The user manual for ifort 2015 Update 4 subroutine PXFFILENO suggests that in the Windows OS, I can get the file descriptor (handle returned from CreateFile) associated with a Fortran File Unit number. I tried the following code accordingly:
CALL PXFPOSIXIO (1,iold,ierror)
CALL PXFFILENO (10,fd,ierror)
extern "C" __declspec(dllexport) void* UOPEN(
_In_ char* lpFileName,
_In_ DWORD dwDesiredAccess,
_In_ DWORD dwShareMode,
_In_opt_ LPSECURITY_ATTRIBUTES lpSecurityAttributes,
_In_ DWORD dwCreationDisposition,
_In_ DWORD dwFlagsAndAttributes,
_In_opt_ HANDLE hTemplateFile,
_In_ int& UNIT)//,
// _In_ int& FLEN)
BOOL bResult1 = CreatePipe(&hReadPipe, &hWritePipe, 0, 100000000);//100e6
DWORD err1 = GetLastError();
//HANDLE hMapping = CreateMailslot(L"Some super cool mailslot for MAAP", 0, 1000000, 0);
// PAGE_READWRITE | SEC_COMMIT
char*Bytes = new char;//100e6
for (int i = 0; i < 99000000; ++i)
Bytes = 'n';
BOOL bResult = WriteFile(hWritePipe, Bytes, 99000000, &bytesWritten, 0);
DWORD err = GetLastError();
//HANDLE hProcess = GetCurrentProcess();
//DuplicateHandle(hProcess, hResult, hProcess, &hFile, 0, FALSE, DUPLICATE_SAME_ACCESS);
//hFile = hResult;
I know that hWritePipe is 0x88, so I would expect fd to be 0x88. However, fd comes back as 3. That is not a valid handle. So, what am I doing wrong? Is the description in the user manual wrong? I very desparately want that handle in the Fortran code to avoid writing spaghetti code.
Your header for UOPN doesn't match the documentation for arguments that are passed by reference, but you don't use these so it probably doesn't matter. I'll admit that I have never played with POSIX I/O so there may be an issue with that. I am playing with some examples and will let you know what I find.
In the intel fortran documentation (Fortran Compiler 15.0), there is mention of pipe I/O in a few places, but there doesn't seem to be a clear definition of whether fortran statements like open, close, read, write can be applied to a pipe. Maybe I haven't found the right section.
Most I/O operations involve a disk file, keyboard, or screen display. Other devices can also be used:
Sockets can be read from or written to if a USEROPEN routine (usually written in C) is used to open the socket.
Pipes opened for read and write access block (wait until data is available) if you issue a READ to an empty pipe.
Pipes opened for read-only access return EOF if you issue a READ to an empty pipe.
Scott - the key "missing" piece is that Fortran talks to the underlying operating system. In Windows, it creates, and talks to the Windows handles. So, in my example, I was able to connect Fortran Unit 10 to a Windows handle of my own choosing that represents a pipe. That handle could have been anything, I just chose a pipe. The reason it works is because it's the kind of handle with which you (or Fortran runtime) can call WriteFile (just like you can call WriteFile with the handle you get if you open a file on a disk), and I'm using a WRITE statement. This is probably easier to follow if you're familiar with the relevant parts of the Windows API.
I have part of the answer to this. The POSIX File Descriptor is NOT a Windows file handle and the documentation doesn't say it is. Unfortunately, there doesn't seem to be a way to convert a POSIX File Descriptor to a Windows handle.