File Handling in NASM

Write X86 menu driven ALP to implement OS commands TYPE, COPY and DELETE using file operations. Provided command line arguments in all cases

%macro print 2			;Macro for printing 
	mov rax, 1		;rax = 1 for sys_write	
	mov rdi, 1		;unsigned int file descriptor
	mov rsi, %1		;Buffer address
	mov rdx, %2		;Buffer length
	syscall		;Makes system call
%endmacro

%macro input 2			;Macro for reading 
	mov rax, 0		;rax = 0 for sys_read
	mov rdi, 0		;unsigned int file descriptor
	mov rsi, %1		;Buffer address
	mov rdx, %2		;Buffer length
	syscall		;Makes system call
%endmacro

%macro Open 1			;Macro for Opening 
	mov rax, 2		;'open' syscall
	mov rdi, %1		;file name
	mov rsi, 0102o		;Read and write mode, create if not(flag)
	mov rdx, 0666o		;permissions set
	syscall		;Makes system call
%endmacro

%macro Read 3			;Macro for reading 
	mov rax, 0		;'Read' syscall
	mov rdi, %1		;file pointer
	mov rsi, %2		;Buffer for read
	mov rdx, %3		;len of data want to read
	syscall		;Makes system call
%endmacro

%macro Write 3			;Macro for Writing 
	mov rax, 01		;'Write' syscall
	mov rdi, %1		;file pointer
	mov rsi, %2		;Buffer for write
	mov rdx, %3		;len of data want to write
	syscall		;Makes system call
%endmacro

%macro Delete 1		;Macro for Deleting  
	mov rax, 87		
	mov rdi, %1		;file name
	syscall		;Makes system call
%endmacro

%macro Close 1			;Macro for closing   
	mov rax, 3		
	mov rdi, %1		;file name
	syscall		;Makes system call
%endmacro


section .data			;For declaring initialized data
	
	mssg db "Write X86 menu driven ALP to implement OS commands 
             TYPE, COPY and DELETE using file operations. 
             Provided command line arguments in all cases"
	mssg_len:equ $ - mssg					
	mssg_name db "AMAN THAKUR 3205"		;Initialising mssg_name 
	mssg_name_len: equ $-mssg_name	
			
	mssg_sel db "--> Select an option from the menu : "
	mssg_sel_len: equ $ - mssg_sel
	mssg_menu db "--> Menu :", 10,
    			 "1. TYPE", 10, 
                 "2. COPY", 10, 
                 "3. DEL", 10,
                 "4. Exit", 10
	mssg_menu_len: equ $ - mssg_menu
	
	;===================Messages printed during input================================= 
	mssg1 db "Original file content : "			
	mssg1_len: equ $-mssg1		
	mssg2 db "Copied file content: "		
	mssg2_len: equ $-mssg2
	
	;===================Messages printed after completion of procedure=====================
	mssg_copy db "Successfully copyed file."
	mssg_copy_len: equ $-mssg_copy
	mssg_del db "Successfully deleted file."
	mssg_del_len: equ $-mssg_del
	
	mssg_error db "Error!!"				
	mssg_error_len:equ $-mssg_error			
	mssg0 db "Invalid number of arguments!"	
	mssg0_len: equ $-mssg0
	space db " "	
	newline db 10						
	cnt db 0
	cnt2 db 0
	
section .bss			;For declaring variables.
	fname1 resb 20		;Reserving 20 Byte.
	fname2 resb 20
	file_ptr1 resq 1	;Reserving quad word for file pointer.
	file_ptr2 resq 1	;Reserving quad word for file pointer.
	file_buffer resb 200	
	buffer_len resb 1	;Reserving 1 Byte.
	choice resb 2		
	
section .text						;Actual code is present.
	global _start					;has to be declared for linker(ld).
	_start: 					;tells linker entry point.
	
	print mssg, mssg_len				;Problem Statement.
	print newline, 1				
	print mssg_name, mssg_name_len		;Name and roll number.
	print newline, 1
	
	;===================Fetching command line Argument=====================
	mov rcx, 00
	pop rcx
	cmp rcx, 3
	jne err
	pop rsi
	pop rsi
	mov rdi, fname1
	loop0:						;Fetching fname1
		mov al, byte[rsi]
		mov byte[rdi], al
		inc rdi
		inc rsi
		inc byte[cnt]
		cmp byte[rsi], 0
		je jump_out
	jmp loop0
	jump_out:
	
	pop rsi
	mov rdi, fname2
	loop1:						;Fetching fname2
		mov al, byte[rsi]
		mov byte[rdi], al
		inc rdi
		inc rsi
		inc byte[cnt2]
		cmp byte[rsi], 0
		je jump_out1
	jmp loop1
	jump_out1:
	
	mov bl, byte[cnt]				
	print fname1, rbx				;Printing fname1
	print newline, 1
	mov bl, byte[cnt2]
	print fname2, rbx				;Printing fname2
	print newline, 1
	
	menu:
		
		print mssg_menu, mssg_menu_len	;Printing menu
		print newline, 1
		print mssg_sel, mssg_sel_len		;Choosing option
		input choice, 2
		
		case_1:
			cmp byte[choice], 31h		
			jne case_2
			call Type			;Calling Type Procedure when choice is 1
			jmp menu
		case_2:	
			cmp byte[choice], 32h
			jne case_3
			call Copy			;Calling Copy Procedure when choice is 2
			jmp menu
		case_3:
			cmp byte[choice], 33h
			jne case_4
			call Del			;Calling Delete Procedure when choice is 3
			jmp menu
		case_4:
			cmp byte[choice], 34h
			je Exit			;Exiting when choice is 1
			print mssg0, mssg0_len
			print newline, 1
			jmp menu
			
	Exit:
	mov rax, 60					;rax = 60 for sys_exit.
	mov rdi, 0
	syscall
	err:
		print mssg_error, mssg_error_len	;Error mssg for invalid input.
		print newline, 1
		print mssg0, mssg0_len
		print newline, 1
		mov rax, 60				
		mov rdi, 0
		syscall
	
	
Type:
	Open fname1					;Opening file fname1
	mov [file_ptr1], rax				;Geting file pointer form rax
	Read [file_ptr1], file_buffer, 100
	mov [buffer_len], rax
	print file_buffer, [buffer_len]		;Printing content of file
	print newline, 1
	Close fname1
	ret
Copy:
	Open fname1					;Opening and printing original file's content first
	mov [file_ptr1], rax
	Read [file_ptr1], file_buffer, 100
	mov [buffer_len], rax
	
	print mssg1, mssg1_len				;Printing original file content
	print newline, 1
	print file_buffer, [buffer_len]
	print newline, 1
	
	Open fname2					;Opening second file to copy from first
	mov [file_ptr2], rax
	Write [file_ptr2], file_buffer, [buffer_len]	;Writing to new file
	Close fname1
	Close fname2					;Closing both file1 and file2
	
	print newline, 1
	print mssg_copy, mssg_copy_len		;Successfully copied.
	print newline, 1
	
	Open fname2					;Opening and printing copied file's content first
	mov [file_ptr2], rax
	Read [file_ptr2], file_buffer, 100
	mov [buffer_len], rax
	
	print mssg2, mssg2_len				;Printing Copied file content
	print newline, 1
	print file_buffer, [buffer_len]
	print newline, 1
	
	
	ret
Del:
	Delete fname2
	print mssg_del, mssg_del_len
	print newline, 1
	print newline, 1
	ret