| package org.apache.lucene.store; |
| |
| /* |
| * 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. |
| */ |
| |
| import java.io.IOException; |
| import java.util.Map; |
| import java.util.Set; |
| |
| import org.apache.lucene.util.BytesRef; |
| import org.apache.lucene.util.UnicodeUtil; |
| |
| /** |
| * Abstract base class for performing write operations of Lucene's low-level |
| * data types. |
| |
| * <p>{@code DataOutput} may only be used from one thread, because it is not |
| * thread safe (it keeps internal state like file position). |
| */ |
| public abstract class DataOutput { |
| |
| /** Writes a single byte. |
| * <p> |
| * The most primitive data type is an eight-bit byte. Files are |
| * accessed as sequences of bytes. All other data types are defined |
| * as sequences of bytes, so file formats are byte-order independent. |
| * |
| * @see IndexInput#readByte() |
| */ |
| public abstract void writeByte(byte b) throws IOException; |
| |
| /** Writes an array of bytes. |
| * @param b the bytes to write |
| * @param length the number of bytes to write |
| * @see DataInput#readBytes(byte[],int,int) |
| */ |
| public void writeBytes(byte[] b, int length) throws IOException { |
| writeBytes(b, 0, length); |
| } |
| |
| /** Writes an array of bytes. |
| * @param b the bytes to write |
| * @param offset the offset in the byte array |
| * @param length the number of bytes to write |
| * @see DataInput#readBytes(byte[],int,int) |
| */ |
| public abstract void writeBytes(byte[] b, int offset, int length) throws IOException; |
| |
| /** Writes an int as four bytes. |
| * <p> |
| * 32-bit unsigned integer written as four bytes, high-order bytes first. |
| * |
| * @see DataInput#readInt() |
| */ |
| public void writeInt(int i) throws IOException { |
| writeByte((byte)(i >> 24)); |
| writeByte((byte)(i >> 16)); |
| writeByte((byte)(i >> 8)); |
| writeByte((byte) i); |
| } |
| |
| /** Writes a short as two bytes. |
| * @see DataInput#readShort() |
| */ |
| public void writeShort(short i) throws IOException { |
| writeByte((byte)(i >> 8)); |
| writeByte((byte) i); |
| } |
| |
| /** Writes an int in a variable-length format. Writes between one and |
| * five bytes. Smaller values take fewer bytes. Negative numbers are |
| * supported, but should be avoided. |
| * <p>VByte is a variable-length format for positive integers is defined where the |
| * high-order bit of each byte indicates whether more bytes remain to be read. The |
| * low-order seven bits are appended as increasingly more significant bits in the |
| * resulting integer value. Thus values from zero to 127 may be stored in a single |
| * byte, values from 128 to 16,383 may be stored in two bytes, and so on.</p> |
| * <p>VByte Encoding Example</p> |
| * <table cellspacing="0" cellpadding="2" border="0"> |
| * <col width="64*"> |
| * <col width="64*"> |
| * <col width="64*"> |
| * <col width="64*"> |
| * <tr valign="top"> |
| * <th align="left" width="25%">Value</th> |
| * <th align="left" width="25%">Byte 1</th> |
| * <th align="left" width="25%">Byte 2</th> |
| * <th align="left" width="25%">Byte 3</th> |
| * </tr> |
| * <tr valign="bottom"> |
| * <td width="25%">0</td> |
| * <td width="25%"><kbd>00000000</kbd></td> |
| * <td width="25%"></td> |
| * <td width="25%"></td> |
| * </tr> |
| * <tr valign="bottom"> |
| * <td width="25%">1</td> |
| * <td width="25%"><kbd>00000001</kbd></td> |
| * <td width="25%"></td> |
| * <td width="25%"></td> |
| * </tr> |
| * <tr valign="bottom"> |
| * <td width="25%">2</td> |
| * <td width="25%"><kbd>00000010</kbd></td> |
| * <td width="25%"></td> |
| * <td width="25%"></td> |
| * </tr> |
| * <tr> |
| * <td valign="top" width="25%">...</td> |
| * <td valign="bottom" width="25%"></td> |
| * <td valign="bottom" width="25%"></td> |
| * <td valign="bottom" width="25%"></td> |
| * </tr> |
| * <tr valign="bottom"> |
| * <td width="25%">127</td> |
| * <td width="25%"><kbd>01111111</kbd></td> |
| * <td width="25%"></td> |
| * <td width="25%"></td> |
| * </tr> |
| * <tr valign="bottom"> |
| * <td width="25%">128</td> |
| * <td width="25%"><kbd>10000000</kbd></td> |
| * <td width="25%"><kbd>00000001</kbd></td> |
| * <td width="25%"></td> |
| * </tr> |
| * <tr valign="bottom"> |
| * <td width="25%">129</td> |
| * <td width="25%"><kbd>10000001</kbd></td> |
| * <td width="25%"><kbd>00000001</kbd></td> |
| * <td width="25%"></td> |
| * </tr> |
| * <tr valign="bottom"> |
| * <td width="25%">130</td> |
| * <td width="25%"><kbd>10000010</kbd></td> |
| * <td width="25%"><kbd>00000001</kbd></td> |
| * <td width="25%"></td> |
| * </tr> |
| * <tr> |
| * <td valign="top" width="25%">...</td> |
| * <td width="25%"></td> |
| * <td width="25%"></td> |
| * <td width="25%"></td> |
| * </tr> |
| * <tr valign="bottom"> |
| * <td width="25%">16,383</td> |
| * <td width="25%"><kbd>11111111</kbd></td> |
| * <td width="25%"><kbd>01111111</kbd></td> |
| * <td width="25%"></td> |
| * </tr> |
| * <tr valign="bottom"> |
| * <td width="25%">16,384</td> |
| * <td width="25%"><kbd>10000000</kbd></td> |
| * <td width="25%"><kbd>10000000</kbd></td> |
| * <td width="25%"><kbd>00000001</kbd></td> |
| * </tr> |
| * <tr valign="bottom"> |
| * <td width="25%">16,385</td> |
| * <td width="25%"><kbd>10000001</kbd></td> |
| * <td width="25%"><kbd>10000000</kbd></td> |
| * <td width="25%"><kbd>00000001</kbd></td> |
| * </tr> |
| * <tr> |
| * <td valign="top" width="25%">...</td> |
| * <td valign="bottom" width="25%"></td> |
| * <td valign="bottom" width="25%"></td> |
| * <td valign="bottom" width="25%"></td> |
| * </tr> |
| * </table> |
| * <p>This provides compression while still being efficient to decode.</p> |
| * |
| * @param i Smaller values take fewer bytes. Negative numbers are |
| * supported, but should be avoided. |
| * @throws IOException If there is an I/O error writing to the underlying medium. |
| * @see DataInput#readVInt() |
| */ |
| public final void writeVInt(int i) throws IOException { |
| while ((i & ~0x7F) != 0) { |
| writeByte((byte)((i & 0x7F) | 0x80)); |
| i >>>= 7; |
| } |
| writeByte((byte)i); |
| } |
| |
| /** Writes a long as eight bytes. |
| * <p> |
| * 64-bit unsigned integer written as eight bytes, high-order bytes first. |
| * |
| * @see DataInput#readLong() |
| */ |
| public void writeLong(long i) throws IOException { |
| writeInt((int) (i >> 32)); |
| writeInt((int) i); |
| } |
| |
| /** Writes an long in a variable-length format. Writes between one and nine |
| * bytes. Smaller values take fewer bytes. Negative numbers are not |
| * supported. |
| * <p> |
| * The format is described further in {@link DataOutput#writeVInt(int)}. |
| * @see DataInput#readVLong() |
| */ |
| public final void writeVLong(long i) throws IOException { |
| assert i >= 0L; |
| while ((i & ~0x7FL) != 0L) { |
| writeByte((byte)((i & 0x7FL) | 0x80L)); |
| i >>>= 7; |
| } |
| writeByte((byte)i); |
| } |
| |
| /** Writes a string. |
| * <p> |
| * Writes strings as UTF-8 encoded bytes. First the length, in bytes, is |
| * written as a {@link #writeVInt VInt}, followed by the bytes. |
| * |
| * @see DataInput#readString() |
| */ |
| public void writeString(String s) throws IOException { |
| final BytesRef utf8Result = new BytesRef(10); |
| UnicodeUtil.UTF16toUTF8(s, 0, s.length(), utf8Result); |
| writeVInt(utf8Result.length); |
| writeBytes(utf8Result.bytes, 0, utf8Result.length); |
| } |
| |
| private static int COPY_BUFFER_SIZE = 16384; |
| private byte[] copyBuffer; |
| |
| /** Copy numBytes bytes from input to ourself. */ |
| public void copyBytes(DataInput input, long numBytes) throws IOException { |
| assert numBytes >= 0: "numBytes=" + numBytes; |
| long left = numBytes; |
| if (copyBuffer == null) |
| copyBuffer = new byte[COPY_BUFFER_SIZE]; |
| while(left > 0) { |
| final int toCopy; |
| if (left > COPY_BUFFER_SIZE) |
| toCopy = COPY_BUFFER_SIZE; |
| else |
| toCopy = (int) left; |
| input.readBytes(copyBuffer, 0, toCopy); |
| writeBytes(copyBuffer, 0, toCopy); |
| left -= toCopy; |
| } |
| } |
| |
| /** |
| * Writes a String map. |
| * <p> |
| * First the size is written as an {@link #writeInt(int) Int32}, |
| * followed by each key-value pair written as two consecutive |
| * {@link #writeString(String) String}s. |
| * |
| * @param map Input map. May be null (equivalent to an empty map) |
| */ |
| public void writeStringStringMap(Map<String,String> map) throws IOException { |
| if (map == null) { |
| writeInt(0); |
| } else { |
| writeInt(map.size()); |
| for(final Map.Entry<String, String> entry: map.entrySet()) { |
| writeString(entry.getKey()); |
| writeString(entry.getValue()); |
| } |
| } |
| } |
| |
| /** |
| * Writes a String set. |
| * <p> |
| * First the size is written as an {@link #writeInt(int) Int32}, |
| * followed by each value written as a |
| * {@link #writeString(String) String}. |
| * |
| * @param set Input set. May be null (equivalent to an empty set) |
| */ |
| public void writeStringSet(Set<String> set) throws IOException { |
| if (set == null) { |
| writeInt(0); |
| } else { |
| writeInt(set.size()); |
| for(String value : set) { |
| writeString(value); |
| } |
| } |
| } |
| } |