{-# LANGUAGE ForeignFunctionInterface #-}

-- | Low-level interface to @XenCtrl@. Each function defined in this module is
-- a ffi call to corresponding c function.

module System.Xen.Low
    (
    -- * Interface
      xc_interface_open
    , xc_interface_close
    -- * Domain
    , xc_domain_getinfo
    -- ** Domain pause
    , xc_domain_pause
    , xc_domain_unpause
    -- ** Domain powerstate
    , xc_domain_shutdown
    , xc_domain_destroy
    ) where

#include <xenctrl.h>

import Foreign.C (CInt(..), CUInt(..))
#if XEN_SYSCTL_INTERFACE_VERSION == 8
import Foreign.C (CIntPtr(..))
#endif
import Foreign.Ptr (Ptr)

import System.Xen.Types (XcHandle(..), DomainInfo(..), DomId(..))

-- | This function opens the handle to the hypervisor interface. Each successful call
--  to this function should have a corresponding call to 'xc_interface_close'.
foreign import ccall unsafe "xc_interface_open"
-- There are some changes in xen 4 in comparsion with 3, 'XcHandle' is not a
-- file descriptor, but a pointer to special structure.
#if XEN_SYSCTL_INTERFACE_VERSION == 8
    xc_interface_open :: CInt  -- ^ Logger, @NULL@ if stderr
                      -> CInt  -- ^ Domain builder logger
                      -> CInt  -- ^ Open flags
                      -> IO XcHandle
#elif XEN_SYSCTL_INTERFACE_VERSION == 6
    xc_interface_open :: IO XcHandle
#endif

-- | This function closes an open hypervisor interface. This function can fail if the
-- handle does not represent an open interface or if there were problems closing the
-- interface. In the latter case the interface is still closed.
foreign import ccall unsafe "xc_interface_close"
    xc_interface_close :: XcHandle -> IO CInt

-- | This function will return information about one or more domains. It is
-- designed to iterate over the list of domains. If a single domain is
-- requested, this function will return the next domain in the list - if
-- one exists. It is, therefore, important in this case to make sure the
-- domain requested was the one returned.
foreign import ccall unsafe "xenctrl.h xc_domain_getinfo"
    xc_domain_getinfo :: XcHandle        -- ^ Handle to the open hypervisor interface
                      -> DomId           -- ^ First domain to enumerate from.
                      -> CUInt           -- ^ The number of requested domains
                      -> Ptr DomainInfo  -- ^ Pointer to the structure that will
                                         -- contain the information for
                                         -- enumerated domains
                      -> IO CInt         -- ^ Number of domains enumerated, -1 on error

-- | This function pauses a domain. A paused domain still exists in memory
-- however it does not receive any timeslices from the hypervisor.
foreign import ccall unsafe "xenctrl.h xc_domain_pause"
    xc_domain_pause :: XcHandle -- ^ Handle to the open hypervisor interface
                    -> DomId    -- ^ Domain to pause
                    -> IO CInt  -- ^ 0 if success, -1 if error

-- | This function unpauses a domain. The domain should have been previously paused.
foreign import ccall unsafe "xenctrl.h xc_domain_unpause"
    xc_domain_unpause :: XcHandle -- ^ Handle to the open hypervisor interface
                      -> DomId    -- ^ Domain to unpause
                      -> IO CInt  -- ^ 0 if success, -1 if error

-- | This function will shutdown a domain. This is intended for use in
-- fully-virtualized domains where this operation is analogous to the
-- sched_op operations in a paravirtualized domain.
foreign import ccall unsafe "xenctrl.h xc_domain_shutdown"
    xc_domain_shutdown :: XcHandle -- ^ Handle to the open hypervisor interface
                       -> DomId    -- ^ Domain to shutdown
                       -> CInt     -- ^ Shutdown reason
                       -> IO CInt  -- ^ 0 if success, -1 if error

-- | This function will destroy a domain. Destroying a domain removes the domain
-- completely from memory. This function should be called after sending the
-- domain a SHUTDOWN control message to free up the domain resources.
foreign import ccall unsafe "xenctrl.h xc_domain_destroy"
    xc_domain_destroy :: XcHandle -- ^ Handle to the open hypervisor interface
                      -> DomId    -- ^ Domain to destroy
                      -> IO CInt  -- ^ 0 if success, -1 if error