libjava/classpath/gnu/regexp/CharIndexedInputStream.java

   1 /* gnu/regexp/CharIndexedInputStream.java
   2    Copyright (C) 1998-2001, 2004, 2006 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package gnu.regexp;
  39 import java.io.BufferedInputStream;
  40 import java.io.IOException;
  41 import java.io.InputStream;
  42
  43 // TODO: move(x) shouldn't rely on calling next() x times
  44
  45 class CharIndexedInputStream implements CharIndexed {
  46     private static final int BUFFER_INCREMENT = 1024;
  47     private static final int UNKNOWN = Integer.MAX_VALUE; // value for end
  48
  49     private BufferedInputStream br;
  50
  51     // so that we don't try to reset() right away
  52     private int index = -1;
  53
  54     private int bufsize = BUFFER_INCREMENT;
  55
  56     private int end = UNKNOWN;
  57
  58     private char cached = OUT_OF_BOUNDS;
  59
  60     // Big enough for a \r\n pair
  61     // lookBehind[0] = most recent
  62     // lookBehind[1] = second most recent
  63     private char[] lookBehind = new char[] { OUT_OF_BOUNDS, OUT_OF_BOUNDS };
  64
  65     CharIndexedInputStream(InputStream str, int index) {
  66         if (str instanceof BufferedInputStream) br = (BufferedInputStream) str;
  67         else br = new BufferedInputStream(str,BUFFER_INCREMENT);
  68         next();
  69         if (index > 0) move(index);
  70     }
  71
  72     private boolean next() {
  73         if (end == 1) return false;
  74         end--; // closer to end
  75
  76         try {
  77             if (index != -1) {
  78                 br.reset();
  79             }
  80             int i = br.read();
  81             br.mark(bufsize);
  82             if (i == -1) {
  83                 end = 1;
  84                 cached = OUT_OF_BOUNDS;
  85                 return false;
  86             }
  87             cached = (char) i;
  88             index = 1;
  89         } catch (IOException e) {
  90             e.printStackTrace();
  91             cached = OUT_OF_BOUNDS;
  92             return false;
  93         }
  94         return true;
  95     }
  96
  97     public char charAt(int index) {
  98         if (index == 0) {
  99             return cached;
 100         } else if (index >= end) {
 101             return OUT_OF_BOUNDS;
 102         } else if (index == -1) {
 103             return lookBehind[0];
 104         } else if (index == -2) {
 105             return lookBehind[1];
 106         } else if (index < -2) {
 107             return OUT_OF_BOUNDS;
 108         } else if (index >= bufsize) {
 109             // Allocate more space in the buffer.
 110             try {
 111                 while (bufsize <= index) bufsize += BUFFER_INCREMENT;
 112                 br.reset();
 113                 br.mark(bufsize);
 114                 br.skip(index-1);
 115             } catch (IOException e) { }
 116         } else if (this.index != index) {
 117             try {
 118                 br.reset();
 119                 br.skip(index-1);
 120             } catch (IOException e) { }
 121         }
 122         char ch = OUT_OF_BOUNDS;
 123
 124         try {
 125             int i = br.read();
 126             this.index = index+1; // this.index is index of next pos relative to charAt(0)
 127             if (i == -1) {
 128                 // set flag that next should fail next time?
 129                 end = index;
 130                 return ch;
 131             }
 132             ch = (char) i;
 133         } catch (IOException ie) { }
 134
 135         return ch;
 136     }
 137
 138     public boolean move(int index) {
 139         // move read position [index] clicks from 'charAt(0)'
 140         boolean retval = true;
 141         while (retval && (index-- > 0)) retval = next();
 142         return retval;
 143     }
 144
 145     public boolean isValid() {
 146         return (cached != OUT_OF_BOUNDS);
 147     }
 148
 149     public CharIndexed lookBehind(int index, int length) {
 150         throw new UnsupportedOperationException(
 151             "difficult to look behind for an input stream");
 152     }
 153
 154     public int length() {
 155         throw new UnsupportedOperationException(
 156             "difficult to tell the length for an input stream");
 157     }
 158 }
 159