CodeDweller/child.cpp

// child.cpp
// Copyright (C) 2014 MicroNeil Research Corporation.
//
// This program is part of the MicroNeil Research Open Library Project. For
// more information go to http://www.microneil.com/OpenLibrary/index.html
//
// This program is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2 of the License, or (at your
// option) any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
// more details.
//
// You should have received a copy of the GNU General Public License along with
// this program; if not, write to the Free Software Foundation, Inc., 59 Temple
// Place, Suite 330, Boston, MA 02111-1307 USA
//==============================================================================

#include <iostream> // Temporary.

#include <stdexcept>

#include "child.hpp"

namespace CodeDweller {

  Child::Child(std::vector<std::string> args) {

    init();

    if (args.size() == 0) {
      //
    } else if (args.size() == 1) {
      cmdline = args[0];
      return;
    }

    // Append all but last command-line arguments.
    for (size_t i = 0; i < args.size() - 1; i++) {
      cmdline += args[i] + " ";
    }
    cmdline += args.back(); // Append last command-line argument.
  }

  Child::Child(std::string childpath) :
    cmdline(childpath) {
    init();
  }

  Child::~Child() {
  }

  void
  Child::init() {
    exitCodeObtainedFlag = false;
    exitCode = 0;
  }

  std::istream *
  Child::reader() {
    return new std::istream(std::cin.rdbuf());
  }

  std::ostream *
  Child::writer() {
    return new std::ostream(std::cout.rdbuf());
  }

  void
  Child::run() {

    // Set the bInheritHandle flag so pipe handles are inherited. 
   SECURITY_ATTRIBUTES securityAttributes; 

   securityAttributes.nLength = sizeof(SECURITY_ATTRIBUTES); 
   securityAttributes.bInheritHandle = true; 
   securityAttributes.lpSecurityDescriptor = NULL; 

   // Create a pipe for the child process's STDOUT.
   HANDLE childStdOutAtChild;
   HANDLE childStdInAtChild;
   int bufferSize = 0;

   if (!CreatePipe(&childStdOutAtParent,
		   &childStdOutAtChild,
		   &securityAttributes,
		   bufferSize)) {
     throw std::runtime_error("Error from CreatePipe for stdout:  " +
			      getErrorText());
   }

   // Ensure the read handle to the pipe for STDOUT is not inherited.
   int inheritFlag = 0;
   if (!SetHandleInformation(childStdOutAtParent,
			     HANDLE_FLAG_INHERIT,
			     inheritFlag) ) {
     throw std::runtime_error("Error from GetHandleInformation for stdout:  " +
			      getErrorText());
   }

   // Create a pipe for the child process's STDIN. 
   if (! CreatePipe(&childStdInAtChild,
		    &childStdInAtParent,
		    &securityAttributes,
		    bufferSize)) {
     throw std::runtime_error("Error from CreatePipe for stdin:  " +
			      getErrorText());
   }

   // Ensure the write handle to the pipe for STDIN is not inherited. 
   if (!SetHandleInformation(childStdInAtParent,
			     HANDLE_FLAG_INHERIT,
			     inheritFlag)) {
     throw std::runtime_error("Error from GetHandleInformation for stdin:  " +
			      getErrorText());
   }
 
  // Set up members of the PROCESS_INFORMATION structure. 
  PROCESS_INFORMATION processInfo; 

  std::fill((char *) &processInfo,
	    ((char *) &processInfo) + sizeof(PROCESS_INFORMATION),
	    0);
 
  // Set up members of the STARTUPINFO structure.  This structure
  // specifies the STDIN and STDOUT handles for redirection.
  STARTUPINFO startInfo;

  std::fill((char *) &startInfo,
	    ((char *) &startInfo) + sizeof(STARTUPINFO),
	    0);
   startInfo.cb = sizeof(STARTUPINFO); 
   startInfo.hStdError = childStdOutAtChild;
   startInfo.hStdOutput = childStdOutAtChild;
   startInfo.hStdInput = childStdInAtChild;
   startInfo.dwFlags |= STARTF_USESTDHANDLES;
 
   // Create the child process. 
   bool createSuccess;
 
   createSuccess = CreateProcess(NULL, 
				 (char *) cmdline.c_str(), // command line 
				 NULL,         	  // process security attributes 
				 NULL,         	  // primary thread security attributes 
				 true,         	  // handles are inherited 
				 0,            	  // creation flags 
				 NULL,         	  // use parent's environment 
				 NULL,         	  // use parent's current directory 
				 &startInfo,   	  // STARTUPINFO pointer 
				 &processInfo);	  // receives PROCESS_INFORMATION 
   
   // If an error occurs, exit the application. 
   if (!createSuccess ) {
     throw std::runtime_error("Error from CreateProcess with "
			      "command line \"" + cmdline + "\":  " +
			      getErrorText());
   }

   // Save the handles to the child process and its primary thread.
   childProcess = processInfo.hProcess;
   childThread = processInfo.hThread;

   // Close the child's end of the pipes.
   CloseHandle(childStdOutAtChild);
   CloseHandle(childStdInAtChild);

  }

  void
  Child::terminate() {

    if (!TerminateProcess(childProcess, terminateExitCode)) {
      throw std::runtime_error("Error terminating the child process:  " +
			       getErrorText());
    }

  }

  int32_t
  Child::result() {

    int result;

    if (!GetExitCodeProcess(childProcess, (LPDWORD) &result)) {
      throw std::runtime_error("Error getting child process exit code:  " +
			       getErrorText());
    }

    return result;
  }

  std::string
  Child::getErrorText() {

    LPVOID winMsgBuf;
    DWORD lastError = GetLastError(); 

    FormatMessage(
		  FORMAT_MESSAGE_ALLOCATE_BUFFER | 
		  FORMAT_MESSAGE_FROM_SYSTEM |
		  FORMAT_MESSAGE_IGNORE_INSERTS,
		  NULL,
		  lastError,
		  MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
		  (char *) &winMsgBuf,
		  0, NULL );

    std::string errMsg((char *) winMsgBuf);

    LocalFree(winMsgBuf);
    return errMsg;
  }

}