| /******************************************************************************* |
| * Copyright (c) 2005, 2006 IBM Corporation and others. |
| * All rights reserved. This program and the accompanying materials |
| * are made available under the terms of the Eclipse Public License v1.0 |
| * which accompanies this distribution, and is available at |
| * http://www.eclipse.org/legal/epl-v10.html |
| * |
| * Contributors: |
| * IBM Corporation - initial API and implementation |
| *******************************************************************************/ |
| package org.eclipse.core.internal.registry; |
| |
| import java.io.*; |
| |
| /** |
| * Provides buffered read from a java.io.RandomAccessFile. |
| */ |
| public class BufferedRandomInputStream extends InputStream { |
| |
| private RandomAccessFile inputFile; |
| private String filePath; // Canonical path to the underlying file used for logging |
| private int buffer_size; // Current size of the buffer |
| private int buffer_pos; // Current read position in the buffer |
| /** |
| * The absolute position in the file where the buffered region starts. |
| */ |
| private long buffer_start = 0; |
| |
| /** |
| * The current value of the RAF's file pointer. |
| */ |
| private long file_pointer; |
| |
| private byte buffer[]; |
| |
| public BufferedRandomInputStream(File file) throws IOException { |
| this(file, 2048); // default buffer size |
| } |
| |
| public BufferedRandomInputStream(File file, int bufferSize) throws IOException { |
| filePath = file.getCanonicalPath(); |
| inputFile = new RandomAccessFile(file, "r"); //$NON-NLS-1$ |
| buffer = new byte[bufferSize]; |
| file_pointer = 0; |
| resetBuffer(); |
| } |
| |
| private void resetBuffer() { |
| buffer_pos = 0; |
| buffer_size = 0; |
| buffer_start = 0; |
| } |
| |
| private int fillBuffer() throws IOException { |
| buffer_pos = 0; |
| buffer_start = file_pointer; |
| buffer_size = inputFile.read(buffer, 0, buffer.length); |
| file_pointer += buffer_size; |
| return buffer_size; |
| } |
| |
| @Override |
| public int read() throws IOException { |
| if (buffer_pos >= buffer_size) { |
| if (fillBuffer() <= 0) |
| return -1; |
| } |
| return buffer[buffer_pos++] & 0xFF; |
| } |
| |
| @Override |
| public int read(byte b[], int off, int len) throws IOException { |
| int available = buffer_size - buffer_pos; |
| if (available < 0) |
| return -1; |
| //the buffer contains all the bytes we need, so copy over and return |
| if (len <= available) { |
| System.arraycopy(buffer, buffer_pos, b, off, len); |
| buffer_pos += len; |
| return len; |
| } |
| // Use portion remaining in the buffer |
| System.arraycopy(buffer, buffer_pos, b, off, available); |
| if (fillBuffer() <= 0) |
| return available; |
| //recursive call to read again until we have the bytes we need |
| return available + read(b, off + available, len - available); |
| } |
| |
| @Override |
| public long skip(long n) throws IOException { |
| if (n <= 0) |
| return 0; |
| |
| int available = buffer_size - buffer_pos; |
| if (n <= available) { |
| buffer_pos += n; |
| return n; |
| } |
| resetBuffer(); |
| final int skipped = inputFile.skipBytes((int) (n - available)); |
| file_pointer += skipped; |
| return available + skipped; |
| } |
| |
| @Override |
| public int available() { |
| return (buffer_size - buffer_pos); |
| } |
| |
| @Override |
| public void close() throws IOException { |
| inputFile.close(); |
| inputFile = null; |
| buffer = null; |
| } |
| |
| @Override |
| public String toString() { |
| return filePath; |
| } |
| |
| /** |
| * Supplies functionality of the {@link java.io.RandomAccessFile#seek(long)} in |
| * a buffer-friendly manner. |
| * |
| * @param pos offset |
| * @throws IOException |
| */ |
| public void seek(long pos) throws IOException { |
| if (pos >= buffer_start && pos < buffer_start + buffer_size) { |
| //seeking within the current buffer |
| buffer_pos = (int) (pos - buffer_start); |
| } else { |
| //seeking outside the buffer - just discard the buffer |
| inputFile.seek(pos); |
| file_pointer = pos; |
| resetBuffer(); |
| } |
| } |
| |
| /** |
| * Supplies functionality of the {@link java.io.RandomAccessFile#length()}. |
| * @return file length |
| * @throws IOException |
| */ |
| public long length() throws IOException { |
| return inputFile.length(); |
| } |
| |
| } |