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#include "json-to-value.hh"
#include <variant>
#include <nlohmann/json.hpp>
#include <nlohmann/detail/exceptions.hpp>
using json = nlohmann::json;
using std::unique_ptr;
namespace nix {
// for more information, refer to
// https://github.com/nlohmann/json/blob/master/include/nlohmann/detail/input/json_sax.hpp
class JSONSax : nlohmann::json_sax<json> {
class JSONState {
protected:
unique_ptr<JSONState> parent;
Value * v;
public:
virtual unique_ptr<JSONState> resolve(EvalState &)
{
throw std::logic_error("tried to close toplevel json parser state");
};
explicit JSONState(unique_ptr<JSONState>&& p) : parent(std::move(p)), v(nullptr) {};
explicit JSONState(Value* v) : v(v) {};
JSONState(JSONState& p) = delete;
Value& value(EvalState & state)
{
if (v == nullptr)
v = state.allocValue();
return *v;
};
virtual ~JSONState() {};
virtual void add() {};
};
class JSONObjectState : public JSONState {
using JSONState::JSONState;
ValueMap attrs = ValueMap();
virtual unique_ptr<JSONState> resolve(EvalState & state) override
{
Value& v = parent->value(state);
state.mkAttrs(v, attrs.size());
for (auto & i : attrs)
v.attrs->push_back(Attr(i.first, i.second));
return std::move(parent);
}
virtual void add() override { v = nullptr; };
public:
void key(string_t& name, EvalState & state)
{
attrs[state.symbols.create(name)] = &value(state);
}
};
class JSONListState : public JSONState {
ValueVector values = ValueVector();
virtual unique_ptr<JSONState> resolve(EvalState & state) override
{
Value& v = parent->value(state);
state.mkList(v, values.size());
for (size_t n = 0; n < values.size(); ++n) {
v.listElems()[n] = values[n];
}
return std::move(parent);
}
virtual void add() override {
values.push_back(v);
v = nullptr;
};
public:
JSONListState(unique_ptr<JSONState>&& p, std::size_t reserve) : JSONState(std::move(p))
{
values.reserve(reserve);
}
};
EvalState & state;
unique_ptr<JSONState> rs;
template<typename T, typename... Args> inline bool handle_value(T f, Args... args)
{
f(rs->value(state), args...);
rs->add();
return true;
}
public:
JSONSax(EvalState & state, Value & v) : state(state), rs(new JSONState(&v)) {};
bool null()
{
return handle_value(mkNull);
}
bool boolean(bool val)
{
return handle_value(mkBool, val);
}
bool number_integer(number_integer_t val)
{
return handle_value(mkInt, val);
}
bool number_unsigned(number_unsigned_t val)
{
return handle_value(mkInt, val);
}
bool number_float(number_float_t val, const string_t& s)
{
return handle_value(mkFloat, val);
}
bool string(string_t& val)
{
return handle_value<void(Value&, const char*)>(mkString, val.c_str());
}
bool start_object(std::size_t len)
{
rs = std::make_unique<JSONObjectState>(std::move(rs));
return true;
}
bool key(string_t& name)
{
dynamic_cast<JSONObjectState*>(rs.get())->key(name, state);
return true;
}
bool end_object() {
rs = rs->resolve(state);
rs->add();
return true;
}
bool end_array() {
return end_object();
}
bool start_array(size_t len) {
rs = std::make_unique<JSONListState>(std::move(rs),
len != std::numeric_limits<size_t>::max() ? len : 128);
return true;
}
bool parse_error(std::size_t, const std::string&, const nlohmann::detail::exception& ex) {
throw JSONParseError(ex.what());
}
};
void parseJSON(EvalState & state, const string & s_, Value & v)
{
JSONSax parser(state, v);
bool res = json::sax_parse(s_, &parser);
if (!res)
throw JSONParseError("Invalid JSON Value");
}
}
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