does WriteFile post a completion packet on finishing immediately when using io completion ports

I know that when WSARecv is used with it may finishes immediately and in such case a completion packet will still be posted and this behavior can be altered using SetFileCompletionNotificationModes

but I want to know the case for files and pipes with WriteFile , if I used iocp to make async reads and writes and an operation has finished immediately will the same behavior take place ? or I have to handle this ?

exist common behavior for all asynchronous api, it implicit described in CancelThreadpoolIo function

note, by design we need call CancelThreadpoolIo when and only when will not notify to the I/O completion port and the associated I/O callback function will not be called.

you must call the CancelThreadpoolIo function for either of the following scenarios:

• An overlapped (asynchronous) I/O operation fails (that is, the asynchronous I/O function call returns failure with an error code
  other than ERROR_IO_PENDING).
• An asynchronous I/O operation returns immediately with success and the file handle associated with the I/O completion object has the
  notification mode FILE_SKIP_COMPLETION_PORT_ON_SUCCESS. The file
  handle will not notify the I/O completion port and the associated I/O callback function will not be called.

so let dwErrorCode error code returned by api (NOERROR if win32 api return TRUE)

the next function say you - will be or not notify to IOCP

bool IsWillBeNotification(ULONG dwErrorCode, BOOL bSkipCompletionPortMode)
{
    switch (dwErrorCode)
    {
    case ERROR_IO_PENDING:
        return true;
    case NOERROR:
        return !bSkipCompletionPortMode;
    default:
        return false;
    }
}

in case we use native API and NTSTATUS

bool IsWillBeNotification(NTSTATUS status, BOOL bSkipCompletionPortMode)
{
    return (status == STATUS_PENDING) || (!NT_ERROR(status) && !bSkipCompletionPortMode);
}

so:

• if STATUS_PENDING - will be IOCP packet
• if NT_ERROR(status) - will be no packet (status in range [0xC0000000, 0xFFFFFFFF] )
• otherwise based on bSkipCompletionPortMode - will be if it not set

note that this is general rule for any asynchronous io api. only NtLockFile/LockFileEx - exception from this rule - can be IOCP notification even if api just fail, due to error inside NtLockFile implementation