Source code of MARS Assembler
First commit of the 4.5 version (latest version available)
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adolphenom
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package mars.mips.instructions;
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import mars.mips.instructions.syscalls.*;
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import mars.*;
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import mars.util.*;
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import java.util.*;
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/*
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Copyright (c) 2003-2006, Pete Sanderson and Kenneth Vollmar
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Developed by Pete Sanderson (psanderson@otterbein.edu)
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and Kenneth Vollmar (kenvollmar@missouristate.edu)
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject
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to the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
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ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
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CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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(MIT license, http://www.opensource.org/licenses/mit-license.html)
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*/
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/****************************************************************************/
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/* This class provides functionality to bring external Syscall definitions
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* into MARS. This permits anyone with knowledge of the Mars public interfaces,
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* in particular of the Memory and Register classes, to write custom MIPS syscall
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* functions. This is adapted from the ToolLoader class, which is in turn adapted
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* from Bret Barker's GameServer class from the book "Developing Games In Java".
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*/
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class SyscallLoader {
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private static final String CLASS_PREFIX = "mars.mips.instructions.syscalls.";
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private static final String SYSCALLS_DIRECTORY_PATH = "mars/mips/instructions/syscalls";
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private static final String SYSCALL_INTERFACE = "Syscall.class";
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private static final String SYSCALL_ABSTRACT = "AbstractSyscall.class";
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private static final String CLASS_EXTENSION = "class";
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private ArrayList syscallList;
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/*
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* Dynamically loads Syscalls into an ArrayList. This method is adapted from
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* the loadGameControllers() method in Bret Barker's GameServer class.
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* Barker (bret@hypefiend.com) is co-author of the book "Developing Games
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* in Java". Also see the "loadMarsTools()" method from ToolLoader class.
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*/
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void loadSyscalls() {
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syscallList = new ArrayList();
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// grab all class files in the same directory as Syscall
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ArrayList candidates = FilenameFinder.getFilenameList(this.getClass( ).getClassLoader(),
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SYSCALLS_DIRECTORY_PATH, CLASS_EXTENSION);
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HashMap syscalls = new HashMap();
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for( int i = 0; i < candidates.size(); i++) {
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String file = (String) candidates.get(i);
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// Do not add class if already encountered (happens if run in MARS development directory)
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if (syscalls.containsKey(file)) {
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continue;
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} else {
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syscalls.put(file,file);
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}
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if ((!file.equals(SYSCALL_INTERFACE)) &&
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(!file.equals(SYSCALL_ABSTRACT)) ) {
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try {
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// grab the class, make sure it implements Syscall, instantiate, add to list
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String syscallClassName = CLASS_PREFIX+file.substring(0, file.indexOf(CLASS_EXTENSION)-1);
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Class clas = Class.forName(syscallClassName);
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if (!Syscall.class.isAssignableFrom(clas)) {
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continue;
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}
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Syscall syscall = (Syscall) clas.newInstance();
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if (findSyscall(syscall.getNumber()) == null) {
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syscallList.add(syscall);
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}
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else {
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throw new Exception("Duplicate service number: "+syscall.getNumber()+
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" already registered to "+
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findSyscall(syscall.getNumber()).getName());
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}
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}
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catch (Exception e) {
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System.out.println("Error instantiating Syscall from file " + file + ": "+e);
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System.exit(0);
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}
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}
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}
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syscallList = processSyscallNumberOverrides(syscallList);
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return;
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}
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// Will get any syscall number override specifications from MARS config file and
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// process them. This will alter syscallList entry for affected names.
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private ArrayList processSyscallNumberOverrides(ArrayList syscallList) {
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ArrayList overrides = new Globals().getSyscallOverrides();
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SyscallNumberOverride override;
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Syscall syscall;
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for (int index=0; index < overrides.size(); index++) {
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override = (SyscallNumberOverride) overrides.get(index);
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boolean match = false;
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for (int i=0; i < syscallList.size(); i++) {
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syscall = (Syscall) syscallList.get(i);
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if (override.getName().equals(syscall.getName())) {
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// we have a match to service name, assign new number
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syscall.setNumber(override.getNumber());
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match = true;
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}
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}
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if (!match) {
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System.out.println("Error: syscall name '"+override.getName()+
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"' in config file does not match any name in syscall list");
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System.exit(0);
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}
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}
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// Wait until end to check for duplicate numbers. To do so earlier
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// would disallow for instance the exchange of numbers between two
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// services. This is N-squared operation but N is small.
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// This will also detect duplicates that accidently occur from addition
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// of a new Syscall subclass to the collection, even if the config file
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// does not contain any overrides.
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Syscall syscallA, syscallB;
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boolean duplicates = false;
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for (int i = 0; i < syscallList.size(); i++) {
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syscallA = (Syscall)syscallList.get(i);
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for (int j = i+1; j < syscallList.size(); j++) {
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syscallB = (Syscall)syscallList.get(j);
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if ( syscallA.getNumber() == syscallB.getNumber()) {
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System.out.println("Error: syscalls "+syscallA.getName()+" and "+
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syscallB.getName()+" are both assigned same number "+syscallA.getNumber());
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duplicates = true;
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}
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}
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}
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if (duplicates) {
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System.exit(0);
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}
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return syscallList;
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}
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/*
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* Method to find Syscall object associated with given service number.
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* Returns null if no associated object found.
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*/
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Syscall findSyscall(int number) {
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// linear search is OK since number of syscalls is small.
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Syscall service, match = null;
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if (syscallList==null) {
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loadSyscalls();
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}
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for (int index=0; index < syscallList.size(); index++) {
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service = (Syscall) syscallList.get(index);
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if (service.getNumber() == number) {
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match = service;
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}
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}
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return match;
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}
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}
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