Command Line Flags in Assembly Language

section .data
    word db "foo", 0
    numb dd 42
    fork db 0
    svar db "bar", 0
    usage db "Usage: program [-word=string] [-numb=int] [-fork] [-svar=string]", 10, 0

section .bss
    argc resd 1
    argv resq 1

section .text
    global _start

_start:
    ; Get command line arguments
    pop dword [argc]
    mov [argv], esp

    ; Parse command line arguments
    mov ecx, [argc]
    mov esi, [argv]
    call parse_args

    ; Print results
    call print_results

    ; Exit program
    mov eax, 60
    xor edi, edi
    syscall

parse_args:
    ; Loop through arguments
    .loop:
        lodsd
        test eax, eax
        jz .done
        
        ; Check for flags
        cmp byte [eax], '-'
        jne .next
        
        inc eax
        cmp dword [eax], 'word'
        je .set_word
        cmp dword [eax], 'numb'
        je .set_numb
        cmp dword [eax], 'fork'
        je .set_fork
        cmp dword [eax], 'svar'
        je .set_svar
        
        jmp .next
        
    .set_word:
        add eax, 5
        mov [word], eax
        jmp .next
    
    .set_numb:
        add eax, 5
        call atoi
        mov [numb], eax
        jmp .next
    
    .set_fork:
        mov byte [fork], 1
        jmp .next
    
    .set_svar:
        add eax, 5
        mov [svar], eax
        
    .next:
        loop .loop
    
    .done:
        ret

print_results:
    ; Print word
    mov eax, 1
    mov edi, 1
    mov esi, word
    mov edx, 4
    syscall
    
    ; Print numb
    mov eax, [numb]
    call print_int
    
    ; Print fork
    movzx eax, byte [fork]
    call print_int
    
    ; Print svar
    mov eax, 1
    mov edi, 1
    mov esi, svar
    mov edx, 4
    syscall
    
    ret

; Helper functions (not implemented for brevity)
atoi:
    ; Convert ASCII to integer
    ret

print_int:
    ; Print integer to stdout
    ret

This Assembly Language code provides a basic implementation of command-line flag parsing, similar to the original Go example. Here’s an explanation of the code:

We define our data in the .data section, including default values for our flags.
The .bss section is used for uninitialized data, where we store the argument count and pointer.
In the _start function (the entry point for Assembly programs), we retrieve the command-line arguments and call our parsing function.
The parse_args function loops through the arguments, checking for flags and updating the corresponding variables when found.
After parsing, we call print_results to output the final values of our flags.
Helper functions like atoi (ASCII to integer) and print_int are mentioned but not implemented for brevity.

To use this program, you would compile it into an executable and run it from the command line with various flags:

$ nasm -f elf64 command_line_flags.asm
$ ld -o command_line_flags command_line_flags.o
$ ./command_line_flags -word=hello -numb=100 -fork -svar=test

Note that this is a simplified version and doesn’t include error handling or more advanced features of the original Go implementation. Assembly Language requires much more low-level management of memory and system calls, which makes the code more verbose and complex compared to higher-level languages.

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Command Line Flags in Assembly Language