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Implemented a extensible JSONParser::Schema base class for customizing how json files are converted to objects. #1448

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Merged
robertosfield merged 2 commits into from
Apr 17, 2025
Merged

Implemented a extensible JSONParser::Schema base class for customizing how json files are converted to objects. #1448

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9aabb94
Added support for customizing the parsing of json files.
robertosfield Apr 17, 2025
02a8491
Warning fixes and code cleanup.
robertosfield Apr 17, 2025
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84 changes: 71 additions & 13 deletions include/vsg/io/json.h
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Original file line number Diff line number Diff line change
Expand Up @@ -23,47 +23,105 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

</editor-fold> */

#include <vsg/core/Objects.h>
#include <vsg/io/ReaderWriter.h>
#include <vsg/io/mem_stream.h>

namespace vsg
{

/// JSON parser based on spec: https://www.json.org/json-en.html
struct JSONParser
struct VSG_DECLSPEC JSONParser
{
std::string buffer;
std::size_t pos = 0;
vsg::mem_stream mstr;
vsg::indentation indent;
mem_stream mstr;

JSONParser();

/// Schema base class to provides a mechanism for customizing the json parsing to handle
/// mapping between json schema's and user data/scene graph objects
struct Schema
{
// array elements [ value, value.. ]
virtual void read_array(JSONParser& parser);
virtual void read_object(JSONParser& parser);
virtual void read_string(JSONParser& parser);
virtual void read_number(JSONParser& parser, std::istream& input);
virtual void read_bool(JSONParser& parser, bool value);
virtual void read_null(JSONParser& parser);

// object properties { name, value; ... }
virtual void read_array(JSONParser& parser, const std::string_view& name);
virtual void read_object(JSONParser& parser, const std::string_view& name);
virtual void read_string(JSONParser& parser, const std::string_view& name);
virtual void read_number(JSONParser& parser, const std::string_view& name, std::istream& input);
virtual void read_bool(JSONParser& parser, const std::string_view& name, bool value);
virtual void read_null(JSONParser& parser, const std::string_view& name);
};

bool read_string(std::string& value);
void read_object(Schema& schema);
void read_array(Schema& schema);

template<typename... Args>
void warning(Args&&... args)
{
warn("Parsing error at pos = ", pos, ". ", std::forward<Args>(args)...);
}

inline bool white_space(char c) const
{
return (c == ' ' || c == '\t' || c == '\r' || c == '\n');
}

bool read_string(std::string& value);

vsg::ref_ptr<vsg::Object> read_array();
vsg::ref_ptr<vsg::Object> read_object();
};
VSG_type_name(vsg::JSONParser);

/// Default support for mapping standard JSON types directly to VSG.
/// JSON objects are mapped to Object metadata.
/// JSON arrays to Objects.
/// string, number and bool are mapped to stringValue, doubleValue and boolValue.
struct VSG_DECLSPEC JSONtoMetaDataSchema : public JSONParser::Schema
{
// object created when parsing JSON file
ref_ptr<Object> object;
ref_ptr<Objects> objects;

void addToArray(ref_ptr<Object> in_object);
void addToObject(const std::string_view& name, ref_ptr<Object> in_object);

// array elements [ value, value.. ]
void read_array(JSONParser& parser) override;
void read_object(JSONParser& parser) override;
void read_string(JSONParser& parser) override;
void read_number(JSONParser& parser, std::istream& input) override;
void read_bool(JSONParser& parser, bool value) override;
void read_null(JSONParser& parser) override;

// object properties { name, value; ... }
void read_array(JSONParser& parser, const std::string_view& name) override;
void read_object(JSONParser& parser, const std::string_view& name) override;
void read_string(JSONParser& parser, const std::string_view& name) override;
void read_number(JSONParser& parser, const std::string_view& name, std::istream& input) override;
void read_bool(JSONParser& parser, const std::string_view& name, bool value) override;
void read_null(JSONParser& parser, const std::string_view& name) override;
};
VSG_type_name(vsg::JSONtoMetaDataSchema);

/// json ReaderWriter
class json : public vsg::Inherit<vsg::ReaderWriter, json>
class json : public Inherit<ReaderWriter, json>
{
public:
json();

vsg::ref_ptr<vsg::Object> read(const vsg::Path&, vsg::ref_ptr<const vsg::Options>) const override;
vsg::ref_ptr<vsg::Object> read(std::istream&, vsg::ref_ptr<const vsg::Options>) const override;
vsg::ref_ptr<vsg::Object> read(const uint8_t* ptr, size_t size, vsg::ref_ptr<const vsg::Options> options = {}) const override;
ref_ptr<Object> read(const Path&, ref_ptr<const Options>) const override;
ref_ptr<Object> read(std::istream&, ref_ptr<const Options>) const override;
ref_ptr<Object> read(const uint8_t* ptr, size_t size, ref_ptr<const Options> options = {}) const override;

vsg::ref_ptr<vsg::Object> _read(std::istream&, vsg::ref_ptr<const vsg::Options>) const;
ref_ptr<Object> _read(std::istream&, ref_ptr<const Options>) const;

bool supportedExtension(const vsg::Path& ext) const;
bool supportedExtension(const Path& ext) const;

bool getFeatures(Features& features) const override;
};
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