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mirror of https://github.com/nlohmann/json synced 2024-12-24 01:30:08 +00:00

added a constructor from an input stream

This commit is contained in:
Niels 2016-02-05 19:24:42 +01:00
parent 104c4b5286
commit 2c720b26ab
6 changed files with 176 additions and 0 deletions

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@ -0,0 +1,55 @@
#include <json.hpp>
using json = nlohmann::json;
int main()
{
// a JSON text
auto text = R"(
{
"Image": {
"Width": 800,
"Height": 600,
"Title": "View from 15th Floor",
"Thumbnail": {
"Url": "http://www.example.com/image/481989943",
"Height": 125,
"Width": 100
},
"Animated" : false,
"IDs": [116, 943, 234, 38793]
}
}
)";
// fill a stream with JSON text
std::stringstream ss;
ss << text;
// create JSON from stream
json j_complete(ss);
std::cout << std::setw(4) << j_complete << "\n\n";
// define parser callback
json::parser_callback_t cb = [](int depth, json::parse_event_t event, json & parsed)
{
// skip object elements with key "Thumbnail"
if (event == json::parse_event_t::key and parsed == json("Thumbnail"))
{
return false;
}
else
{
return true;
}
};
// fill a stream with JSON text
ss.clear();
ss << text;
// create JSON from stream (with callback)
json j_filtered(ss, cb);
std::cout << std::setw(4) << j_filtered << '\n';
}

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@ -0,0 +1 @@
<a target="_blank" href="http://melpon.org/wandbox/permlink/lUltfC5TlmxeUq5X"><b>online</b></a>

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@ -0,0 +1,34 @@
{
"Image": {
"Animated": false,
"Height": 600,
"IDs": [
116,
943,
234,
38793
],
"Thumbnail": {
"Height": 125,
"Url": "http://www.example.com/image/481989943",
"Width": 100
},
"Title": "View from 15th Floor",
"Width": 800
}
}
{
"Image": {
"Animated": false,
"Height": 600,
"IDs": [
116,
943,
234,
38793
],
"Title": "View from 15th Floor",
"Width": 800
}
}

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@ -1806,6 +1806,31 @@ class basic_json
}
}
/*!
@brief construct a JSON value given an input stream
@param[in,out] i stream to read a serialized JSON value from
@param[in] cb a parser callback function of type @ref parser_callback_t
which is used to control the deserialization by filtering unwanted values
(optional)
@complexity Linear in the length of the input. The parser is a predictive
LL(1) parser. The complexity can be higher if the parser callback function
@a cb has a super-linear complexity.
@note A UTF-8 byte order mark is silently ignored.
@liveexample{The example below demonstrates constructing a JSON value from
a `std::stringstream` with and without callback
function.,basic_json__istream}
@since version 2.0.0
*/
basic_json(std::istream& i, parser_callback_t cb = nullptr)
{
*this = parser(i, cb).parse();
}
///////////////////////////////////////
// other constructors and destructor //
///////////////////////////////////////

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@ -1806,6 +1806,31 @@ class basic_json
}
}
/*!
@brief construct a JSON value given an input stream
@param[in,out] i stream to read a serialized JSON value from
@param[in] cb a parser callback function of type @ref parser_callback_t
which is used to control the deserialization by filtering unwanted values
(optional)
@complexity Linear in the length of the input. The parser is a predictive
LL(1) parser. The complexity can be higher if the parser callback function
@a cb has a super-linear complexity.
@note A UTF-8 byte order mark is silently ignored.
@liveexample{The example below demonstrates constructing a JSON value from
a `std::stringstream` with and without callback
function.,basic_json__istream}
@since version 2.0.0
*/
basic_json(std::istream& i, parser_callback_t cb = nullptr)
{
*this = parser(i, cb).parse();
}
///////////////////////////////////////
// other constructors and destructor //
///////////////////////////////////////

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@ -1264,6 +1264,42 @@ TEST_CASE("constructors")
}
}
}
SECTION("create a JSON value from an input stream")
{
SECTION("sts::stringstream")
{
std::stringstream ss;
ss << "[\"foo\",1,2,3,false,{\"one\":1}]";
json j(ss);
CHECK(j == json({"foo", 1, 2, 3, false, {{"one", 1}}}));
}
SECTION("with callback function")
{
std::stringstream ss;
ss << "[\"foo\",1,2,3,false,{\"one\":1}]";
json j(ss, [](int, json::parse_event_t, const json & val)
{
// filter all number(2) elements
if (val == json(2))
{
return false;
}
else
{
return true;
}
});
CHECK(j == json({"foo", 1, 3, false, {{"one", 1}}}));
}
SECTION("std::ifstream")
{
std::ifstream f("test/json_tests/pass1.json");
json j(f);
}
}
}
TEST_CASE("other constructors and destructor")