{-# LANGUAGE CPP #-}
-- |
-- Module      : Streamly.Internal.Data.Array
-- Copyright   : (c) 2019 Composewell Technologies
--
-- License     : BSD3
-- Maintainer  : streamly@composewell.com
-- Stability   : experimental
-- Portability : GHC
--
module Streamly.Internal.Data.Array
    (
    -- * Setup
    -- $setup

    -- * Design Notes
    -- $design

    -- * The Array Type
      Array

    -- * Construction

    -- Pure List APIs
    , A.fromListN
    , A.fromList

    -- Stream Folds
    , fromStreamN
    , fromStream

    -- Monadic Folds
    , A.writeN      -- drop new
    , A.writeNAligned
    , A.write       -- full buffer
    , writeLastN

    -- * Elimination
    -- ** Conversion
    , A.toList

    -- ** Streams
    , A.read
    , A.readRev

    -- ** Unfolds
    , reader
    , readerUnsafe
    , A.readerRev
    , producer -- experimental

    -- * Random Access
    -- , (!!)
    , getIndex
    , A.unsafeIndex -- XXX Rename to getIndexUnsafe??
    , getIndexRev
    , last           -- XXX getIndexLast?
    , getIndices
    , getIndicesFromThenTo
    -- , getIndicesFrom    -- read from a given position to the end of file
    -- , getIndicesUpto    -- read from beginning up to the given position
    -- , getIndicesFromTo
    -- , getIndicesFromRev  -- read from a given position to the beginning of file
    -- , getIndicesUptoRev  -- read from end to the given position in file

    -- * Size
    , length
    , null

    -- * Search
    , binarySearch
    , findIndicesOf
    -- , findIndexOf
    -- , find

    -- * Casting
    , cast
    , asBytes
    , castUnsafe
    , asPtrUnsafe
    , asCStringUnsafe
    , A.unsafeFreeze -- asImmutableUnsafe?
    , A.unsafeThaw   -- asMutableUnsafe?

    -- * Subarrays
    , getSliceUnsafe
    -- , getSlice
    , genSlicesFromLen
    , getSlicesFromLen
    , splitOn

    -- * Streaming Operations
    , streamTransform

    -- ** Folding
    , streamFold
    , fold

    -- * Deprecated
    , A.toStream
    , A.toStreamRev
    )
where

#include "inline.hs"
#include "ArrayMacros.h"

import Control.Exception (assert)
import Control.Monad (when)
import Control.Monad.IO.Class (MonadIO(..))
import Data.Functor.Identity (Identity)
import Data.Proxy (Proxy(..))
import Data.Word (Word8)
import Foreign.C.String (CString)
import Foreign.Ptr (castPtr)
import Foreign.Storable (Storable)
import Streamly.Internal.Data.Unboxed
    ( Unbox
    , peekWith
    , sizeOf
    )
import Prelude hiding (length, null, last, map, (!!), read, concat)

import Streamly.Internal.Data.Array.Mut.Type (ArrayUnsafe(..))
import Streamly.Internal.Data.Array.Type
    (Array(..), length, asPtrUnsafe)
import Streamly.Internal.Data.Fold.Type (Fold(..))
import Streamly.Internal.Data.Producer.Type (Producer(..))
import Streamly.Internal.Data.Stream.StreamD (Stream)
import Streamly.Internal.Data.Tuple.Strict (Tuple3Fused'(..))
import Streamly.Internal.Data.Unfold.Type (Unfold(..))
import Streamly.Internal.System.IO (unsafeInlineIO)

import qualified Streamly.Internal.Data.Array.Mut.Type as MA
import qualified Streamly.Internal.Data.Array.Mut as MA
import qualified Streamly.Internal.Data.Array.Type as A
import qualified Streamly.Internal.Data.Fold as FL
import qualified Streamly.Internal.Data.Producer.Type as Producer
import qualified Streamly.Internal.Data.Producer as Producer
import qualified Streamly.Internal.Data.Ring.Unboxed as RB
import qualified Streamly.Internal.Data.Stream.StreamD as D
import qualified Streamly.Internal.Data.Stream.StreamD as Stream
import qualified Streamly.Internal.Data.Unfold as Unfold

#include "DocTestDataArray.hs"

-- $design
--
-- To summarize:
--
--  * Arrays are finite and fixed in size
--  * provide /O(1)/ access to elements
--  * store only data and not functions
--  * provide efficient IO interfacing
--
-- 'Foldable' instance is not provided because the implementation would be much
-- less efficient compared to folding via streams.  'Semigroup' and 'Monoid'
-- instances should be used with care; concatenating arrays using binary
-- operations can be highly inefficient.  Instead, use
-- 'Streamly.Internal.Data.Stream.Chunked.toArray' to concatenate N
-- arrays at once.
--
-- Each array is one pointer visible to the GC.  Too many small arrays (e.g.
-- single byte) are only as good as holding those elements in a Haskell list.
-- However, small arrays can be compacted into large ones to reduce the
-- overhead. To hold 32GB memory in 32k sized buffers we need 1 million arrays
-- if we use one array for each chunk. This is still significant to add
-- pressure to GC.

-------------------------------------------------------------------------------
-- Construction
-------------------------------------------------------------------------------

-- | Create an 'Array' from the first N elements of a stream. The array is
-- allocated to size N, if the stream terminates before N elements then the
-- array may hold less than N elements.
--
-- /Pre-release/
{-# INLINE fromStreamN #-}
fromStreamN :: (MonadIO m, Unbox a) => Int -> Stream m a -> m (Array a)
fromStreamN :: forall (m :: * -> *) a.
(MonadIO m, Unbox a) =>
Int -> Stream m a -> m (Array a)
fromStreamN Int
n Stream m a
m = do
    forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (Int
n forall a. Ord a => a -> a -> Bool
< Int
0) forall a b. (a -> b) -> a -> b
$ forall a. HasCallStack => [Char] -> a
error [Char]
"writeN: negative write count specified"
    forall (m :: * -> *) a.
(MonadIO m, Unbox a) =>
Int -> Stream m a -> m (Array a)
A.fromStreamDN Int
n Stream m a
m

-- | Create an 'Array' from a stream. This is useful when we want to create a
-- single array from a stream of unknown size. 'writeN' is at least twice
-- as efficient when the size is already known.
--
-- Note that if the input stream is too large memory allocation for the array
-- may fail.  When the stream size is not known, `chunksOf` followed by
-- processing of indvidual arrays in the resulting stream should be preferred.
--
-- /Pre-release/
{-# INLINE fromStream #-}
fromStream :: (MonadIO m, Unbox a) => Stream m a -> m (Array a)
fromStream :: forall (m :: * -> *) a.
(MonadIO m, Unbox a) =>
Stream m a -> m (Array a)
fromStream = forall (m :: * -> *) a b.
Monad m =>
Fold m a b -> Stream m a -> m b
Stream.fold forall (m :: * -> *) a. (MonadIO m, Unbox a) => Fold m a (Array a)
A.write
-- write m = A.fromStreamD $ D.fromStreamK m

-------------------------------------------------------------------------------
-- Elimination
-------------------------------------------------------------------------------

{-# INLINE_NORMAL producer #-}
producer :: forall m a. (Monad m, Unbox a) => Producer m (Array a) a
producer :: forall (m :: * -> *) a.
(Monad m, Unbox a) =>
Producer m (Array a) a
producer =
    forall (m :: * -> *) a c b.
Functor m =>
(a -> c) -> (c -> a) -> Producer m c b -> Producer m a b
Producer.translate forall a. Array a -> MutArray a
A.unsafeThaw forall a. MutArray a -> Array a
A.unsafeFreeze
        forall a b. (a -> b) -> a -> b
$ forall (m :: * -> *) a.
(Monad m, Unbox a) =>
(forall b. IO b -> m b) -> Producer m (MutArray a) a
MA.producerWith (forall (m :: * -> *) a. Monad m => a -> m a
return forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a. IO a -> a
unsafeInlineIO)

-- | Unfold an array into a stream.
--
{-# INLINE_NORMAL reader #-}
reader :: forall m a. (Monad m, Unbox a) => Unfold m (Array a) a
reader :: forall (m :: * -> *) a. (Monad m, Unbox a) => Unfold m (Array a) a
reader = forall (m :: * -> *) a b. Producer m a b -> Unfold m a b
Producer.simplify forall (m :: * -> *) a.
(Monad m, Unbox a) =>
Producer m (Array a) a
producer

-- | Unfold an array into a stream, does not check the end of the array, the
-- user is responsible for terminating the stream within the array bounds. For
-- high performance application where the end condition can be determined by
-- a terminating fold.
--
-- Written in the hope that it may be faster than "read", however, in the case
-- for which this was written, "read" proves to be faster even though the core
-- generated with unsafeRead looks simpler.
--
-- /Pre-release/
--
{-# INLINE_NORMAL readerUnsafe #-}
readerUnsafe :: forall m a. (Monad m, Unbox a) => Unfold m (Array a) a
readerUnsafe :: forall (m :: * -> *) a. (Monad m, Unbox a) => Unfold m (Array a) a
readerUnsafe = forall (m :: * -> *) a b s.
(s -> m (Step s b)) -> (a -> m s) -> Unfold m a b
Unfold forall {m :: * -> *} {a} {a} {a}.
(Monad m, Unbox a) =>
ArrayUnsafe a -> m (Step (ArrayUnsafe a) a)
step forall {m :: * -> *} {a} {a}.
Monad m =>
Array a -> m (ArrayUnsafe a)
inject
    where

    inject :: Array a -> m (ArrayUnsafe a)
inject (Array MutableByteArray
contents Int
start Int
end) =
        forall (m :: * -> *) a. Monad m => a -> m a
return (forall a. MutableByteArray -> Int -> Int -> ArrayUnsafe a
ArrayUnsafe MutableByteArray
contents Int
end Int
start)

    {-# INLINE_LATE step #-}
    step :: ArrayUnsafe a -> m (Step (ArrayUnsafe a) a)
step (ArrayUnsafe MutableByteArray
contents Int
end Int
p) = do
            -- unsafeInlineIO allows us to run this in Identity monad for pure
            -- toList/foldr case which makes them much faster due to not
            -- accumulating the list and fusing better with the pure consumers.
            --
            -- This should be safe as the array contents are guaranteed to be
            -- evaluated/written to before we peek at them.
            let !x :: a
x = forall a. IO a -> a
unsafeInlineIO forall a b. (a -> b) -> a -> b
$ forall a. Unbox a => MutableByteArray -> Int -> IO a
peekWith MutableByteArray
contents Int
p
            let !p1 :: Int
p1 = INDEX_NEXT(p,a)
            forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ forall s a. a -> s -> Step s a
D.Yield a
x (forall a. MutableByteArray -> Int -> Int -> ArrayUnsafe a
ArrayUnsafe MutableByteArray
contents Int
end Int
p1)

-- |
--
-- >>> import qualified Streamly.Internal.Data.Array.Type as Array
-- >>> null arr = Array.byteLength arr == 0
--
-- /Pre-release/
{-# INLINE null #-}
null :: Array a -> Bool
null :: forall a. Array a -> Bool
null Array a
arr = forall a. Array a -> Int
A.byteLength Array a
arr forall a. Eq a => a -> a -> Bool
== Int
0

-- | Like 'getIndex' but indexes the array in reverse from the end.
--
-- /Pre-release/
{-# INLINE getIndexRev #-}
getIndexRev :: forall a. Unbox a => Int -> Array a -> Maybe a
getIndexRev :: forall a. Unbox a => Int -> Array a -> Maybe a
getIndexRev Int
i Array a
arr =
    forall a. IO a -> a
unsafeInlineIO
        forall a b. (a -> b) -> a -> b
$ do
                let elemPtr :: Int
elemPtr = RINDEX_OF(arrEnd arr, i, a)
                if Int
i forall a. Ord a => a -> a -> Bool
>= Int
0 Bool -> Bool -> Bool
&& Int
elemPtr forall a. Ord a => a -> a -> Bool
>= forall a. Array a -> Int
arrStart Array a
arr
                then forall a. a -> Maybe a
Just forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> forall a. Unbox a => MutableByteArray -> Int -> IO a
peekWith (forall a. Array a -> MutableByteArray
arrContents Array a
arr) Int
elemPtr
                else forall (m :: * -> *) a. Monad m => a -> m a
return forall a. Maybe a
Nothing

-- |
--
-- >>> import qualified Streamly.Internal.Data.Array as Array
-- >>> last arr = Array.getIndexRev arr 0
--
-- /Pre-release/
{-# INLINE last #-}
last :: Unbox a => Array a -> Maybe a
last :: forall a. Unbox a => Array a -> Maybe a
last = forall a. Unbox a => Int -> Array a -> Maybe a
getIndexRev Int
0

-------------------------------------------------------------------------------
-- Folds with Array as the container
-------------------------------------------------------------------------------

-- | @writeLastN n@ folds a maximum of @n@ elements from the end of the input
-- stream to an 'Array'.
--
{-# INLINE writeLastN #-}
writeLastN ::
       (Storable a, Unbox a, MonadIO m) => Int -> Fold m a (Array a)
writeLastN :: forall a (m :: * -> *).
(Storable a, Unbox a, MonadIO m) =>
Int -> Fold m a (Array a)
writeLastN Int
n
    | Int
n forall a. Ord a => a -> a -> Bool
<= Int
0 = forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap (forall a b. a -> b -> a
const forall a. Monoid a => a
mempty) forall (m :: * -> *) a. Monad m => Fold m a ()
FL.drain
    | Bool
otherwise = forall a. MutArray a -> Array a
A.unsafeFreeze forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> forall (m :: * -> *) a b s.
(s -> a -> m (Step s b))
-> m (Step s b) -> (s -> m b) -> Fold m a b
Fold forall {m :: * -> *} {a} {c} {b}.
(MonadIO m, Storable a, Num c) =>
Tuple3Fused' (Ring a) (Ptr a) c
-> a -> m (Step (Tuple3Fused' (Ring a) (Ptr a) c) b)
step forall {b}. m (Step (Tuple3Fused' (Ring a) (Ptr a) Int) b)
initial forall {m :: * -> *} {a}.
(MonadIO m, Unbox a, Storable a) =>
Tuple3Fused' (Ring a) (Ptr a) Int -> m (MutArray a)
done

    where

    step :: Tuple3Fused' (Ring a) (Ptr a) c
-> a -> m (Step (Tuple3Fused' (Ring a) (Ptr a) c) b)
step (Tuple3Fused' Ring a
rb Ptr a
rh c
i) a
a = do
        Ptr a
rh1 <- forall (m :: * -> *) a. MonadIO m => IO a -> m a
liftIO forall a b. (a -> b) -> a -> b
$ forall a. Storable a => Ring a -> Ptr a -> a -> IO (Ptr a)
RB.unsafeInsert Ring a
rb Ptr a
rh a
a
        forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ forall s b. s -> Step s b
FL.Partial forall a b. (a -> b) -> a -> b
$ forall a b c. a -> b -> c -> Tuple3Fused' a b c
Tuple3Fused' Ring a
rb Ptr a
rh1 (c
i forall a. Num a => a -> a -> a
+ c
1)

    initial :: m (Step (Tuple3Fused' (Ring a) (Ptr a) Int) b)
initial =
        let f :: (a, b) -> Step (Tuple3Fused' a b Int) b
f (a
a, b
b) = forall s b. s -> Step s b
FL.Partial forall a b. (a -> b) -> a -> b
$ forall a b c. a -> b -> c -> Tuple3Fused' a b c
Tuple3Fused' a
a b
b (Int
0 :: Int)
         in forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap forall {a} {b} {b}. (a, b) -> Step (Tuple3Fused' a b Int) b
f forall a b. (a -> b) -> a -> b
$ forall (m :: * -> *) a. MonadIO m => IO a -> m a
liftIO forall a b. (a -> b) -> a -> b
$ forall a. Storable a => Int -> IO (Ring a, Ptr a)
RB.new Int
n

    done :: Tuple3Fused' (Ring a) (Ptr a) Int -> m (MutArray a)
done (Tuple3Fused' Ring a
rb Ptr a
rh Int
i) = do
        MutArray a
arr <- forall (m :: * -> *) a. MonadIO m => IO a -> m a
liftIO forall a b. (a -> b) -> a -> b
$ forall (m :: * -> *) a.
(MonadIO m, Unbox a) =>
Int -> m (MutArray a)
MA.newPinned Int
n
        forall {m :: * -> *} {a} {b}.
(MonadIO m, Storable a) =>
Int -> Ptr a -> (b -> a -> m b) -> b -> Ring a -> m b
foldFunc Int
i Ptr a
rh forall {m :: * -> *} {a}.
(MonadIO m, Unbox a) =>
MutArray a -> a -> m (MutArray a)
snoc' MutArray a
arr Ring a
rb

    -- XXX We should write a read unfold for ring.
    snoc' :: MutArray a -> a -> m (MutArray a)
snoc' MutArray a
b a
a = forall (m :: * -> *) a. MonadIO m => IO a -> m a
liftIO forall a b. (a -> b) -> a -> b
$ forall {m :: * -> *} {a}.
(MonadIO m, Unbox a) =>
MutArray a -> a -> m (MutArray a)
MA.snocUnsafe MutArray a
b a
a

    foldFunc :: Int -> Ptr a -> (b -> a -> m b) -> b -> Ring a -> m b
foldFunc Int
i
        | Int
i forall a. Ord a => a -> a -> Bool
< Int
n = forall (m :: * -> *) a b.
(MonadIO m, Storable a) =>
Ptr a -> (b -> a -> m b) -> b -> Ring a -> m b
RB.unsafeFoldRingM
        | Bool
otherwise = forall (m :: * -> *) a b.
(MonadIO m, Storable a) =>
Ptr a -> (b -> a -> m b) -> b -> Ring a -> m b
RB.unsafeFoldRingFullM

-------------------------------------------------------------------------------
-- Random Access
-------------------------------------------------------------------------------

-------------------------------------------------------------------------------
-- Searching
-------------------------------------------------------------------------------

-- | Given a sorted array, perform a binary search to find the given element.
-- Returns the index of the element if found.
--
-- /Unimplemented/
{-# INLINE binarySearch #-}
binarySearch :: a -> Array a -> Maybe Int
binarySearch :: forall a. a -> Array a -> Maybe Int
binarySearch = forall a. HasCallStack => a
undefined

-- find/findIndex etc can potentially be implemented more efficiently on arrays
-- compared to streams by using SIMD instructions.
-- We can also return a bit array instead.

-- | Perform a linear search to find all the indices where a given element is
-- present in an array.
--
-- /Unimplemented/
findIndicesOf :: (a -> Bool) -> Unfold Identity (Array a) Int
findIndicesOf :: forall a. (a -> Bool) -> Unfold Identity (Array a) Int
findIndicesOf = forall a. HasCallStack => a
undefined

{-
findIndexOf :: (a -> Bool) -> Array a -> Maybe Int
findIndexOf p = Unfold.fold Fold.one . Stream.unfold (findIndicesOf p)

find :: (a -> Bool) -> Array a -> Bool
find = Unfold.fold Fold.null . Stream.unfold (findIndicesOf p)
-}

-------------------------------------------------------------------------------
-- Folds
-------------------------------------------------------------------------------

-- XXX We can potentially use SIMD instructions on arrays to fold faster.

-------------------------------------------------------------------------------
-- Slice
-------------------------------------------------------------------------------

-- | /O(1)/ Slice an array in constant time.
--
-- Caution: The bounds of the slice are not checked.
--
-- /Unsafe/
--
-- /Pre-release/
{-# INLINE getSliceUnsafe #-}
getSliceUnsafe ::
       forall a. Unbox a
    => Int -- ^ starting index
    -> Int -- ^ length of the slice
    -> Array a
    -> Array a
getSliceUnsafe :: forall a. Unbox a => Int -> Int -> Array a -> Array a
getSliceUnsafe Int
index Int
len (Array MutableByteArray
contents Int
start Int
e) =
    let size :: Int
size = SIZE_OF(a)
        start1 :: Int
start1 = Int
start forall a. Num a => a -> a -> a
+ (Int
index forall a. Num a => a -> a -> a
* Int
size)
        end1 :: Int
end1 = Int
start1 forall a. Num a => a -> a -> a
+ (Int
len forall a. Num a => a -> a -> a
* Int
size)
     in forall a. HasCallStack => Bool -> a -> a
assert (Int
end1 forall a. Ord a => a -> a -> Bool
<= Int
e) (forall a. MutableByteArray -> Int -> Int -> Array a
Array MutableByteArray
contents Int
start1 Int
end1)

-- | Split the array into a stream of slices using a predicate. The element
-- matching the predicate is dropped.
--
-- /Pre-release/
{-# INLINE splitOn #-}
splitOn :: (Monad m, Unbox a) =>
    (a -> Bool) -> Array a -> Stream m (Array a)
splitOn :: forall (m :: * -> *) a.
(Monad m, Unbox a) =>
(a -> Bool) -> Array a -> Stream m (Array a)
splitOn a -> Bool
predicate Array a
arr =
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap (\(Int
i, Int
len) -> forall a. Unbox a => Int -> Int -> Array a -> Array a
getSliceUnsafe Int
i Int
len Array a
arr)
        forall a b. (a -> b) -> a -> b
$ forall (m :: * -> *) a.
Monad m =>
(a -> Bool) -> Stream m a -> Stream m (Int, Int)
D.sliceOnSuffix a -> Bool
predicate (forall (m :: * -> *) a. (Monad m, Unbox a) => Array a -> Stream m a
A.toStreamD Array a
arr)

{-# INLINE genSlicesFromLen #-}
genSlicesFromLen :: forall m a. (Monad m, Unbox a)
    => Int -- ^ from index
    -> Int -- ^ length of the slice
    -> Unfold m (Array a) (Int, Int)
genSlicesFromLen :: forall (m :: * -> *) a.
(Monad m, Unbox a) =>
Int -> Int -> Unfold m (Array a) (Int, Int)
genSlicesFromLen Int
from Int
len =
    forall a c (m :: * -> *) b.
(a -> c) -> Unfold m c b -> Unfold m a b
Unfold.lmap forall a. Array a -> MutArray a
A.unsafeThaw (forall (m :: * -> *) a.
(Monad m, Unbox a) =>
Int -> Int -> Unfold m (MutArray a) (Int, Int)
MA.genSlicesFromLen Int
from Int
len)

-- | Generate a stream of slices of specified length from an array, starting
-- from the supplied array index. The last slice may be shorter than the
-- requested length.
--
-- /Pre-release//
{-# INLINE getSlicesFromLen #-}
getSlicesFromLen :: forall m a. (Monad m, Unbox a)
    => Int -- ^ from index
    -> Int -- ^ length of the slice
    -> Unfold m (Array a) (Array a)
getSlicesFromLen :: forall (m :: * -> *) a.
(Monad m, Unbox a) =>
Int -> Int -> Unfold m (Array a) (Array a)
getSlicesFromLen Int
from Int
len =
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap forall a. MutArray a -> Array a
A.unsafeFreeze
        forall a b. (a -> b) -> a -> b
$ forall a c (m :: * -> *) b.
(a -> c) -> Unfold m c b -> Unfold m a b
Unfold.lmap forall a. Array a -> MutArray a
A.unsafeThaw (forall (m :: * -> *) a.
(Monad m, Unbox a) =>
Int -> Int -> Unfold m (MutArray a) (MutArray a)
MA.getSlicesFromLen Int
from Int
len)

-------------------------------------------------------------------------------
-- Random reads and writes
-------------------------------------------------------------------------------

-- XXX Change this to a partial function instead of a Maybe type? And use
-- MA.getIndex instead.
--
-- | /O(1)/ Lookup the element at the given index. Index starts from 0.
--
{-# INLINE getIndex #-}
getIndex :: forall a. Unbox a => Int -> Array a -> Maybe a
getIndex :: forall a. Unbox a => Int -> Array a -> Maybe a
getIndex Int
i Array a
arr =
    forall a. IO a -> a
unsafeInlineIO
        forall a b. (a -> b) -> a -> b
$ do
                let elemPtr :: Int
elemPtr = forall a. Array a -> Int
INDEX_OF(arrStart arr, i, a)
                if Int
i forall a. Ord a => a -> a -> Bool
>= Int
0 Bool -> Bool -> Bool
&& INDEX_VALID(elemPtr, arrEnd arr, a)
                then forall a. a -> Maybe a
Just forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> forall a. Unbox a => MutableByteArray -> Int -> IO a
peekWith (forall a. Array a -> MutableByteArray
arrContents Array a
arr) Int
elemPtr
                else forall (m :: * -> *) a. Monad m => a -> m a
return forall a. Maybe a
Nothing

-- | Given a stream of array indices, read the elements on those indices from
-- the supplied Array. An exception is thrown if an index is out of bounds.
--
-- This is the most general operation. We can implement other operations in
-- terms of this:
--
-- @
-- read =
--      let u = lmap (\arr -> (0, length arr - 1)) Unfold.enumerateFromTo
--       in Unfold.lmap f (getIndices arr)
--
-- readRev =
--      let i = length arr - 1
--       in Unfold.lmap f (getIndicesFromThenTo i (i - 1) 0)
-- @
--
-- /Pre-release/
{-# INLINE getIndices #-}
getIndices :: (Monad m, Unbox a) => Stream m Int -> Unfold m (Array a) a
getIndices :: forall (m :: * -> *) a.
(Monad m, Unbox a) =>
Stream m Int -> Unfold m (Array a) a
getIndices Stream m Int
m =
    let unf :: Unfold m (MutArray a) a
unf = forall (m :: * -> *) a.
(Monad m, Unbox a) =>
(forall b. IO b -> m b) -> Stream m Int -> Unfold m (MutArray a) a
MA.getIndicesD (forall (m :: * -> *) a. Monad m => a -> m a
return forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a. IO a -> a
unsafeInlineIO) Stream m Int
m
     in forall a c (m :: * -> *) b.
(a -> c) -> Unfold m c b -> Unfold m a b
Unfold.lmap forall a. Array a -> MutArray a
A.unsafeThaw Unfold m (MutArray a) a
unf

-- | Unfolds @(from, then, to, array)@ generating a finite stream whose first
-- element is the array value from the index @from@ and the successive elements
-- are from the indices in increments of @then@ up to @to@. Index enumeration
-- can occur downwards or upwards depending on whether @then@ comes before or
-- after @from@.
--
-- @
-- getIndicesFromThenTo =
--     let f (from, next, to, arr) =
--             (Stream.enumerateFromThenTo from next to, arr)
--      in Unfold.lmap f getIndices
-- @
--
-- /Unimplemented/
{-# INLINE getIndicesFromThenTo #-}
getIndicesFromThenTo :: Unfold m (Int, Int, Int, Array a) a
getIndicesFromThenTo :: forall (m :: * -> *) a. Unfold m (Int, Int, Int, Array a) a
getIndicesFromThenTo = forall a. HasCallStack => a
undefined

-------------------------------------------------------------------------------
-- Transform via stream operations
-------------------------------------------------------------------------------

-- for non-length changing operations we can use the original length for
-- allocation. If we can predict the length then we can use the prediction for
-- new allocation. Otherwise we can use a hint and adjust dynamically.

{-
-- | Transform an array into another array using a pipe transformation
-- operation.
--
{-# INLINE runPipe #-}
runPipe :: (MonadIO m, Unbox a, Unbox b)
    => Pipe m a b -> Array a -> m (Array b)
runPipe f arr = P.runPipe (toArrayMinChunk (length arr)) $ f (A.read arr)
-}

-- XXX For transformations that cannot change the number of elements e.g. "map"
-- we can use a predetermined array length.
--
-- | Transform an array into another array using a stream transformation
-- operation.
--
-- /Pre-release/
{-# INLINE streamTransform #-}
streamTransform :: forall m a b. (MonadIO m, Unbox a, Unbox b)
    => (Stream m a -> Stream m b) -> Array a -> m (Array b)
streamTransform :: forall (m :: * -> *) a b.
(MonadIO m, Unbox a, Unbox b) =>
(Stream m a -> Stream m b) -> Array a -> m (Array b)
streamTransform Stream m a -> Stream m b
f Array a
arr =
    forall (m :: * -> *) a b.
Monad m =>
Fold m a b -> Stream m a -> m b
Stream.fold (forall (m :: * -> *) a.
(MonadIO m, Unbox a) =>
Int -> Fold m a (Array a)
A.writeWith (forall a. Unbox a => Array a -> Int
length Array a
arr)) forall a b. (a -> b) -> a -> b
$ Stream m a -> Stream m b
f (forall (m :: * -> *) a. (Monad m, Unbox a) => Array a -> Stream m a
A.read Array a
arr)

-------------------------------------------------------------------------------
-- Casts
-------------------------------------------------------------------------------

-- | Cast an array having elements of type @a@ into an array having elements of
-- type @b@. The array size must be a multiple of the size of type @b@
-- otherwise accessing the last element of the array may result into a crash or
-- a random value.
--
-- /Pre-release/
--
castUnsafe ::
#ifdef DEVBUILD
    Unbox b =>
#endif
    Array a -> Array b
castUnsafe :: forall a b. Array a -> Array b
castUnsafe (Array MutableByteArray
contents Int
start Int
end) =
    forall a. MutableByteArray -> Int -> Int -> Array a
Array MutableByteArray
contents Int
start Int
end

-- | Cast an @Array a@ into an @Array Word8@.
--
--
asBytes :: Array a -> Array Word8
asBytes :: forall a. Array a -> Array Word8
asBytes = forall a b. Array a -> Array b
castUnsafe

-- | Cast an array having elements of type @a@ into an array having elements of
-- type @b@. The length of the array should be a multiple of the size of the
-- target element otherwise 'Nothing' is returned.
--
--
cast :: forall a b. (Unbox b) => Array a -> Maybe (Array b)
cast :: forall a b. Unbox b => Array a -> Maybe (Array b)
cast Array a
arr =
    let len :: Int
len = forall a. Array a -> Int
A.byteLength Array a
arr
        r :: Int
r = Int
len forall a. Integral a => a -> a -> a
`mod` SIZE_OF(b)
     in if Int
r forall a. Eq a => a -> a -> Bool
/= Int
0
        then forall a. Maybe a
Nothing
        else forall a. a -> Maybe a
Just forall a b. (a -> b) -> a -> b
$ forall a b. Array a -> Array b
castUnsafe Array a
arr

-- | Convert an array of any type into a null terminated CString Ptr.
--
-- /Unsafe/
--
-- /O(n) Time: (creates a copy of the array)/
--
-- /Pre-release/
--
asCStringUnsafe :: Array a -> (CString -> IO b) -> IO b
asCStringUnsafe :: forall a b. Array a -> (CString -> IO b) -> IO b
asCStringUnsafe Array a
arr CString -> IO b
act = do
    -- XXX Ensure a pinned allocation here.
    let arr1 :: Array Word8
arr1 = forall a. Array a -> Array Word8
asBytes Array a
arr forall a. Semigroup a => a -> a -> a
<> forall a. Unbox a => [a] -> Array a
A.fromList [Word8
0]
    forall (m :: * -> *) a b.
MonadIO m =>
Array a -> (Ptr a -> m b) -> m b
asPtrUnsafe Array Word8
arr1 forall a b. (a -> b) -> a -> b
$ \Ptr Word8
ptr -> CString -> IO b
act (forall a b. Ptr a -> Ptr b
castPtr Ptr Word8
ptr)

-------------------------------------------------------------------------------
-- Folds
-------------------------------------------------------------------------------

-- XXX We can directly use toStreamD and D.fold here.

-- | Fold an array using a 'Fold'.
--
-- /Pre-release/
{-# INLINE fold #-}
fold :: forall m a b. (Monad m, Unbox a) => Fold m a b -> Array a -> m b
fold :: forall (m :: * -> *) a b.
(Monad m, Unbox a) =>
Fold m a b -> Array a -> m b
fold Fold m a b
f Array a
arr = forall (m :: * -> *) a b.
Monad m =>
Fold m a b -> Stream m a -> m b
Stream.fold Fold m a b
f (forall (m :: * -> *) a. (Monad m, Unbox a) => Array a -> Stream m a
A.read Array a
arr)

-- | Fold an array using a stream fold operation.
--
-- /Pre-release/
{-# INLINE streamFold #-}
streamFold :: (Monad m, Unbox a) => (Stream m a -> m b) -> Array a -> m b
streamFold :: forall (m :: * -> *) a b.
(Monad m, Unbox a) =>
(Stream m a -> m b) -> Array a -> m b
streamFold Stream m a -> m b
f Array a
arr = Stream m a -> m b
f (forall (m :: * -> *) a. (Monad m, Unbox a) => Array a -> Stream m a
A.read Array a
arr)