package org.apache.lucene.store; import java.io.IOException; /** * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /** * A memory-resident {@link IndexInput} implementation. * * @version $Id: RAMInputStream.java 632120 2008-02-28 21:13:59Z mikemccand $ */ class RAMInputStream extends IndexInput implements Cloneable { static final int BUFFER_SIZE = RAMOutputStream.BUFFER_SIZE; private RAMFile file; private long length; private byte[] currentBuffer; private int currentBufferIndex; private int bufferPosition; private long bufferStart; private int bufferLength; RAMInputStream(RAMFile f) throws IOException { file = f; length = file.length; if (length/BUFFER_SIZE >= Integer.MAX_VALUE) { throw new IOException("Too large RAMFile! "+length); } // make sure that we switch to the // first needed buffer lazily currentBufferIndex = -1; currentBuffer = null; } public void close() { // nothing to do here } public long length() { return length; } public byte readByte() throws IOException { if (bufferPosition >= bufferLength) { currentBufferIndex++; switchCurrentBuffer(true); } return currentBuffer[bufferPosition++]; } public void readBytes(byte[] b, int offset, int len) throws IOException { while (len > 0) { if (bufferPosition >= bufferLength) { currentBufferIndex++; switchCurrentBuffer(true); } int remainInBuffer = bufferLength - bufferPosition; int bytesToCopy = len < remainInBuffer ? len : remainInBuffer; System.arraycopy(currentBuffer, bufferPosition, b, offset, bytesToCopy); offset += bytesToCopy; len -= bytesToCopy; bufferPosition += bytesToCopy; } } private final void switchCurrentBuffer(boolean enforceEOF) throws IOException { if (currentBufferIndex >= file.numBuffers()) { // end of file reached, no more buffers left if (enforceEOF) throw new IOException("Read past EOF"); else { // Force EOF if a read takes place at this position currentBufferIndex--; bufferPosition = BUFFER_SIZE; } } else { currentBuffer = (byte[]) file.getBuffer(currentBufferIndex); bufferPosition = 0; bufferStart = (long) BUFFER_SIZE * (long) currentBufferIndex; long buflen = length - bufferStart; bufferLength = buflen > BUFFER_SIZE ? BUFFER_SIZE : (int) buflen; } } public long getFilePointer() { return currentBufferIndex < 0 ? 0 : bufferStart + bufferPosition; } public void seek(long pos) throws IOException { if (currentBuffer==null || pos < bufferStart || pos >= bufferStart + BUFFER_SIZE) { currentBufferIndex = (int) (pos / BUFFER_SIZE); switchCurrentBuffer(false); } bufferPosition = (int) (pos % BUFFER_SIZE); } }