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Improvements on HJson creation #47

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Improvements on HJson creation #47

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a2e4a6b
Add override flag to MapProxy destructor, helps with warnings on new …
lawnighthawk Dec 17, 2023
919bdeb
Add functions that use rvalue references
lawnighthawk Dec 17, 2023
64710c8
Protect new functions behind a define for C++17
lawnighthawk Dec 17, 2023
2c148e1
Ensure we can call insert on an empty value and it becomes a Map
lawnighthawk Dec 17, 2023
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11 changes: 10 additions & 1 deletion include/hjson/hjson.h
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Original file line number Diff line number Diff line change
Expand Up @@ -293,6 +293,15 @@ class Value {
Value& at(const std::string& key);
const Value& at(const char *key) const;
Value& at(const char *key);

#if __cplusplus >= 201703L
// These are functions available in C++17 and greater only
// This function will add a value to a vector without a copy
void push_back(Value&&);
// This function can insert a value into the map without an allocation
void insert(const std::string&key, Value&&);
#endif // __cplusplus >= 201703L

// Iterations are always done in alphabetical key order. Returns a default
// constructed iterator if this Value is of any other type than Map.
std::map<std::string, Value>::iterator begin();
Expand Down Expand Up @@ -367,7 +376,7 @@ class MapProxy : public Value {
MapProxy(Value&&);

public:
~MapProxy();
~MapProxy() override;
MapProxy& operator =(const MapProxy&);
MapProxy& operator =(const Value&);
MapProxy& operator =(Value&&);
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35 changes: 35 additions & 0 deletions src/hjson_value.cpp
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Expand Up @@ -347,6 +347,27 @@ Value& Value::at(const char *name) {
return at(std::string(name));
}

#if __cplusplus >= 201703L
void Value::insert(const std::string&key, Value&& other)
{
switch (prv->type)
{
case Type::Undefined:
prv->~ValueImpl();
// Recreate the private object using the same memory block.
new(&(*prv)) ValueImpl(Type::Map);
// Fall through
case Type::Map:
try {
prv->m->m.insert_or_assign(key, std::move(other));
} catch(const std::out_of_range&) {}
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What would cause std::out_of_range to be thrown, and why should it be ignored?

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You are right in that it does not make a lot of sense, maybe just not have a catch and throw whatever exception came from the container?

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Yes better to not have a catch.

return;
default:
throw type_mismatch("Must be of type Map for that operation.");
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The implementation seems to support type Undefined too, not just type Map.

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true, this implementation follows a similar scheme as to that of operator [] , where if the Value is of type undefined, we assume the user wanted map and thus we convert it to a map type and then treat it as a map insertion.

}
}
#endif // __cplusplus >= 201703L


const Value Value::operator[](const std::string& name) const {
if (prv->type == Type::Undefined) {
Expand Down Expand Up @@ -1326,6 +1347,20 @@ void Value::push_back(const Value& other) {
prv->v->push_back(other);
}

#if __cplusplus >= 201703L
void Value::push_back(Value&& other) {
if (prv->type == Type::Undefined) {
prv->~ValueImpl();
// Recreate the private object using the same memory block.
new(&(*prv)) ValueImpl(Type::Vector);
} else if (prv->type != Type::Vector) {
throw type_mismatch("Must be of type Undefined or Vector for that operation.");
}

prv->v->push_back(std::move(other));
}
#endif // __cplusplus >= 201703L


void Value::move(int from, int to) {
switch (prv->type)
Expand Down