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283 lines
8.9 KiB
283 lines
8.9 KiB
/*
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* Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*/
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package java.io;
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/**
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* A <code>ByteArrayInputStream</code> 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</code> method.
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* <p>
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* Closing a <tt>ByteArrayInputStream</tt> 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 <tt>IOException</tt>.
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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 JDK1.0
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*/
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public
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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]</code>
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* through <code>buf[count-1]</code> are the
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* only bytes that can ever be read from the
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* stream; element <code>buf[pos]</code> 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</code>.
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* The next byte to be read from the input stream buffer
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* will be <code>buf[pos]</code>.
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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()</code> method.
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* The current buffer position is set to this point by the
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* <code>reset()</code> 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 JDK1.1
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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</code>.
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* It is one greater than the position of
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* the last byte within <code>buf</code> 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</code>
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* so that it uses <code>buf</code> 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</code>
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* is <code>0</code> and the initial value
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* of <code>count</code> is the length of
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* <code>buf</code>.
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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</code>
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* that uses <code>buf</code> as its
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* buffer array. The initial value of <code>pos</code>
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* is <code>offset</code> and the initial value
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* of <code>count</code> is the minimum of <code>offset+length</code>
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* and <code>buf.length</code>.
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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</code> in the range
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* <code>0</code> to <code>255</code>. 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</code> is returned.
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* <p>
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* This <code>read</code> method
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* cannot block.
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*
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* @return the next byte of data, or <code>-1</code> 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</code> bytes of data into an array of bytes
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* from this input stream.
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* If <code>pos</code> equals <code>count</code>,
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* then <code>-1</code> is returned to indicate
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* end of file. Otherwise, the number <code>k</code>
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* of bytes read is equal to the smaller of
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* <code>len</code> and <code>count-pos</code>.
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* If <code>k</code> is positive, then bytes
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* <code>buf[pos]</code> through <code>buf[pos+k-1]</code>
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* are copied into <code>b[off]</code> through
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* <code>b[off+k-1]</code> in the manner performed
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* by <code>System.arraycopy</code>. The
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* value <code>k</code> is added into <code>pos</code>
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* and <code>k</code> is returned.
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* <p>
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* This <code>read</code> 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</code>
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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</code> if there is no more data because the end of
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* the stream has been reached.
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* @exception NullPointerException If <code>b</code> is <code>null</code>.
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* @exception IndexOutOfBoundsException If <code>off</code> is negative,
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* <code>len</code> is negative, or <code>len</code> is greater than
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* <code>b.length - off</code>
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*/
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public synchronized int read(byte b[], int off, int len) {
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if (b == null) {
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throw new NullPointerException();
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} else if (off < 0 || len < 0 || len > b.length - off) {
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throw new IndexOutOfBoundsException();
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}
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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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/**
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* Skips <code>n</code> 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</code>
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* of bytes to be skipped is equal to the smaller
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* of <code>n</code> and <code>count-pos</code>.
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* The value <code>k</code> is added into <code>pos</code>
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* and <code>k</code> 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</code>,
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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</code> supports mark/reset. The
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* <code>markSupported</code> method of <code>ByteArrayInputStream</code>
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* always returns <code>true</code>.
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*
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* @since JDK1.1
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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</code> for this class
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* has no meaning.
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*
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* @since JDK1.1
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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 <tt>ByteArrayInputStream</tt> 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 <tt>IOException</tt>.
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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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