WebExtension: Native wrapper: replace TEMPFILE with file path,

And return it. In preparation for a “View database” feature in the
WebExtension.

browser-plugins/webextension/native-wrapper/CMakeLists.txt

@@ -4,6 +4,7 @@ set(INSTALL_MOZILLA_NMH_DIR
   "${CMAKE_INSTALL_PREFIX}/${MOZILLA_NMH_DIR}")
 
 add_executable(${PROJECT_NAME}_wrapper ${PROJECT_NAME}_wrapper.cpp)
+target_link_libraries(${PROJECT_NAME}_wrapper stdc++fs)
 install(TARGETS ${PROJECT_NAME}_wrapper DESTINATION ${MOZILLA_NMH_DIR})
 
 add_custom_command(

browser-plugins/webextension/native-wrapper/remwharead_wrapper.cpp

@@ -16,6 +16,7 @@
 
 #include <string>
 #include <iostream>
+#include <experimental/filesystem>
 #include <cstdint>
 #include <cstdlib>
 #include <sys/wait.h>
@@ -26,6 +27,8 @@ using std::cout;
 using std::uint32_t;
 using std::system;
 
+namespace fs = std::experimental::filesystem;
+
 const string read_input()
 {
     string input;
@@ -75,12 +78,36 @@ int launch(const string &args)
 
 int main()
 {
-    const string args = read_input();
+    string args = read_input();
+    size_t pos = args.find("TEMPFILE");
+    string tmpfile;
+
+    if (pos != string::npos)
+    {
+        try
+        {
+            tmpfile = fs::temp_directory_path() / "remwharead.html";
+            args.replace(pos, 8, tmpfile);
+        }
+        catch (const fs::filesystem_error &e)
+        {
+            send_message("Could not create temporary file.");
+            return 3;
+        }
+    }
+
     int ret = launch(args);
 
     if (ret == 0)
     {
-        send_message("Command successful.");
+        if (!tmpfile.empty())
+        {
+            send_message("FILE:" + tmpfile);
+        }
+        else
+        {
+            send_message("Command successful.");
+        }
     }
     else
     {