Prototype working on GCC and Clang

extras/tests/JsonDeserializer/JsonDeserializer.cpp

@@ -0,0 +1,126 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2020
+// MIT License
+
+#include <ArduinoJson.h>
+#include <malloc.h>
+#include <setjmp.h>
+#include <catch.hpp>
+
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4611)  // interaction between '_setjmp' and C++ object
+                                 // destruction is non-portable
+#endif
+
+size_t STACK = 1000;
+
+class IncrementalDeserializer {
+  struct Reader {
+    IncrementalDeserializer* _parent;
+
+   public:
+    Reader(IncrementalDeserializer* parent) : _parent(parent) {}
+
+    Reader(Reader& other) : _parent(other._parent) {}
+
+    int read() {
+      // std::cout << "read()" << std::endl;
+      if (_parent->_size == 0)
+        pause();
+      // std::cout << "avail = " << _parent->_size << std::endl;
+      // std::cout << "avail = " << _parent->_data << std::endl;
+      int result = _parent->_data[0];
+      consume(1);
+      // std::cout << "read() -> " << result << std::endl;
+      return result;
+    }
+
+    size_t readBytes(char* buffer, size_t length) {
+      // std::cout << "readBytes()" << std::endl;
+      if (_parent->_size == 0)
+        pause();
+      if (length > _parent->_size)
+        length = _parent->_size;
+      memcpy(buffer, _parent->_data, length);
+      consume(length);
+      return length;
+    }
+
+   private:
+    void pause() {
+      // std::cout << "pause" << std::endl;
+      if (setjmp(_parent->_back_to_reader) == 0) {
+        // std::cout << "paused" << std::endl;
+        longjmp(_parent->_back_to_program, 1);
+      }
+      // std::cout << "resumed" << std::endl;
+    }
+
+    void consume(size_t n) {
+      _parent->_data += n;
+      _parent->_size -= n;
+    }
+  };
+
+  jmp_buf _back_to_program;
+  jmp_buf _back_to_reader;
+  JsonDocument* _doc;
+  const char* _data;
+  size_t _size;
+  DeserializationError _result;
+
+ public:
+  IncrementalDeserializer(JsonDocument& doc) : _doc(&doc) {}
+
+  void start() {
+    // std::cout << "start()" << std::endl;
+    _data = 0;
+    _size = 0;
+    _result = DeserializationError::IncompleteInput;
+    if (setjmp(_back_to_program) == 0) {
+      char space[STACK];     // Reserve enough space for main to run
+      space[STACK - 1] = 1;  // Do not optimize array out of existence
+      (void)space;
+      Reader reader(this);
+      _result = deserializeJson(*_doc, reader);
+      longjmp(_back_to_program, 2);
+    }
+  }
+
+  bool feed(const char* data, size_t size) {
+    // std::cout << "feed()" << std::endl;
+    _data = data;
+    _size = size;
+    switch (setjmp(_back_to_program)) {
+      case 0:
+        longjmp(_back_to_reader, 1);
+      case 1:
+        // std::cout << "feed() -> false" << std::endl;
+        return false;  // need more data
+      default:
+        // std::cout << "feed() -> true" << std::endl;
+        return true;  // done
+    }
+  }
+
+  DeserializationError result() const {
+    return _result;
+  }
+};
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+TEST_CASE("prout") {
+  StaticJsonDocument<1024> doc;
+  IncrementalDeserializer deserializer(doc);
+
+  SECTION("basics") {
+    deserializer.start();
+    REQUIRE(deserializer.feed("{\"answ", 6) == false);
+    REQUIRE(deserializer.feed("er\":42}", 7) == true);
+    REQUIRE(doc["answer"] == 42);
+  }
+}