Moving and consolidating repos

x86_64/strings/SubroutineToPrintStrings/subroutinetoprintspring.asm

@@ -0,0 +1,21 @@
+
+
+
+section .data
+    text db "Hello, World!", 10
+
+section .text
+    global _start
+
+_start:
+    mov rax, 1
+    mov rdi, 1
+    mov rsi, text
+    mov rdx, 14
+    syscall 
+
+    mov rax, 60
+    mov rdi, 0
+    syscall 
+
+

x86_64/strings/reverse.asm

@@ -0,0 +1,123 @@
+;;
+;; initialized data
+;;
+section .data
+	SYS_WRITE	equ 1
+	STD_OUT		equ 1
+	SYS_EXIT	equ 60
+	EXIT_CODE	equ 0
+
+	NEW_LINE	db 0xa
+	INPUT		db "Hello world!"
+
+;;
+;; non initialized data
+;;
+section .bss
+	OUTPUT	resb 1
+
+;;
+;; code
+;;
+section .text
+	global	_start
+
+;;
+;; main routine
+;;
+_start:
+	;; get addres of INPUT
+	mov	rsi, INPUT
+	;; zeroize rcx for counter
+	xor	rcx, rcx
+	; df = 0 si++
+	cld
+	; remember place after function call
+	mov	rdi, $ + 15
+	;; get string lengt
+	call	calculateStrLength
+	;; write zeros to rax
+	xor	rax, rax
+	;; additional counter for reverseStr
+	xor	rdi, rdi
+	;; reverse string
+	jmp	reverseStr
+
+;;
+;; calculate length of string
+;;
+calculateStrLength:
+	;; check is it end of string
+	cmp	byte [rsi], 0
+	;; if yes exit from function
+	je	exitFromRoutine
+	;; load byte from rsi to al and inc rsi
+	lodsb
+	;; push symbol to stack
+	push	rax
+	;; increase counter
+	inc	rcx
+	;; loop again
+	jmp	calculateStrLength
+
+;;
+;; back to _start
+;;
+exitFromRoutine:
+	;; push return addres to stack again
+	push	rdi
+	;; return to _start
+	ret
+
+;;
+;; reverse string
+;;
+;; 31 in stack
+reverseStr:
+	;; check is it end of string
+	cmp	rcx, 0
+	;; if yes print result string
+	je	printResult
+	;; get symbol from stack
+	pop	rax
+	;; write it to output buffer
+	mov	[OUTPUT + rdi], rax
+	;; decrease length counter
+	dec	rcx
+	;; increase additional length counter (for write syscall)
+	inc	rdi
+	;; loop again
+	jmp	reverseStr
+
+;;
+;; Print result string
+;;
+printResult:
+	mov	rdx, rdi
+	mov	rax, 1
+	mov	rdi, 1
+	mov	rsi, OUTPUT
+	syscall
+	jmp	printNewLine
+
+;;
+;; Print new line
+;;
+printNewLine:
+	mov	rax, SYS_WRITE
+	mov	rdi, STD_OUT
+	mov	rsi, NEW_LINE
+	mov	rdx, 1
+	syscall
+	jmp	exit
+
+;;
+;; Exit from program
+;;
+exit:
+	;; syscall number
+	mov	rax, SYS_EXIT
+	;; exit code
+	mov	rdi, EXIT_CODE
+	;; call sys_exit
+	syscall