293 lines
9.8 KiB
Java
293 lines
9.8 KiB
Java
/*
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* Copyright (c) 1994, 2018, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.io;
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import java.util.Arrays;
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import java.util.Objects;
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/**
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* A {@code ByteArrayInputStream} contains
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* an internal buffer that contains bytes that
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* may be read from the stream. An internal
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* counter keeps track of the next byte to
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* be supplied by the {@code read} method.
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* <p>
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* Closing a {@code ByteArrayInputStream} has no effect. The methods in
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* this class can be called after the stream has been closed without
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* generating an {@code IOException}.
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*
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* @author Arthur van Hoff
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* @see java.io.StringBufferInputStream
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* @since 1.0
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*/
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public class ByteArrayInputStream extends InputStream {
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/**
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* An array of bytes that was provided
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* by the creator of the stream. Elements {@code buf[0]}
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* through {@code buf[count-1]} are the
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* only bytes that can ever be read from the
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* stream; element {@code buf[pos]} is
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* the next byte to be read.
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*/
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protected byte buf[];
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/**
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* The index of the next character to read from the input stream buffer.
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* This value should always be nonnegative
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* and not larger than the value of {@code count}.
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* The next byte to be read from the input stream buffer
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* will be {@code buf[pos]}.
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*/
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protected int pos;
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/**
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* The currently marked position in the stream.
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* ByteArrayInputStream objects are marked at position zero by
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* default when constructed. They may be marked at another
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* position within the buffer by the {@code mark()} method.
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* The current buffer position is set to this point by the
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* {@code reset()} method.
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* <p>
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* If no mark has been set, then the value of mark is the offset
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* passed to the constructor (or 0 if the offset was not supplied).
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*
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* @since 1.1
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*/
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protected int mark = 0;
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/**
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* The index one greater than the last valid character in the input
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* stream buffer.
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* This value should always be nonnegative
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* and not larger than the length of {@code buf}.
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* It is one greater than the position of
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* the last byte within {@code buf} that
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* can ever be read from the input stream buffer.
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*/
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protected int count;
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/**
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* Creates a {@code ByteArrayInputStream}
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* so that it uses {@code buf} as its
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* buffer array.
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* The buffer array is not copied.
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* The initial value of {@code pos}
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* is {@code 0} and the initial value
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* of {@code count} is the length of
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* {@code buf}.
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*
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* @param buf the input buffer.
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*/
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public ByteArrayInputStream(byte buf[]) {
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this.buf = buf;
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this.pos = 0;
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this.count = buf.length;
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}
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/**
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* Creates {@code ByteArrayInputStream}
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* that uses {@code buf} as its
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* buffer array. The initial value of {@code pos}
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* is {@code offset} and the initial value
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* of {@code count} is the minimum of {@code offset+length}
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* and {@code buf.length}.
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* The buffer array is not copied. The buffer's mark is
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* set to the specified offset.
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*
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* @param buf the input buffer.
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* @param offset the offset in the buffer of the first byte to read.
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* @param length the maximum number of bytes to read from the buffer.
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*/
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public ByteArrayInputStream(byte buf[], int offset, int length) {
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this.buf = buf;
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this.pos = offset;
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this.count = Math.min(offset + length, buf.length);
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this.mark = offset;
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}
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/**
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* Reads the next byte of data from this input stream. The value
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* byte is returned as an {@code int} in the range
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* {@code 0} to {@code 255}. If no byte is available
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* because the end of the stream has been reached, the value
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* {@code -1} is returned.
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* <p>
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* This {@code read} method
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* cannot block.
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*
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* @return the next byte of data, or {@code -1} if the end of the
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* stream has been reached.
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*/
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public synchronized int read() {
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return (pos < count) ? (buf[pos++] & 0xff) : -1;
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}
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/**
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* Reads up to {@code len} bytes of data into an array of bytes from this
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* input stream. If {@code pos} equals {@code count}, then {@code -1} is
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* returned to indicate end of file. Otherwise, the number {@code k} of
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* bytes read is equal to the smaller of {@code len} and {@code count-pos}.
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* If {@code k} is positive, then bytes {@code buf[pos]} through
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* {@code buf[pos+k-1]} are copied into {@code b[off]} through
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* {@code b[off+k-1]} in the manner performed by {@code System.arraycopy}.
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* The value {@code k} is added into {@code pos} and {@code k} is returned.
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* <p>
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* This {@code read} method cannot block.
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*
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* @param b the buffer into which the data is read.
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* @param off the start offset in the destination array {@code b}
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* @param len the maximum number of bytes read.
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* @return the total number of bytes read into the buffer, or
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* {@code -1} if there is no more data because the end of
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* the stream has been reached.
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* @throws NullPointerException If {@code b} is {@code null}.
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* @throws IndexOutOfBoundsException If {@code off} is negative,
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* {@code len} is negative, or {@code len} is greater than
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* {@code b.length - off}
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*/
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public synchronized int read(byte b[], int off, int len) {
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Objects.checkFromIndexSize(off, len, b.length);
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if (pos >= count) {
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return -1;
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}
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int avail = count - pos;
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if (len > avail) {
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len = avail;
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}
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if (len <= 0) {
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return 0;
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}
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System.arraycopy(buf, pos, b, off, len);
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pos += len;
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return len;
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}
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public synchronized byte[] readAllBytes() {
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byte[] result = Arrays.copyOfRange(buf, pos, count);
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pos = count;
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return result;
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}
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public int readNBytes(byte[] b, int off, int len) {
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int n = read(b, off, len);
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return n == -1 ? 0 : n;
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}
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public synchronized long transferTo(OutputStream out) throws IOException {
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int len = count - pos;
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out.write(buf, pos, len);
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pos = count;
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return len;
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}
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/**
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* Skips {@code n} bytes of input from this input stream. Fewer
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* bytes might be skipped if the end of the input stream is reached.
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* The actual number {@code k}
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* of bytes to be skipped is equal to the smaller
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* of {@code n} and {@code count-pos}.
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* The value {@code k} is added into {@code pos}
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* and {@code k} is returned.
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*
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* @param n the number of bytes to be skipped.
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* @return the actual number of bytes skipped.
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*/
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public synchronized long skip(long n) {
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long k = count - pos;
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if (n < k) {
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k = n < 0 ? 0 : n;
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}
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pos += k;
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return k;
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}
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/**
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* Returns the number of remaining bytes that can be read (or skipped over)
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* from this input stream.
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* <p>
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* The value returned is {@code count - pos},
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* which is the number of bytes remaining to be read from the input buffer.
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*
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* @return the number of remaining bytes that can be read (or skipped
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* over) from this input stream without blocking.
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*/
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public synchronized int available() {
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return count - pos;
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}
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/**
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* Tests if this {@code InputStream} supports mark/reset. The
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* {@code markSupported} method of {@code ByteArrayInputStream}
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* always returns {@code true}.
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*
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* @since 1.1
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*/
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public boolean markSupported() {
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return true;
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}
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/**
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* Set the current marked position in the stream.
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* ByteArrayInputStream objects are marked at position zero by
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* default when constructed. They may be marked at another
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* position within the buffer by this method.
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* <p>
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* If no mark has been set, then the value of the mark is the
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* offset passed to the constructor (or 0 if the offset was not
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* supplied).
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*
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* <p> Note: The {@code readAheadLimit} for this class
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* has no meaning.
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*
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* @since 1.1
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*/
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public void mark(int readAheadLimit) {
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mark = pos;
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}
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/**
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* Resets the buffer to the marked position. The marked position
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* is 0 unless another position was marked or an offset was specified
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* in the constructor.
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*/
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public synchronized void reset() {
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pos = mark;
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}
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/**
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* Closing a {@code ByteArrayInputStream} has no effect. The methods in
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* this class can be called after the stream has been closed without
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* generating an {@code IOException}.
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*/
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public void close() throws IOException {
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}
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}
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