------------------------------------------------------
+; void print_char(rdi = caractere)
+; ------------------------------------------------------------
+print_char:
+	push rbp
+	mov rbp, rsp
+
+	SAVE_REGS
+
+	mov al, dil              ; coloca o caractere em al (parte baixa de rax)
+	mov byte [int_buf], al   ; usa o mesmo buffer global
+
+	mov rax, 1               ; syscall write
+	mov rdi, 1               ; stdout
+	lea rsi, [int_buf]
+	mov rdx, 1
+	syscall
+
+	RESTORE_REGS
+
+	mov rsp, rbp
+	pop rbp
+	ret
+
+; ------------------------------------------------------------
+; void print_str(rdi = ptr string \0-terminated)
+; ------------------------------------------------------------
+print_str:
+	push rbp
+	mov rbp, rsp
+
+	SAVE_REGS
+	
+	mov rsi, rdi            ; ponteiro string
+	xor rcx, rcx
+
+.count_loop:
+	cmp byte [rsi + rcx], 0
+	je .write
+	inc rcx
+	jmp .count_loop
+
+.write:
+	mov rax, 1              ; syscall write
+	mov rdi, 1              ; stdout
+	mov rdx, rcx            ; tamanho string
+	syscall
+
+	RESTORE_REGS
+	
+	mov rsp, rbp
+	pop rbp
+	ret
+
+; ------------------------------------------------------------
+; void print_int(rax = inteiro, sem newline)
+; ------------------------------------------------------------
+print_int:
+	push rbp
+	mov rbp, rsp
+
+	SAVE_REGS
+
+	mov rdi, rax
+	lea rsi, [int_buf + 21] ; aponta para o fim do buffer
+	mov byte [rsi], 0       ; opcional: zero-termina
+
+	cmp rdi, 0
+	jne .convert
+
+	; zero
+	dec rsi
+	mov byte [rsi], '0'
+	jmp .write
+
+.convert:
+	mov rax, rdi
+	mov rbx, 10
+	xor rcx, rcx
+
+	cmp rdi, 0
+	jge .conv_loop
+
+	neg rax
+	mov rcx, 1              ; sinal negativo
+
+.conv_loop:
+	xor rdx, rdx
+	div rbx
+	add dl, '0'
+	dec rsi
+	mov [rsi], dl
+	test rax, rax
+	jnz .conv_loop
+
+	test rcx, rcx
+	jz .write
+
+	dec rsi
+	mov byte [rsi], '-'
+
+.write:
+	mov rax, 1              ; syscall write
+	mov rdi, 1              ; stdout
+	mov rdx, int_buf + 21
+	sub rdx, rsi
+	syscall
+
+	RESTORE_REGS
+	
+	mov rsp, rbp
+	pop rbp
+	ret
+