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.
