dn_comp/dn_expand example add

Author: Artiom N.

src/book01/ch02/cpp/CMakeLists.txt

@@ -5,4 +5,5 @@ add_subdirectory(ip_convert)
 
 if (NOT WIN32)
 	add_subdirectory(net_db)
+	add_subdirectory(dn_comp_expand)
 endif()

src/book01/ch02/cpp/dn_comp_expand/CMakeLists.txt

@@ -0,0 +1,5 @@
+cmake_minimum_required(VERSION 3.10)
+
+project("${CHAPTER_NAME}dn-comp-expand" C CXX)
+
+add_executable("${PROJECT_NAME}" main.cpp)

src/book01/ch02/cpp/dn_comp_expand/main.cpp

@@ -0,0 +1,41 @@
+extern "C"
+{
+#include <arpa/nameser.h>
+#include <netinet/in.h>
+#include <resolv.h>
+}
+
+#include <array>
+#include <iostream>
+
+
+int main()
+{
+    std::array<unsigned char, 256> buf;
+    unsigned char *dnptrs = nullptr;
+    unsigned char *lastdnptr = nullptr;
+
+    if (auto result = dn_comp("www.google.com", buf.data(), buf.size(), &dnptrs, &lastdnptr); result != -1)
+    {
+        std::cout << "Len = " << result << "\n"
+                  << std::string(buf.begin(), buf.begin() + result) << "\n"
+                  << "DP = " << (dnptrs ? reinterpret_cast<const char *>(dnptrs) : "nullptr") << "\n"
+                  << "LDP = " << (lastdnptr ? reinterpret_cast<const char *>(lastdnptr) : "nullptr") << std::endl;
+
+        std::array<char, 256> exp_buf;
+
+        if ((result = dn_expand(buf.data(), buf.data() + result, buf.data(), exp_buf.data(), exp_buf.size())) != -1)
+        {
+            std::cout << "Len = " << result << "\n"
+                      << std::string(exp_buf.begin(), exp_buf.begin() + result) << "\n"
+                      << std::endl;
+            return EXIT_SUCCESS;
+        }
+
+        perror("dn_expand");
+        return EXIT_FAILURE;
+    }
+    perror("dn_comp");
+
+    return EXIT_FAILURE;
+}