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Some tweaks for reading/writing #1609

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fe2c15d
Some tweaks:
May 27, 2025
c8b5efc
Merge branch 'master' into feat/reading_writing_20250527
baylesj Nov 12, 2025
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10 changes: 5 additions & 5 deletions include/json/json.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6,10 +6,10 @@
#ifndef JSON_JSON_H_INCLUDED
#define JSON_JSON_H_INCLUDED

#include "config.h"
#include "json_features.h"
#include "reader.h"
#include "value.h"
#include "writer.h"
#include "config.h" // IWYU pragma: export
#include "json_features.h" // IWYU pragma: export
#include "reader.h" // IWYU pragma: export
#include "value.h" // IWYU pragma: export
#include "writer.h" // IWYU pragma: export

#endif // JSON_JSON_H_INCLUDED
5 changes: 4 additions & 1 deletion include/json/reader.h
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Expand Up @@ -74,7 +74,7 @@ class JSON_API Reader {
* \return \c true if the document was successfully parsed, \c false if an
* error occurred.
*/
bool parse(const std::string& document, Value& root,
bool parse(std::string_view document, Value& root,
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@baylesj baylesj Nov 12, 2025

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This causes a compile time error in the build since we don't support string_view currently. I believe JsonCpp is on C++11? And std::string_view was added in C++17.

We have been talking about a major version change so it's quite possible bumping the standard could be part of that version change. But right now I don't think we can land this specific part of the change unfortunately.

bool collectComments = true);

/** \brief Read a Value from a <a HREF="http://www.json.org">JSON</a>
Expand Down Expand Up @@ -400,6 +400,9 @@ class JSON_API CharReaderBuilder : public CharReader::Factory {
bool JSON_API parseFromStream(CharReader::Factory const&, IStream&, Value* root,
String* errs);

bool JSON_API parseFromString(CharReader::Factory const&, std::string_view,
Value* root, JSONCPP_STRING* errs);

/** \brief Read from 'sin' into 'root'.
*
* Always keep comments from the input JSON.
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1 change: 1 addition & 0 deletions include/json/writer.h
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Expand Up @@ -143,6 +143,7 @@ class JSON_API StreamWriterBuilder : public StreamWriter::Factory {
* \snippet src/lib_json/json_writer.cpp StreamWriterBuilderDefaults
*/
static void setDefaults(Json::Value* settings);
static void updateDefaults(const Json::Value& settings);
};

/** \brief Abstract class for writers.
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11 changes: 10 additions & 1 deletion src/lib_json/json_reader.cpp
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Expand Up @@ -79,7 +79,7 @@ Reader::Reader() : features_(Features::all()) {}

Reader::Reader(const Features& features) : features_(features) {}

bool Reader::parse(const std::string& document, Value& root,
bool Reader::parse(std::string_view document, Value& root,
bool collectComments) {
document_.assign(document.begin(), document.end());
const char* begin = document_.c_str();
Expand Down Expand Up @@ -1998,6 +1998,15 @@ bool parseFromStream(CharReader::Factory const& fact, IStream& sin, Value* root,
return reader->parse(begin, end, root, errs);
}

bool parseFromString(
CharReader::Factory const& fact, std::string_view doc, Value* root, JSONCPP_STRING* errs) {
char const* begin = doc.data();
char const* end = begin + doc.size();
// Note that we do not actually need a null-terminator.
CharReaderPtr const reader(fact.newCharReader());
return reader->parse(begin, end, root, errs);
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@baylesj baylesj Nov 12, 2025

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Nit: I think it's fine to have begin and end inline here:

return reader->parse(doc.data(), doc.data() + doc.size(), root, errs);

Seems clear enough to me.

}

IStream& operator>>(IStream& sin, Value& root) {
CharReaderBuilder b;
String errs;
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32 changes: 22 additions & 10 deletions src/lib_json/json_writer.cpp
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Expand Up @@ -1170,18 +1170,30 @@ bool StreamWriterBuilder::validate(Json::Value* invalid) const {
Value& StreamWriterBuilder::operator[](const String& key) {
return settings_[key];
}
// static
void StreamWriterBuilder::setDefaults(Json::Value* settings) {

static Json::Value& global_settings_ = *new Json::Value([] {
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@baylesj baylesj Nov 12, 2025

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This is declaring a new global static, which may have implications for some libraries around storage and memory. For example, in Chrome, global statics like this aren't usually allowed.

Is there a performance or other benefit causing this change? I'm not aware of any.

//! [StreamWriterBuilderDefaults]
(*settings)["commentStyle"] = "All";
(*settings)["indentation"] = "\t";
(*settings)["enableYAMLCompatibility"] = false;
(*settings)["dropNullPlaceholders"] = false;
(*settings)["useSpecialFloats"] = false;
(*settings)["emitUTF8"] = false;
(*settings)["precision"] = 17;
(*settings)["precisionType"] = "significant";
Json::Value settings;
settings["commentStyle"] = "All";
settings["indentation"] = "\t";
settings["enableYAMLCompatibility"] = false;
settings["dropNullPlaceholders"] = false;
settings["useSpecialFloats"] = false;
settings["emitUTF8"] = false;
settings["precision"] = 17;
settings["precisionType"] = "significant";
//! [StreamWriterBuilderDefaults]
return settings;
}());

// static
void StreamWriterBuilder::setDefaults(Json::Value* settings) {
*settings = global_settings_;
}

// static
void StreamWriterBuilder::updateDefaults(const Json::Value& settings) {
global_settings_ = settings;
}

String writeString(StreamWriter::Factory const& factory, Value const& root) {
Expand Down
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