The `ShortString` can represent zero-terminated strings up to `MaxSize` chars (excluding the terminating zero) and store a value to determine the length of the contained string in the last character `str[LenPos]` by storing `MaxSize - length` there. If the string to store has the maximal length of `MaxSize` (excluding the terminating zero) then `str[LenPos]` will store `0` and therefore act as the string terminator as well. For getting the string length back from that value just use `MaxSize - str[LenPos]`.
This allows to store `11`-chars strings in 32-bit mode and `15`-chars strings in 64-bit mode inline (for `UTF8`-encoded strings).
Since the payload (the `Data` union) of the current implementation of `GenericValue` is `12 bytes` (32 bit) or `16 bytes` (64 bit) it could store `UTF8`-encoded strings up to `10` or `14` chars plus the `terminating zero` character plus the string length:
``` C++
struct ShortString {
enum { MaxSize = sizeof(GenericValue::String) / sizeof(Ch) - sizeof(unsigned char) };
Ch str[MaxSize];
unsigned char length;
}; // at most as many bytes as "String" above => 12 bytes in 32-bit mode, 16 bytes in 64-bit mode
```
This is achieved by introducing additional `kInlineStrFlag` and `kShortStringFlag` flags. When setting a new string value in `SetStringRaw(s, alloc)` it is first checked if the string is short enough to fit into the `inline string buffer` and if so the given source string will be copied into the new `ShortString` target instead of allocating additional memory for it.
Some 64-bit integers cannot be represented losslessly as a double.
Due to a typo in the operator==, the comparison has been performed
after a double conversion in too many cases.
Before applying the simplifications in ed282b814, the SFINAE check for the
GenericValue(bool) constructor has been broken in MSVC 2005. Add a static
assert as a safe-guard against future reappearance of this problem.
In order to match GenericValue and its derived classes for the
SFINAE-implementation of some of the operators/functions, this
meta-function matches all types equal to or derived from a given
class. See std::is_base_of<B,D> available in C++11.
Define RAPIDJSON_HAS_CXX_TYPETRAITS to use the C++11 implementation.
Some (older) compilers have problems with compile-time constants.
This commit simplifies the implementation of the helper classes
in order to improve compiler support, especially be removing the
need of partial template specialisation.
No functional changes.
Prepare equalto_operator tests to test comparisons between
* GenericValue and GenericDocument
* GenericValue with different SourceAllocator types
Both combinations currently fail due to ambiguities with the
templated operators on several compilers.
As reported in #113, recent versions of Clang complain about
ambiguous overloads for some comparison operator instantiations,
especially if the deduced template type is a GenericValue.
Add an explicit, non-templated version for now (which is a better
match).
This only solves part of the problem, as comparisons between
* GenericValue & GenericDocument
* GenericValue with different SourceAllocator types
will still cause ambiguities.
Some users may want to use RapidJSON with std::string objects. This commits
adds an (opt-in) feature to include some basic support. The implementation
uses std::basic_string<Ch> as generic string type.
Support currently covers:
* construction
* comparison
No special APIs for AddMember or PushBack have been added, as std::string
most probably requires copying (or an explicit StringRef() call).
By restructuring the call forwarding of the various operator== and
operator!= overloads, new overloads can be added by simply adding an
additional member operator==.
Additionally, the "Ch*" overloads are dropped in favour of an SFINAE
version that removes the pointer variants from matching the templated
operator== (see also operator=).
