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Diffstat (limited to 'src/libutil/json.hh')
-rw-r--r-- | src/libutil/json.hh | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/src/libutil/json.hh b/src/libutil/json.hh new file mode 100644 index 000000000000..595e9bbe3491 --- /dev/null +++ b/src/libutil/json.hh @@ -0,0 +1,181 @@ +#pragma once + +#include <iostream> +#include <vector> +#include <cassert> + +namespace nix { + +void toJSON(std::ostream & str, const char * start, const char * end); +void toJSON(std::ostream & str, const char * s); + +template<typename T> +void toJSON(std::ostream & str, const T & n); + +class JSONWriter +{ +protected: + + struct JSONState + { + std::ostream & str; + bool indent; + size_t depth = 0; + std::vector<JSONWriter *> stack; + JSONState(std::ostream & str, bool indent) : str(str), indent(indent) { } + ~JSONState() + { + assert(stack.empty()); + } + }; + + JSONState * state; + + bool first = true; + + JSONWriter(std::ostream & str, bool indent); + + JSONWriter(JSONState * state); + + ~JSONWriter(); + + void assertActive() + { + assert(!state->stack.empty() && state->stack.back() == this); + } + + void comma(); + + void indent(); +}; + +class JSONObject; +class JSONPlaceholder; + +class JSONList : JSONWriter +{ +private: + + friend class JSONObject; + friend class JSONPlaceholder; + + void open(); + + JSONList(JSONState * state) + : JSONWriter(state) + { + open(); + } + +public: + + JSONList(std::ostream & str, bool indent = false) + : JSONWriter(str, indent) + { + open(); + } + + ~JSONList(); + + template<typename T> + JSONList & elem(const T & v) + { + comma(); + toJSON(state->str, v); + return *this; + } + + JSONList list(); + + JSONObject object(); + + JSONPlaceholder placeholder(); +}; + +class JSONObject : JSONWriter +{ +private: + + friend class JSONList; + friend class JSONPlaceholder; + + void open(); + + JSONObject(JSONState * state) + : JSONWriter(state) + { + open(); + } + + void attr(const std::string & s); + +public: + + JSONObject(std::ostream & str, bool indent = false) + : JSONWriter(str, indent) + { + open(); + } + + ~JSONObject(); + + template<typename T> + JSONObject & attr(const std::string & name, const T & v) + { + attr(name); + toJSON(state->str, v); + return *this; + } + + JSONList list(const std::string & name); + + JSONObject object(const std::string & name); + + JSONPlaceholder placeholder(const std::string & name); +}; + +class JSONPlaceholder : JSONWriter +{ + +private: + + friend class JSONList; + friend class JSONObject; + + JSONPlaceholder(JSONState * state) + : JSONWriter(state) + { + } + + void assertValid() + { + assertActive(); + assert(first); + } + +public: + + JSONPlaceholder(std::ostream & str, bool indent = false) + : JSONWriter(str, indent) + { + } + + ~JSONPlaceholder() + { + assert(!first || std::uncaught_exception()); + } + + template<typename T> + void write(const T & v) + { + assertValid(); + first = false; + toJSON(state->str, v); + } + + JSONList list(); + + JSONObject object(); +}; + +} |