org.eclipse.linuxtools.tmf.core/src/org/eclipse/linuxtools/tmf/core/io/BufferedRandomAccessFile.java

   1 /*******************************************************************************
   2  * Copyright (c) 2010 Ericsson
   3  *
   4  * All rights reserved. This program and the accompanying materials are
   5  * made available under the terms of the Eclipse Public License v1.0 which
   6  * accompanies this distribution, and is available at
   7  * http://www.eclipse.org/legal/epl-v10.html
   8  *
   9  * Contributors:
  10  *   Patrick Tasse - Initial API and implementation, based on article by Nick Zhang
  11  *                   (http://www.javaworld.com/javatips/jw-javatip26.html)
  12  ******************************************************************************/
  13
  14 package org.eclipse.linuxtools.tmf.core.io;
  15
  16 import java.io.File;
  17 import java.io.IOException;
  18 import java.io.RandomAccessFile;
  19 import java.nio.charset.Charset;
  20
  21 /**
  22  * A class to mitigate the Java I/O inefficiency of RandomAccessFile.
  23  *
  24  * @version 1.0
  25  * @author Patrick Tasse
  26  */
  27 public class BufferedRandomAccessFile extends RandomAccessFile {
  28
  29         private static final int DEFAULT_BUF_SIZE = 8192;
  30         private static final Charset CHARSET_UTF8 = Charset.forName("UTF-8"); //$NON-NLS-1$
  31
  32         final int BUF_SIZE;
  33         byte buffer[];
  34         int buf_end = 0;
  35         int buf_pos = 0;
  36         long real_pos = 0;
  37         StringBuilder sb = new StringBuilder();
  38
  39         public BufferedRandomAccessFile(String name, String mode) throws IOException {
  40                 this(name, mode, DEFAULT_BUF_SIZE);
  41         }
  42
  43         public BufferedRandomAccessFile(File file, String mode) throws IOException {
  44                 this(file, mode, DEFAULT_BUF_SIZE);
  45         }
  46
  47         public BufferedRandomAccessFile(String name, String mode, int bufsize) throws IOException {
  48             super(name, mode);
  49             invalidate();
  50             BUF_SIZE = bufsize;
  51             buffer = new byte[BUF_SIZE];
  52     }
  53
  54         public BufferedRandomAccessFile(File file, String mode, int bufsize) throws IOException {
  55             super(file, mode);
  56             invalidate();
  57             BUF_SIZE = bufsize;
  58             buffer = new byte[BUF_SIZE];
  59     }
  60
  61         @Override
  62     public final int read() throws IOException{
  63                 if (buf_pos >= buf_end) {
  64                         if (fillBuffer() < 0) {
  65                                 return -1;
  66                         }
  67                 }
  68                 if (buf_end == 0) {
  69                         return -1;
  70                 }
  71         return buffer[buf_pos++];
  72         }
  73
  74         @Override
  75     public int read(byte b[], int off, int len) throws IOException {
  76                 int leftover = buf_end - buf_pos;
  77                 if (len <= leftover) {
  78                         System.arraycopy(buffer, buf_pos, b, off, len);
  79                         buf_pos += len;
  80                         return len;
  81                 }
  82                 for(int i = 0; i < len; i++) {
  83                         int c = this.read();
  84                         if (c != -1) {
  85                                 b[off+i] = (byte) c;
  86                         } else {
  87                                 return i;
  88                         }
  89                 }
  90                 return len;
  91         }
  92
  93         @Override
  94     public long getFilePointer() throws IOException{
  95                 long l = real_pos;
  96                 return (l - buf_end + buf_pos);
  97         }
  98
  99         @Override
 100     public void seek(long pos) throws IOException {
 101                 int n = (int) (real_pos - pos);
 102                 if(n >= 0 && n <= buf_end) {
 103                         buf_pos = buf_end - n;
 104                 } else {
 105                         super.seek(pos);
 106                         invalidate();
 107                 }
 108         }
 109
 110         public final String getNextLine() throws IOException {
 111                 String str = null;
 112                 if (buf_end - buf_pos <= 0) {
 113                         if (fillBuffer() < 0) {
 114                                 return null;
 115                         }
 116                 }
 117                 int lineend = -1;
 118                 for (int i = buf_pos; i < buf_end; i++) {
 119                         if (buffer[i] == '\n') {
 120                                 lineend = i;
 121                                 break;
 122                         }
 123                 }
 124                 if (lineend < 0) {
 125                         sb.delete(0, sb.length());
 126                         int c;
 127                         while (((c = read()) != -1) && (c != '\n')) {
 128                                 sb.append((char) c);
 129                         }
 130                         if ((c == -1) && (sb.length() == 0)) {
 131                                 return null;
 132                         }
 133                         if (sb.charAt(sb.length() - 1) == '\r') {
 134                                 sb.deleteCharAt(sb.length() - 1);
 135                         }
 136                         return sb.toString();
 137                 }
 138                 if (lineend > 0 && buffer[lineend - 1] == '\r' && lineend > buf_pos) {
 139                         str = new String(buffer, buf_pos, lineend - buf_pos - 1, CHARSET_UTF8);
 140                 } else {
 141                         str = new String(buffer, buf_pos, lineend - buf_pos, CHARSET_UTF8);
 142                 }
 143                 buf_pos = lineend + 1;
 144                 return str;
 145         }
 146
 147         private int fillBuffer() throws IOException {
 148                 int n = super.read(buffer, 0, BUF_SIZE);
 149                 if (n >= 0) {
 150                         real_pos += n;
 151                         buf_end = n;
 152                         buf_pos = 0;
 153                 }
 154                 return n;
 155         }
 156
 157         private void invalidate() throws IOException {
 158                 buf_end = 0;
 159                 buf_pos = 0;
 160                 real_pos = super.getFilePointer();
 161         }
 162 }