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/*
* Copyright (C) 2005-2022 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.
*/
package it.unimi.dsi.fastutil.io;
/** Simple, fast and repositionable byte-array input stream.
*
* Warning: this class implements the correct semantics
* of {@link #read(byte[], int, int)} as described in {@link java.io.InputStream}.
* The implementation given in {@link java.io.ByteArrayInputStream} is broken,
* but it will never be fixed because it's too late.
*
* @author Sebastiano Vigna
*/
public class FastByteArrayInputStream extends MeasurableInputStream implements RepositionableStream {
/** The array backing the input stream. */
public byte[] array;
/** The first valid entry. */
public int offset;
/** The number of valid bytes in {@link #array} starting from {@link #offset}. */
public int length;
/** The current position as a distance from {@link #offset}. */
private int position;
/** The current mark as a position, or -1 if no mark exists. */
private int mark;
/** Creates a new array input stream using a given array fragment.
*
* @param array the backing array.
* @param offset the first valid entry of the array.
* @param length the number of valid bytes.
*/
public FastByteArrayInputStream(final byte[] array, final int offset, final int length) {
this.array = array;
this.offset = offset;
this.length = length;
}
/** Creates a new array input stream using a given array.
*
* @param array the backing array.
*/
public FastByteArrayInputStream(final byte[] array) {
this(array, 0, array.length);
}
@Override
public boolean markSupported() {
return true;
}
@Override
public void reset() {
position = mark;
}
/** Closing a fast byte array input stream has no effect. */
@Override
public void close() {}
@Override
public void mark(final int dummy) {
mark = position;
}
@Override
public int available() {
return length - position;
}
@Override
public long skip(long n) {
if (n <= length - position) {
position += (int)n;
return n;
}
n = length - position;
position = length;
return n;
}
@Override
public int read() {
if (length == position) return -1;
return array[offset + position++] & 0xFF;
}
/** Reads bytes from this byte-array input stream as
* specified in {@link java.io.InputStream#read(byte[], int, int)}.
* Note that the implementation given in {@link java.io.ByteArrayInputStream#read(byte[], int, int)}
* will return -1 on a zero-length read at EOF, contrarily to the specification. We won't.
*/
@Override
public int read(final byte b[], final int offset, final int length) {
if (this.length == this.position) return length == 0 ? 0 : -1;
final int n = Math.min(length, this.length - this.position);
System.arraycopy(array, this.offset + this.position, b, offset, n);
this.position += n;
return n;
}
@Override
public long position() {
return position;
}
@Override
public void position(final long newPosition) {
position = (int)Math.min(newPosition, length);
}
@Override
public long length() {
return length;
}
}