it.unimi.dsi.fastutil.io.FastMultiByteArrayInputStream Maven / Gradle / Ivy
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package it.unimi.dsi.fastutil.io;
/*
* Copyright (C) 2005-2016 Sebastiano Vigna
*
* 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.EOFException;
import java.io.IOException;
import java.io.InputStream;
/** Simple, fast and repositionable byte array input stream that multiplexes its content among several arrays.
*
* This class is significantly slower than {@link FastByteArrayInputStream},
* but it can hold 256 PiB of data. The relevant constructor is {@link #FastMultiByteArrayInputStream(InputStream, long)},
* which fetches a stream and loads it into a sequence of byte arrays.
*
* @author Sebastiano Vigna
* @author Paolo Boldi
s */
public class FastMultiByteArrayInputStream extends MeasurableInputStream implements RepositionableStream {
/** The number of bits of an array slice index. */
public final static int SLICE_BITS = 10;
/** The maximum length of an array slice. */
public final static int SLICE_SIZE = 1 << SLICE_BITS;
/** The mask to retrieve a slice offset. */
public final static int SLICE_MASK = SLICE_SIZE - 1;
/** The array of arrays backing the input stream, plus an additional {@code null} entry. */
public byte[][] array;
/** The current array. */
public byte[] current;
/** The number of valid bytes in {@link #array}. */
public long length;
/** The current position. */
private long position;
/** Creates a new multi-array input stream loading it from a measurable input stream.
*
* @param is the input stream that will fill the array.
*/
public FastMultiByteArrayInputStream( final MeasurableInputStream is ) throws IOException {
this( is, is.length() );
}
/** Creates a new multi-array input stream loading it from an input stream.
*
* @param is the input stream that will fill the array.
* @param size the number of bytes to be read from is.
*/
public FastMultiByteArrayInputStream( final InputStream is, long size ) throws IOException {
length = size;
array = new byte[ (int)( ( size + SLICE_SIZE - 1 ) / SLICE_SIZE ) + 1 ][];
for( int i = 0; i < array.length - 1; i++ ) {
array[ i ] = new byte[ size >= SLICE_SIZE ? SLICE_SIZE : (int)size ];
// It is important *not* to use is.read() directly because of bug #6478546
if ( BinIO.loadBytes( is, array[ i ] ) != array[ i ].length ) throw new EOFException();
size -= array[ i ].length;
}
current = array[ 0 ];
}
/** Creates a new multi-array input stream sharing the backing arrays of another multi-array input stream.
*
* @param is the multi-array input stream to replicate.
*/
public FastMultiByteArrayInputStream( final FastMultiByteArrayInputStream is ) {
this.array = is.array;
this.length = is.length;
this.current = array[ 0 ];
}
/** Creates a new multi-array input stream using a given array.
*
* @param array the backing array.
*/
public FastMultiByteArrayInputStream( final byte[] array ) {
if ( array.length == 0 ) this.array = new byte[ 1 ][];
else {
this.array = new byte[ 2 ][];
this.array[ 0 ] = array;
this.length = array.length;
this.current = array;
}
}
/** Returns the number of bytes that can be read (or skipped over) from this input stream without blocking.
*
* Note that this number may be smaller than the number of bytes actually
* available from the stream if this number exceeds {@link Integer#MAX_VALUE}.
*
* @return the minimum among the number of available bytes and {@link Integer#MAX_VALUE}.
*/
public int available() {
return (int)Math.min( Integer.MAX_VALUE, length - position );
}
public long skip( long n ) {
if ( n > length - position ) n = length - position;
position += n;
updateCurrent();
return n;
}
public int read() {
if ( length == position ) return -1;
final int disp = (int)( position++ & SLICE_MASK );
if ( disp == 0 ) updateCurrent();
return current[ disp ] & 0xFF;
}
public int read( final byte[] b, int offset, final int length ) {
final long remaining = this.length - position;
if ( remaining == 0 ) return length == 0 ? 0 : -1;
int n = (int)Math.min( length, remaining );
final int m = n;
for(;;) {
final int disp = (int)( position & SLICE_MASK );
if ( disp == 0 ) updateCurrent();
final int res = Math.min( n, current.length - disp );
System.arraycopy( current, disp, b, offset, res );
n -= res;
position += res;
if ( n == 0 ) return m;
offset += res;
}
}
private void updateCurrent() {
current = array[ (int)( position >>> SLICE_BITS ) ];
}
public long position() {
return position;
}
public void position( final long newPosition ) {
position = Math.min( newPosition, length );
updateCurrent();
}
@Override
public long length() throws IOException {
return length;
}
/** NOP. */
public void close() {}
public boolean markSupported() {
return false;
}
public void mark( final int dummy ) {
throw new UnsupportedOperationException();
}
public void reset() {
throw new UnsupportedOperationException();
}
}