# hello.s
#
# Ask for the user's name, then print:
# Hello <name>
# five times.

.section .rodata

prompt:
    .ascii "What is your name? "
prompt_end:

hello:
    .ascii "Hello "
hello_end:

newline:
    .byte 10                   # ASCII newline: '\n'


.section .bss

    .align 16
name_buf:
    .skip 64                   # Reserve 64 bytes for the name


.section .text

    .global _start

_start:
    # write(STDOUT, prompt, prompt_length)
    mov $1, %rax               # syscall 1: write
    mov $1, %rdi               # file descriptor 1: stdout
    lea prompt(%rip), %rsi     # address of prompt
    mov $(prompt_end - prompt), %rdx
    syscall

    # read(STDIN, name_buf, 63)
    xor %rax, %rax             # syscall 0: read
    xor %rdi, %rdi             # file descriptor 0: stdin
    lea name_buf(%rip), %rsi
    mov $63, %rdx
    syscall

    # RAX contains the number of bytes read.
    # Exit if read returned zero or an error.
    test %rax, %rax
    jle exit

    # Save the length of the name in R12.
    mov %rax, %r12

    # Remove the trailing newline entered by the user.
    lea name_buf(%rip), %rbx
    cmpb $10, -1(%rbx,%r12)
    jne repeat_setup
    dec %r12

repeat_setup:
    mov $5, %r13               # Loop counter

repeat_loop:
    # Write "Hello "
    mov $1, %rax
    mov $1, %rdi
    lea hello(%rip), %rsi
    mov $(hello_end - hello), %rdx
    syscall

    # Write the user's name
    mov $1, %rax
    mov $1, %rdi
    lea name_buf(%rip), %rsi
    mov %r12, %rdx
    syscall

    # Write newline
    mov $1, %rax
    mov $1, %rdi
    lea newline(%rip), %rsi
    mov $1, %rdx
    syscall

    dec %r13
    jne repeat_loop

exit:
    # exit(0)
    mov $60, %rax              # syscall 60: exit
    xor %rdi, %rdi             # exit status 0
    syscall