48 lines
1.3 KiB
Plaintext
48 lines
1.3 KiB
Plaintext
# check keyboard for a key
|
|
# return 0 on no keypress or unrecognized key
|
|
#
|
|
# We need to do this in machine code because Mu doesn't have global variables
|
|
# yet (for the keyboard buffer).
|
|
|
|
== code
|
|
|
|
read-key: # kbd: (addr keyboard) -> result/eax: byte
|
|
# . prologue
|
|
55/push-ebp
|
|
89/<- %ebp 4/r32/esp
|
|
# . save registers
|
|
51/push-ecx
|
|
# result = 0
|
|
b8/copy-to-eax 0/imm32
|
|
# ecx = keyboard
|
|
8b/-> *(ebp+8) 1/r32/ecx
|
|
81 7/subop/compare %ecx 0/imm32
|
|
{
|
|
75/jump-if-!= break/disp8
|
|
# var buffer-byte-addr/ecx: (addr byte)
|
|
8b/-> *Keyboard-buffer:read 1/r32/CL
|
|
81 0/subop/add %ecx Keyboard-buffer:data/imm32
|
|
# var next-key/eax: byte = *buffer-byte-addr
|
|
8a/byte-> *ecx 0/r32/AL
|
|
# if (next-key != 0) lock and remove from keyboard buffer
|
|
81 7/subop/compare %eax 0/imm32
|
|
{
|
|
74/jump-if-= break/disp8
|
|
fa/disable-interrupts
|
|
c6 0/subop/copy-byte *ecx 0/imm8
|
|
ff 0/subop/increment *Keyboard-buffer:read
|
|
81 4/subop/and *Keyboard-buffer:read 0x0f/imm32
|
|
fb/enable-interrupts
|
|
}
|
|
# return
|
|
eb $read-key:end/disp8
|
|
}
|
|
# TODO: fake keyboard
|
|
$read-key:end:
|
|
# . restore registers
|
|
59/pop-to-ecx
|
|
# . epilogue
|
|
89/<- %esp 5/r32/ebp
|
|
5d/pop-to-ebp
|
|
c3/return
|