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// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: projects/12/Keyboard.jack
/**
* A library for handling user input from the keyboard.
*/
class Keyboard {
/** Initializes the keyboard. */
function void init() {
return;
}
/**
* Returns the character of the currently pressed key on the keyboard;
* if no key is currently pressed, returns 0.
*
* Recognizes all ASCII characters, as well as the following keys:
* new line = 128 = String.newline()
* backspace = 129 = String.backspace()
* left arrow = 130
* up arrow = 131
* right arrow = 132
* down arrow = 133
* home = 134
* End = 135
* page up = 136
* page down = 137
* insert = 138
* delete = 139
* ESC = 140
* F1 - F12 = 141 - 152
*/
function char keyPressed() {
return Memory.peek(24576);
}
/**
* Waits until a key is pressed on the keyboard and released,
* then echoes the key to the screen, and returns the character
* of the pressed key.
*/
function char readChar() {
var int key, key1;
let key = 0;
while (key = 0) {
let key = Memory.peek(24576);
}
let key1 = key;
while (key1 = key) {
let key1 = Memory.peek(24576);
}
if ((key > 31) & (key < 127) | (key = 128) | (key = 129)) {
do Output.printChar(key);
}
return key;
}
/**
* Displays the message on the screen, reads from the keyboard the entered
* text until a newline character is detected, echoes the text to the screen,
* and returns its value. Also handles user backspaces.
*/
function String readLine(String message) {
var int c;
var String s;
let s = String.new(140);
do Output.printString(message);
let c = Keyboard.readChar();
while (~(c = 128)) {
if (c = 129) {
if (s.length() > 0) {
do s.eraseLastChar();
}
} else {
do s.appendChar(c);
}
let c = Keyboard.readChar();
}
return s;
}
/**
* Displays the message on the screen, reads from the keyboard the entered
* text until a newline character is detected, echoes the text to the screen,
* and returns its integer value (until the first non-digit character in the
* entered text is detected). Also handles user backspaces.
*/
function int readInt(String message) {
var String s;
do Output.printString(message);
let s = Keyboard.readLine("");
return s.intValue();
}
}
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