Adding an example of sax like parser using buffered content (could be a socket)

Author: pmalhaire

example/cpp11/CMakeLists.txt

@@ -6,6 +6,7 @@ IF (MSGPACK_CXX11)
     LIST (APPEND exec_PROGRAMS
         container.cpp
         non_def_con_class.cpp
+        socket_stream_example.cpp
     )
 
     FOREACH (source_file ${exec_PROGRAMS})

example/cpp11/socket_stream_example.cpp

@@ -0,0 +1,157 @@
+#include <iostream>
+#include <sstream>
+#include <msgpack.hpp>
+
+struct json_like_visitor : msgpack::v2::null_visitor {
+    json_like_visitor(std::string& s):m_s(s), m_ref(false) {} // m_ref is false by default
+
+    bool visit_nil() {
+        m_s += "null";
+        return true;
+    }
+    bool visit_boolean(bool v) {
+        if (v) m_s += "true";
+        else m_s += "false";
+        return true;
+    }
+    bool visit_positive_integer(uint64_t v) {
+        std::stringstream ss;
+        ss << v;
+        m_s += ss.str();
+        return true;
+    }
+    bool visit_negative_integer(int64_t v) {
+        std::stringstream ss;
+        ss << v;
+        m_s += ss.str();
+        return true;
+    }
+    bool visit_str(const char* v, uint32_t size) {
+        // I omit escape process.
+        m_s += '"' + std::string(v, size) + '"';
+        return true;
+    }
+    bool start_array(uint32_t /*num_elements*/) {
+        m_s += "[";
+        return true;
+    }
+    bool end_array_item() {
+        m_s += ",";
+        return true;
+    }
+    bool end_array() {
+        m_s.erase(m_s.size() - 1, 1); // remove the last ','
+        m_s += "]";
+        return true;
+    }
+    bool start_map(uint32_t /*num_kv_pairs*/) {
+        m_s += "{";
+        return true;
+    }
+    bool end_map_key() {
+        m_s += ":";
+        return true;
+    }
+    bool end_map_value() {
+        m_s += ",";
+        return true;
+    }
+    bool end_map() {
+        m_s.erase(m_s.size() - 1, 1); // remove the last ','
+        m_s += "}";
+        return true;
+    }
+    void parse_error(size_t /*parsed_offset*/, size_t /*error_offset*/) {
+        std::cerr << "parse error"<<std::endl;
+    }
+    void insufficient_bytes(size_t /*parsed_offset*/, size_t /*error_offset*/) {
+        std::cout << "insufficient bytes"<<std::endl;
+    }
+    std::string& m_s;
+
+    // These two functions are required by parser.
+    void set_referenced(bool ref) { m_ref = ref; }
+    bool referenced() const { return m_ref; }
+    bool m_ref;
+};
+
+struct do_nothing {
+    void operator()(char* /*buffer*/) {
+    }
+};
+
+class json_like_printer : public msgpack::parser<json_like_printer, do_nothing>,
+                          public json_like_visitor {
+    typedef parser<json_like_printer, do_nothing> parser_t;
+public:
+    json_like_printer(std::size_t initial_buffer_size = MSGPACK_UNPACKER_INIT_BUFFER_SIZE)
+        :parser_t(do_nothing_, initial_buffer_size),
+         json_like_visitor(json_str_) {
+    }
+
+    json_like_visitor& visitor() { return *this; }
+    void print() { std::cout << json_str_ << std::endl; json_str_.clear();}
+private:
+    do_nothing do_nothing_;
+    std::string json_str_;
+};
+
+template <typename T>
+struct ref_buffer {
+    ref_buffer(T& t):t(t) {}
+    void write(char const* ptr, std::size_t len) {
+        if (len > t.buffer_capacity()) {
+            t.reserve_buffer(len - t.buffer_capacity());
+        }
+        std::memcpy(t.buffer(), ptr, len);
+        t.buffer_consumed(len);
+    }
+    T& t;
+};
+
+#define BUFFERING_SIZE_MAX 100
+
+//simulates streamed content (a socket for example)
+bool produce( std::stringstream & ss, char* buff, std::size_t& size)
+{
+    ss.read(buff, BUFFERING_SIZE_MAX);
+    size = ss.gcount();
+    return (size > 0);
+}
+
+//shows how you can treat data 
+void consume( const char* buff, const std::size_t size, 
+    ref_buffer<json_like_printer> & rb,
+    json_like_printer & jp
+    )
+{
+    rb.write(buff,size);
+    while( jp.next() )
+    {
+        //here we print the data, you could do any wanted processing
+        jp.print();
+    }  
+}
+
+int main() {
+
+    std::vector<std::vector<int>> vvi1 { { 1,2,3,4,5}, { 6,7,8,9,10} }; 
+    std::vector<std::vector<int>> vvi2 { { 11,12,13,14,15}, { 16,17,18,19,20} };
+
+    std::stringstream ss;
+    
+    msgpack::pack(ss, vvi1);
+    msgpack::pack(ss, vvi2);
+
+    char buffer[BUFFERING_SIZE_MAX];
+    std::size_t size = 0;
+
+    json_like_printer jp(1); // set initial buffer size explicitly
+    ref_buffer<json_like_printer> rb(jp);
+
+    while( produce(ss,buffer,size) )
+    {
+        consume(buffer, size, rb, jp);
+    }
+
+}