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Merge pull request #3307 from yorickvP/yorickvp/nlohmann-fromJSON

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builtins.fromJSON: use nlohmann/json parser instead of custom parser
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Eelco Dolstra 2020-01-10 01:03:07 +01:00 committed by GitHub
parent 04bbfa692f a350d0beb0
commit 72a50756bb
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1 changed files with 135 additions and 205 deletions
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340
src/libexpr/json-to-value.cc
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@ -1,232 +1,162 @@
#include "json-to-value.hh"
#include <cstring>
#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() {};
};
static void skipWhitespace(const char * & s)
{
while (*s == ' ' || *s == '\t' || *s == '\n' || *s == '\r') s++;
}
/*
Parse an unicode escape sequence (4 hex characters following \u) in JSON string
*/
static string parseUnicodeEscapeSequence(const char * & s)
{
int codepoint = 0;
const auto factors = { 12u, 8u, 4u, 0u };
for (const auto factor : factors)
{
if (!*s) throw JSONParseError("got end-of-string in JSON string while parsing \\u sequence");
if (*s >= '0' and *s <= '9') {
codepoint += static_cast<int>((static_cast<unsigned int>(*s) - 0x30u) << factor);
} else if (*s >= 'A' and *s <= 'F') {
codepoint += static_cast<int>((static_cast<unsigned int>(*s) - 0x37u) << factor);
} else if (*s >= 'a' and *s <= 'f') {
codepoint += static_cast<int>((static_cast<unsigned int>(*s) - 0x57u) << factor);
} else {
throw JSONParseError(format("illegal character '%1%' in \\u escape sequence.") % *s);
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);
}
s++;
}
if ((codepoint > 0xd7ff && codepoint < 0xe000) || codepoint > 0x10ffff) {
throw JSONParseError("Unicode escape sequence is not a Unicode scalar value");
}
// taken from cpptoml.h
std::string result;
// See Table 3-6 of the Unicode standard
if (codepoint <= 0x7f)
{
// 1-byte codepoints: 00000000 0xxxxxxx
// repr: 0xxxxxxx
result += static_cast<char>(codepoint & 0x7f);
}
else if (codepoint <= 0x7ff)
{
// 2-byte codepoints: 00000yyy yyxxxxxx
// repr: 110yyyyy 10xxxxxx
//
// 0x1f = 00011111
// 0xc0 = 11000000
//
result += static_cast<char>(0xc0 | ((codepoint >> 6) & 0x1f));
//
// 0x80 = 10000000
// 0x3f = 00111111
//
result += static_cast<char>(0x80 | (codepoint & 0x3f));
}
else if (codepoint <= 0xffff)
{
// 3-byte codepoints: zzzzyyyy yyxxxxxx
// repr: 1110zzzz 10yyyyyy 10xxxxxx
//
// 0xe0 = 11100000
// 0x0f = 00001111
//
result += static_cast<char>(0xe0 | ((codepoint >> 12) & 0x0f));
result += static_cast<char>(0x80 | ((codepoint >> 6) & 0x1f));
result += static_cast<char>(0x80 | (codepoint & 0x3f));
}
else
{
// 4-byte codepoints: 000uuuuu zzzzyyyy yyxxxxxx
// repr: 11110uuu 10uuzzzz 10yyyyyy 10xxxxxx
//
// 0xf0 = 11110000
// 0x07 = 00000111
//
result += static_cast<char>(0xf0 | ((codepoint >> 18) & 0x07));
result += static_cast<char>(0x80 | ((codepoint >> 12) & 0x3f));
result += static_cast<char>(0x80 | ((codepoint >> 6) & 0x3f));
result += static_cast<char>(0x80 | (codepoint & 0x3f));
}
return result;
}
static string parseJSONString(const char * & s)
{
string res;
if (*s++ != '"') throw JSONParseError("expected JSON string");
while (*s != '"') {
if (!*s) throw JSONParseError("got end-of-string in JSON string");
if (*s == '\\') {
s++;
if (*s == '"') res += '"';
else if (*s == '\\') res += '\\';
else if (*s == '/') res += '/';
else if (*s == 'b') res += '\b';
else if (*s == 'f') res += '\f';
else if (*s == 'n') res += '\n';
else if (*s == 'r') res += '\r';
else if (*s == 't') res += '\t';
else if (*s == 'u') {
res += parseUnicodeEscapeSequence(++s);
// to neuter the outside s++
s--;
} else throw JSONParseError("invalid escaped character in JSON string");
s++;
} else
res += *s++;
}
s++;
return res;
}
static void parseJSON(EvalState & state, const char * & s, Value & v)
{
skipWhitespace(s);
if (!*s) throw JSONParseError("expected JSON value");
if (*s == '[') {
s++;
ValueVector values;
values.reserve(128);
skipWhitespace(s);
while (1) {
if (values.empty() && *s == ']') break;
Value * v2 = state.allocValue();
parseJSON(state, s, *v2);
values.push_back(v2);
skipWhitespace(s);
if (*s == ']') break;
if (*s != ',') throw JSONParseError("expected ',' or ']' after JSON array element");
s++;
virtual void add() override { v = nullptr; };
public:
void key(string_t& name, EvalState & state)
{
attrs[state.symbols.create(name)] = &value(state);
}
s++;
state.mkList(v, values.size());
for (size_t n = 0; n < values.size(); ++n)
v.listElems()[n] = values[n];
}
};
else if (*s == '{') {
s++;
ValueMap attrs;
while (1) {
skipWhitespace(s);
if (attrs.empty() && *s == '}') break;
string name = parseJSONString(s);
skipWhitespace(s);
if (*s != ':') throw JSONParseError("expected ':' in JSON object");
s++;
Value * v2 = state.allocValue();
parseJSON(state, s, *v2);
attrs[state.symbols.create(name)] = v2;
skipWhitespace(s);
if (*s == '}') break;
if (*s != ',') throw JSONParseError("expected ',' or '}' after JSON member");
s++;
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);
}
state.mkAttrs(v, attrs.size());
for (auto & i : attrs)
v.attrs->push_back(Attr(i.first, i.second));
v.attrs->sort();
s++;
}
else if (*s == '"') {
mkString(v, parseJSONString(s));
}
else if (isdigit(*s) || *s == '-' || *s == '.' ) {
// Buffer into a string first, then use built-in C++ conversions
std::string tmp_number;
ValueType number_type = tInt;
while (isdigit(*s) || *s == '-' || *s == '.' || *s == 'e' || *s == 'E') {
if (*s == '.' || *s == 'e' || *s == 'E')
number_type = tFloat;
tmp_number += *s++;
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);
}
};
try {
if (number_type == tFloat)
mkFloat(v, stod(tmp_number));
else
mkInt(v, stol(tmp_number));
} catch (std::invalid_argument & e) {
throw JSONParseError("invalid JSON number");
} catch (std::out_of_range & e) {
throw JSONParseError("out-of-range JSON number");
}
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;
}
else if (strncmp(s, "true", 4) == 0) {
s += 4;
mkBool(v, true);
public:
JSONSax(EvalState & state, Value & v) : state(state), rs(new JSONState(&v)) {};
bool null()
{
return handle_value(mkNull);
}
else if (strncmp(s, "false", 5) == 0) {
s += 5;
mkBool(v, false);
bool boolean(bool val)
{
return handle_value(mkBool, val);
}
else if (strncmp(s, "null", 4) == 0) {
s += 4;
mkNull(v);
bool number_integer(number_integer_t val)
{
return handle_value(mkInt, val);
}
else throw JSONParseError("unrecognised JSON value");
}
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)
{
const char * s = s_.c_str();
parseJSON(state, s, v);
skipWhitespace(s);
if (*s) throw JSONParseError(format("expected end-of-string while parsing JSON value: %1%") % s);
JSONSax parser(state, v);
bool res = json::sax_parse(s_, &parser);
if (!res)
throw JSONParseError("Invalid JSON Value");
}
}