Mercurial > hg4j
view src/org/tmatesoft/hg/internal/FilterDataAccess.java @ 338:3cfa4d908fc9
Add options to control DataAccessProvider, allow to turn off use of file memory mapping in particular to solve potential sharing violation (os file handle gets released on MappedByteByffer being GC'd, not on FileChannel.close())
author | Artem Tikhomirov <tikhomirov.artem@gmail.com> |
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date | Tue, 15 Nov 2011 04:47:03 +0100 |
parents | facfd8518367 |
children | 5e95b0da26f2 |
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/* * Copyright (c) 2011 TMate Software Ltd * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; version 2 of the License. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * For information on how to redistribute this software under * the terms of a license other than GNU General Public License * contact TMate Software at support@hg4j.com */ package org.tmatesoft.hg.internal; import java.io.IOException; /** * XXX Perhaps, DataAccessSlice? Unlike FilterInputStream, we limit amount of data read from DataAccess being filtered. * * * @author Artem Tikhomirov * @author TMate Software Ltd. */ public class FilterDataAccess extends DataAccess { private final DataAccess dataAccess; private final int offset; private final int length; private int count; public FilterDataAccess(DataAccess dataAccess, int offset, int length) { this.dataAccess = dataAccess; this.offset = offset; this.length = length; count = length; } protected int available() { return count; } @Override public FilterDataAccess reset() throws IOException { count = length; return this; } @Override public boolean isEmpty() { return count <= 0; } @Override public int length() { return length; } @Override public void seek(int localOffset) throws IOException { if (localOffset < 0 || localOffset > length) { throw new IllegalArgumentException(); } dataAccess.seek(offset + localOffset); count = (int) (length - localOffset); } @Override public void skip(int bytes) throws IOException { int newCount = count - bytes; if (newCount < 0 || newCount > length) { throw new IllegalArgumentException(); } seek(length - newCount); /* can't use next code because don't want to rewind backing DataAccess on reset() i.e. this.reset() modifies state of this instance only, while filtered DA may go further. Only actual this.skip/seek/read would rewind it to desired position dataAccess.skip(bytes); count = newCount; */ } @Override public byte readByte() throws IOException { if (count <= 0) { throw new IllegalArgumentException("Underflow"); // XXX be descriptive } if (count == length) { dataAccess.seek(offset); } count--; return dataAccess.readByte(); } @Override public void readBytes(byte[] b, int off, int len) throws IOException { if (len == 0) { return; } if (count <= 0 || len > count) { throw new IllegalArgumentException(String.format("Underflow. Bytes left: %d, asked to read %d", count, len)); } if (count == length) { dataAccess.seek(offset); } dataAccess.readBytes(b, off, len); count -= len; } // done shall be no-op, as we have no idea what's going on with DataAccess we filter }