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.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import org.apache.lucene.util.IOUtils;
/**
* Abstract base class for performing read operations of Lucene's low-level
* data types.
*
* <p>{@code DataInput} may only be used from one thread, because it is not
* thread safe (it keeps internal state like file position). To allow
* multithreaded use, every {@code DataInput} instance must be cloned before
* used in another thread. Subclasses must therefore implement {@link #clone()},
* returning a new {@code DataInput} which operates on the same underlying
* resource, but positioned independently.
*/
public abstract class DataInput implements Cloneable {
/** Reads and returns a single byte.
* @see DataOutput#writeByte(byte)
*/
public abstract byte readByte() throws IOException;
/** Reads a specified number of bytes into an array at the specified offset.
* @param b the array to read bytes into
* @param offset the offset in the array to start storing bytes
* @param len the number of bytes to read
* @see DataOutput#writeBytes(byte[],int)
*/
public abstract void readBytes(byte[] b, int offset, int len)
throws IOException;
/** Reads a specified number of bytes into an array at the
* specified offset with control over whether the read
* should be buffered (callers who have their own buffer
* should pass in "false" for useBuffer). Currently only
* {@link BufferedIndexInput} respects this parameter.
* @param b the array to read bytes into
* @param offset the offset in the array to start storing bytes
* @param len the number of bytes to read
* @param useBuffer set to false if the caller will handle
* buffering.
* @see DataOutput#writeBytes(byte[],int)
*/
public void readBytes(byte[] b, int offset, int len, boolean useBuffer)
throws IOException
{
// Default to ignoring useBuffer entirely
readBytes(b, offset, len);
}
/** Reads two bytes and returns a short.
* @see DataOutput#writeByte(byte)
*/
public short readShort() throws IOException {
return (short) (((readByte() & 0xFF) << 8) | (readByte() & 0xFF));
}
/** Reads four bytes and returns an int.
* @see DataOutput#writeInt(int)
*/
public int readInt() throws IOException {
return ((readByte() & 0xFF) << 24) | ((readByte() & 0xFF) << 16)
| ((readByte() & 0xFF) << 8) | (readByte() & 0xFF);
}
/** Reads an int stored in variable-length format. Reads between one and
* five bytes. Smaller values take fewer bytes. Negative numbers are not
* supported.
* <p>
* The format is described further in {@link DataOutput#writeVInt(int)}.
*
* @see DataOutput#writeVInt(int)
*/
public int readVInt() throws IOException {
/* This is the original code of this method,
* but a Hotspot bug (see LUCENE-2975) corrupts the for-loop if
* readByte() is inlined. So the loop was unwinded!
byte b = readByte();
int i = b & 0x7F;
for (int shift = 7; (b & 0x80) != 0; shift += 7) {
b = readByte();
i |= (b & 0x7F) << shift;
}
return i;
*/
byte b = readByte();
if (b >= 0) return b;
int i = b & 0x7F;
b = readByte();
i |= (b & 0x7F) << 7;
if (b >= 0) return i;
b = readByte();
i |= (b & 0x7F) << 14;
if (b >= 0) return i;
b = readByte();
i |= (b & 0x7F) << 21;
if (b >= 0) return i;
b = readByte();
// Warning: the next ands use 0x0F / 0xF0 - beware copy/paste errors:
i |= (b & 0x0F) << 28;
if ((b & 0xF0) == 0) return i;
throw new IOException("Invalid vInt detected (too many bits)");
}
/** Reads eight bytes and returns a long.
* @see DataOutput#writeLong(long)
*/
public long readLong() throws IOException {
return (((long)readInt()) << 32) | (readInt() & 0xFFFFFFFFL);
}
/** Reads a long stored in variable-length format. Reads 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 DataOutput#writeVLong(long)
*/
public long readVLong() throws IOException {
/* This is the original code of this method,
* but a Hotspot bug (see LUCENE-2975) corrupts the for-loop if
* readByte() is inlined. So the loop was unwinded!
byte b = readByte();
long i = b & 0x7F;
for (int shift = 7; (b & 0x80) != 0; shift += 7) {
b = readByte();
i |= (b & 0x7FL) << shift;
}
return i;
*/
byte b = readByte();
if (b >= 0) return b;
long i = b & 0x7FL;
b = readByte();
i |= (b & 0x7FL) << 7;
if (b >= 0) return i;
b = readByte();
i |= (b & 0x7FL) << 14;
if (b >= 0) return i;
b = readByte();
i |= (b & 0x7FL) << 21;
if (b >= 0) return i;
b = readByte();
i |= (b & 0x7FL) << 28;
if (b >= 0) return i;
b = readByte();
i |= (b & 0x7FL) << 35;
if (b >= 0) return i;
b = readByte();
i |= (b & 0x7FL) << 42;
if (b >= 0) return i;
b = readByte();
i |= (b & 0x7FL) << 49;
if (b >= 0) return i;
b = readByte();
i |= (b & 0x7FL) << 56;
if (b >= 0) return i;
throw new IOException("Invalid vLong detected (negative values disallowed)");
}
/** Reads a string.
* @see DataOutput#writeString(String)
*/
public String readString() throws IOException {
int length = readVInt();
final byte[] bytes = new byte[length];
readBytes(bytes, 0, length);
return new String(bytes, 0, length, IOUtils.CHARSET_UTF_8);
}
/** Returns a clone of this stream.
*
* <p>Clones of a stream access the same data, and are positioned at the same
* point as the stream they were cloned from.
*
* <p>Expert: Subclasses must ensure that clones may be positioned at
* different points in the input from each other and from the stream they
* were cloned from.
*/
@Override
public DataInput clone() {
try {
return (DataInput) super.clone();
} catch (CloneNotSupportedException e) {
throw new Error("This cannot happen: Failing to clone DataInput");
}
}
/** Reads a Map<String,String> previously written
* with {@link DataOutput#writeStringStringMap(Map)}. */
public Map<String,String> readStringStringMap() throws IOException {
final Map<String,String> map = new HashMap<String,String>();
final int count = readInt();
for(int i=0;i<count;i++) {
final String key = readString();
final String val = readString();
map.put(key, val);
}
return map;
}
/** Reads a Set<String> previously written
* with {@link DataOutput#writeStringSet(Set)}. */
public Set<String> readStringSet() throws IOException {
final Set<String> set = new HashSet<String>();
final int count = readInt();
for(int i=0;i<count;i++) {
set.add(readString());
}
return set;
}
}