RFR [9] Add blocking bulk read to java.io.InputStream

[Roger Riggs]

Hi Chris,

A minor inconsistency about the unmodified contents of b[off].

  * <p> The first byte read is stored into element {@code b[off]}

vs.

   * <p> In every case, elements {@code b[0]} through {@code b[off *- 
1*]} and
   * elements__{@code b[off+len]} through {@code b[b.length-1]} are 
unaffected.

I think there's a missing -1;  and perhaps an awkward sentence when off = 0;

Roger


On 4/23/2015 5:01 AM, Chris Hegarty wrote:
> A while back when we added the long overdue java.io.InputStream.transferTo method, there was support for adding a blocking bulk read operation. This has been sitting in a branch in the sandbox since then. I would like to revive it with the intention of bringing it into 9. The motivation for this addition is provide library support for a common pattern found when reading from input streams.
>
> /**
>   * Reads some bytes from the input stream into the given byte array. This
>   * method blocks until {@code len} bytes of input data have been read, or
>   * end of stream is detected. The number of bytes actually read, possibly
>   * zero, is returned. This method does not close the input stream.
>   *
>   * <p> In the case where end of stream is reached before {@code len} bytes
>   * have been read, then the actual number of bytes read will be returned.
>   * When this stream reaches end of stream, further invocations of this
>   * method will return zero.
>   *
>   * <p> If {@code len} is zero, then no bytes are read and {@code 0} is
>   * returned; otherwise, there is an attempt to read up to {@code len} bytes.
>   *
>   * <p> The first byte read is stored into element {@code b[off]}, the next
>   * one in to {@code b[off+1]}, and so on. The number of bytes read is, at
>   * most, equal to {@code len}. Let <i>k</i> be the number of bytes actually
>   * read; these bytes will be stored in elements {@code b[off]} through
>   * {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i>
>   * {@code ]} through {@code b[off+len-1]} unaffected.
>   *
>   * <p> In every case, elements {@code b[0]} through {@code b[off]} and
>   * elements{@code b[off+len]} through {@code b[b.length-1]} are unaffected.
>   *
>   * <p> The behavior for the case where the input stream is <i>asynchronously
>   * closed</i>, or the thread interrupted during the read, is highly input
>   * stream specific, and therefore not specified.
>   *
>   * <p> If an I/O error occurs reading from the input stream, then it may do
>   * so after some bytes have been read. Consequently the input stream may be
>   * in an inconsistent state. It is strongly recommended that the stream be
>   * promptly closed if an I/O error occurs.
>   *
>   * @param  b the buffer into which the data is read
>   * @param  off the start offset in {@code b} at which the data is written
>   * @param  len the maximum number of bytes to read
>   * @return the actual number of bytes read into the buffer
>   * @throws IOException if an I/O error occurs
>   * @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}
>   *
>   * @since 1.9
>   */
> public int readBytes(byte[] b, int off, int len) throws IOException {
>      Objects.requireNonNull(b);
>      if (off < 0 || len < 0 || len > b.length - off)
>          throw new IndexOutOfBoundsException();
>      int n = 0;
>      while (n < len) {
>          int count = read(b, off + n, len - n);
>          if (count < 0)
>              break;
>          n += count;
>      }
>      return n;
> }
>
> -Chris.