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manually merged pull request #41
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@nlohmann
nlohmann committed May 3, 2015
1 parent faae8bb commit 952cbbc
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Showing 3 changed files with 249 additions and 45 deletions.
2 changes: 1 addition & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -380,7 +380,7 @@ I deeply appreciate the help of the following people.
- [wancw](https://github.com/wanwc) fixed a bug that hindered the class to compile with Clang.
- Tomas Åblad found a bug in the iterator implementation.
- [Joshua C. Randall](https://github.com/jrandall) fixed a bug in the floating-point serialization.
- [Aaron Burghardt](https://github.com/aburgh) implemented code to parse streams incrementally.
- [Aaron Burghardt](https://github.com/aburgh) implemented code to parse streams incrementally. Furthermore, he greatly improved the parser class by allowing the definition of a filter function to discard undesired elements while parsing.
- [Daniel Kopeček](https://github.com/dkopecek) fixed a bug in the compilation with GCC 5.0.
- [Florian Weber](https://github.com/Florianjw) fixed a bug in and improved the performance of the comparison operators.

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146 changes: 124 additions & 22 deletions src/json.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -191,9 +191,35 @@ class basic_json
string, ///< string value
boolean, ///< boolean value
number_integer, ///< number value (integer)
number_float ///< number value (floating-point)
number_float, ///< number value (floating-point)
discarded ///< (internal) indicates the parser callback chose not to keep the value
};

//////////////////////////
// JSON parser callback //
//////////////////////////

/// JSON callback event enumeration
enum class parse_event_t : uint8_t
{
object_start, ///< start an object scope (found a '{' token)
object_end, ///< end of an object scope (found '}' token)
array_start, ///< start of an array scope (found '[' token)
array_end, ///< end of an array scope (found ']' token)
key, ///< found an object key within an object scope
value ///< a value in an appropriate context (i.e., following a tag in an object scope)
};

/// per-element parser callback type
using parser_callback_t = std::function<bool(int depth, parse_event_t event,
const basic_json& parsed)>;

/// default parser callback returns true to keep all elements
static bool default_callback(int, parse_event_t, const basic_json&)
{
return true;
}

/*!
@brief comparison operator for JSON value types
Expand Down Expand Up @@ -233,6 +259,7 @@ class basic_json
switch (m_type)
{
case (value_t::null):
case (value_t::discarded):
{
break;
}
Expand Down Expand Up @@ -598,6 +625,7 @@ class basic_json
switch (m_type)
{
case (value_t::null):
case (value_t::discarded):
{
break;
}
Expand Down Expand Up @@ -790,6 +818,12 @@ class basic_json
return m_type == value_t::string;
}

// return whether value is discarded
inline bool is_discarded() const noexcept
{
return m_type == value_t::discarded;
}

/// return the type of the object (implicit)
inline operator value_t() const noexcept
{
Expand Down Expand Up @@ -1610,6 +1644,7 @@ class basic_json
switch (m_type)
{
case (value_t::null):
case (value_t::discarded):
{
break;
}
Expand Down Expand Up @@ -1827,6 +1862,8 @@ class basic_json
return lhs.m_value.number_integer == rhs.m_value.number_integer;
case (value_t::number_float):
return approx(lhs.m_value.number_float, rhs.m_value.number_float);
case (value_t::discarded):
return false;
}
}
else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_float)
Expand Down Expand Up @@ -1875,6 +1912,8 @@ class basic_json
return lhs.m_value.number_integer < rhs.m_value.number_integer;
case (value_t::number_float):
return lhs.m_value.number_float < rhs.m_value.number_float;
case (value_t::discarded):
return false;
}
}
else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_float)
Expand Down Expand Up @@ -1942,15 +1981,15 @@ class basic_json
/////////////////////

/// deserialize from string
static basic_json parse(const string_t& s)
static basic_json parse(const string_t& s, parser_callback_t cb = default_callback)
{
return parser(s).parse();
return parser(s, cb).parse();
}

/// deserialize from stream
static basic_json parse(std::istream& i)
static basic_json parse(std::istream& i, parser_callback_t cb = default_callback)
{
return parser(i).parse();
return parser(i, cb).parse();
}

/// deserialize from stream
Expand Down Expand Up @@ -2003,6 +2042,11 @@ class basic_json
return "boolean";
}

case (value_t::discarded):
{
return "discarded";
}

default:
{
return "number";
Expand Down Expand Up @@ -2231,6 +2275,10 @@ class basic_json
return string_t(buf.data());
}

case (value_t::discarded):
{
return "<discarded>";
}
default:
{
return "null";
Expand Down Expand Up @@ -4521,14 +4569,15 @@ class basic_json
{
public:
/// constructor for strings
inline parser(const string_t& s) : m_lexer(s)
inline parser(const string_t& s, parser_callback_t cb = default_callback) : callback(cb), m_lexer(s)
{
// read first token
get_token();
}

/// a parser reading from an input stream
inline parser(std::istream& _is) : m_lexer(&_is)
inline parser(std::istream& _is, parser_callback_t cb = default_callback) : callback(cb),
m_lexer(&_is)
{
// read first token
get_token();
Expand All @@ -4537,7 +4586,7 @@ class basic_json
/// public parser interface
inline basic_json parse()
{
basic_json result = parse_internal();
basic_json result = parse_internal(true);

expect(lexer::token_type::end_of_input);

Expand All @@ -4546,14 +4595,19 @@ class basic_json

private:
/// the actual parser
inline basic_json parse_internal()
inline basic_json parse_internal(bool keep)
{
auto result = basic_json(value_t::discarded);

switch (last_token)
{
case (lexer::token_type::begin_object):
{
// explicitly set result to object to cope with {}
basic_json result(value_t::object);
if (keep and (keep = callback(depth++, parse_event_t::object_start, result)))
{
// explicitly set result to object to cope with {}
result = basic_json(value_t::object);
}

// read next token
get_token();
Expand All @@ -4562,6 +4616,10 @@ class basic_json
if (last_token == lexer::token_type::end_object)
{
get_token();
if (keep and not (keep = callback(--depth, parse_event_t::object_end, result)))
{
result = basic_json(value_t::discarded);
}
return result;
}

Expand All @@ -4578,27 +4636,44 @@ class basic_json
expect(lexer::token_type::value_string);
const auto key = m_lexer.get_string();

bool keep_tag = false;
if (keep)
{
keep_tag = callback(depth, parse_event_t::key, basic_json(key));
}

// parse separator (:)
get_token();
expect(lexer::token_type::name_separator);

// parse and add value
get_token();
result.m_value.object->emplace(key, parse_internal());
auto value = parse_internal(keep);
if (keep and keep_tag and not value.is_discarded())
{
result[key] = value;
}
}
while (last_token == lexer::token_type::value_separator);

// closing }
expect(lexer::token_type::end_object);
get_token();
if (keep and not callback(--depth, parse_event_t::object_end, result))
{
result = basic_json(value_t::discarded);
}

return result;
}

case (lexer::token_type::begin_array):
{
// explicitly set result to object to cope with []
basic_json result(value_t::array);
if (keep and (keep = callback(depth++, parse_event_t::array_start, result)))
{
// explicitly set result to object to cope with []
result = basic_json(value_t::array);
}

// read next token
get_token();
Expand All @@ -4607,6 +4682,10 @@ class basic_json
if (last_token == lexer::token_type::end_array)
{
get_token();
if (not callback(--depth, parse_event_t::array_end, result))
{
result = basic_json(value_t::discarded);
}
return result;
}

Expand All @@ -4619,41 +4698,53 @@ class basic_json
get_token();
}

// parse and add value
result.m_value.array->emplace_back(parse_internal());
// parse value
auto value = parse_internal(keep);
if (keep and not value.is_discarded())
{
result.push_back(value);
}
}
while (last_token == lexer::token_type::value_separator);

// closing ]
expect(lexer::token_type::end_array);
get_token();
if (keep and not callback(--depth, parse_event_t::array_end, result))
{
result = basic_json(value_t::discarded);
}

return result;
}

case (lexer::token_type::literal_null):
{
get_token();
return basic_json(nullptr);
result = basic_json(nullptr);
break;
}

case (lexer::token_type::value_string):
{
const auto s = m_lexer.get_string();
get_token();
return basic_json(s);
result = basic_json(s);
break;
}

case (lexer::token_type::literal_true):
{
get_token();
return basic_json(true);
result = basic_json(true);
break;
}

case (lexer::token_type::literal_false):
{
get_token();
return basic_json(false);
result = basic_json(false);
break;
}

case (lexer::token_type::value_number):
Expand All @@ -4675,13 +4766,14 @@ class basic_json
if (approx(float_val, static_cast<number_float_t>(int_val)))
{
// we basic_json not lose precision -> return int
return basic_json(int_val);
result = basic_json(int_val);
}
else
{
// we would lose precision -> returnfloat
return basic_json(float_val);
result = basic_json(float_val);
}
break;
}

default:
Expand All @@ -4693,6 +4785,12 @@ class basic_json
throw std::invalid_argument(error_msg);
}
}

if (keep and not callback(depth, parse_event_t::value, result))
{
result = basic_json(value_t::discarded);
}
return result;
}

/// get next token from lexer
Expand All @@ -4715,6 +4813,10 @@ class basic_json
}

private:
/// levels of recursion
int depth = 0;
/// callback function
parser_callback_t callback;
/// the type of the last read token
typename lexer::token_type last_token = lexer::token_type::uninitialized;
/// the lexer
Expand Down
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