GenericValue: add copy constructor and CopyFrom #16
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Instead of always just shallowly referencing the potentially allocated strings when calling the Handler::String function, request a copy in case the string has been allocated from an Allocator before. This is necessary to avoid double free()s of the string memory, especially when using the Handler to create a deep copy of a Value. The explicit comparison against '0' is done to suppress the warning C4800 on MSVC, see pah/rapidjson#5.
To allow deep copying from an existing GenericValue, an
explicit "copy constructor" (with required Allocator param)
and an "CopyFrom" assignment function are added.
Document d; Document::AllocatorType& a = d.GetAllocator();
Value v1("foo");
// Value v2(v1); // not allowed
Value v2(v1,a); // make a copy
RAPIDJSON_ASSERT(v1.IsString()); // v1 untouched
d.SetArray().PushBack(v1,a).PushBack(v2,a);
RAPIDJSON_ASSERT(v1.Empty() && v2.Empty());
v2.CopyFrom(d,a); // copy whole document
RAPIDJSON_ASSERT(d.IsArray() && d.Size()); // d untouched
v1.SetObject().AddMember( "array", v2, a );
d.PushBack(v1,a);
Additionally, the Handler implementation in GenericDocument is made
private again, restricting access to GenericReader and GenericValue.
This commit adds some simple tests for the deep-copying of values, either based on the explicit constructor, or the CopyFrom function. It uses the CrtAllocator to test for possible double-free errors due to insufficient copying.
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Closing, to be resubmitted against |
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To allow deep copying from an existing
GenericValue, an explicit "copy constructor" (with required Allocator param) and aCopyFromassignment function are added.The strings in the source value are copied, if and only if they have been allocated as a copy during their construction (determined by
kCopyFlag). This is needed to avoid doublefree()s or problems with differing lifetimes of the allocated string storage.Additionally, the
Handlerimplementation inGenericDocumentis made private again, restricting access toGenericReaderandGenericValue.