Add 'third_party/nix/' from commit 'be66c7a6b24e3c3c6157fd37b86c7203d14acf10'

git-subtree-dir: third_party/nix
git-subtree-mainline: cf8cd640c1
git-subtree-split: be66c7a6b24e3c3c6157fd37b86c7203d14acf10

third_party/nix/src/libutil/json.hh

@@ -0,0 +1,189 @@
+#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;
+        size_t stack = 0;
+        JSONState(std::ostream & str, bool indent) : str(str), indent(indent) { }
+        ~JSONState()
+        {
+            assert(stack == 0);
+        }
+    };
+
+    JSONState * state;
+
+    bool first = true;
+
+    JSONWriter(std::ostream & str, bool indent);
+
+    JSONWriter(JSONState * state);
+
+    ~JSONWriter();
+
+    void assertActive()
+    {
+        assert(state->stack != 0);
+    }
+
+    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(const JSONObject & obj) = delete;
+
+    JSONObject(JSONObject && obj)
+        : JSONWriter(obj.state)
+    {
+        obj.state = 0;
+    }
+
+    ~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();
+};
+
+}