//
// dup2.cpp
//
//      Copyright (c) Microsoft Corporation. All rights reserved.
//
// Defines _dup2() and _dup2_nolock, which duplicate lowio file handles
//
#include <corecrt_internal_lowio.h>



static int __cdecl dup2_nolock(int const source_fh, int const target_fh) throw()
{
    if ((_osfile(source_fh) & FOPEN) == 0)
    {
        // If the source handle is not open, return an error.  Noe that the
        // DuplicateHandle API will not detect this error, because it implies
        // that _osfhnd(source_fh) == INVALID_HANDLE_VALUE, and this is a 
        // legal HANDLE value to be duplicated.
        errno = EBADF;
        _doserrno = 0;
        _ASSERTE(("Invalid file descriptor. File possibly closed by a different thread",0));
        return -1;
    }

    // If the target is open, close it first.  We ignore the possibility of an
    // error here:  an error simply means that the OS handle value may remain
    // bound for the duration of the process.
    if (_osfile(target_fh) & FOPEN)
    {
        _close_nolock(target_fh);
    }

    // Duplicate the source file onto the target file:
    intptr_t new_osfhandle;

    BOOL const result = DuplicateHandle(
        GetCurrentProcess(),
        reinterpret_cast<HANDLE>(_get_osfhandle(source_fh)),
        GetCurrentProcess(),
        &reinterpret_cast<HANDLE&>(new_osfhandle),
        0,
        TRUE,
        DUPLICATE_SAME_ACCESS);

    if (!result)
    {
        __acrt_errno_map_os_error(GetLastError());
        return -1;
    }

    __acrt_lowio_set_os_handle(target_fh, new_osfhandle);

    // Copy the _osfile information, with the FNOINHERIT bit cleared:
    _osfile(target_fh) = _osfile(source_fh) & ~FNOINHERIT;
    _textmode(target_fh) = _textmode(source_fh);
    _tm_unicode(target_fh) = _tm_unicode(source_fh);

    return 0;
}



// _dup2() makes the target file handle a duplicate of the source file handle,
// so that both handles refer to the same file.  If the target handle is open
// upon entry, it is closed so that it is not leaked.
//
// Returns 0 if successful; returns -1 and sets errno on failure.
extern "C" int __cdecl _dup2(int const source_fh, int const target_fh)
{
    _CHECK_FH_CLEAR_OSSERR_RETURN( source_fh, EBADF, -1 );
    _VALIDATE_CLEAR_OSSERR_RETURN((source_fh >= 0 && (unsigned)source_fh < (unsigned)_nhandle), EBADF, -1);
    _VALIDATE_CLEAR_OSSERR_RETURN((_osfile(source_fh) & FOPEN), EBADF, -1);
    _CHECK_FH_CLEAR_OSSERR_RETURN( target_fh, EBADF, -1 );
    _VALIDATE_CLEAR_OSSERR_RETURN(((unsigned)target_fh < _NHANDLE_), EBADF, -1);

    // Make sure there is an __crt_lowio_handle_data struct corresponding to the target_fh:
    if (target_fh >= _nhandle && __acrt_lowio_ensure_fh_exists(target_fh) != 0)
        return -1;

    // If the source and target are the same, return success (we've already
    // verified that the file handle is open, above).  This is for conformance
    // with the POSIX specification for dup2.
    if (source_fh == target_fh)
        return 0;

    // Obtain the two file handle locks.  In order to prevent deadlock, we
    // always obtain the lock for the lower-numbered file handle first:
    if (source_fh < target_fh)
    {
        __acrt_lowio_lock_fh(source_fh);
        __acrt_lowio_lock_fh(target_fh);
    }
    else if (source_fh > target_fh)
    {
        __acrt_lowio_lock_fh(target_fh);
        __acrt_lowio_lock_fh(source_fh);
    }

    int result = 0;

    __try
    {
        result = dup2_nolock(source_fh, target_fh);
    }
    __finally
    {
        // The order in which we unlock the file handles does not matter:
        __acrt_lowio_unlock_fh(source_fh);
        __acrt_lowio_unlock_fh(target_fh);
    }
    return result;
}