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Merge pull request #3307 from yorickvP/yorickvp/nlohmann-fromJSON
builtins.fromJSON: use nlohmann/json parser instead of custom parser
This commit is contained in:
Eelco Dolstra
GitHub
commit
72a50756bb
@ -1,232 +1,162 @@
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#include "json-to-value.hh"
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#include <cstring>
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#include <variant>
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#include <nlohmann/json.hpp>
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#include <nlohmann/detail/exceptions.hpp>
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using json = nlohmann::json;
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using std::unique_ptr;
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namespace nix {
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// for more information, refer to
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// https://github.com/nlohmann/json/blob/master/include/nlohmann/detail/input/json_sax.hpp
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class JSONSax : nlohmann::json_sax<json> {
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class JSONState {
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protected:
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unique_ptr<JSONState> parent;
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Value * v;
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public:
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virtual unique_ptr<JSONState> resolve(EvalState &)
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{
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throw std::logic_error("tried to close toplevel json parser state");
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};
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explicit JSONState(unique_ptr<JSONState>&& p) : parent(std::move(p)), v(nullptr) {};
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explicit JSONState(Value* v) : v(v) {};
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JSONState(JSONState& p) = delete;
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Value& value(EvalState & state)
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{
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if (v == nullptr)
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v = state.allocValue();
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return *v;
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};
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virtual ~JSONState() {};
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virtual void add() {};
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};
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static void skipWhitespace(const char * & s)
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{
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while (*s == ' ' || *s == '\t' || *s == '\n' || *s == '\r') s++;
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}
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/*
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Parse an unicode escape sequence (4 hex characters following \u) in JSON string
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*/
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static string parseUnicodeEscapeSequence(const char * & s)
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{
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int codepoint = 0;
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const auto factors = { 12u, 8u, 4u, 0u };
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for (const auto factor : factors)
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{
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if (!*s) throw JSONParseError("got end-of-string in JSON string while parsing \\u sequence");
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if (*s >= '0' and *s <= '9') {
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codepoint += static_cast<int>((static_cast<unsigned int>(*s) - 0x30u) << factor);
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} else if (*s >= 'A' and *s <= 'F') {
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codepoint += static_cast<int>((static_cast<unsigned int>(*s) - 0x37u) << factor);
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} else if (*s >= 'a' and *s <= 'f') {
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codepoint += static_cast<int>((static_cast<unsigned int>(*s) - 0x57u) << factor);
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} else {
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throw JSONParseError(format("illegal character '%1%' in \\u escape sequence.") % *s);
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class JSONObjectState : public JSONState {
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using JSONState::JSONState;
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ValueMap attrs = ValueMap();
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virtual unique_ptr<JSONState> resolve(EvalState & state) override
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{
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Value& v = parent->value(state);
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state.mkAttrs(v, attrs.size());
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for (auto & i : attrs)
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v.attrs->push_back(Attr(i.first, i.second));
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return std::move(parent);
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}
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s++;
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}
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if ((codepoint > 0xd7ff && codepoint < 0xe000) || codepoint > 0x10ffff) {
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throw JSONParseError("Unicode escape sequence is not a Unicode scalar value");
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}
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// taken from cpptoml.h
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std::string result;
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// See Table 3-6 of the Unicode standard
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if (codepoint <= 0x7f)
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{
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// 1-byte codepoints: 00000000 0xxxxxxx
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// repr: 0xxxxxxx
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result += static_cast<char>(codepoint & 0x7f);
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}
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else if (codepoint <= 0x7ff)
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{
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// 2-byte codepoints: 00000yyy yyxxxxxx
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// repr: 110yyyyy 10xxxxxx
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//
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// 0x1f = 00011111
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// 0xc0 = 11000000
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//
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result += static_cast<char>(0xc0 | ((codepoint >> 6) & 0x1f));
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//
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// 0x80 = 10000000
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// 0x3f = 00111111
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//
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result += static_cast<char>(0x80 | (codepoint & 0x3f));
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}
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else if (codepoint <= 0xffff)
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{
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// 3-byte codepoints: zzzzyyyy yyxxxxxx
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// repr: 1110zzzz 10yyyyyy 10xxxxxx
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//
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// 0xe0 = 11100000
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// 0x0f = 00001111
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//
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result += static_cast<char>(0xe0 | ((codepoint >> 12) & 0x0f));
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result += static_cast<char>(0x80 | ((codepoint >> 6) & 0x1f));
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result += static_cast<char>(0x80 | (codepoint & 0x3f));
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}
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else
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{
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// 4-byte codepoints: 000uuuuu zzzzyyyy yyxxxxxx
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// repr: 11110uuu 10uuzzzz 10yyyyyy 10xxxxxx
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//
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// 0xf0 = 11110000
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// 0x07 = 00000111
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//
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result += static_cast<char>(0xf0 | ((codepoint >> 18) & 0x07));
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result += static_cast<char>(0x80 | ((codepoint >> 12) & 0x3f));
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result += static_cast<char>(0x80 | ((codepoint >> 6) & 0x3f));
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result += static_cast<char>(0x80 | (codepoint & 0x3f));
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}
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return result;
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}
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static string parseJSONString(const char * & s)
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{
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string res;
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if (*s++ != '"') throw JSONParseError("expected JSON string");
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while (*s != '"') {
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if (!*s) throw JSONParseError("got end-of-string in JSON string");
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if (*s == '\\') {
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s++;
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if (*s == '"') res += '"';
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else if (*s == '\\') res += '\\';
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else if (*s == '/') res += '/';
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else if (*s == 'b') res += '\b';
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else if (*s == 'f') res += '\f';
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else if (*s == 'n') res += '\n';
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else if (*s == 'r') res += '\r';
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else if (*s == 't') res += '\t';
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else if (*s == 'u') {
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res += parseUnicodeEscapeSequence(++s);
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// to neuter the outside s++
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s--;
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} else throw JSONParseError("invalid escaped character in JSON string");
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s++;
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} else
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res += *s++;
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}
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s++;
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return res;
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}
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static void parseJSON(EvalState & state, const char * & s, Value & v)
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{
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skipWhitespace(s);
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if (!*s) throw JSONParseError("expected JSON value");
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if (*s == '[') {
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s++;
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ValueVector values;
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values.reserve(128);
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skipWhitespace(s);
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while (1) {
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if (values.empty() && *s == ']') break;
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Value * v2 = state.allocValue();
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parseJSON(state, s, *v2);
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values.push_back(v2);
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skipWhitespace(s);
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if (*s == ']') break;
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if (*s != ',') throw JSONParseError("expected ',' or ']' after JSON array element");
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s++;
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virtual void add() override { v = nullptr; };
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public:
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void key(string_t& name, EvalState & state)
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{
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attrs[state.symbols.create(name)] = &value(state);
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}
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s++;
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state.mkList(v, values.size());
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for (size_t n = 0; n < values.size(); ++n)
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v.listElems()[n] = values[n];
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}
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};
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else if (*s == '{') {
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s++;
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ValueMap attrs;
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while (1) {
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skipWhitespace(s);
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if (attrs.empty() && *s == '}') break;
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string name = parseJSONString(s);
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skipWhitespace(s);
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if (*s != ':') throw JSONParseError("expected ':' in JSON object");
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s++;
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Value * v2 = state.allocValue();
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parseJSON(state, s, *v2);
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attrs[state.symbols.create(name)] = v2;
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skipWhitespace(s);
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if (*s == '}') break;
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if (*s != ',') throw JSONParseError("expected ',' or '}' after JSON member");
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s++;
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class JSONListState : public JSONState {
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ValueVector values = ValueVector();
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virtual unique_ptr<JSONState> resolve(EvalState & state) override
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{
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Value& v = parent->value(state);
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state.mkList(v, values.size());
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for (size_t n = 0; n < values.size(); ++n) {
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v.listElems()[n] = values[n];
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}
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return std::move(parent);
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}
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state.mkAttrs(v, attrs.size());
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for (auto & i : attrs)
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v.attrs->push_back(Attr(i.first, i.second));
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v.attrs->sort();
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s++;
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}
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else if (*s == '"') {
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mkString(v, parseJSONString(s));
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}
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else if (isdigit(*s) || *s == '-' || *s == '.' ) {
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// Buffer into a string first, then use built-in C++ conversions
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std::string tmp_number;
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ValueType number_type = tInt;
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while (isdigit(*s) || *s == '-' || *s == '.' || *s == 'e' || *s == 'E') {
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if (*s == '.' || *s == 'e' || *s == 'E')
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number_type = tFloat;
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tmp_number += *s++;
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virtual void add() override {
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values.push_back(v);
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v = nullptr;
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};
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public:
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JSONListState(unique_ptr<JSONState>&& p, std::size_t reserve) : JSONState(std::move(p))
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{
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values.reserve(reserve);
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}
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};
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try {
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if (number_type == tFloat)
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mkFloat(v, stod(tmp_number));
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else
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mkInt(v, stol(tmp_number));
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} catch (std::invalid_argument & e) {
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throw JSONParseError("invalid JSON number");
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} catch (std::out_of_range & e) {
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throw JSONParseError("out-of-range JSON number");
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}
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EvalState & state;
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unique_ptr<JSONState> rs;
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template<typename T, typename... Args> inline bool handle_value(T f, Args... args)
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{
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f(rs->value(state), args...);
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rs->add();
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return true;
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}
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else if (strncmp(s, "true", 4) == 0) {
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s += 4;
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mkBool(v, true);
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public:
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JSONSax(EvalState & state, Value & v) : state(state), rs(new JSONState(&v)) {};
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bool null()
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{
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return handle_value(mkNull);
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}
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else if (strncmp(s, "false", 5) == 0) {
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s += 5;
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mkBool(v, false);
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bool boolean(bool val)
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{
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return handle_value(mkBool, val);
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}
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else if (strncmp(s, "null", 4) == 0) {
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s += 4;
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mkNull(v);
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bool number_integer(number_integer_t val)
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{
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return handle_value(mkInt, val);
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}
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else throw JSONParseError("unrecognised JSON value");
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}
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bool number_unsigned(number_unsigned_t val)
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{
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return handle_value(mkInt, val);
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}
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bool number_float(number_float_t val, const string_t& s)
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{
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return handle_value(mkFloat, val);
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}
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bool string(string_t& val)
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{
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return handle_value<void(Value&, const char*)>(mkString, val.c_str());
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}
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bool start_object(std::size_t len)
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{
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rs = std::make_unique<JSONObjectState>(std::move(rs));
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return true;
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}
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bool key(string_t& name)
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{
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dynamic_cast<JSONObjectState*>(rs.get())->key(name, state);
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return true;
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}
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bool end_object() {
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rs = rs->resolve(state);
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rs->add();
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return true;
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}
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bool end_array() {
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return end_object();
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}
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bool start_array(size_t len) {
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rs = std::make_unique<JSONListState>(std::move(rs),
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len != std::numeric_limits<size_t>::max() ? len : 128);
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return true;
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}
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bool parse_error(std::size_t, const std::string&, const nlohmann::detail::exception& ex) {
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throw JSONParseError(ex.what());
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}
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};
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void parseJSON(EvalState & state, const string & s_, Value & v)
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{
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const char * s = s_.c_str();
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parseJSON(state, s, v);
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skipWhitespace(s);
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if (*s) throw JSONParseError(format("expected end-of-string while parsing JSON value: %1%") % s);
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JSONSax parser(state, v);
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bool res = json::sax_parse(s_, &parser);
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if (!res)
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throw JSONParseError("Invalid JSON Value");
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}
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}
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