JSONHandler.hh
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#ifndef JSONHANDLER_HH
#define JSONHANDLER_HH
#include <qpdf/JSON.hh>
#include <functional>
#include <map>
#include <memory>
#include <string>
// This class allows a sax-like walk through a JSON object with
// functionality that mostly mirrors QPDFArgParser. It is primarily
// here to facilitate automatic generation of some of the code to help
// keep QPDFJob json consistent with command-line arguments.
class JSONHandler
{
public:
// A QPDFUsage exception is thrown if there are any errors
// validating the JSON object.
JSONHandler();
~JSONHandler() = default;
// Based on the type of handler, expect the object to be of a
// certain type. QPDFUsage is thrown otherwise. Multiple handlers
// may be registered, which allows the object to be of various
// types. If an anyHandler is added, no other handler will be
// called. There is no "final" handler -- if the top-level is a
// dictionary or array, just use its end handler.
typedef std::function<void(std::string const& path, JSON value)> json_handler_t;
typedef std::function<void(std::string const& path)> void_handler_t;
typedef std::function<void(std::string const& path, std::string const& value)> string_handler_t;
typedef std::function<void(std::string const& path, bool value)> bool_handler_t;
// If an any handler is added, it will be called for any value
// including null, and no other handler will be called.
void addAnyHandler(json_handler_t fn);
// If any of the remaining handlers are registered, each
// registered handle will be called.
void addNullHandler(void_handler_t fn);
void addStringHandler(string_handler_t fn);
void addNumberHandler(string_handler_t fn);
void addBoolHandler(bool_handler_t fn);
void addDictHandlers(json_handler_t start_fn, void_handler_t end_fn);
void addDictKeyHandler(std::string const& key, std::shared_ptr<JSONHandler>);
void addFallbackDictHandler(std::shared_ptr<JSONHandler>);
void addArrayHandlers(
json_handler_t start_fn, void_handler_t end_fn, std::shared_ptr<JSONHandler> item_handlers);
// Apply handlers recursively to a JSON object.
void handle(std::string const& path, JSON j);
private:
JSONHandler(JSONHandler const&) = delete;
static void usage(std::string const& msg);
struct Handlers
{
Handlers() :
any_handler(nullptr),
null_handler(nullptr),
string_handler(nullptr),
number_handler(nullptr),
bool_handler(nullptr),
dict_start_handler(nullptr),
dict_end_handler(nullptr),
array_start_handler(nullptr),
array_end_handler(nullptr),
final_handler(nullptr)
{
}
json_handler_t any_handler;
void_handler_t null_handler;
string_handler_t string_handler;
string_handler_t number_handler;
bool_handler_t bool_handler;
json_handler_t dict_start_handler;
void_handler_t dict_end_handler;
json_handler_t array_start_handler;
void_handler_t array_end_handler;
void_handler_t final_handler;
std::map<std::string, std::shared_ptr<JSONHandler>> dict_handlers;
std::shared_ptr<JSONHandler> fallback_dict_handler;
std::shared_ptr<JSONHandler> array_item_handler;
};
class Members
{
friend class JSONHandler;
public:
~Members() = default;
private:
Members() = default;
Members(Members const&) = delete;
Handlers h;
};
std::shared_ptr<Members> m;
};
#endif // JSONHANDLER_HH