Mercurial > hg4j
view src/org/tmatesoft/hg/internal/FilterDataAccess.java @ 157:d5268ca7715b
Merged branch wrap-data-access into default for resource-friendly data access. Updated API to promote that friendliness to clients (channels, not byte[]). More exceptions
author | Artem Tikhomirov <tikhomirov.artem@gmail.com> |
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date | Wed, 09 Mar 2011 05:22:17 +0100 |
parents | src/com/tmate/hgkit/fs/FilterDataAccess.java@9429c7bd1920 |
children | b413b16d10a5 |
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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 long offset; private final int length; private int count; public FilterDataAccess(DataAccess dataAccess, long 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 long length() { return length; } @Override public void seek(long 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 (count <= 0 || len > count) { throw new IllegalArgumentException("Underflow"); // XXX be descriptive } 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 }