[Development] API review request: CBOR Stream reader and writer

[Thiago Macieira]

On segunda-feira, 22 de janeiro de 2018 01:37:40 PST Thiago Macieira wrote:
> Binary JSON validating:
>          97,003559      task-clock:u (msec)
>        237.092.857      cycles
>        437.005.872      instructions
> [15.2% was spent in QIODevice::readAll, 59.1% in fromBinaryData]
> 
> JSON parsing:
>         273,359723      task-clock:u (msec)
>        793.297.513      cycles
>      2.698.607.303      instructions
> [4.7% in readAll(), 78.2% in fromJson]
> 
> CBOR parsing:
>         341,311535      task-clock
>        885.053.081      cycles
>      2.548.803.851      instructions

After fixing the converter example to properly use mmap in all three cases, 
plus refactoring the CBOR parser to operate on a pre-loaded array and use 
larger buffer than single-digit byte counts, the numbers are:

Binary JSON:
         69,844846      task-clock:u (msec)
       196.906.259      cycles:u
       422.255.714      instructions:u
[There's no readAll(); 70.2% of the time is spent inside 
QJsonPrivate::Object::isValid]

JSON:
        255,809132      task-clock:u (msec)
       771.771.000      cycles:u
     2.690.966.058      instructions:u
[80.2% inside QJsonPrivate::Parser::parseValue, 58.7% inside 
QJsonPrivate::Parser::parseString and 16.3% inside QUtf8Functions::fromUtf8]

CBOR:
        239,059121      task-clock:u (msec)
       562.474.857      cycles:u
     1.431.590.428      instructions:u
[71.6% inside QCborValue::fromCbor, 65.0% inside 
QCborContainerPrivate::decodeStringFromCbor, 25.5% inside 
QCborStreamReader::readStringChunk plus 12.6% inside QUtf8::isValidUtf8]
-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center