Library enhancement proposal for copying data from/to Reader/Writer InputStream/OutputStream

[Patrick Reinhart]

> Patrick, as soon as I get feedback from Alan and Paul I'll merge these changes into the current version.
> 
> 1. I wonder if it makes sense to provide an additional method where client specifies CharBuffer to be used?
> Moreover if the first argument is CharSequence then we don't even need a buffer:
> 
> /**
> * Reads all characters from a readable and appends them to an appendable.
> *
> * @param source       the readable to read from ({@code source != null})
> * @param target       the appendable to append to ({@code target != null})
> *
> * @return             the number of characters copied
> *
> * @throws IOException if an I/O error occurs when reading or appending
> */
> public static long copy(Readable source, Appendable target)
>        throws IOException {
>    Objects.requireNonNull(source, "source");
>    Objects.requireNonNull(target, "target");
> 
>    if (source instanceof CharSequence)
>        return copy1((CharSequence) source, target);
> 
>    return copy0(source, target, CharBuffer.allocate(BUFFER_SIZE));
> }
> 
> /**
> * Reads all characters from a readable and appends them to an appendable.
> *
> * @param source       the readable to read from ({@code source != null})
> * @param target       the appendable to append to ({@code target != null})
> * @param buffer       the intermediate buffer to use
> *                     ({@code buffer != null && buffer.hasRemaining()
> *                             && !buffer.isReadOnly()})
> * @return             the number of characters copied
> * @throws IOException if an I/O error occurs when reading or appending
> */
> public static long copy(Readable source, Appendable target,
>                        CharBuffer buffer) throws IOException {
>    Objects.requireNonNull(source, "source");
>    Objects.requireNonNull(target, "target");
>    Objects.requireNonNull(buffer, "buffer");
>    if (!buffer.hasRemaining())
>        throw new IllegalArgumentException("Insufficient buffer size");
>    if (buffer.isReadOnly())
>        throw new IllegalArgumentException("buffer is read only");
>    return copy0(source, target, buffer);
> }
> 
> private static long copy1(CharSequence source, Appendable target)
>        throws IOException {
>    long copied = source.length();
>    target.append(source);
>    return copied;
> }
> 
> private static long copy0(Readable source, Appendable target,
>                          CharBuffer buffer) throws IOException {
> 

Seems reasonable to me. Will you add those changes additionally to mine then? 


> 2. I think guts of the copy method could be changed to something like this:
> 
>    long copied = 0L;
> +   int oldLim = buffer.limit();
> 
>    for (int read; (read = source.read(buffer)) > -1; copied += read) {
> 	buffer.flip();
>        target.append(buffer, 0, read);
> +       buffer.limit(oldLim);
>    }
>    return copied;
> 
> Otherwise on each iteration you're potentially shrinking available buffer storage based on
> amount of data read into it (if I'm not mistaken). So each time you should restore the limit.

There I’m not that experienced either. I’m shamed about it, but never used CharBuffer by myself so far… (my implementation could therefore be not completely correct)


> 3. We should think of revisiting and including the only method from sun.misc.IOUtils. Removing
> the class and reparenting its dependencies. 

That would be a followup task - on the way to authorship ;-)

-Patrick