Canonicalize.hs

{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}

-- | Capnproto message canonicalization, per:
--
-- https://capnproto.org/encoding.html#canonicalization
module Capnp.Canonicalize
  ( canonicalize,
    canonicalizeMut,
  )
where

-- Note [Allocation strategy]
--
-- The implementation makes use of knowledge of how we allocate values inside
-- a message; in particular, we assume objects are allocated sequentially,
-- and that if the first segment is big enough we will never allocate a second
-- segment.
--
-- If we ever make the allocator plugable, we will have to revisit this and
-- ensure that our assumptions still hold.

-- Note [Other assumptions]
--
-- This code relies on the fact that Capnp.Pointer.serializePointer does the
-- canonicalization of zero-sized struct pointers for us; see the comments there
-- for more details.

-- import qualified Language.Haskell.TH as TH

import Capnp.Bits (WordCount)
import qualified Capnp.Message as M
import Capnp.Mutability (Mutability (..), unsafeThaw)
import Capnp.TraversalLimit (LimitT)
import qualified Capnp.Untyped as U
import Control.Monad.ST (RealWorld)
import Data.Foldable (for_)
import Data.Maybe (isNothing)
import Data.Traversable (for)
import Data.Word
import Internal.BuildPure (PureBuilder)

-- | Return a canonicalized message with a copy of the given struct as its
-- root. returns a (message, segment) pair, where the segment is the first
-- and only segment of the returned message.
--
-- In addition to the usual reasons for failure when reading a message (traversal limit,
-- malformed messages), this can fail if the message does not fit in a single segment,
-- as the canonical form requires single-segment messages.
canonicalize :: U.RWCtx m s => U.Struct 'Const -> m (M.Message ('Mut s), M.Segment ('Mut s))
canonicalize s = unsafeThaw s >>= canonicalizeMut
{-# SPECIALIZE canonicalize :: U.Struct 'Const -> LimitT IO (M.Message ('Mut RealWorld), M.Segment ('Mut RealWorld)) #-}
{-# SPECIALIZE canonicalize :: U.Struct 'Const -> PureBuilder s (M.Message ('Mut s), M.Segment ('Mut s)) #-}

canonicalizeMut :: U.RWCtx m s => U.Struct ('Mut s) -> m (M.Message ('Mut s), M.Segment ('Mut s))
canonicalizeMut rootStructIn = do
  let msgIn = U.message @U.Struct rootStructIn
  -- Note [Allocation strategy]
  words <- totalWords msgIn
  msgOut <- M.newMessage $ Just words
  rootStructOut <- cloneCanonicalStruct rootStructIn msgOut
  U.setRoot rootStructOut
  segOut <- M.getSegment msgOut 0
  pure (msgOut, segOut)
{-# SPECIALIZE canonicalizeMut :: U.Struct ('Mut RealWorld) -> LimitT IO (M.Message ('Mut RealWorld), M.Segment ('Mut RealWorld)) #-}
{-# SPECIALIZE canonicalizeMut :: U.Struct ('Mut s) -> PureBuilder s (M.Message ('Mut s), M.Segment ('Mut s)) #-}

totalWords :: U.ReadCtx m mut => M.Message mut -> m WordCount
totalWords msg = do
  -- Note [Allocation strategy]
  segCount <- M.numSegs msg
  sizes <- for [0 .. segCount - 1] $ \i -> do
    seg <- M.getSegment msg i
    M.numWords seg
  pure $ sum sizes

cloneCanonicalStruct :: U.RWCtx m s => U.Struct ('Mut s) -> M.Message ('Mut s) -> m (U.Struct ('Mut s))
{-# SPECIALIZE cloneCanonicalStruct :: U.Struct ('Mut RealWorld) -> M.Message ('Mut RealWorld) -> LimitT IO (U.Struct ('Mut RealWorld)) #-}
{-# SPECIALIZE cloneCanonicalStruct :: U.Struct ('Mut s) -> M.Message ('Mut s) -> PureBuilder s (U.Struct ('Mut s)) #-}
cloneCanonicalStruct structIn msgOut = do
  (nWords, nPtrs) <- findCanonicalSectionCounts structIn
  structOut <- U.allocStruct msgOut (fromIntegral nWords) (fromIntegral nPtrs)
  copyCanonicalStruct structIn structOut
  pure structOut

copyCanonicalStruct :: U.RWCtx m s => U.Struct ('Mut s) -> U.Struct ('Mut s) -> m ()
{-# SPECIALIZE copyCanonicalStruct :: U.Struct ('Mut RealWorld) -> U.Struct ('Mut RealWorld) -> LimitT IO () #-}
{-# SPECIALIZE copyCanonicalStruct :: U.Struct ('Mut s) -> U.Struct ('Mut s) -> PureBuilder s () #-}
copyCanonicalStruct structIn structOut = do
  let nWords = fromIntegral $ U.structWordCount structOut
      nPtrs = fromIntegral $ U.structPtrCount structOut
  for_ [0 .. nWords - 1] $ \i -> do
    word <- U.getData i structIn
    U.setData word i structOut
  for_ [0 .. nPtrs - 1] $ \i -> do
    ptrIn <- U.getPtr i structIn
    ptrOut <- cloneCanonicalPtr ptrIn (U.message @U.Struct structOut)
    U.setPtr ptrOut i structOut

findCanonicalSectionCounts :: U.ReadCtx m mut => U.Struct mut -> m (Word16, Word16)
{-# SPECIALIZE findCanonicalSectionCounts :: U.Struct ('Mut RealWorld) -> LimitT IO (Word16, Word16) #-}
{-# SPECIALIZE findCanonicalSectionCounts :: U.Struct ('Mut s) -> PureBuilder s (Word16, Word16) #-}
findCanonicalSectionCounts struct = do
  nWords <- canonicalSectionCount (== 0) (`U.getData` struct) (fromIntegral $ U.structWordCount struct)
  nPtrs <- canonicalSectionCount isNothing (`U.getPtr` struct) (fromIntegral $ U.structPtrCount struct)
  pure (nWords, nPtrs)

canonicalSectionCount :: Monad m => (a -> Bool) -> (Int -> m a) -> Int -> m Word16
canonicalSectionCount _ _ 0 = pure 0
canonicalSectionCount isDefault getIndex total = do
  value <- getIndex (total - 1)
  if isDefault value
    then canonicalSectionCount isDefault getIndex (total - 1)
    else pure $ fromIntegral total

cloneCanonicalPtr :: U.RWCtx m s => Maybe (U.Ptr ('Mut s)) -> M.Message ('Mut s) -> m (Maybe (U.Ptr ('Mut s)))
{-# SPECIALIZE cloneCanonicalPtr :: Maybe (U.Ptr ('Mut RealWorld)) -> M.Message ('Mut RealWorld) -> LimitT IO (Maybe (U.Ptr ('Mut RealWorld))) #-}
{-# SPECIALIZE cloneCanonicalPtr :: Maybe (U.Ptr ('Mut s)) -> M.Message ('Mut s) -> PureBuilder s (Maybe (U.Ptr ('Mut s))) #-}
cloneCanonicalPtr ptrIn msgOut =
  case ptrIn of
    Nothing ->
      pure Nothing
    Just (U.PtrCap cap) -> do
      client <- U.getClient cap
      Just . U.PtrCap <$> U.appendCap msgOut client
    Just (U.PtrStruct struct) ->
      Just . U.PtrStruct <$> cloneCanonicalStruct struct msgOut
    Just (U.PtrList list) ->
      Just . U.PtrList <$> cloneCanonicalList list msgOut

cloneCanonicalList :: U.RWCtx m s => U.List ('Mut s) -> M.Message ('Mut s) -> m (U.List ('Mut s))
{-# SPECIALIZE cloneCanonicalList :: U.List ('Mut RealWorld) -> M.Message ('Mut RealWorld) -> LimitT IO (U.List ('Mut RealWorld)) #-}
{-# SPECIALIZE cloneCanonicalList :: U.List ('Mut s) -> M.Message ('Mut s) -> PureBuilder s (U.List ('Mut s)) #-}
cloneCanonicalList listIn msgOut =
  case listIn of
    U.List0 l -> U.List0 <$> U.allocList0 msgOut (U.length l)
    U.List1 l -> U.List1 <$> (U.allocList1 msgOut (U.length l) >>= copyCanonicalDataList l)
    U.List8 l -> U.List8 <$> (U.allocList8 msgOut (U.length l) >>= copyCanonicalDataList l)
    U.List16 l -> U.List16 <$> (U.allocList16 msgOut (U.length l) >>= copyCanonicalDataList l)
    U.List32 l -> U.List32 <$> (U.allocList32 msgOut (U.length l) >>= copyCanonicalDataList l)
    U.List64 l -> U.List64 <$> (U.allocList64 msgOut (U.length l) >>= copyCanonicalDataList l)
    U.ListPtr l -> U.ListPtr <$> (U.allocListPtr msgOut (U.length l) >>= copyCanonicalPtrList l)
    U.ListStruct l -> U.ListStruct <$> cloneCanonicalStructList l msgOut

copyCanonicalDataList lin lout = do
  U.copyListOf lout lin
  pure lout

copyCanonicalPtrList ::
  U.RWCtx m s =>
  U.ListOf ('U.Ptr 'Nothing) ('Mut s) ->
  U.ListOf ('U.Ptr 'Nothing) ('Mut s) ->
  m (U.ListOf ('U.Ptr 'Nothing) ('Mut s))
{-# SPECIALIZE copyCanonicalPtrList ::
  U.ListOf ('U.Ptr 'Nothing) ('Mut RealWorld) ->
  U.ListOf ('U.Ptr 'Nothing) ('Mut RealWorld) ->
  LimitT IO (U.ListOf ('U.Ptr 'Nothing) ('Mut RealWorld))
  #-}
{-# SPECIALIZE copyCanonicalPtrList ::
  U.ListOf ('U.Ptr 'Nothing) ('Mut s) ->
  U.ListOf ('U.Ptr 'Nothing) ('Mut s) ->
  PureBuilder s (U.ListOf ('U.Ptr 'Nothing) ('Mut s))
  #-}
copyCanonicalPtrList listIn listOut = do
  for_ [0 .. U.length listIn - 1] $ \i -> do
    ptrIn <- U.index i listIn
    ptrOut <- cloneCanonicalPtr ptrIn (U.message @(U.ListOf ('U.Ptr 'Nothing)) listOut)
    U.setIndex ptrOut i listOut
  pure listOut

cloneCanonicalStructList ::
  U.RWCtx m s =>
  U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut s) ->
  M.Message ('Mut s) ->
  m (U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut s))
{-# SPECIALIZE cloneCanonicalStructList ::
  U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut RealWorld) ->
  M.Message ('Mut RealWorld) ->
  LimitT IO (U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut RealWorld))
  #-}
{-# SPECIALIZE cloneCanonicalStructList ::
  U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut s) ->
  M.Message ('Mut s) ->
  PureBuilder s (U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut s))
  #-}
cloneCanonicalStructList listIn msgOut = do
  (nWords, nPtrs) <- findCanonicalListSectionCounts listIn
  listOut <- U.allocCompositeList msgOut nWords nPtrs (U.length listIn)
  copyCanonicalStructList listIn listOut
  pure listOut

copyCanonicalStructList ::
  U.RWCtx m s =>
  U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut s) ->
  U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut s) ->
  m ()
{-# SPECIALIZE copyCanonicalStructList ::
  U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut RealWorld) ->
  U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut RealWorld) ->
  LimitT IO ()
  #-}
{-# SPECIALIZE copyCanonicalStructList ::
  U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut s) ->
  U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut s) ->
  PureBuilder s ()
  #-}
copyCanonicalStructList listIn listOut =
  for_ [0 .. U.length listIn - 1] $ \i -> do
    structIn <- U.index i listIn
    structOut <- U.index i listOut
    copyCanonicalStruct structIn structOut

findCanonicalListSectionCounts ::
  U.ReadCtx m mut =>
  U.ListOf ('U.Ptr ('Just 'U.Struct)) mut ->
  m (Word16, Word16)
{-# SPECIALIZE findCanonicalListSectionCounts ::
  U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut RealWorld) -> LimitT IO (Word16, Word16)
  #-}
{-# SPECIALIZE findCanonicalListSectionCounts ::
  U.ListOf ('U.Ptr ('Just 'U.Struct)) ('Mut s) -> PureBuilder s (Word16, Word16)
  #-}
findCanonicalListSectionCounts list = go 0 0 0
  where
    go i !nWords !nPtrs
      | i >= U.length list =
          pure (nWords, nPtrs)
      | otherwise = do
          struct <- U.index i list
          (nWords', nPtrs') <- findCanonicalSectionCounts struct
          go (i + 1) (max nWords nWords') (max nPtrs nPtrs')

{-
do
    -- Generate specializations for various functions above.
    --
    -- TODO: Figure out why this version doesn't seem to be taking
    -- effect; having the explicit SPECIALIZE pragmas written out
    -- literally results in a 15-20% speedup vs. trying to generate
    -- them with template haskell. But ew.
    --
    -- TODO(cleanup): find some way to group the signature & the specialization together
    -- without duplicating everything.
    let specializations :: [(TH.Name, [TH.TypeQ])]
        specializations =
            [ ( 'copyCanonicalStructList
              , each $ \mutIn mutOut m ->
                    [t| U.ListOf $mutIn (U.Struct $mutIn)
                        -> U.ListOf $mutOut (U.Struct $mutOut) -> $m ()
                    |]
              )
            , ( 'copyCanonicalDataList
              , each $ \mutIn mutOut m -> do
                    a <- pure . TH.VarT <$> TH.newName "a"
                    [t| U.ListOf $mutIn $a -> U.ListOf $mutOut $a -> $m (U.ListOf $mutOut $a) |]
              )
            , ( 'copyCanonicalPtrList
              , each $ \mutIn mutOut m ->
                    [t| U.ListOf $mutIn (Maybe (U.Ptr $mutIn))
                        -> U.ListOf $mutOut (Maybe (U.Ptr $mutOut))
                        -> $m (U.ListOf $mutOut (Maybe (U.Ptr $mutOut)))
                    |]
              )
            , ( 'cloneCanonicalPtr
              , each $ \mutIn mutOut m ->
                    [t| Maybe (U.Ptr $mutIn) -> M.Message $mutOut -> $m (Maybe (U.Ptr $mutOut)) |]
              )
            , ( 'cloneCanonicalList
              , each $ \mutIn mutOut m ->
                    [t| U.List $mutIn -> M.Message $mutOut -> $m (U.List $mutOut) |]
              )
            , ( 'cloneCanonicalStruct
              , each $ \mutIn mutOut m ->
                    [t| U.Struct $mutIn -> M.Message $mutOut -> $m (U.Struct $mutOut) |]
              )
            , ( 'copyCanonicalStruct
              , each $ \mutIn mutOut m ->
                    [t| U.Struct $mutIn -> U.Struct $mutOut -> $m () |]
              )
            ]
        each f = do
            let s = pure $ TH.VarT (TH.mkName "s")
            (m, s) <- [ ( [t| LimitT IO |], [t| RealWorld |] )
                      , ( [t| PureBuilder $s |], s )
                      ]
            mutIn <- [ [t| 'Const |], [t| 'Mut $s |] ]
            pure $ f mutIn [t| 'Mut $s |] m
{-
            map
                (\t -> f t [t| 'Mut RealWorld |] [t| LimitT IO |])
                [ [t| 'Const |], [t| 'Mut RealWorld |] ]
-}
    concat <$> for specializations (\(name, types) -> do
        for types $ \mkType -> do
            t <- mkType
            pure $ TH.PragmaD $ TH.SpecialiseP name t Nothing TH.AllPhases)
-}