Reading Files in Assembly Language

Here’s the translation of the Go code for reading files into Assembly Language, with explanations in Markdown format suitable for Hugo:

; Reading and writing files are basic tasks needed for
; many programs. First we'll look at some examples of
; reading files.

section .data
    filename db '/tmp/dat', 0
    read_mode db 'r', 0
    format_string db '%d bytes: %s', 10, 0
    format_string2 db '%d bytes @ %d: %s', 10, 0

section .bss
    file_handle resq 1
    buffer resb 100

section .text
    global main
    extern fopen
    extern fread
    extern fseek
    extern printf
    extern fclose

main:
    ; Open the file
    push read_mode
    push filename
    call fopen
    add esp, 8
    mov [file_handle], eax

    ; Read some bytes from the beginning of the file
    push 5
    push 1
    push buffer
    push dword [file_handle]
    call fread
    add esp, 16

    ; Print the read bytes
    push buffer
    push eax
    push format_string
    call printf
    add esp, 12

    ; Seek to a known location in the file
    push 0  ; SEEK_SET
    push 6
    push dword [file_handle]
    call fseek
    add esp, 12

    ; Read from the new position
    push 2
    push 1
    push buffer
    push dword [file_handle]
    call fread
    add esp, 16

    ; Print the read bytes
    push buffer
    push 6  ; offset
    push eax
    push format_string2
    call printf
    add esp, 16

    ; Close the file
    push dword [file_handle]
    call fclose
    add esp, 4

    ret

; Note: Error checking is omitted for brevity. In a real program,
; you should check for errors after each system call.

This Assembly Language code demonstrates basic file operations similar to the original example. Here’s a breakdown of what it does:

It defines the necessary data, including the filename and format strings for output.
The main function opens the file using fopen.
It reads 5 bytes from the beginning of the file using fread.
The read bytes are printed using printf.
The file pointer is moved to position 6 using fseek.
It reads 2 bytes from the new position.
These bytes are printed along with their position in the file.
Finally, the file is closed using fclose.

This code provides a basic example of file reading operations in Assembly Language. Note that error checking has been omitted for brevity, but in a real program, you should always check for errors after system calls.

To run this program, you would need to assemble it into an object file and then link it with the C standard library. The exact commands may vary depending on your assembler and operating system.

$ nasm -f elf64 reading-files.asm
$ gcc -no-pie reading-files.o -o reading-files
$ ./reading-files

Remember to create the /tmp/dat file with some content before running the program:

$ echo "hello" > /tmp/dat
$ echo "world" >> /tmp/dat

This example demonstrates basic file operations in Assembly Language, including opening a file, reading from it, seeking to different positions, and closing the file.

Base64 Encoding in Assembly Language

Writing Files in Assembly Language

Learn X By Example

Title here

Reading Files in Assembly Language