[WIP] add support for TypedArrays/arrayBuffer/nodejs' Buffer

[dotnetCarpenter]

Currently failing to implement tests for TypedArray.

In assert.strictEqual (equals (actual) (expected), true); the Setoid.test test fails unconditionaly for a TypedArray (Uint8Array).

Need help ;)

Reproduce:

const S = require ('./internal/sanctuary');
const eq = require ('./internal/eq');

eq (S.unchecked.drop (1) (new Uint8Array([10, 20, 30, 40, 50]))) (S.unchecked.Just (new Uint8Array([20, 30, 40, 50])));

PS. For now my goal is to support various Buffers for unchecked functions, since it seems like this should be opt-in and I don't know how to implement support in https://github.com/sanctuary-js/sanctuary-def yet.

[davidchambers]

I don't think this makes sense.

Here is the type of take:

take :: (Applicative f, Foldable f, Monoid (f a)) => Integer -> f a -> Maybe (f a)

We could specialize this by replacing f with Array and a with String:

take :: Integer -> Array String -> Maybe (Array String)

Doing the same with Uint8Array results in a nonsensical type:

take :: Integer -> Uint8Array String -> Maybe (Uint8Array String)

Uint8Array is a type rather than a type constructor: these arrays only ever contain 8-bit unsigned integers.

One could define a specialized function:

takeUint8 :: Integer -> Uint8Array -> Maybe Uint8Array

[dotnetCarpenter]

@davidchambers How would I go about implementing specialised functions for Sanctuary?

Would TypedArray encompass all of Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, Float32Array, Float64Array, BigInt64Array and BigUint64Array?

takeTypedArray :: Integer -> TypedArray -> Maybe TypedArray

[davidchambers]

The hypothetical TypedArray type is problematic because it would allow takeTypedArray to take a Uint8Array but return a Maybe Float64Array.

The simplest solution would be to define a specialized function for each type.

[dotnetCarpenter]

So that would be 11 specialized functions, just for take?

takeInt8Array :: Integer -> Int8Array -> Maybe Int8Array

takeUint8Array :: NonNegativeInteger -> Uint8Array -> Maybe Uint8Array

takeUint8ClampedArray :: NonNegativeInteger -> Uint8ClampedArray -> Maybe Uint8ClampedArray

takeInt16Array :: Integer -> Int16Array -> Maybe Int16Array

takeUint16Array :: NonNegativeInteger -> Uint16Array -> Maybe Uint16Array

takeInt32Array :: Integer -> Int32Array -> Maybe Int32Array

takeUint32Array :: NonNegativeInteger -> Uint32Array -> Maybe Uint32Array

takeFloat32Array :: ValidNumber -> Float32Array -> Maybe Float32Array

takeFloat64Array :: ValidNumber -> Float64Array -> Maybe Float64Array

Does Sanctuary support BigInt?

takeBigInt64Array :: BigInt -> BigInt64Array -> Maybe BigInt64Array

takeBigUint64Array :: NonNegativeBigInt -> BigUint64Array -> Maybe BigUint64Array

But actually, before going down this rabbit hole. I'm much more interested in support for Nodejs' Buffer since I deal with a database that returns Buffers.

takeBuffer :: NonNegativeInteger -> Buffer -> Maybe Buffer

dropBuffer :: NonNegativeInteger -> Buffer -> Maybe Buffer

takeLastBuffer :: NonNegativeInteger -> Buffer -> Maybe Buffer

dropLastBuffer :: NonNegativeInteger -> Buffer -> Maybe Buffer

takeWhileBuffer :: (a -> Boolean) -> Buffer -> Buffer

dropWhileBuffer :: (a -> Boolean) -> Buffer -> Buffer

Ref: NonNegativeInteger

[dotnetCarpenter]

I tried to look through some code a few months back to find context for this. I did not find anything.

But as I recall, I got a Buffer from the database and wanted to use S.unchecked.drop but the Array,isArray check in _takeDrop would not let me, so I used .slice instead without a Maybe.

Changing that one line, made it all work in Sanctuary but .... here I am.

[Avaq]

If I'd want to take from a Buffer, I'd probably do something like:

// firstFiveBytes :: Buffer -> Maybe Buffer
const firstFiveBytes = S.pipe ([
  Array.from,
  S.take (5),
  S.map (Buffer.from),
])

[dotnetCarpenter]

@Avaq I'm imagining that working with Buffers without converting them to Array would be faster overall. But I should write some code to compare with.

There is only one line that need to change in Sanctuary in order to support Buffers, so it should be fairly easy to compare.

But it won't be today :)

[imcotton]

Quick note: slice creates a copy of internal memory v.s. subarray keeps its ArrayBuffer untouched (shared).