> On 21 Dec 2017, at 11:05, Brian Burkhalter <[email protected]>
> wrote:
>
> Hi Paul,
>
> On Dec 21, 2017, at 10:28 AM, Paul Sandoz <[email protected]
> <mailto:[email protected]>> wrote:
>
>> This looks ok, i think it’s definitely reached it’s complexity budget, and
>> arguably over spent.
>
> I concur that this horse is almost dead from the beatings but since I already
> hacked up Peter’s suggestion which eliminates intermediate copies I might as
> well hang it out there (see below).
That looks ok to me, i think keeping the buf allocation at the top of the loop
tends to simplify the reasoning.
>
>> —
>>
>> I do have one follow on investigation we discussed off list that is worth
>> measuring. At the end use the Unsafe array allocation with no zeroing, since
>> the resulting array will be fully written into. This might result in an
>> observable improvement.
>
> I’ve not forgotten about that but do not know whether we want to include it
> as part of this issue or a subsequent one.
>
I suggest a follow on investigation.
Paul.
> Thanks,
>
> Brian
>
> public byte[] readAllBytes() throws IOException {
> List<byte[]> bufs = null;
> byte[] result = null;
> int total = 0;
> int n;
> do {
> byte[] buf = new byte[DEFAULT_BUFFER_SIZE];
> int nread = 0;
>
> // read to EOF which may read more or less than buffer size
> while ((n = read(buf, nread, buf.length - nread)) > 0) {
> nread += n;
> }
>
> if (nread > 0) {
> if (MAX_BUFFER_SIZE - total < nread) {
> throw new OutOfMemoryError("Required array size too
> large");
> }
> total += nread;
> if (result == null) {
> result = buf;
> } else {
> if (bufs == null) {
> bufs = new ArrayList<>();
> bufs.add(result);
> }
> bufs.add(buf);
> }
> }
> } while (n >= 0); // if the last call to read returned -1, then break
>
> if (bufs == null) {
> if (result == null) {
> return new byte[0];
> }
> return result.length == total ?
> result : Arrays.copyOf(result, total);
> }
>
> result = new byte[total];
> int offset = 0;
> int remaining = total;
> for (byte[] b : bufs) {
> int len = Math.min(b.length, remaining);
> System.arraycopy(b, 0, result, offset, len);
> offset += len;
> remaining -= len;
> }
>
> return result;
> }
