banan-os/bootloader/bios/command_line.S

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.code16
.section .stage2
# fills command line buffer
# NO REGISTERS SAVED
.global read_user_command_line
read_user_command_line:
# print initial command line
movw $command_line_enter_msg, %si
call puts
movw $command_line_buffer, %si
call puts
# prepare registers for input
movw $command_line_enter_msg, %si
movw $command_line_buffer, %di
.read_user_command_line_goto_end:
cmpb $0, (%di)
jz .read_user_command_line_loop
incw %di
jmp .read_user_command_line_goto_end
.read_user_command_line_loop:
call getc
cmpb $'\b', %al
je .read_user_command_line_backspace
# Not sure if some BIOSes return '\n' as enter, but check it just in case
cmpb $'\r', %al
je .read_user_command_line_done
cmpb $'\n', %al
je .read_user_command_line_done
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pushw %ax
call isprint
testb %al, %al
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jz .read_user_command_line_loop
popw %ax
# put byte to buffer
movb %al, (%di)
incw %di
# print byte
call putc
jmp .read_user_command_line_loop
.read_user_command_line_backspace:
# don't do anything if at the beginning
cmpw $command_line_buffer, %di
je .read_user_command_line_loop
# decrement buffer pointer
decw %di
# erase byte in display
call print_backspace
jmp .read_user_command_line_loop
.read_user_command_line_done:
# null terminate command line
movb $0, (%di)
call print_newline
ret
command_line_enter_msg:
.asciz "cmdline: "
.global command_line
command_line:
# 100 character command line
command_line_buffer:
.ascii "root=/dev/sda2"
.skip 100 - 28