[SOLVED] mips Java MIPS Syscall Code 100 (in our Mars only)

MIPS Syscall Code 100 (in our Mars only)

MIPS Syscall Code 100
(files: mars/mips/instructions/syscalls/SyscallGame.java and mars/MMIOInput.java

inside the Mars .jar zipped file. Unzip the .jar. Run Windows script

compileJavaGame.bat inside the .jar to compile the files and create the updated Mars

.jar with them. SyscallGame.java in MarsTesterjar contains the code of a testing

program for the Submarines game. It opens up when the game screen opens up.)

Overview

A MIPS syscall of code 100 is defined in our special Mars package. It is for the

game development using a MIPS program running in Mars.

Game Framework

A game is composed of a number of game objects. It can also have an array of

images stored in it. Each game object created has an unique ID for identification. A

game object can represent one of the following three things (or none of them):

Image by associating the object with a non-negative index number to an

image in the image array of the game.

Text by associating the object with a single-line text string. Note that

new-line characters such as
inside the string will be removed.

Integer by associating the object with an integer.

An object can represent only one piece of Image, Text or Integer. Setting an

association of an object will remove any other associations of it. For example,

associating Text with an object will remove the Image or Integer currently associated

with it. To make an object represent nothing, we can associate it with a negative image

index number. That is also the initial association of an object when it is created.

Game Drawing

The game draws each game object (if it does not represent nothing). The objects

are drawn in an ascending order of their IDs. The game screens pixels go from left to

right in the x-axis and from top to bottom in the y-axis. Both x and y values start from

0. Each game object is drawn based on its pixel location (x, y), which can be set using

the syscall. For drawing an Image object, the associated image will be drawn with its

top-left corner at the (x, y) pixel of the game screen. For drawing Text or Integer

object, the associated text string or integer will be drawn in such a way that the (x, y)

pixel is the left-most pixel of the baseline of the text or integer. The following

illustration shows where the baseline is.

If an object is Text or Integer, the color and font used for drawing it can also be set

using the syscall.

Game Input

Any keystrokes on the game screen will be stored as the input on the MIPS

program using Memory-Mapped Input Output (MMIO). Thus, the MIPS program

should check or read the input according to the MMIO specification. In this game

every keystroke generates an input. But the ASCII code stored in the input for a

non-character keystroke is undefined. Also, the game does not support pressing or

holding down multiple keys at the same time.

Syscall Usage

For this syscall of code 100, $v0 is set to 100. $a0 is the action code set to indicate

what action the syscall should do. The parameters for an action will be passed using

some other registers (see the table below). Any errors generated during the syscalls

action will terminate the MIPS program immediately. But the game screen, if any, will

not be closed for debugging purpose. It can always be closed by clicking its windows

Close button (the x icon on the top-right corner).

Action Action

code

($a0)

Parameters Example

Create game 1 $a1 = game screen width.

$a2 = game screen height.

$a3 = base address of a string

for games title.

.data

title .asciiz Star Wars

.text

li $v0, 100

li $a0, 1

li $a1, 800

li $a2, 600

la $a3, title

syscall

Create game

objects (any

existing ones

will be

2 $a1 = number of objects (at

most 231) to create.

All the objects initially

represent nothing and are

li $v0, 100

li $a0, 2

li $a1, 20

syscall

removed first) assigned the IDs 0, 1, 2, ,

$a1 1, respectively.

Set the image

array in game

3 $a1 = base address of a string

of the images file paths (see

the Note below) delimited by

semi-colons. The images will

be stored in an array in the

game.

The order of the images in the

string is preserved in the array

with the array index no.

starting from 0.

.data

images .asciiz

background.gif;

tank.gif;gun.gif

.text

li $v0, 100

li $a0, 3

li $a1, images

syscall

Create and

show the game

screen

4li $v0, 100

li $a0, 4

syscall

Set the game

background

image

5 $a1 = index no. to the

background image in the

games image array, or a

negative number for filling the

background with a black color.

li $v0, 100

li $a0, 5

li $a1, 47

syscall

Redraw the

game screen

showing any

updates of the

game objects

since the last

call of Redraw

6li $v0, 100

li $a0, 6

syscall

Close the game

window and

destroy the

game

7li $v0, 100

li $a0, 7

syscall

Set game

object to

represent

Image

11 $a1 = object ID

$a2 = index no. to an image in

the games image array, or a

negative number for resetting

this object to represent nothing.

li $v0, 100

li $a0, 11

li $a1, 17

li $a2, 0

syscall

or

li $v0, 100

li $a0, 11

li $a1, 17

li $a1, -1

syscall

Set game

objects

location

12 $a1 = object ID

$a2 = x-coordinate

$a3 = y-coordinate

li $v0, 100

li $a0, 12

li $a1, 4

li $a2, 220

li $a3, 342

syscall

Set game

object to

represent Text

(single-line

text only)

13 $a1 = object ID

$a2 = base address of the text

string.

Any new-line characters such

as
inside the string will be

removed.

.data

scoreText .asciiz Score:

.text

li $v0, 100

li $a0, 13

li $a1, 56

la $a2, scoreText

syscall

Set game

object to

represent

Integer

14 $a1 = object ID

$a2 = the integer

li $v0, 100

li $a0, 14

li $a1, 56

li $a2, 970 # i.e. a score

syscall

Set game

objects color

for drawing

Text or Integer

15 $a1 = object ID

$a2 = integer for a color that is

a combination of red, green

and blue components (byte 0

for blue, byte 1 for green, byte

2 for red, byte 3 is not used).

An object has a black color set

initially.

li $v0, 100

li $a0, 15

li $a1, 56

li $a2, 0xff00ff # purple

syscall

Set game

objects font

for drawing

Text or Integer

16 $a1 = object ID

$a2 = font size

$a3 = non-zero for using Bold

font, or else 0.

$t0 = non-zero for using Italic

font, or else 0.

An object has a font of size 16

and Plain style set initially.

li $v0, 100

li $a0, 16

li $a1, 56

li $a2, 32

li $a3, 1

li $t0, 0

syscall

Play sound in

loop

17 $a1 = sound ID li $v0, 100

li $a0, 17

li $a1, 0

syscall

Play sound for

once

18 $a1 = sound ID li $v0, 100

li $a0, 18

li $a1, 0

syscall

Note: Use only GIF, PNG or JPG images. The file path of an image can be specified

using Relative path (e.g., back.gif or img/car.jpg) or Absolute path (e.g.,

c:/img/car.jpg on Windows or /img/tank.png on Unix). A Relative path is relative

to the current user folder of running Mars (by default, the folder of the Mars .jar

program file). / not should always be used to separate folders in specifying the

path, even when running Mars on Windows.