+++ /dev/null
-package org.apache.lucene.util;
-
-import java.io.EOFException;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.OutputStream;
-
-/**
- * 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.
- */
-
-/**
- * Variable-length encoding of 32-bit integers, into 8-bit bytes. A number is encoded as follows:
- * <ul>
- * <li>If it is less than 127 and non-negative (i.e., if the number uses only 7 bits), it is encoded as
- * as single byte: 0bbbbbbb.
- * <li>If its highest nonzero bit is greater than bit 6 (0x40), it is represented as a series of
- * bytes, each byte's
- * 7 LSB containing bits from the original value, with the MSB set for all but the last
- * byte. The first encoded byte contains the highest nonzero bits from the
- * original; the second byte contains the next 7 MSB; and so on, with the last byte
- * containing the 7 LSB of the original.
- * </ul>
- * Examples:
- * <ol>
- * <li>n = 117 = 1110101: This has fewer than 8 significant bits, and so is encoded as
- * 01110101 = 0x75.
- * <li>n = 100000 = (binary) 11000011010100000. This has 17 significant bits, and so needs
- * three Vint8 bytes. Left-zero-pad it to a multiple of 7 bits, then split it into chunks of 7
- * and add an MSB, 0 for the last byte, 1 for the others: 1|0000110 1|0001101 0|0100000
- * = 0x86 0x8D 0x20.
- * </ol>
- * This encoder/decoder will correctly handle any 32-bit integer, but for negative numbers,
- * and positive numbers with more than 28 significant bits, encoding requires 5 bytes; this
- * is not an efficient encoding scheme for large
- * positive numbers or any negative number.
- * <p>
- * <b>Compatibility:</b><br>
- * This class has been used in products that have shipped to customers, and is needed to
- * decode legacy data. Do not modify this class in ways that will break compatibility.
- *
- * @lucene.experimental
- */
-public class Vint8 {
-
- /**
- * Because Java lacks call-by-reference, this class boxes the decoding position, which
- * is initially set by the caller, and returned after decoding, incremented by the number
- * of bytes processed.
- */
- public static class Position {
- /**
- * Creates a position value set to zero.
- */
- public Position() {
- // The initial position is zero by default.
- }
- /**
- * Creates a position set to {@code initialPosition}.
- * @param initialPosition The starting decoding position in the source buffer.
- */
- public Position(int initialPosition) {
- this.pos = initialPosition;
- }
- /**
- * The value passed by reference.
- */
- public int pos;
- }
-
- /**
- * Returns the number of bytes needed to encode {@code number}.
- * @param number The number whose encoded length is needed.
- * @return The number of bytes needed to encode {@code number}.
- */
- public static int bytesNeeded(int number) {
- if ((number & ~0x7F) == 0) {
- return 1;
- } else if ((number & ~0x3FFF) == 0) {
- return 2;
- } else if ((number & ~0x1FFFFF) == 0) {
- return 3;
- } else if ((number & ~0xFFFFFFF) == 0) {
- return 4;
- } else {
- return 5;
- }
- }
-
- /**
- * The maximum number of bytes needed to encode a number using {@code Vint8}.
- */
- public static final int MAXIMUM_BYTES_NEEDED = 5;
-
- /**
- * Encodes {@code number} to {@code out}.
- * @param number The value to be written in encoded form, to {@code out}.
- * @param out The output stream receiving the encoded bytes.
- * @exception IOException If there is a problem writing to {@code out}.
- */
- public static void encode(int number, OutputStream out) throws IOException {
- if ((number & ~0x7F) == 0) {
- out.write(number);
- } else if ((number & ~0x3FFF) == 0) {
- out.write(0x80 | (number >> 7));
- out.write(0x7F & number);
- } else if ((number & ~0x1FFFFF) == 0) {
- out.write(0x80 | (number >> 14));
- out.write(0x80 | (number >> 7));
- out.write(0x7F & number);
- } else if ((number & ~0xFFFFFFF) == 0) {
- out.write(0x80 | (number >> 21));
- out.write(0x80 | (number >> 14));
- out.write(0x80 | (number >> 7));
- out.write(0x7F & number);
- } else {
- out.write(0x80 | (number >> 28));
- out.write(0x80 | (number >> 21));
- out.write(0x80 | (number >> 14));
- out.write(0x80 | (number >> 7));
- out.write(0x7F & number);
- }
- }
-
- /**
- * Encodes {@code number} into {@code dest}, starting at offset {@code start} from
- * the beginning of the array. This method assumes {@code dest} is large enough to
- * hold the required number of bytes.
- * @param number The number to be encoded.
- * @param dest The destination array.
- * @param start The starting offset in the array.
- * @return The number of bytes used in the array.
- */
- public static int encode(int number, byte[] dest, int start) {
- if ((number & ~0x7F) == 0) {
- dest[start] = (byte) number;
- return 1;
- } else if ((number & ~0x3FFF) == 0) {
- dest[start] = (byte) (0x80 | ((number & 0x3F80) >> 7));
- dest[start + 1] = (byte) (number & 0x7F);
- return 2;
- } else if ((number & ~0x1FFFFF) == 0) {
- dest[start] = (byte) (0x80 | ((number & 0x1FC000) >> 14));
- dest[start + 1] = (byte) (0x80 | ((number & 0x3F80) >> 7));
- dest[start + 2] = (byte) (number & 0x7F);
- return 3;
- } else if ((number & ~0xFFFFFFF) == 0) {
- dest[start] = (byte) (0x80 | ((number & 0xFE00000) >> 21));
- dest[start + 1] = (byte) (0x80 | ((number & 0x1FC000) >> 14));
- dest[start + 2] = (byte) (0x80 | ((number & 0x3F80) >> 7));
- dest[start + 3] = (byte) (number & 0x7F);
- return 4;
- } else {
- dest[start] = (byte) (0x80 | ((number & 0xF0000000) >> 28));
- dest[start + 1] = (byte) (0x80 | ((number & 0xFE00000) >> 21));
- dest[start + 2] = (byte) (0x80 | ((number & 0x1FC000) >> 14));
- dest[start + 3] = (byte) (0x80 | ((number & 0x3F80) >> 7));
- dest[start + 4] = (byte) (number & 0x7F);
- return 5;
- }
- }
-
- /**
- * Decodes a 32-bit integer from {@code bytes}, beginning at offset {@code pos.pos}.
- * The decoded value is returned, and {@code pos.pos} is incremented by the number of
- * bytes processed.
- * @param bytes The byte array containing an encoded value.
- * @param pos On entry, the starting position in the array; on return, one greater
- * than the position of the last byte decoded in the call.
- * @return The decoded value.
- */
- public static int decode(byte[] bytes, Position pos) {
- int value = 0;
- while (true) {
- byte first = bytes[pos.pos];
- ++pos.pos;
- value |= first & 0x7F;
- if ((first & 0x80) == 0) {
- return value;
- }
- value <<= 7;
- }
- }
-
- /**
- * Decodes a 32-bit integer from bytes read from {@code in}. Bytes are read,
- * one at a time, from {@code in}, and it is assumed they represent a 32-bit
- * integer encoded using this class's encoding scheme. The decoded value is
- * returned.
- * @param in The input stream containing the encoded bytes.
- * @return The decoded value.
- * @exception EOFException If the stream ends before a value has been decoded.
- */
- public static int decode(InputStream in) throws IOException {
- int value = 0;
- while (true) {
- int first = in.read();
- if (first < 0) {
- throw new EOFException();
- }
- value |= first & 0x7F;
- if ((first & 0x80) == 0) {
- return value;
- }
- value <<= 7;
- }
- }
-
- /**
- * The default ctor is made private because all methods of this class are static.
- */
- private Vint8() {
- // Just making it impossible to instantiate.
- }
-
-}
fnp / pylucene.git / blobdiff