org/jpc/emulator/memory/codeblock/ArrayBackedInstructionSource.java

   1 /*
   2     JPC-RR: A x86 PC Hardware Emulator
   3     Release 1
   4
   5     Copyright (C) 2007-2009 Isis Innovation Limited
   6     Copyright (C) 2009 H. Ilari Liusvaara
   7
   8     This program is free software; you can redistribute it and/or modify
   9     it under the terms of the GNU General Public License version 2 as published by
  10     the Free Software Foundation.
  11
  12     This program is distributed in the hope that it will be useful,
  13     but WITHOUT ANY WARRANTY; without even the implied warranty of
  14     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15     GNU General Public License for more details.
  16
  17     You should have received a copy of the GNU General Public License along
  18     with this program; if not, write to the Free Software Foundation, Inc.,
  19     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  20
  21     Based on JPC x86 PC Hardware emulator,
  22     A project from the Physics Dept, The University of Oxford
  23
  24     Details about original JPC can be found at:
  25
  26     www-jpc.physics.ox.ac.uk
  27
  28 */
  29
  30 package org.jpc.emulator.memory.codeblock;
  31
  32 /**
  33  * Converts a pair of microcode and x86 offset arrays into an instruction source.
  34  * <p>
  35  * This is used by the <code>FASTCompiler</code> to convert the arrays backing
  36  * an interpreted codeblock into an instruction source.
  37  * @author Chris Dennis
  38  */
  39 public class ArrayBackedInstructionSource implements InstructionSource {
  40
  41     private int[] microcodes;
  42     private int[] positions;
  43     private int readOffset;
  44     private int operationEnd;
  45     private int operationStart;
  46     private int x86Start;
  47     private int x86End;
  48
  49     /**
  50      * Constructs an instruction source backed by the given arrays.
  51      * <p>
  52      * Copies of these arrays are not taken, but in turn the arrays supplied are
  53      * not modified.  Care must be taken to avoid modifying the supplied arrays
  54      * in other code.
  55      * @param microcodes array of microcode values
  56      * @param positions array of x86 offsets
  57      */
  58     public ArrayBackedInstructionSource(int[] microcodes, int[] positions) {
  59         this.microcodes = microcodes;
  60         this.positions = positions;
  61
  62         x86Start = 0;
  63         x86End = 0;
  64     }
  65
  66     public void reset() {
  67         x86Start = 0;
  68         x86End = 0;
  69         readOffset=0;
  70         operationEnd=0;
  71         operationStart=0;
  72     }
  73
  74     public boolean getNext() {
  75         if (operationEnd >= microcodes.length) {
  76             return false;
  77         }
  78
  79         operationStart = readOffset = operationEnd++;
  80         x86Start = x86End;
  81
  82         while ((operationEnd < microcodes.length) && (positions[operationEnd] == positions[operationEnd - 1])) {
  83             operationEnd++;
  84         }
  85
  86         x86End = positions[operationEnd - 1];
  87
  88         return true;
  89     }
  90
  91     public int getMicrocode() {
  92         if (readOffset < operationEnd) {
  93             return microcodes[readOffset++];
  94         } else {
  95             System.err.println("Critical error: Attempting to read past end of microcode array.");
  96             throw new IllegalStateException("Read past end of microcode array");
  97         }
  98     }
  99
 100     public int getLength() {
 101         return operationEnd - operationStart;
 102     }
 103
 104     public int getX86Length() {
 105         return x86End - x86Start;
 106     }
 107 }