Need SetFilePointerEx

[vinniefalco]

I'll add it, this is a reminder

[vinniefalco]

This is not as easy as I thought, I added these two items in the correct place:

BOOST_SYMBOL_IMPORT boost::detail::winapi::BOOL_ WINAPI
SetFilePointerEx(
    boost::detail::winapi::HANDLE_ hFile,
    boost::detail::winapi::LARGE_INTEGER_ lpDistanceToMove,
    boost::detail::winapi::PLARGE_INTEGER_ lpNewFilePointer,
    boost::detail::winapi::DWORD_ dwMoveMethod);

and

using ::SetFilePointerEx;

But I get an error:

1>C:\Program Files (x86)\Windows Kits\10\Include\10.0.15063.0\um\fileapi.h(1112): error C2733: 'SetFilePointerEx': second C linkage of overloaded function not allowed
1>C:\Users\vinnie\lib\boost_1_64_0\boost/detail/winapi/file_management.hpp(162): note: see declaration of 'SetFilePointerEx'

Oddly, SetFilePointer works fine and they look quite similar.

[Lastique]

It can't be added without including windows.h because the function takes LARGE_INTEGER by value, which requires it to be defined. It cannot be defined in Boost.WinAPI because that will result in conflicts when windows.h is also included.

The error you're seeing is because Windows SDK declares the function with ::LARGE_INTEGER type and boost::detail::winapi::LARGE_INTEGER_ is a different type (although declared to have the same binary layout as ::LARGE_INTEGER). It works for other functions that take LARGE_INTEGER by pointer because we can just cast the pointer before forwarding the call, but it doesn't work if the function takes it by value.

[vinniefalco]

How do you feel about this

inline
boost::detail::winapi::BOOL_
set_file_pointer_ex(
    boost::detail::winapi::HANDLE_ hFile,
    boost::detail::winapi::LARGE_INTEGER_ lpDistanceToMove,
    boost::detail::winapi::PLARGE_INTEGER_ lpNewFilePointer,
    boost::detail::winapi::DWORD_ dwMoveMethod)
{
    auto dwHighPart = lpDistanceToMove.u.HighPart;
    auto dwLowPart = boost::detail::winapi::SetFilePointer(
        hFile,
        lpDistanceToMove.u.LowPart,
        &dwHighPart,
        dwMoveMethod);
    if(dwLowPart == boost::detail::winapi::INVALID_SET_FILE_POINTER_)
        return 0;
    if(lpNewFilePointer)
    {
        lpNewFilePointer->u.LowPart = dwLowPart;
        lpNewFilePointer->u.HighPart = dwHighPart;
    }
    return 1;
}

[Lastique]

This doesn't work if the position is beyond 4 GiB, right? This may be ok for some applications and not ok for others.

In general, Boost.WinAPI does not contain any logic or tries to emulate the missing API. I think this kind of code is better placed in the user's code.

[vinniefalco]

It should work for large files. I agree that Boost should not try to emulate it - thanks.