[英]How do you convert from an Unboxed Vector to a JS TypedArray on GHCJS?
I have an element of type Data.Vector.Unboxed.Vector Word32
. 我有一个
Data.Vector.Unboxed.Vector Word32
类型的元素。 I want to convert that to a native JS TypedArray
(an Uint32Array
, specifically). 我想将其转换为本机JS
TypedArray
(特别是Uint32Array
)。 I'm aware of toJsArray
and toJsValListOf
, but both functions deal with lists, not vectors, and are inefficient. 我知道
toJsArray
和toJsValListOf
,但两个函数都处理列表,而不是向量,并且效率低下。 How can I convert an unboxed Vector
directly to a JS TypedArray
? 如何将未装箱的
Vector
直接转换为JS TypedArray
?
I was able to solve this up to marshalling to an Int32Array
instead of an Uint32Array
; 我能够解决这个问题,然后编组到
Int32Array
而不是Uint32Array
; probably someone who has actually known GHCJS for more than the one hour I've put into this will be able to expand on this so that you get your Uint32Array
(or you can just make a hacked-up version of GHCJS.Buffer
that supports a getUint32Array
operation). 可能有人已经知道GHCJS超过一小时我已经投入使用这个将能够扩展到这一点,以便你得到你的
Uint32Array
(或者你可以制作一个GHCJS.Buffer
-up版本的GHCJS.Buffer
支持一个getUint32Array
操作)。
The idea is to get the ByteArray
underlying the Vector
representation, and then slice
it so that only the relevant portion remains: 我们的想法是让
ByteArray
成为Vector
表示的基础,然后将其slice
以便只保留相关部分:
import Data.Vector.Unboxed as V
import Data.Word
import qualified Data.Vector.Unboxed.Base as B
import qualified Data.Vector.Primitive as P
import GHCJS.Types
import qualified GHCJS.Buffer as Buffer
import JavaScript.TypedArray (Int32Array)
-- TODO: generalize this to all types that support unboxed vectors...
toI32Array :: Vector Word32 -> Int32Array
toI32Array (B.V_Word32 (P.Vector offset len bs)) =
js_slice offset (offset + len) $ Buffer.getInt32Array (Buffer.fromByteArray bs)
foreign import javascript unsafe "$3.slice($1, $2)" js_slice :: Int -> Int -> Int32Array -> Int32Array
-- should be
-- foreign import javascript unsafe "$3.slice($1, $2)" js_slice :: Int -> Int -> SomeTypedArray a m -> SomeTypedArray a m
-- but alas, JavaScript.TypedArray.Internal.Type is a hidden module
Here's some example code using it: 以下是使用它的一些示例代码:
v :: Vector Word32
v = V.fromList [1, 2, 3]
foreign import javascript unsafe "console.debug($1);" js_debug :: JSVal -> IO ()
main = do
let v' = toI32Array v
js_debug $ jsval v'
If you look at the console in a browser, you can check that jsval v'
does indeed have type Int32Array
. 如果你在浏览器中查看控制台,你可以检查
jsval v'
确实有Int32Array
类型。
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