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 public class BufferedRandomAccessFile extends RandomAccessFile {
  22
  23         private static final int DEFAULT_BUF_SIZE = 8192;
  24         private static final Charset CHARSET_UTF8 = Charset.forName("UTF-8"); //$NON-NLS-1$
  25
  26         final int BUF_SIZE;
  27         byte buffer[];
  28         int buf_end = 0;
  29         int buf_pos = 0;
  30         long real_pos = 0;
  31         StringBuilder sb = new StringBuilder();
  32
  33         public BufferedRandomAccessFile(String name, String mode) throws IOException {
  34                 this(name, mode, DEFAULT_BUF_SIZE);
  35         }
  36
  37         public BufferedRandomAccessFile(File file, String mode) throws IOException {
  38                 this(file, mode, DEFAULT_BUF_SIZE);
  39         }
  40
  41         public BufferedRandomAccessFile(String name, String mode, int bufsize) throws IOException {
  42             super(name, mode);
  43             invalidate();
  44             BUF_SIZE = bufsize;
  45             buffer = new byte[BUF_SIZE];
  46     }
  47
  48         public BufferedRandomAccessFile(File file, String mode, int bufsize) throws IOException {
  49             super(file, mode);
  50             invalidate();
  51             BUF_SIZE = bufsize;
  52             buffer = new byte[BUF_SIZE];
  53     }
  54
  55         @Override
  56     public final int read() throws IOException{
  57                 if (buf_pos >= buf_end) {
  58                         if (fillBuffer() < 0) {
  59                                 return -1;
  60                         }
  61                 }
  62                 if (buf_end == 0) {
  63                         return -1;
  64                 } else {
  65                         return buffer[buf_pos++];
  66                 }
  67         }
  68
  69         @Override
  70     public int read(byte b[], int off, int len) throws IOException {
  71                 int leftover = buf_end - buf_pos;
  72                 if (len <= leftover) {
  73                         System.arraycopy(buffer, buf_pos, b, off, len);
  74                         buf_pos += len;
  75                         return len;
  76                 }
  77                 for(int i = 0; i < len; i++) {
  78                         int c = this.read();
  79                         if (c != -1) {
  80                                 b[off+i] = (byte) c;
  81                         } else {
  82                                 return i;
  83                         }
  84                 }
  85                 return len;
  86         }
  87
  88         @Override
  89     public long getFilePointer() throws IOException{
  90                 long l = real_pos;
  91                 return (l - buf_end + buf_pos);
  92         }
  93
  94         @Override
  95     public void seek(long pos) throws IOException {
  96                 int n = (int) (real_pos - pos);
  97                 if(n >= 0 && n <= buf_end) {
  98                         buf_pos = buf_end - n;
  99                 } else {
 100                         super.seek(pos);
 101                         invalidate();
 102                 }
 103         }
 104
 105         public final String getNextLine() throws IOException {
 106                 String str = null;
 107                 if (buf_end - buf_pos <= 0) {
 108                         if (fillBuffer() < 0) {
 109                                 return null;
 110                         }
 111                 }
 112                 int lineend = -1;
 113                 for (int i = buf_pos; i < buf_end; i++) {
 114                         if (buffer[i] == '\n') {
 115                                 lineend = i;
 116                                 break;
 117                         }
 118                 }
 119                 if (lineend < 0) {
 120                         sb.delete(0, sb.length());
 121                         int c;
 122                         while (((c = read()) != -1) && (c != '\n')) {
 123                                 sb.append((char) c);
 124                         }
 125                         if ((c == -1) && (sb.length() == 0)) {
 126                                 return null;
 127                         }
 128                         if (sb.charAt(sb.length() - 1) == '\r') {
 129                                 sb.deleteCharAt(sb.length() - 1);
 130                         }
 131                         return sb.toString();
 132                 }
 133                 if (lineend > 0 && buffer[lineend - 1] == '\r' && lineend > buf_pos) {
 134                         str = new String(buffer, buf_pos, lineend - buf_pos - 1, CHARSET_UTF8);
 135                 } else {
 136                         str = new String(buffer, buf_pos, lineend - buf_pos, CHARSET_UTF8);
 137                 }
 138                 buf_pos = lineend + 1;
 139                 return str;
 140         }
 141
 142         private int fillBuffer() throws IOException {
 143                 int n = super.read(buffer, 0, BUF_SIZE);
 144                 if (n >= 0) {
 145                         real_pos += n;
 146                         buf_end = n;
 147                         buf_pos = 0;
 148                 }
 149                 return n;
 150         }
 151
 152         private void invalidate() throws IOException {
 153                 buf_end = 0;
 154                 buf_pos = 0;
 155                 real_pos = super.getFilePointer();
 156         }
 157 }