ByteArrayInputStream
ByteArrayInputStream
/*
* Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE 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
* @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;
}
int avail = count - pos;
if (len > avail) {
len = avail;
}
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) {
long k = count - pos;
if (n < k) {
k = n < 0 ? 0 : n;
}
pos += k;
return k;
}
/**
* 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>.
*/
public void close() throws IOException {
}
}
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