Convert DITLs to JSON

rapidjson/example/filterkey/filterkey.cpp

@@ -0,0 +1,135 @@
+// JSON filterkey example with SAX-style API.
+
+// This example parses JSON text from stdin with validation.
+// During parsing, specified key will be filtered using a SAX handler.
+// It re-output the JSON content to stdout without whitespace.
+
+#include "rapidjson/reader.h"
+#include "rapidjson/writer.h"
+#include "rapidjson/filereadstream.h"
+#include "rapidjson/filewritestream.h"
+#include "rapidjson/error/en.h"
+#include <stack>
+
+using namespace rapidjson;
+
+// This handler forwards event into an output handler, with filtering the descendent events of specified key.
+template <typename OutputHandler>
+class FilterKeyHandler {
+public:
+    typedef char Ch;
+
+    FilterKeyHandler(OutputHandler& outputHandler, const Ch* keyString, SizeType keyLength) : 
+        outputHandler_(outputHandler), keyString_(keyString), keyLength_(keyLength), filterValueDepth_(), filteredKeyCount_()
+    {}
+
+    bool Null()             { return filterValueDepth_ > 0 ? EndValue() : outputHandler_.Null()    && EndValue(); }
+    bool Bool(bool b)       { return filterValueDepth_ > 0 ? EndValue() : outputHandler_.Bool(b)   && EndValue(); }
+    bool Int(int i)         { return filterValueDepth_ > 0 ? EndValue() : outputHandler_.Int(i)    && EndValue(); }
+    bool Uint(unsigned u)   { return filterValueDepth_ > 0 ? EndValue() : outputHandler_.Uint(u)   && EndValue(); }
+    bool Int64(int64_t i)   { return filterValueDepth_ > 0 ? EndValue() : outputHandler_.Int64(i)  && EndValue(); }
+    bool Uint64(uint64_t u) { return filterValueDepth_ > 0 ? EndValue() : outputHandler_.Uint64(u) && EndValue(); }
+    bool Double(double d)   { return filterValueDepth_ > 0 ? EndValue() : outputHandler_.Double(d) && EndValue(); }
+    bool RawNumber(const Ch* str, SizeType len, bool copy) { return filterValueDepth_ > 0 ? EndValue() : outputHandler_.RawNumber(str, len, copy) && EndValue(); }
+    bool String   (const Ch* str, SizeType len, bool copy) { return filterValueDepth_ > 0 ? EndValue() : outputHandler_.String   (str, len, copy) && EndValue(); }
+    
+    bool StartObject() { 
+        if (filterValueDepth_ > 0) {
+            filterValueDepth_++;
+            return true;
+        }
+        else {
+            filteredKeyCount_.push(0);
+            return outputHandler_.StartObject();
+        }
+    }
+    
+    bool Key(const Ch* str, SizeType len, bool copy) { 
+        if (filterValueDepth_ > 0) 
+            return true;
+        else if (len == keyLength_ && std::memcmp(str, keyString_, len) == 0) {
+            filterValueDepth_ = 1;
+            return true;
+        }
+        else {
+            ++filteredKeyCount_.top();
+            return outputHandler_.Key(str, len, copy);
+        }
+    }
+
+    bool EndObject(SizeType) {
+        if (filterValueDepth_ > 0) {
+            filterValueDepth_--;
+            return EndValue();
+        }
+        else {
+            // Use our own filtered memberCount
+            SizeType memberCount = filteredKeyCount_.top();
+            filteredKeyCount_.pop();
+            return outputHandler_.EndObject(memberCount) && EndValue();
+        }
+    }
+
+    bool StartArray() {
+        if (filterValueDepth_ > 0) {
+            filterValueDepth_++;
+            return true;
+        }
+        else
+            return outputHandler_.StartArray();
+    }
+
+    bool EndArray(SizeType elementCount) {
+        if (filterValueDepth_ > 0) {
+            filterValueDepth_--;
+            return EndValue();
+        }
+        else
+            return outputHandler_.EndArray(elementCount) && EndValue();
+    }
+
+private:
+    FilterKeyHandler(const FilterKeyHandler&);
+    FilterKeyHandler& operator=(const FilterKeyHandler&);
+
+    bool EndValue() {
+        if (filterValueDepth_ == 1) // Just at the end of value after filtered key
+            filterValueDepth_ = 0;
+        return true;
+    }
+    
+    OutputHandler& outputHandler_;
+    const char* keyString_;
+    const SizeType keyLength_;
+    unsigned filterValueDepth_;
+    std::stack<SizeType> filteredKeyCount_;
+};
+
+int main(int argc, char* argv[]) {
+    if (argc != 2) {
+        fprintf(stderr, "filterkey key < input.json > output.json\n");
+        return 1;
+    }
+
+    // Prepare JSON reader and input stream.
+    Reader reader;
+    char readBuffer[65536];
+    FileReadStream is(stdin, readBuffer, sizeof(readBuffer));
+
+    // Prepare JSON writer and output stream.
+    char writeBuffer[65536];
+    FileWriteStream os(stdout, writeBuffer, sizeof(writeBuffer));
+    Writer<FileWriteStream> writer(os);
+
+    // Prepare Filter
+    FilterKeyHandler<Writer<FileWriteStream> > filter(writer, argv[1], static_cast<SizeType>(strlen(argv[1])));
+
+    // JSON reader parse from the input stream, filter handler filters the events, and forward to writer.
+    // i.e. the events flow is: reader -> filter -> writer
+    if (!reader.Parse(is, filter)) {
+        fprintf(stderr, "\nError(%u): %s\n", static_cast<unsigned>(reader.GetErrorOffset()), GetParseError_En(reader.GetParseErrorCode()));
+        return 1;
+    }
+
+    return 0;
+}