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616 lines
15 KiB
616 lines
15 KiB
/*
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* @(#)Interpreter.java 2.1 2003/10/07
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*
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* Copyright (C) 1999, 2003 D.A. Watt and D.F. Brown
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* Dept. of Computing Science, University of Glasgow, Glasgow G12 8QQ Scotland
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* and School of Computer and Math Sciences, The Robert Gordon University,
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* St. Andrew Street, Aberdeen AB25 1HG, Scotland.
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* All rights reserved.
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*
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* This software is provided free for educational use only. It may
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* not be used for commercial purposes without the prior written permission
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* of the authors.
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*/
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package Triangle.AbstractMachine;
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import java.io.DataInputStream;
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import java.io.FileInputStream;
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import java.io.FileNotFoundException;
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import java.io.IOException;
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public class Interpreter {
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static String objectName;
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// DATA STORE
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static int[] data = new int[1024];
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// DATA STORE REGISTERS AND OTHER REGISTERS
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final static int CB = 0, SB = 0, HB = 1024; // = upper bound of data array + 1
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static int CT, CP, ST, HT, LB, status;
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// status values
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final static int running = 0, halted = 1, failedDataStoreFull = 2, failedInvalidCodeAddress = 3,
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failedInvalidInstruction = 4, failedOverflow = 5, failedZeroDivide = 6, failedIOError = 7;
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static long accumulator;
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static int content(int r) {
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// Returns the current content of register r,
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// even if r is one of the pseudo-registers L1..L6.
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switch (r) {
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case Machine.CBr:
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return CB;
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case Machine.CTr:
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return CT;
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case Machine.PBr:
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return Machine.PB;
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case Machine.PTr:
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return Machine.PT;
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case Machine.SBr:
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return SB;
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case Machine.STr:
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return ST;
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case Machine.HBr:
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return HB;
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case Machine.HTr:
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return HT;
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case Machine.LBr:
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return LB;
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case Machine.L1r:
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return data[LB];
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case Machine.L2r:
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return data[data[LB]];
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case Machine.L3r:
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return data[data[data[LB]]];
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case Machine.L4r:
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return data[data[data[data[LB]]]];
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case Machine.L5r:
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return data[data[data[data[data[LB]]]]];
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case Machine.L6r:
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return data[data[data[data[data[data[LB]]]]]];
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case Machine.CPr:
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return CP;
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default:
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return 0;
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}
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}
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// PROGRAM STATUS
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static void dump() {
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// Writes a summary of the machine state.
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int addr, staticLink, dynamicLink, localRegNum;
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System.out.println("");
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System.out.println("State of data store and registers:");
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System.out.println("");
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if (HT == HB)
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System.out.println(" |--------| (heap is empty)");
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else {
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System.out.println(" HB-->");
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System.out.println(" |--------|");
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for (addr = HB - 1; addr >= HT; addr--) {
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System.out.print(addr + ":");
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if (addr == HT)
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System.out.print(" HT-->");
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else
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System.out.print(" ");
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System.out.println("|" + data[addr] + "|");
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}
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System.out.println(" |--------|");
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}
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System.out.println(" |////////|");
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System.out.println(" |////////|");
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if (ST == SB)
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System.out.println(" |--------| (stack is empty)");
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else {
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dynamicLink = LB;
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staticLink = LB;
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localRegNum = Machine.LBr;
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System.out.println(" ST--> |////////|");
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System.out.println(" |--------|");
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for (addr = ST - 1; addr >= SB; addr--) {
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System.out.print(addr + ":");
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if (addr == SB)
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System.out.print(" SB-->");
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else if (addr == staticLink) {
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switch (localRegNum) {
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case Machine.LBr:
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System.out.print(" LB-->");
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break;
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case Machine.L1r:
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System.out.print(" L1-->");
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break;
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case Machine.L2r:
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System.out.print(" L2-->");
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break;
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case Machine.L3r:
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System.out.print(" L3-->");
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break;
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case Machine.L4r:
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System.out.print(" L4-->");
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break;
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case Machine.L5r:
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System.out.print(" L5-->");
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break;
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case Machine.L6r:
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System.out.print(" L6-->");
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break;
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}
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staticLink = data[addr];
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localRegNum = localRegNum + 1;
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} else
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System.out.print(" ");
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if ((addr == dynamicLink) && (dynamicLink != SB))
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System.out.print("|SL=" + data[addr] + "|");
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else if ((addr == dynamicLink + 1) && (dynamicLink != SB))
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System.out.print("|DL=" + data[addr] + "|");
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else if ((addr == dynamicLink + 2) && (dynamicLink != SB))
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System.out.print("|RA=" + data[addr] + "|");
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else
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System.out.print("|" + data[addr] + "|");
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System.out.println("");
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if (addr == dynamicLink) {
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System.out.println(" |--------|");
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dynamicLink = data[addr + 1];
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}
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}
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}
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System.out.println("");
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}
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static void showStatus() {
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// Writes an indication of whether and why the program has terminated.
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System.out.println("");
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switch (status) {
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case running:
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System.out.println("Program is running.");
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break;
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case halted:
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System.out.println("Program has halted normally.");
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break;
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case failedDataStoreFull:
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System.out.println("Program has failed due to exhaustion of Data Store.");
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break;
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case failedInvalidCodeAddress:
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System.out.println("Program has failed due to an invalid code address.");
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break;
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case failedInvalidInstruction:
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System.out.println("Program has failed due to an invalid instruction.");
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break;
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case failedOverflow:
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System.out.println("Program has failed due to overflow.");
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break;
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case failedZeroDivide:
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System.out.println("Program has failed due to division by zero.");
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break;
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case failedIOError:
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System.out.println("Program has failed due to an IO error.");
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break;
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}
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if (status != halted)
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dump();
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}
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// INTERPRETATION
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static void checkSpace(int spaceNeeded) {
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// Signals failure if there is not enough space to expand the stack or
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// heap by spaceNeeded.
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if (HT - ST < spaceNeeded)
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status = failedDataStoreFull;
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}
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static boolean isTrue(int datum) {
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// Tests whether the given datum represents true.
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return (datum == Machine.trueRep);
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}
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static boolean equal(int size, int addr1, int addr2) {
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// Tests whether two multi-word objects are equal, given their common
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// size and their base addresses.
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boolean eq;
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int index;
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eq = true;
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index = 0;
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while (eq && (index < size))
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if (data[addr1 + index] == data[addr2 + index])
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index = index + 1;
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else
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eq = false;
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return eq;
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}
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static int overflowChecked(long datum) {
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// Signals failure if the datum is too large to fit into a single word,
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// otherwise returns the datum as a single word.
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if ((-Machine.maxintRep <= datum) && (datum <= Machine.maxintRep))
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return (int) datum;
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else {
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status = failedOverflow;
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return 0;
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}
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}
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static int toInt(boolean b) {
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return b ? Machine.trueRep : Machine.falseRep;
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}
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static int currentChar;
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static int readInt() throws java.io.IOException {
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int temp = 0;
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int sign = 1;
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do {
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currentChar = System.in.read();
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} while (Character.isWhitespace((char) currentChar));
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if ((currentChar == '-') || (currentChar == '+'))
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do {
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sign = (currentChar == '-') ? -1 : 1;
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currentChar = System.in.read();
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} while ((currentChar == '-') || currentChar == '+');
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if (Character.isDigit((char) currentChar))
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do {
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temp = temp * 10 + (currentChar - '0');
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currentChar = System.in.read();
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} while (Character.isDigit((char) currentChar));
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return sign * temp;
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}
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static void callPrimitive(int primitiveDisplacement) {
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// Invokes the given primitive routine.
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int addr, size;
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char ch;
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switch (primitiveDisplacement) {
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case Machine.idDisplacement:
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break; // nothing to be done
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case Machine.notDisplacement:
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data[ST - 1] = toInt(!isTrue(data[ST - 1]));
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break;
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case Machine.andDisplacement:
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ST = ST - 1;
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data[ST - 1] = toInt(isTrue(data[ST - 1]) & isTrue(data[ST]));
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break;
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case Machine.orDisplacement:
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ST = ST - 1;
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data[ST - 1] = toInt(isTrue(data[ST - 1]) | isTrue(data[ST]));
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break;
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case Machine.succDisplacement:
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data[ST - 1] = overflowChecked(data[ST - 1] + 1);
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break;
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case Machine.predDisplacement:
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data[ST - 1] = overflowChecked(data[ST - 1] - 1);
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break;
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case Machine.negDisplacement:
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data[ST - 1] = -data[ST - 1];
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break;
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case Machine.addDisplacement:
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ST = ST - 1;
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accumulator = data[ST - 1];
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data[ST - 1] = overflowChecked(accumulator + data[ST]);
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break;
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case Machine.subDisplacement:
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ST = ST - 1;
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accumulator = data[ST - 1];
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data[ST - 1] = overflowChecked(accumulator - data[ST]);
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break;
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case Machine.multDisplacement:
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ST = ST - 1;
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accumulator = data[ST - 1];
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data[ST - 1] = overflowChecked(accumulator * data[ST]);
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break;
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case Machine.divDisplacement:
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ST = ST - 1;
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accumulator = data[ST - 1];
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if (data[ST] != 0)
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data[ST - 1] = (int) (accumulator / data[ST]);
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else
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status = failedZeroDivide;
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break;
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case Machine.modDisplacement:
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ST = ST - 1;
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accumulator = data[ST - 1];
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if (data[ST] != 0)
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data[ST - 1] = (int) (accumulator % data[ST]);
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else
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status = failedZeroDivide;
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break;
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case Machine.ltDisplacement:
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ST = ST - 1;
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data[ST - 1] = toInt(data[ST - 1] < data[ST]);
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break;
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case Machine.leDisplacement:
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ST = ST - 1;
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data[ST - 1] = toInt(data[ST - 1] <= data[ST]);
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break;
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case Machine.geDisplacement:
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ST = ST - 1;
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data[ST - 1] = toInt(data[ST - 1] >= data[ST]);
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break;
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case Machine.gtDisplacement:
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ST = ST - 1;
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data[ST - 1] = toInt(data[ST - 1] > data[ST]);
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break;
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case Machine.eqDisplacement:
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size = data[ST - 1]; // size of each comparand
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ST = ST - 2 * size;
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data[ST - 1] = toInt(equal(size, ST - 1, ST - 1 + size));
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break;
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case Machine.neDisplacement:
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size = data[ST - 1]; // size of each comparand
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ST = ST - 2 * size;
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data[ST - 1] = toInt(!equal(size, ST - 1, ST - 1 + size));
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break;
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case Machine.eolDisplacement:
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data[ST] = toInt(currentChar == '\n');
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ST = ST + 1;
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break;
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case Machine.eofDisplacement:
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data[ST] = toInt(currentChar == -1);
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ST = ST + 1;
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break;
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case Machine.getDisplacement:
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ST = ST - 1;
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addr = data[ST];
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try {
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currentChar = System.in.read();
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} catch (java.io.IOException s) {
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status = failedIOError;
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}
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data[addr] = currentChar;
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break;
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case Machine.putDisplacement:
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ST = ST - 1;
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ch = (char) data[ST];
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System.out.print(ch);
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break;
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case Machine.geteolDisplacement:
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try {
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while ((currentChar = System.in.read()) != '\n')
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;
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} catch (java.io.IOException s) {
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status = failedIOError;
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}
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break;
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case Machine.puteolDisplacement:
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System.out.println("");
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break;
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case Machine.getintDisplacement:
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ST = ST - 1;
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addr = data[ST];
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try {
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accumulator = readInt();
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} catch (java.io.IOException s) {
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status = failedIOError;
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}
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data[addr] = (int) accumulator;
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break;
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case Machine.putintDisplacement:
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ST = ST - 1;
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accumulator = data[ST];
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System.out.print(accumulator);
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break;
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case Machine.newDisplacement:
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size = data[ST - 1];
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checkSpace(size);
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HT = HT - size;
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data[ST - 1] = HT;
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break;
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case Machine.disposeDisplacement:
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ST = ST - 1; // no action taken at present
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break;
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}
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}
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static void interpretProgram() {
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// Runs the program in code store.
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Instruction currentInstr;
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int op, r, n, d, addr, index;
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// Initialize registers ...
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ST = SB;
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HT = HB;
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LB = SB;
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CP = CB;
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status = running;
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do {
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// Fetch instruction ...
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currentInstr = Machine.code[CP];
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// Decode instruction ...
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op = currentInstr.op;
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r = currentInstr.r;
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n = currentInstr.n;
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d = currentInstr.d;
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// Execute instruction ...
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switch (op) {
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case Machine.LOADop:
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addr = d + content(r);
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checkSpace(n);
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for (index = 0; index < n; index++)
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data[ST + index] = data[addr + index];
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ST = ST + n;
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CP = CP + 1;
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break;
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case Machine.LOADAop:
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addr = d + content(r);
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checkSpace(1);
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data[ST] = addr;
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ST = ST + 1;
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CP = CP + 1;
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break;
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case Machine.LOADIop:
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ST = ST - 1;
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addr = data[ST];
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checkSpace(n);
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for (index = 0; index < n; index++)
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data[ST + index] = data[addr + index];
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ST = ST + n;
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CP = CP + 1;
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break;
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case Machine.LOADLop:
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checkSpace(1);
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data[ST] = d;
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ST = ST + 1;
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CP = CP + 1;
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break;
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case Machine.STOREop:
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addr = d + content(r);
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ST = ST - n;
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for (index = 0; index < n; index++)
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data[addr + index] = data[ST + index];
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CP = CP + 1;
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break;
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case Machine.STOREIop:
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ST = ST - 1;
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addr = data[ST];
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ST = ST - n;
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for (index = 0; index < n; index++)
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data[addr + index] = data[ST + index];
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CP = CP + 1;
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break;
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case Machine.CALLop:
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addr = d + content(r);
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if (addr >= Machine.PB) {
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callPrimitive(addr - Machine.PB);
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CP = CP + 1;
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} else {
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checkSpace(3);
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if ((0 <= n) && (n <= 15))
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data[ST] = content(n); // static link
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else
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status = failedInvalidInstruction;
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data[ST + 1] = LB; // dynamic link
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data[ST + 2] = CP + 1; // return address
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LB = ST;
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ST = ST + 3;
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CP = addr;
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}
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break;
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case Machine.CALLIop:
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ST = ST - 2;
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addr = data[ST + 1];
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if (addr >= Machine.PB) {
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callPrimitive(addr - Machine.PB);
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CP = CP + 1;
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} else {
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// data[ST] = static link already
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data[ST + 1] = LB; // dynamic link
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data[ST + 2] = CP + 1; // return address
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LB = ST;
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ST = ST + 3;
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CP = addr;
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}
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break;
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case Machine.RETURNop:
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addr = LB - d;
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CP = data[LB + 2];
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LB = data[LB + 1];
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ST = ST - n;
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for (index = 0; index < n; index++)
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data[addr + index] = data[ST + index];
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ST = addr + n;
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break;
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case Machine.PUSHop:
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checkSpace(d);
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ST = ST + d;
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CP = CP + 1;
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break;
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case Machine.POPop:
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addr = ST - n - d;
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ST = ST - n;
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for (index = 0; index < n; index++)
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data[addr + index] = data[ST + index];
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ST = addr + n;
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CP = CP + 1;
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break;
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case Machine.JUMPop:
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CP = d + content(r);
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break;
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case Machine.JUMPIop:
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ST = ST - 1;
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CP = data[ST];
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break;
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case Machine.JUMPIFop:
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ST = ST - 1;
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if (data[ST] == n)
|
|
CP = d + content(r);
|
|
else
|
|
CP = CP + 1;
|
|
break;
|
|
case Machine.HALTop:
|
|
status = halted;
|
|
break;
|
|
}
|
|
if ((CP < CB) || (CP >= CT))
|
|
status = failedInvalidCodeAddress;
|
|
} while (status == running);
|
|
}
|
|
|
|
// LOADING
|
|
|
|
static void loadObjectProgram(String objectName) {
|
|
// Loads the TAM object program into code store from the named file.
|
|
|
|
FileInputStream objectFile = null;
|
|
DataInputStream objectStream = null;
|
|
|
|
int addr;
|
|
boolean finished = false;
|
|
|
|
try {
|
|
objectFile = new FileInputStream(objectName);
|
|
objectStream = new DataInputStream(objectFile);
|
|
|
|
addr = Machine.CB;
|
|
while (!finished) {
|
|
Machine.code[addr] = Instruction.read(objectStream);
|
|
if (Machine.code[addr] == null)
|
|
finished = true;
|
|
else
|
|
addr = addr + 1;
|
|
}
|
|
CT = addr;
|
|
objectFile.close();
|
|
} catch (FileNotFoundException s) {
|
|
CT = CB;
|
|
System.err.println("Error opening object file: " + s);
|
|
} catch (IOException s) {
|
|
CT = CB;
|
|
System.err.println("Error reading object file: " + s);
|
|
}
|
|
}
|
|
|
|
// RUNNING
|
|
|
|
public static void main(String[] args) {
|
|
System.out.println("********** TAM Interpreter (Java Version 2.1) **********");
|
|
|
|
if (args.length == 1)
|
|
objectName = args[0];
|
|
else
|
|
objectName = "obj.tam";
|
|
|
|
loadObjectProgram(objectName);
|
|
if (CT != CB) {
|
|
interpretProgram();
|
|
showStatus();
|
|
}
|
|
}
|
|
}
|
|
|