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package java.io;

import java.util.Arrays;
import java.util.Objects;


A ByteArrayInputStream 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 read method. 
 Closing a ByteArrayInputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException. 
Author: Arthur van Hoff
See Also:
Since:  1.0
/**
 * A {@code ByteArrayInputStream} 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} method.
 * <p>
 * Closing a {@code ByteArrayInputStream} has no effect. The methods in
 * this class can be called after the stream has been closed without
 * generating an {@code IOException}.
 *
 * @author  Arthur van Hoff
 * @see     java.io.StringBufferInputStream
 * @since   1.0
 */
public class ByteArrayInputStream extends InputStream {

    
An array of bytes that was provided by the creator of the stream. Elements buf[0] through buf[count-1] are the only bytes that can ever be read from the stream; element buf[pos] is the next byte to be read. 
/**
     * An array of bytes that was provided
     * by the creator of the stream. Elements {@code buf[0]}
     * through {@code buf[count-1]} are the
     * only bytes that can ever be read from the
     * stream;  element {@code buf[pos]} 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 count. The next byte to be read from the input stream buffer will be buf[pos]. 
/**
     * 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}.
     * The next byte to be read from the input stream buffer
     * will be {@code buf[pos]}.
     */
    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 mark() method. The current buffer position is set to this point by the reset() method. 

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:  1.1
/**
     * 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()} method.
     * The current buffer position is set to this point by the
     * {@code reset()} 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   1.1
     */
    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 buf. It is one greater than the position of the last byte within buf that can ever be read from the input stream buffer. 
/**
     * 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}.
     * It  is one greater than the position of
     * the last byte within {@code buf} that
     * can ever be read  from the input stream buffer.
     */
    protected int count;

    
Creates a ByteArrayInputStream so that it uses buf as its buffer array. The buffer array is not copied. The initial value of pos is 0 and the initial value of count is the length of buf. 
Params:
  • buf –   the input buffer.
/**
     * Creates a {@code ByteArrayInputStream}
     * so that it  uses {@code buf} as its
     * buffer array.
     * The buffer array is not copied.
     * The initial value of {@code pos}
     * is {@code 0} and the initial value
     * of  {@code count} is the length of
     * {@code buf}.
     *
     * @param   buf   the input buffer.
     */
    public ByteArrayInputStream(byte buf[]) {
        this.buf = buf;
        this.pos = 0;
        this.count = buf.length;
    }

    
Creates ByteArrayInputStream that uses buf as its buffer array. The initial value of pos is offset and the initial value of count is the minimum of offset+length and buf.length. The buffer array is not copied. The buffer's mark is set to the specified offset. 
Params:
  • buf –      the input buffer.
  • offset –   the offset in the buffer of the first byte to read.
  • length –   the maximum number of bytes to read from the buffer.
/**
     * Creates {@code ByteArrayInputStream}
     * that uses {@code buf} as its
     * buffer array. The initial value of {@code pos}
     * is {@code offset} and the initial value
     * of {@code count} is the minimum of {@code offset+length}
     * and {@code buf.length}.
     * 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 int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. 
 This read method cannot block. 
Returns: the next byte of data, or -1 if the end of the stream has been reached.
/**
     * Reads the next byte of data from this input stream. The value
     * byte is returned as an {@code int} in the range
     * {@code 0} to {@code 255}. If no byte is available
     * because the end of the stream has been reached, the value
     * {@code -1} is returned.
     * <p>
     * This {@code read} method
     * cannot block.
     *
     * @return  the next byte of data, or {@code -1} if the end of the
     *          stream has been reached.
     */
    public synchronized int read() {
        return (pos < count) ? (buf[pos++] & 0xff) : -1;
    }

    
Reads up to len bytes of data into an array of bytes from this input stream. If pos equals count, then -1 is returned to indicate end of file. Otherwise, the number k of bytes read is equal to the smaller of len and count-pos. If k is positive, then bytes buf[pos] through buf[pos+k-1] are copied into b[off] through b[off+k-1] in the manner performed by System.arraycopy. The value k is added into pos and k is returned. 
 This read method cannot block. 
Params:
  • b –     the buffer into which the data is read.
  • off –  the start offset in the destination array b
  • len –   the maximum number of bytes read.
Throws:
Returns: the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
/**
     * Reads up to {@code len} bytes of data into an array of bytes from this
     * input stream.  If {@code pos} equals {@code count}, then {@code -1} is
     * returned to indicate end of file.  Otherwise, the  number {@code k} of
     * bytes read is equal to the smaller of {@code len} and {@code count-pos}.
     * If {@code k} is positive, then bytes {@code buf[pos]} through
     * {@code buf[pos+k-1]} are copied into {@code b[off]} through
     * {@code b[off+k-1]} in the manner performed by {@code System.arraycopy}.
     * The value {@code k} is added into {@code pos} and {@code k} is returned.
     * <p>
     * This {@code read} method cannot block.
     *
     * @param   b     the buffer into which the data is read.
     * @param   off   the start offset in the destination array {@code b}
     * @param   len   the maximum number of bytes read.
     * @return  the total number of bytes read into the buffer, or
     *          {@code -1} if there is no more data because the end of
     *          the stream has been reached.
     * @throws  NullPointerException If {@code b} is {@code null}.
     * @throws  IndexOutOfBoundsException If {@code off} is negative,
     * {@code len} is negative, or {@code len} is greater than
     * {@code b.length - off}
     */
    public synchronized int read(byte b[], int off, int len) {
        Objects.checkFromIndexSize(off, len, b.length);

        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;
    }

    public synchronized byte[] readAllBytes() {
        byte[] result = Arrays.copyOfRange(buf, pos, count);
        pos = count;
        return result;
    }

    public int readNBytes(byte[] b, int off, int len) {
        int n = read(b, off, len);
        return n == -1 ? 0 : n;
    }

    public synchronized long transferTo(OutputStream out) throws IOException {
        int len = count - pos;
        out.write(buf, pos, len);
        pos = count;
        return len;
    }

    
Skips n bytes of input from this input stream. Fewer bytes might be skipped if the end of the input stream is reached. The actual number k of bytes to be skipped is equal to the smaller of n and count-pos. The value k is added into pos and k is returned. 
Params:
  • n –   the number of bytes to be skipped.
Returns: the actual number of bytes skipped.
/**
     * Skips {@code n} 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}
     * of bytes to be skipped is equal to the smaller
     * of {@code n} and  {@code count-pos}.
     * The value {@code k} is added into {@code pos}
     * and {@code k} 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.

 The value returned is count - pos, which is the number of bytes remaining to be read from the input buffer. 
Returns: the number of remaining bytes that can be read (or skipped
         over) from this input stream without blocking.
/**
     * 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},
     * 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 InputStream supports mark/reset. The markSupported method of ByteArrayInputStream always returns true. 
Since:  1.1
/**
     * Tests if this {@code InputStream} supports mark/reset. The
     * {@code markSupported} method of {@code ByteArrayInputStream}
     * always returns {@code true}.
     *
     * @since   1.1
     */
    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.


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).

 Note: The readAheadLimit for this class has no meaning. 
Since:  1.1
/**
     * 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} for this class
     *  has no meaning.
     *
     * @since   1.1
     */
    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.

/**
     * 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 ByteArrayInputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException. 
/**
     * Closing a {@code ByteArrayInputStream} has no effect. The methods in
     * this class can be called after the stream has been closed without
     * generating an {@code IOException}.
     */
    public void close() throws IOException {
    }

}