package org.apache.lucene.store;
/**
* Copyright 2004 The Apache Software Foundation
*
* Licensed 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;
/** Abstract base class for input from a file in a {@link Directory}. A
* random-access input stream. Used for all Lucene index input operations.
* @see Directory
* @see OutputStream
*/
public abstract class InputStream implements Cloneable {
static final int BUFFER_SIZE = OutputStream.BUFFER_SIZE;
private byte[] buffer;
private char[] chars;
private long bufferStart = 0; // position in file of buffer
private int bufferLength = 0; // end of valid bytes
private int bufferPosition = 0; // next byte to read
protected long length; // set by subclasses
/** Reads and returns a single byte.
* @see OutputStream#writeByte(byte)
*/
public final byte readByte() throws IOException {
if (bufferPosition >= bufferLength)
refill();
return buffer[bufferPosition++];
}
/** 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 OutputStream#writeBytes(byte[],int)
*/
public final void readBytes(byte[] b, int offset, int len)
throws IOException {
if (len < BUFFER_SIZE) {
for (int i = 0; i < len; i++) // read byte-by-byte
b[i + offset] = (byte)readByte();
} else { // read all-at-once
long start = getFilePointer();
seekInternal(start);
readInternal(b, offset, len);
bufferStart = start + len; // adjust stream variables
bufferPosition = 0;
bufferLength = 0; // trigger refill() on read
}
}
/** Reads four bytes and returns an int.
* @see OutputStream#writeInt(int)
*/
public final 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.
* @see OutputStream#writeVInt(int)
*/
public final int readVInt() throws IOException {
byte b = readByte();
int i = b & 0x7F;
for (int shift = 7; (b & 0x80) != 0; shift += 7) {
b = readByte();
i |= (b & 0x7F) << shift;
}
return i;
}
/** Reads eight bytes and returns a long.
* @see OutputStream#writeLong(long)
*/
public final 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. */
public final long readVLong() throws IOException {
byte b = readByte();
long i = b & 0x7F;
for (int shift = 7; (b & 0x80) != 0; shift += 7) {
b = readByte();
i |= (b & 0x7FL) << shift;
}
return i;
}
/** Reads a string.
* @see OutputStream#writeString(String)
*/
public final String readString() throws IOException {
int length = readVInt();
if (chars == null || length > chars.length)
chars = new char[length];
readChars(chars, 0, length);
return new String(chars, 0, length);
}
/** Reads UTF-8 encoded characters into an array.
* @param buffer the array to read characters into
* @param start the offset in the array to start storing characters
* @param length the number of characters to read
* @see OutputStream#writeChars(String,int,int)
*/
public final void readChars(char[] buffer, int start, int length)
throws IOException {
final int end = start + length;
for (int i = start; i < end; i++) {
byte b = readByte();
if ((b & 0x80) == 0)
buffer[i] = (char)(b & 0x7F);
else if ((b & 0xE0) != 0xE0) {
buffer[i] = (char)(((b & 0x1F) << 6)
| (readByte() & 0x3F));
} else
buffer[i] = (char)(((b & 0x0F) << 12)
| ((readByte() & 0x3F) << 6)
| (readByte() & 0x3F));
}
}
private void refill() throws IOException {
long start = bufferStart + bufferPosition;
long end = start + BUFFER_SIZE;
if (end > length) // don't read past EOF
end = length;
bufferLength = (int)(end - start);
if (bufferLength == 0)
throw new IOException("read past EOF");
if (buffer == null)
buffer = new byte[BUFFER_SIZE]; // allocate buffer lazily
readInternal(buffer, 0, bufferLength);
bufferStart = start;
bufferPosition = 0;
}
/** Expert: implements buffer refill. Reads bytes from the current position
* in the input.
* @param b the array to read bytes into
* @param offset the offset in the array to start storing bytes
* @param length the number of bytes to read
*/
protected abstract void readInternal(byte[] b, int offset, int length)
throws IOException;
/** Closes the stream to futher operations. */
public abstract void close() throws IOException;
/** Returns the current position in this file, where the next read will
* occur.
* @see #seek(long)
*/
public final long getFilePointer() {
return bufferStart + bufferPosition;
}
/** Sets current position in this file, where the next read will occur.
* @see #getFilePointer()
*/
public final void seek(long pos) throws IOException {
if (pos >= bufferStart && pos < (bufferStart + bufferLength))
bufferPosition = (int)(pos - bufferStart); // seek within buffer
else {
bufferStart = pos;
bufferPosition = 0;
bufferLength = 0; // trigger refill() on read()
seekInternal(pos);
}
}
/** Expert: implements seek. Sets current position in this file, where the
* next {@link #readInternal(byte[],int,int)} will occur.
* @see #readInternal(byte[],int,int)
*/
protected abstract void seekInternal(long pos) throws IOException;
/** The number of bytes in the file. */
public final long length() {
return length;
}
/** 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.
*/
public Object clone() {
InputStream clone = null;
try {
clone = (InputStream)super.clone();
} catch (CloneNotSupportedException e) {}
if (buffer != null) {
clone.buffer = new byte[BUFFER_SIZE];
System.arraycopy(buffer, 0, clone.buffer, 0, bufferLength);
}
clone.chars = null;
return clone;
}
}
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