Initial prototype with text encoding backend for arraybuffer morphisms

with string

Author: AlexaDeWit

Diff for: .gitignore

@@ -4,3 +4,5 @@ bower_components/
 node_modules/
 .psci
 .psci_modules/
+yarn-error.log
+yarn.lock

Diff for: README.md

@@ -13,3 +13,7 @@ ArrayBuffer bindings for PureScript.
 
 Module documentation is [published on Pursuit](http://pursuit.purescript.org/packages/purescript-arraybuffer).
 
+
+## Important Usage Notes
+
+- Usage of the ArrayBuffer<->String conversion functions requires the import of the NPM package 'text-encoding'.

Diff for: bower.json

@@ -16,7 +16,8 @@
     "purescript-arraybuffer-types": "^2.0.0",
     "purescript-maybe": "^4.0.0",
     "purescript-effect": "^2.0.0",
-    "purescript-uint": "^4.0.0"
+    "purescript-uint": "^4.0.0",
+    "purescript-text-encoding": "^0.0.7"
   },
   "devDependencies": {
     "purescript-debug": "^4.0.0",

Diff for: package.json

@@ -0,0 +1,12 @@
+{
+  "name": "purescript-arraybuffer",
+  "version": "7.0.0",
+  "main": "index.js",
+  "repository": "git@github.com:jacereda/purescript-arraybuffer.git",
+  "author": "https://github.com/jacereda",
+  "license": "MIT",
+  "devDependencies": {
+    "text-encoding": "^0.6.4"
+  }
+
+}

Diff for: src/Data/ArrayBuffer/ArrayBuffer.js

@@ -25,21 +25,3 @@ exports.fromArray = function(s) {
 exports.fromIntArray = function(s) {
   return (new Uint8Array(s)).buffer;
 };
-
-exports.fromString = function(s) {
-  var buf = new ArrayBuffer(s.length*2);
-  var bufView = new Uint16Array(buf);
-  for (var i=0, strLen=s.length; i<strLen; i++) {
-    bufView[i] = s.charCodeAt(i);
-  }
- return buf;
-};
-
-exports.decodeToStringImpl = function(just, nothing, buffer) {
-  try {
-    return just(String.fromCharCode.apply(null, new Uint16Array(buffer)));
-  }
-  catch (e) {
-    return nothing;
-  }
-};

Diff for: src/Data/ArrayBuffer/ArrayBuffer.purs

@@ -7,10 +7,17 @@ module Data.ArrayBuffer.ArrayBuffer ( create
                                     , decodeToString
                                    ) where
 
-import Effect (Effect)
-import Data.Maybe (Maybe(..))
-import Data.Function.Uncurried (Fn3, runFn3)
+import Data.ArrayBuffer.DataView (whole, buffer)
+import Data.ArrayBuffer.Typed (asUint8Array, dataView)
 import Data.ArrayBuffer.Types (ArrayBuffer, ByteOffset, ByteLength)
+import Data.Either (Either)
+import Data.Function.Uncurried (Fn3, runFn3)
+import Data.TextDecoder (decodeUtf8)
+import Data.TextEncoder (encodeUtf8)
+import Effect (Effect)
+import Effect.Exception (Error)
+import Prelude ((<<<))
+
 
 -- | Create an `ArrayBuffer` with the given capacity.
 foreign import create :: ByteLength -> Effect ArrayBuffer
@@ -30,13 +37,16 @@ foreign import fromArray :: Array Number -> ArrayBuffer
 -- | Convert an array into an `ArrayBuffer` representation.
 foreign import fromIntArray :: Array Int -> ArrayBuffer
 
--- | Convert a string into an `ArrayBuffer` representation.
-foreign import fromString :: String -> ArrayBuffer
-
-foreign import decodeToStringImpl :: Fn3 (String -> Maybe String) (Maybe String) ArrayBuffer (Maybe String)
-
--- | Convert an ArrayBuffer into a string. Uses fromCharCode and thus does not support full utf-16
--- | Is currently only defined for ArrayBuffers with even numbers of bytes, as it assumes the ArrayBuffer encodes string data.
--- | For more general string-encoding forms of data, use a base64 or other encoding scheme.
-decodeToString :: ArrayBuffer -> Maybe String
-decodeToString = runFn3 decodeToStringImpl Just Nothing
+-- | Convert a UTF-8 encoded `ArrayBuffer` into a `String`.
+-- | Serves as a quick utility function for a common use-case. For more use-cases,
+-- | see: [purescript-text-encoding](https://pursuit.purescript.org/packages/purescript-text-encoding/0.0.7)
+-- | Requires the TextDecoder class available. A polyfill can be found in the npm package "text-encoding"
+decodeToString :: ArrayBuffer -> Either Error String
+decodeToString = decodeUtf8 <<< asUint8Array <<< whole
+
+-- | Convert a  `String` into a UTF-8 encoded `ArrayBuffer`.
+-- | Serves as a quick utility function for a common use-case. For more use-cases,
+-- | see: [purescript-text-encoding](https://pursuit.purescript.org/packages/purescript-text-encoding/0.0.7)
+-- | Requires the TextDecoder class available. A polyfill can be found in the npm package "text-encoding"
+fromString :: String -> ArrayBuffer
+fromString = buffer <<< dataView <<< encodeUtf8

Diff for: test/Main.purs

@@ -6,8 +6,10 @@ import Effect (Effect)
 import Data.ArrayBuffer.ArrayBuffer as AB
 import Data.ArrayBuffer.DataView as DV
 import Data.ArrayBuffer.Typed as TA
+import Data.Either (fromRight)
 import Data.Maybe (Maybe(..), isNothing)
 import Data.UInt (fromInt, pow)
+import Partial.Unsafe (unsafePartial)
 import Test.QuickCheck (quickCheck', (<?>), quickCheck)
 
 assertEffEquals :: forall a. Eq a => Show a => a -> Effect a -> Effect Unit
@@ -35,9 +37,9 @@ main = do
   assertEquals (Just 2) $ DV.byteLength <$> DV.slice 2 2 ab4
   assertEquals 4 $ AB.byteLength $ AB.fromArray [1.0, 2.0, 3.0, 4.0]
   assertEquals 4 $ AB.byteLength $ AB.fromIntArray [1, 2, 3, 4]
-  assertEquals 8 $ AB.byteLength $ AB.fromString "hola"
-  assertEquals 8 $ AB.byteLength $ AB.fromString "hóla"
-  assertEquals 10 $ AB.byteLength $ AB.fromString "hóla¡"
+  assertEquals 4 $ AB.byteLength $ AB.fromString "hola"
+  assertEquals 5 $ AB.byteLength $ AB.fromString "hóla"
+  assertEquals 7 $ AB.byteLength $ AB.fromString "hóla¡"
   assertEquals 8 $ AB.byteLength $ DV.buffer $ DV.whole ab8
   assertEquals 8 $ AB.byteLength $ DV.buffer $ TA.dataView $ TA.asInt8Array $ DV.whole ab8
 
@@ -51,9 +53,14 @@ main = do
 
   quickCheck
     \(s) ->
-      Just s == (AB.decodeToString $ AB.fromString s)
-      <?> "Isormorphic arraybuffer conversion with string failed for input "
-      <> s
+        let
+          result = (unsafePartial $ fromRight $ AB.decodeToString $ AB.fromString s)
+        in
+          s == result
+          <?> "Isormorphic arraybuffer conversion with string failed for input\n"
+          <> s
+          <> " which, after the round trip, result in\n"
+          <> result
 
   assertEquals [1.0, 2.0, 3.0] $ TA.toArray <<< TA.asInt8Array <<< DV.whole $ AB.fromArray [1.0, 2.0, 3.0]