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/* * @(#)ByteArrayInputStream.java 1.47 05/11/17 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package java.io; /** * A <code>ByteArrayInputStream</code> contains * an internal buffer that contains bytes that * may be read from the stream. An internal * counter keeps track of the next byte to * be supplied by the <code>read</code> method. * <p> * Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in * this class can be called after the stream has been closed without * generating an <tt>IOException</tt>. * * @author Arthur van Hoff * @version 1.47, 11/17/05 * @see java.io.StringBufferInputStream * @since JDK1.0 */ public class ByteArrayInputStream extends InputStream { /** * An array of bytes that was provided * by the creator of the stream. Elements <code>buf[0]</code> * through <code>buf[count-1]</code> are the * only bytes that can ever be read from the * stream; element <code>buf[pos]</code> is * the next byte to be read. */ protected byte buf[]; /** * The index of the next character to read from the input stream buffer. * This value should always be nonnegative * and not larger than the value of <code>count</code>. * The next byte to be read from the input stream buffer * will be <code>buf[pos]</code>. */ protected int pos; /** * The currently marked position in the stream. * ByteArrayInputStream objects are marked at position zero by * default when constructed. They may be marked at another * position within the buffer by the <code>mark()</code> method. * The current buffer position is set to this point by the * <code>reset()</code> method. * <p> * If no mark has been set, then the value of mark is the offset * passed to the constructor (or 0 if the offset was not supplied). * * @since JDK1.1 */ protected int mark = 0; /** * The index one greater than the last valid character in the input * stream buffer. * This value should always be nonnegative * and not larger than the length of <code>buf</code>. * It is one greater than the position of * the last byte within <code>buf</code> that * can ever be read from the input stream buffer. */ protected int count; /** * Creates a <code>ByteArrayInputStream</code> * so that it uses <code>buf</code> as its * buffer array. * The buffer array is not copied. * The initial value of <code>pos</code> * is <code>0</code> and the initial value * of <code>count</code> is the length of * <code>buf</code>. * * @param buf the input buffer. */ public ByteArrayInputStream(byte buf[]) { this.buf = buf; this.pos = 0; this.count = buf.length; } /** * Creates <code>ByteArrayInputStream</code> * that uses <code>buf</code> as its * buffer array. The initial value of <code>pos</code> * is <code>offset</code> and the initial value * of <code>count</code> is the minimum of <code>offset+length</code> * and <code>buf.length</code>. * The buffer array is not copied. The buffer's mark is * set to the specified offset. * * @param buf the input buffer. * @param offset the offset in the buffer of the first byte to read. * @param length the maximum number of bytes to read from the buffer. */ public ByteArrayInputStream(byte buf[], int offset, int length) { this.buf = buf; this.pos = offset; this.count = Math.min(offset + length, buf.length); this.mark = offset; } /** * Reads the next byte of data from this input stream. The value * byte is returned as an <code>int</code> in the range * <code>0</code> to <code>255</code>. If no byte is available * because the end of the stream has been reached, the value * <code>-1</code> is returned. * <p> * This <code>read</code> method * cannot block. * * @return the next byte of data, or <code>-1</code> if the end of the * stream has been reached. */ public synchronized int read() { return (pos < count) ? (buf[pos++] & 0xff) : -1; } /** * Reads up to <code>len</code> bytes of data into an array of bytes * from this input stream. * If <code>pos</code> equals <code>count</code>, * then <code>-1</code> is returned to indicate * end of file. Otherwise, the number <code>k</code> * of bytes read is equal to the smaller of * <code>len</code> and <code>count-pos</code>. * If <code>k</code> is positive, then bytes * <code>buf[pos]</code> through <code>buf[pos+k-1]</code> * are copied into <code>b[off]</code> through * <code>b[off+k-1]</code> in the manner performed * by <code>System.arraycopy</code>. The * value <code>k</code> is added into <code>pos</code> * and <code>k</code> is returned. * <p> * This <code>read</code> method cannot block. * * @param b the buffer into which the data is read. * @param off the start offset in the destination array <code>b</code> * @param len the maximum number of bytes read. * @return the total number of bytes read into the buffer, or * <code>-1</code> if there is no more data because the end of * the stream has been reached. * @exception NullPointerException If <code>b</code> is <code>null</code>. * @exception IndexOutOfBoundsException If <code>off</code> is negative, * <code>len</code> is negative, or <code>len</code> is greater than * <code>b.length - off</code> */ public synchronized int read(byte b[], int off, int len) { if (b == null) { throw new NullPointerException(); } else if (off < 0 || len < 0 || len > b.length - off) { throw new IndexOutOfBoundsException(); } if (pos >= count) { return -1; } if (pos + len > count) { len = count - pos; } if (len <= 0) { return 0; } System.arraycopy(buf, pos, b, off, len); pos += len; return len; } /** * Skips <code>n</code> bytes of input from this input stream. Fewer * bytes might be skipped if the end of the input stream is reached. * The actual number <code>k</code> * of bytes to be skipped is equal to the smaller * of <code>n</code> and <code>count-pos</code>. * The value <code>k</code> is added into <code>pos</code> * and <code>k</code> is returned. * * @param n the number of bytes to be skipped. * @return the actual number of bytes skipped. */ public synchronized long skip(long n) { if (pos + n > count) { n = count - pos; } if (n < 0) { return 0; } pos += n; return n; } /** * Returns the number of remaining bytes that can be read (or skipped over) * from this input stream. * <p> * The value returned is <code>count - pos</code>, * which is the number of bytes remaining to be read from the input buffer. * * @return the number of remaining bytes that can be read (or skipped * over) from this input stream without blocking. */ public synchronized int available() { return count - pos; } /** * Tests if this <code>InputStream</code> supports mark/reset. The * <code>markSupported</code> method of <code>ByteArrayInputStream</code> * always returns <code>true</code>. * * @since JDK1.1 */ public boolean markSupported() { return true; } /** * Set the current marked position in the stream. * ByteArrayInputStream objects are marked at position zero by * default when constructed. They may be marked at another * position within the buffer by this method. * <p> * If no mark has been set, then the value of the mark is the * offset passed to the constructor (or 0 if the offset was not * supplied). * * <p> Note: The <code>readAheadLimit</code> for this class * has no meaning. * * @since JDK1.1 */ public void mark(int readAheadLimit) { mark = pos; } /** * Resets the buffer to the marked position. The marked position * is 0 unless another position was marked or an offset was specified * in the constructor. */ public synchronized void reset() { pos = mark; } /** * Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in * this class can be called after the stream has been closed without * generating an <tt>IOException</tt>. * <p> */ public void close() throws IOException { } }