RFR: 4926314: Optimize Reader.read(CharBuffer) [v4]
plevart at openjdk.java.net
Mon Jan 18 08:57:43 UTC 2021
On Sat, 9 Jan 2021 23:06:22 GMT, Philippe Marschall <github.com+471021+marschall at openjdk.org> wrote:
>> Implement three optimiztations for Reader.read(CharBuffer)
>> * Add a code path for heap buffers in Reader#read to use the backing array instead of allocating a new one.
>> * Change the code path for direct buffers in Reader#read to limit the intermediate allocation to `TRANSFER_BUFFER_SIZE`.
>> * Implement `InputStreamReader#read(CharBuffer)` and delegate to `StreamDecoder`.
>> * Implement `StreamDecoder#read(CharBuffer)` and avoid buffer allocation.
> Philippe Marschall has updated the pull request incrementally with one additional commit since the last revision:
> Add unit tests
> - add unit test for Reader#read(CharBuffer)
> - add unit test for InputStreamReader#reader(CharBuffer)
> - test with both on-heap and off-heap buffers
src/java.base/share/classes/java/io/Reader.java line 207:
> 205: target.put(cbuf, 0, n);
> 206: nread += n;
> 207: remaining -= n;
Wouldn't there be a possibility for target.put(cbuf, 0, n) to throw BufferOverflowException ?
- there's room (remaining) for TRANSFER_BUFFER_SIZE + 1 characters in target
- cbuff is sized to TRANSFER_BUFFER_SIZE
- 1st iteration of do loop transfers TRANSFER_BUFFER_SIZE charasters (remaining == 1)
- 2nd iteration reads > 1 (up to TRANSFER_BUFFER_SIZE) characters
- target.put throws BufferOverflowException
You have to limit the amount read in each iteration to be Math.min(remaining, cbuf.length)
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