I have written a simple hierarchical json-parser, using POCO JSON, to be used as a sax parser.
Is their any difference in the result if i use a string or a stream as input to the parse method, see call below, or are the different constructors equivalent?
Parser parser;
DefaultHandler handler;
parser.setHandler(&handler);
parser.parse(input);
In terms of memory consumption, speed etc?
std::string version is just a wrapper that creates stream on your behalf, so at the end the total will be roughly the same, string is just more convenient for user.
[EDIT]
This was changed for 1.5.2 - wrapping was removed so that now both (stream and string) versions iterate. The Benchmark Example can be used to determine how much is stream slower than string.
[/EDIT]
Please note that there are some breaking changes coming in 1.5.2 - DefaultHandler name was removed and internally handler has been turned into auto-created smart pointer (that's the main reason we had to obsolete DefaultHandler so existing code would not pass stack-created handler to the smart pointer, it was not a good design to start with). So, in 1.5.2, explicit handler creation will not be needed anymore for default parsing:
std::string json = "{ \"test\" : null }";
Parser parser;
Var result = parser.parse(json);
If you are concerned with performance, note also that Poco::JSON parser speed, as it stands now, is poor and we will be using either the very fast parser from Poco::Web::JSON or something faster (if we can find/write it). Bottom line, 1.5.x is still W.I.P.
Hope this helps.
EDIT:
Benchmarks on Windows and Mac (~15MB JSON file):
Windows
Poco::JSON: 1 195 313 [us]
Poco::Web::JSON: 403 320 [us]
json-parser: 321 289 [us]
libjson: 610 352 [us]
MAC (clang)
Poco::JSON: 480 965 [us]
Poco::Web::JSON: 176 297 [us]
json-parser: 220 172 [us]