| /* |
| * 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. |
| */ |
| package org.apache.lucene.store; |
| |
| import java.io.EOFException; |
| import java.io.IOException; |
| import java.nio.ByteBuffer; |
| import java.nio.ByteOrder; |
| |
| /** Base implementation class for buffered {@link IndexInput}. */ |
| public abstract class BufferedIndexInput extends IndexInput implements RandomAccessInput { |
| |
| private static final ByteBuffer EMPTY_BYTEBUFFER = |
| ByteBuffer.allocate(0).order(ByteOrder.LITTLE_ENDIAN); |
| ; |
| |
| /** Default buffer size set to {@value #BUFFER_SIZE}. */ |
| public static final int BUFFER_SIZE = 1024; |
| |
| /** Minimum buffer size allowed */ |
| public static final int MIN_BUFFER_SIZE = 8; |
| |
| // The normal read buffer size defaults to 1024, but |
| // increasing this during merging seems to yield |
| // performance gains. However we don't want to increase |
| // it too much because there are quite a few |
| // BufferedIndexInputs created during merging. See |
| // LUCENE-888 for details. |
| /** A buffer size for merges set to {@value #MERGE_BUFFER_SIZE}. */ |
| public static final int MERGE_BUFFER_SIZE = 4096; |
| |
| private final int bufferSize; |
| |
| private ByteBuffer buffer = EMPTY_BYTEBUFFER; |
| |
| private long bufferStart = 0; // position in file of buffer |
| |
| @Override |
| public final byte readByte() throws IOException { |
| if (buffer.hasRemaining() == false) { |
| refill(); |
| } |
| return buffer.get(); |
| } |
| |
| public BufferedIndexInput(String resourceDesc) { |
| this(resourceDesc, BUFFER_SIZE); |
| } |
| |
| public BufferedIndexInput(String resourceDesc, IOContext context) { |
| this(resourceDesc, bufferSize(context)); |
| } |
| |
| /** Inits BufferedIndexInput with a specific bufferSize */ |
| public BufferedIndexInput(String resourceDesc, int bufferSize) { |
| super(resourceDesc); |
| checkBufferSize(bufferSize); |
| this.bufferSize = bufferSize; |
| } |
| |
| /** Returns buffer size */ |
| public final int getBufferSize() { |
| return bufferSize; |
| } |
| |
| private void checkBufferSize(int bufferSize) { |
| if (bufferSize < MIN_BUFFER_SIZE) |
| throw new IllegalArgumentException( |
| "bufferSize must be at least MIN_BUFFER_SIZE (got " + bufferSize + ")"); |
| } |
| |
| @Override |
| public final void readBytes(byte[] b, int offset, int len) throws IOException { |
| readBytes(b, offset, len, true); |
| } |
| |
| @Override |
| public final void readBytes(byte[] b, int offset, int len, boolean useBuffer) throws IOException { |
| int available = buffer.remaining(); |
| if (len <= available) { |
| // the buffer contains enough data to satisfy this request |
| if (len > 0) // to allow b to be null if len is 0... |
| buffer.get(b, offset, len); |
| } else { |
| // the buffer does not have enough data. First serve all we've got. |
| if (available > 0) { |
| buffer.get(b, offset, available); |
| offset += available; |
| len -= available; |
| } |
| // and now, read the remaining 'len' bytes: |
| if (useBuffer && len < bufferSize) { |
| // If the amount left to read is small enough, and |
| // we are allowed to use our buffer, do it in the usual |
| // buffered way: fill the buffer and copy from it: |
| refill(); |
| if (buffer.remaining() < len) { |
| // Throw an exception when refill() could not read len bytes: |
| buffer.get(b, offset, buffer.remaining()); |
| throw new EOFException("read past EOF: " + this); |
| } else { |
| buffer.get(b, offset, len); |
| } |
| } else { |
| // The amount left to read is larger than the buffer |
| // or we've been asked to not use our buffer - |
| // there's no performance reason not to read it all |
| // at once. Note that unlike the previous code of |
| // this function, there is no need to do a seek |
| // here, because there's no need to reread what we |
| // had in the buffer. |
| long after = bufferStart + buffer.position() + len; |
| if (after > length()) throw new EOFException("read past EOF: " + this); |
| readInternal(ByteBuffer.wrap(b, offset, len)); |
| bufferStart = after; |
| buffer.limit(0); // trigger refill() on read |
| } |
| } |
| } |
| |
| @Override |
| public final short readShort() throws IOException { |
| if (Short.BYTES <= buffer.remaining()) { |
| return buffer.getShort(); |
| } else { |
| return super.readShort(); |
| } |
| } |
| |
| @Override |
| public final int readInt() throws IOException { |
| if (Integer.BYTES <= buffer.remaining()) { |
| return buffer.getInt(); |
| } else { |
| return super.readInt(); |
| } |
| } |
| |
| @Override |
| public final long readLong() throws IOException { |
| if (Long.BYTES <= buffer.remaining()) { |
| return buffer.getLong(); |
| } else { |
| return super.readLong(); |
| } |
| } |
| |
| // Computes an offset into the current buffer from an absolute position to read |
| // `width` bytes from. If the buffer does not contain the position, then we |
| // readjust the bufferStart and refill. |
| private long resolvePositionInBuffer(long pos, int width) throws IOException { |
| long index = pos - bufferStart; |
| if (index >= 0 && index <= buffer.limit() - width) { |
| return index; |
| } |
| if (index < 0) { |
| // if we're moving backwards, then try and fill up the previous page rather than |
| // starting again at the current pos, to avoid successive backwards reads reloading |
| // the same data over and over again. We also check that we can read `width` |
| // bytes without going over the end of the buffer |
| bufferStart = Math.max(bufferStart - bufferSize, pos + width - bufferSize); |
| bufferStart = Math.max(bufferStart, 0); |
| bufferStart = Math.min(bufferStart, pos); |
| } else { |
| // we're moving forwards, reset the buffer to start at pos |
| bufferStart = pos; |
| } |
| buffer.limit(0); // trigger refill() on read |
| seekInternal(bufferStart); |
| refill(); |
| return pos - bufferStart; |
| } |
| |
| @Override |
| public final byte readByte(long pos) throws IOException { |
| long index = resolvePositionInBuffer(pos, Byte.BYTES); |
| return buffer.get((int) index); |
| } |
| |
| @Override |
| public final short readShort(long pos) throws IOException { |
| long index = resolvePositionInBuffer(pos, Short.BYTES); |
| return buffer.getShort((int) index); |
| } |
| |
| @Override |
| public final int readInt(long pos) throws IOException { |
| long index = resolvePositionInBuffer(pos, Integer.BYTES); |
| return buffer.getInt((int) index); |
| } |
| |
| @Override |
| public final long readLong(long pos) throws IOException { |
| long index = resolvePositionInBuffer(pos, Long.BYTES); |
| return buffer.getLong((int) index); |
| } |
| |
| private void refill() throws IOException { |
| long start = bufferStart + buffer.position(); |
| long end = start + bufferSize; |
| if (end > length()) // don't read past EOF |
| end = length(); |
| int newLength = (int) (end - start); |
| if (newLength <= 0) throw new EOFException("read past EOF: " + this); |
| |
| if (buffer == EMPTY_BYTEBUFFER) { |
| buffer = |
| ByteBuffer.allocate(bufferSize).order(ByteOrder.LITTLE_ENDIAN); // allocate buffer lazily |
| seekInternal(bufferStart); |
| } |
| buffer.position(0); |
| buffer.limit(newLength); |
| bufferStart = start; |
| readInternal(buffer); |
| // Make sure sub classes don't mess up with the buffer. |
| assert buffer.order() == ByteOrder.LITTLE_ENDIAN : buffer.order(); |
| assert buffer.remaining() == 0 : "should have thrown EOFException"; |
| assert buffer.position() == newLength; |
| buffer.flip(); |
| } |
| |
| /** |
| * Expert: implements buffer refill. Reads bytes from the current position in the input. |
| * |
| * @param b the buffer to read bytes into |
| */ |
| protected abstract void readInternal(ByteBuffer b) throws IOException; |
| |
| @Override |
| public final long getFilePointer() { |
| return bufferStart + buffer.position(); |
| } |
| |
| @Override |
| public final void seek(long pos) throws IOException { |
| if (pos >= bufferStart && pos < (bufferStart + buffer.limit())) |
| buffer.position((int) (pos - bufferStart)); // seek within buffer |
| else { |
| bufferStart = pos; |
| buffer.limit(0); // trigger refill() on read |
| seekInternal(pos); |
| } |
| } |
| |
| /** |
| * Expert: implements seek. Sets current position in this file, where the next {@link |
| * #readInternal(ByteBuffer)} will occur. |
| * |
| * @see #readInternal(ByteBuffer) |
| */ |
| protected abstract void seekInternal(long pos) throws IOException; |
| |
| @Override |
| public BufferedIndexInput clone() { |
| BufferedIndexInput clone = (BufferedIndexInput) super.clone(); |
| |
| clone.buffer = EMPTY_BYTEBUFFER; |
| clone.bufferStart = getFilePointer(); |
| |
| return clone; |
| } |
| |
| @Override |
| public IndexInput slice(String sliceDescription, long offset, long length) throws IOException { |
| return wrap(sliceDescription, this, offset, length); |
| } |
| |
| /** Returns default buffer sizes for the given {@link IOContext} */ |
| public static int bufferSize(IOContext context) { |
| switch (context.context) { |
| case MERGE: |
| return MERGE_BUFFER_SIZE; |
| case DEFAULT: |
| case FLUSH: |
| case READ: |
| default: |
| return BUFFER_SIZE; |
| } |
| } |
| |
| /** |
| * Wraps a portion of another IndexInput with buffering. |
| * |
| * <p><b>Please note:</b> This is in most cases ineffective, because it may double buffer! |
| */ |
| public static BufferedIndexInput wrap( |
| String sliceDescription, IndexInput other, long offset, long length) { |
| return new SlicedIndexInput(sliceDescription, other, offset, length); |
| } |
| |
| /** Implementation of an IndexInput that reads from a portion of a file. */ |
| private static final class SlicedIndexInput extends BufferedIndexInput { |
| IndexInput base; |
| long fileOffset; |
| long length; |
| |
| SlicedIndexInput(String sliceDescription, IndexInput base, long offset, long length) { |
| super( |
| (sliceDescription == null) |
| ? base.toString() |
| : (base.toString() + " [slice=" + sliceDescription + "]"), |
| BufferedIndexInput.BUFFER_SIZE); |
| if (offset < 0 || length < 0 || offset + length > base.length()) { |
| throw new IllegalArgumentException( |
| "slice() " + sliceDescription + " out of bounds: " + base); |
| } |
| this.base = base.clone(); |
| this.fileOffset = offset; |
| this.length = length; |
| } |
| |
| @Override |
| public SlicedIndexInput clone() { |
| SlicedIndexInput clone = (SlicedIndexInput) super.clone(); |
| clone.base = base.clone(); |
| clone.fileOffset = fileOffset; |
| clone.length = length; |
| return clone; |
| } |
| |
| @Override |
| protected void readInternal(ByteBuffer b) throws IOException { |
| long start = getFilePointer(); |
| if (start + b.remaining() > length) { |
| throw new EOFException("read past EOF: " + this); |
| } |
| base.seek(fileOffset + start); |
| base.readBytes(b.array(), b.position(), b.remaining()); |
| b.position(b.position() + b.remaining()); |
| } |
| |
| @Override |
| protected void seekInternal(long pos) {} |
| |
| @Override |
| public void close() throws IOException { |
| base.close(); |
| } |
| |
| @Override |
| public long length() { |
| return length; |
| } |
| } |
| } |