JSON Schema validator #254
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snej
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I did this so the JSON Schema benchmark could be fully optimized.
Code adapted from Litecore's StringUtils.cc
- FLEvalJSONPointer() exposes impl::Path::evalJSONPointer(). - It now properly handles an empty path. - It now properly handles a path with a trailing "/". - It now properly handles those weird "~" escapes (see RFC 6901.)
Exposes existing internal method.
As an optimization, allow a Dict iterator to be created with its SharedKeys already known; saves a lookup.
The jsonsl parser we use follows an older version of the JSON spec which didn't allow a document to be a scalar value, only an array or object. I've run into this issue a few times lately -- for example, JSON Schema considers `true` or `false` a valid schema, but we can't parse it, so a few tests in their test suite break. I made a small change to JSONConverter to detect when the input isn't an array or object, and wrap it in `[...]` so that jsonsl can parse it. (But meanwhile it ignores the outer array when parsing.)
A weird edge case that showed up when running the JSON Schema test suite, which includes some JSONPointer paths with empty-string components. The bug is that `_table.find(str)` finds the entry for the empty string, but the following test `entry.key != nullslice` fails because an empty slice compares as == nullslice since they're both empty. The proper way to test whether a slice is not nullslice is to use `if(entry.key)`, which doesn't work here because `__usuallyTrue` requires a boolean, or `entry.key.buf != nullptr`.
There's no reason for it to be an instance method, and the optimizations I'm making to Dict require calling it without having a SharedKeys instance.
These came about from profiling the JSONSchema validator, and speed up the travel-sample validation benchmark by about 10%. (1) `DictImpl::get(int)` uses a binary search, but for small Dicts it's faster to just scan all the keys, especially since we can precompute what the two bytes of the matching key must be. (2) `DictImpl::get(slice,SharedKeys*)` can skip looking up the Dict's SharedKeys (which is slow) if the key isn't alphanumeric since it won't ever be a shared key. (2) `DictImpl::get(Dict::key&)` shouldn't waste any time looking up sharedKeys if it already knows the numeric key. I also changed its boolean `_hasNumericKey` flag into an int8_t with three states: 0 for unknown, 1 for true, and -1 for "can't be a shared key". This latter state avoids trying to look up the key every single time when it won't ever succeed.
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JSONSchemaclass parses a JSON Schema and validates Fleece Values against it. See header file for class documentation. You may want to look at the JSON Schema docs / tutorial.Other Fleece API changes supporting this:
slice::UTF8Length(), which counts the number of UTF-8 code pointsFLEvalJSONPointer(), a wrapper aroundfleece::impl::Path::evalJSONPointer()FLDictIterator_BeginSK(), exposing the existing ability to pass a SharedKeys to a Dict::iteratorBug fixes:
fleece::impl::Path::evalJSONPointer()(it didn't handle escaped keys)Optimizations: