Implement pushing of MIME data to Jupyter.

tools/Jupyter/kernel/tools/Jupyter/Kernel.cpp

@@ -2,9 +2,63 @@
 // Created by Axel Naumann on 09/12/15.
 //
 
+//#include "cling/Interpreter/Jupyter/Kernel.h"
+
 #include "cling/Interpreter/Interpreter.h"
 #include "cling/Interpreter/Value.h"
 
+#include <map>
+#include <string>
+
+namespace cling {
+  namespace Jupyter {
+    struct MIMEDataRef {
+      const char* m_Data;
+      const long m_Size;
+
+      MIMEDataRef(const std::string& str):
+      m_Data(str.c_str()), m_Size((long)str.length() + 1) {}
+      MIMEDataRef(const char* str):
+      MIMEDataRef(std::string(str)) {}
+      MIMEDataRef(const char* data, long size):
+      m_Data(data), m_Size(size) {}
+    };
+
+    /// Push MIME stuff to Jupyter. To be called from user code.
+    ///\param contentDict - dictionary of MIME type versus content. E.g.
+    /// {{"text/html", {"<div></div>", }}
+    void pushOutput(const std::map<std::string, MIMEDataRef> contentDict) {
+      FILE* outpipe = popen("???", "w");
+
+      // Pipe sees (all numbers are longs, except for the first:
+      // - num bytes in a long (sent as a single unsigned char!)
+      // - num elements of the MIME dictionary; Jupyter selects one to display.
+      // For each MIME dictionary element:
+      //   - MIME type as 0-terminated string
+      //   - size of MIME data buffer (including the terminating 0 for
+      //     0-terminated strings)
+      //   - MIME data buffer
+
+      // Write number of dictionary elements (and the size of that number in a
+      // char)
+      unsigned char sizeLong = sizeof(long);
+      fwrite(&sizeLong, 1, 1, outpipe);
+      long dictSize = contentDict.size();
+      fwrite(&dictSize, sizeof(long), 1, outpipe);
+
+      for (auto iContent: contentDict) {
+        const std::string& mimeType = iContent.first;
+        fwrite(mimeType.c_str(), mimeType.size() + 1, 1, outpipe);
+        const MIMEDataRef& mimeData = iContent.second;
+        fwrite(&mimeData.m_Size, sizeof(long), 1, outpipe);
+        fwrite(mimeData.m_Data, mimeData.m_Size, 1, outpipe);
+      }
+
+      pclose(outpipe);
+    }
+  } // namespace Jupyter
+} // namespace cling
+
 extern "C" {
 ///\{
 ///\name Cling4CTypes
@@ -14,7 +68,8 @@ extern "C" {
 using TheInterpreter = void ;
 
 /// Create an interpreter object.
-TheInterpreter *cling_create(int argc, const char *argv[], const char* llvmdir) {
+TheInterpreter*
+cling_create(int argc, const char *argv[], const char* llvmdir) {
   auto interp = new cling::Interpreter(argc, argv, llvmdir);
   return interp;
 }
@@ -34,8 +89,10 @@ int cling_eval(TheInterpreter *interpVP, const char *code) {
   cling::Interpreter::CompilationResult Res = interp->process(code /*, V*/);
   if (Res != cling::Interpreter::kSuccess)
     return 1;
+  cling::Jupyter::pushOutput({{"text/html", "You just executed C++ code!"}});
   return 0;
 }
+
 ///\}
 
 } // extern "C"