@@ -5,402 +5,152 @@
55-- | Writing to an `ArrayBuffer` is an `Effect`ful activity, so most
66-- | functions in this module must be run in a `MonadEffect` context.
77-- |
8−-- | For operations for working with `ArrayBuffer`, see
8+-- | For other operations for working with `ArrayBuffer`, see
99-- | module
1010-- | [`Data.ArrayBuffer.ArrayBuffer`](https://pursuit.purescript.org/packages/purescript-arraybuffer/docs/Data.ArrayBuffer.ArrayBuffer)
11−-- | in package __purescript-arraybuffer__.
11+-- | in package __arraybuffer__.
1212module Data.ArrayBuffer.Builder
13−( PutM
14−, Put
15−, execPutM
16−, execPut
17−, putArrayBuffer
18−, putUint8
19−, putInt8
20−, putUint16be
21−, putUint16le
22−, putInt16be
23−, putInt16le
24−, putUint32be
25−, putUint32le
26−, putInt32be
27−, putInt32le
28−, putFloat32be
29−, putFloat32le
30−, putFloat64be
31−, putFloat64le
32−, Builder
33−, (<>>)
34−, execBuilder
35−, singleton
36−, snoc
37−, encodeUint8
38−, encodeInt8
39−, encodeUint16be
40−, encodeUint16le
41−, encodeInt16be
42−, encodeInt16le
43−, encodeUint32be
44−, encodeUint32le
45−, encodeInt32be
46−, encodeInt32le
47−, encodeFloat32be
48−, encodeFloat32le
49−, encodeFloat64be
50−, encodeFloat64le
51−)
52−where
13+ ( PutM
14+ , Put
15+ , execPutM
16+ , execPut
17+ , subBuilder
18+ , putArrayBuffer
19+ , putDataView
20+ , putDataBuff
21+ , putUint8
22+ , putInt8
23+ , putUint16be
24+ , putUint16le
25+ , putInt16be
26+ , putInt16le
27+ , putUint32be
28+ , putUint32le
29+ , putInt32be
30+ , putInt32le
31+ , putFloat32be
32+ , putFloat32le
33+ , putFloat64be
34+ , putFloat64le
35+ , module Data.ArrayBuffer.Builder.Internal
36+ ) where
5337
5438import Prelude
5539
56−import Control.Monad.Writer.Trans (WriterT, execWriterT, tell)
57−import Data.ArrayBuffer.ArrayBuffer as AB
58−import Data.ArrayBuffer.DataView as DV
59−import Data.ArrayBuffer.Typed as AT
60−import Data.ArrayBuffer.Types (ArrayBuffer, Uint8Array)
40+import Control.Monad.Rec.Class (class MonadRec)
41+import Control.Monad.Writer.Trans (WriterT, execWriterT, tell, lift)
42+import Data.ArrayBuffer.Builder.Internal (Builder, DataBuff(..), length, toView, (<>>))
43+import Data.ArrayBuffer.Builder.Internal as Internal
44+import Data.ArrayBuffer.Types (ArrayBuffer, DataView)
6145import Data.Float32 (Float32)
62−import Data.Maybe (Maybe(..))
6346import Data.UInt (UInt)
6447import Effect (Effect)
65−import Effect.Class (class MonadEffect, liftEffect)
48+import Effect.Class (class MonadEffect)
6649
67−-- | The `PutM` monad is a Writer transformer monad which
68−-- | [gives us access to do-notation](https://wiki.haskell.org/Do_notation_considered_harmful#Library_design)
69−-- | for building `ArrayBuffer`s.
50+-- | The `PutM` monad is a `WriterT Builder` transformer monad which
51+-- | gives us do-notation for the `Builder` monoid. The base monad must be
52+-- | a `MonadEffect`.
53+-- |
54+-- | To append `Builder`s in this monad call `tell`, or any of the `put*`
55+-- | functions in this module.
7056type PutM = WriterT Builder
7157
72−-- | `Put` monad is the non-transformer version of `PutM`.
58+-- | The `PutM` type reified to `Effect`, in other words `WriterT Builder Effect`.
7359type Put = PutM Effect
7460
75−-- | Monoidal builder for `ArrayBuffer`s.
76−-- |
77−-- | ### Left-associative `<>>` append operator
61+-- | Build an `ArrayBuffer` with do-notation in any `MonadEffect`. *O(n)* Stack-safe.
62+execPutM :: forall m. MonadEffect m => MonadRec m => PutM m Unit -> m ArrayBuffer
63+execPutM = Internal.execBuilder <=< execWriterT
64+
65+-- | Build an `ArrayBuffer` with do-notation in `Effect`. *O(n)* Stack-safe.
66+execPut :: Put Unit -> Effect ArrayBuffer
67+execPut = execPutM
68+
69+-- | Build up a sub-`Builder` without `tell`ing it to the `Writer` yet.
7870-- |
79−-- | __TL;DR__ You probably don't want to use the `Builder` monoid directly
80−-- | in your code, it’s better to use the `PutM` monad with do-notation instead.
71+-- | One case where we might want to call a `subBuilder` is when
72+-- | serializing length-prefixed messages in some protocol. In that case,
73+-- | we must serialize the message first, calculate the message length,
74+-- | append the message length, and then append the message.
8175-- |
82−-- | The `Builder` monoid in this library is efficient when we `snoc` single
83−-- | items onto the end of it, or when we only `cons` single items to the
84−-- | beginning, but it can be less efficient when we are mixing `cons` and
85−-- | `snoc`.
86−-- | This matters when we're appending three or more `Builder`s
87−-- | in one associative expression, because the
88−-- | `Semigroup` append operator `<>` is right-associative.
76+-- | In a `PutM` monad do-block, we can
8977-- |
90−-- | To solve this, we provide an operator `<>>` for appending `Builders`.
91−-- | `<>>` is exactly the same as `<>`, but left-associative.
92−-- | This only matters when we're chaining together three
93−-- | or more `Builder`s in a single associative expression.
94−-- | Instead of
95−-- | ```
96−-- | builder₁ <> builder₂ <> builder₃
97−-- | ```
98−-- | we should always prefer to
99−-- | write
10078-- | ```
101−-- | builder₁ <>> builder₂ <>> builder₃
102−-- | ```
103−-- | so that we get the efficient
104−-- | `snoc`ing of `Builder`s.
105−-- |
106−-- | If we build our `ArrayBuffer`s with the `PutM` monad instead of appending by
107−-- | using the `Semigroup` instance of `Builder`, then we always get the efficient
108−-- | `snoc` case.
79+-- | do
80+-- | messageBuilder <- subBuilder $ do
81+-- | putField1
82+-- | putField2
10983-- |
110−data Builder
111− = Node Builder ArrayBuffer Builder
112− | Null
113−
114−instance semigroupBuilder :: Semigroup Builder where
115− append Null Null = Null
116− append l Null = l
117− append Null r = r
118− append l (Node Null rx rr) = Node l rx rr -- this is the snoc case
119− append (Node ll lx Null) r = Node ll lx r -- found the rightmost Null
120− -- of the left tree
121− append (Node ll lx lr) r = Node ll lx $ append lr r -- search down the right
122− -- side of the left tree
123− -- to find the rightmost
124− -- Null
125−
126−infixl 5 append as <>>
127−
128−instance monoidBuilder :: Monoid Builder where
129− mempty = Null
130−
131−-- | `Builder` is not an instance of `Foldable` because `Builder` is monomorphic.
132−foldl :: forall b. (b -> ArrayBuffer -> b) -> b -> Builder -> b
133−foldl f a Null = a
134−foldl f a (Node l x r) = foldl f (f (foldl f a l) x) r
135−
136−-- | Monomorphic foldM copied from
137−-- | [`Data.Foldable.foldM`](https://pursuit.purescript.org/packages/purescript-foldable-traversable/4.1.1/docs/Data.Foldable#v:foldM)
138−foldM :: forall b m. (Monad m) => (b -> ArrayBuffer -> m b) -> b -> Builder -> m b
139−foldM f a0 = foldl (\ma b -> ma >>= flip f b) (pure a0)
140−
141−-- | Construct a `Builder` with a single `ArrayBuffer`. *O(1)*
142−singleton :: ArrayBuffer -> Builder
143−singleton buf = Node Null buf Null
144−
145−-- | Add an `ArrayBuffer` to the end of the `Builder`. *O(1)*
146−snoc :: Builder -> ArrayBuffer -> Builder
147−snoc bs x = Node bs x Null
148−
149−-- | Build a single `ArrayBuffer` from a `Builder`. *O(n)*
150−execBuilder :: forall m. (MonadEffect m) => Builder -> m ArrayBuffer
151−execBuilder bldr = do
152− let buflen = foldl (\b a -> b + AB.byteLength a) 0 bldr
153− -- Allocate the final ArrayBuffer
154− buf <- liftEffect $ AB.empty buflen
155− -- Then copy each ArrayBuffer into the final ArrayBuffer.
156− -- To memcpy from one ArrayBuffer to another, apparently we have to first view
157− -- both ArrayBuffers as ArrayView (Typed Array).
158− newview <- liftEffect (AT.whole buf :: Effect Uint8Array)
159− _ <- foldM
160− ( \offset a -> do
161− aview <- liftEffect (AT.whole a :: Effect Uint8Array)
162− _ <- liftEffect $ AT.setTyped newview (Just offset) aview
163− pure $ offset + AB.byteLength a
164− ) 0 bldr
165− pure buf
166−
167−-- | Build an `ArrayBuffer` with do-notation in any `MonadEffect`. *O(n)*
168−execPutM :: forall m. (MonadEffect m) => PutM m Unit -> m ArrayBuffer
169−execPutM = execBuilder <=< execWriterT
170−
171−-- | Build an `ArrayBuffer` with do-notation. *O(n)*
172−execPut :: Put Unit -> Effect ArrayBuffer
173−execPut = execPutM
84+-- | putInt32be $ length messageBuilder
85+-- | tell messageBuilder
86+-- | ```
87+subBuilder :: forall m. Monad m => PutM m Unit -> PutM m Builder
88+subBuilder = lift <<< execWriterT
17489
17590-- | Append an `ArrayBuffer` to the builder.
176−putArrayBuffer :: forall m. (MonadEffect m) => ArrayBuffer -> PutM m Unit
177−putArrayBuffer = tell <<< singleton
91+putArrayBuffer :: forall m. Monad m => ArrayBuffer -> PutM m Unit
92+putArrayBuffer = tell <<< Internal.singleton <<< Internal.Buff
17893
179−-- | Serialize an 8-bit unsigned integer (byte) into a new `ArrayBuffer`.
180−encodeUint8 :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
181−encodeUint8 x = do
182− buf <- liftEffect $ AB.empty 1
183− _ <- liftEffect $ DV.setUint8 (DV.whole buf) 0 x
184− pure buf
94+-- | Append a `DataView` to the builder.
95+putDataView :: forall m. Monad m => DataView -> PutM m Unit
96+putDataView = tell <<< Internal.singleton <<< Internal.View
18597
186−-- | Append an 8-bit unsigned integer (byte) to the builder.
187−putUint8 :: forall m. (MonadEffect m) => UInt -> PutM m Unit
188−putUint8 = putArrayBuffer <=< encodeUint8
98+-- | Append either an `ArrayBuffer` or a `DataView` to the builder.
99+putDataBuff :: forall m. Monad m => DataBuff -> PutM m Unit
100+putDataBuff = tell <<< Internal.singleton
189101
190−-- | Serialize an 8-bit two’s-complement signed integer (char) into a new `ArrayBuffer`.
191−encodeInt8 :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
192−encodeInt8 x = do
193− buf <- liftEffect $ AB.empty 1
194− _ <- liftEffect $ DV.setInt8 (DV.whole buf) 0 x
195− pure buf
102+-- | Append an 8-bit unsigned integer (byte) to the builder.
103+putUint8 :: forall m. MonadEffect m => UInt -> PutM m Unit
104+putUint8 = putArrayBuffer <=< Internal.encodeUint8
196105
197106-- | Append an 8-bit two’s-complement signed integer (char) to the builder.
198−putInt8 :: forall m. (MonadEffect m) => Int -> PutM m Unit
199−putInt8 = putArrayBuffer <=< encodeInt8
200−
201−-- | Serialize a 16-bit big-endian unsigned integer into a new `ArrayBuffer`.
202−encodeUint16be :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
203−encodeUint16be x = do
204− buf <- liftEffect $ AB.empty 2
205− _ <- liftEffect $ DV.setUint16be (DV.whole buf) 0 x
206− pure buf
107+putInt8 :: forall m. MonadEffect m => Int -> PutM m Unit
108+putInt8 = putArrayBuffer <=< Internal.encodeInt8
207109
208110-- | Append a 16-bit big-endian unsigned integer to the builder.
209−putUint16be :: forall m. (MonadEffect m) => UInt -> PutM m Unit
210−putUint16be = putArrayBuffer <=< encodeUint16be
211−
212−-- | Serialize a 16-bit little-endian unsigned integer into a new `ArrayBuffer`.
213−encodeUint16le :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
214−encodeUint16le x = do
215− buf <- liftEffect $ AB.empty 2
216− _ <- liftEffect $ DV.setUint16le (DV.whole buf) 0 x
217− pure buf
111+putUint16be :: forall m. MonadEffect m => UInt -> PutM m Unit
112+putUint16be = putArrayBuffer <=< Internal.encodeUint16be
218113
219114-- | Append a 16-bit little-endian unsigned integer to the builder.
220−putUint16le :: forall m. (MonadEffect m) => UInt -> PutM m Unit
221−putUint16le = putArrayBuffer <=< encodeUint16le
222−
223−-- | Serialize a 16-bit big-endian two’s-complement signed integer into a new `ArrayBuffer`.
224−encodeInt16be :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
225−encodeInt16be x = do
226− buf <- liftEffect $ AB.empty 2
227− _ <- liftEffect $ DV.setInt16be (DV.whole buf) 0 x
228− pure buf
115+putUint16le :: forall m. MonadEffect m => UInt -> PutM m Unit
116+putUint16le = putArrayBuffer <=< Internal.encodeUint16le
229117
230118-- | Append a 16-bit big-endian two’s-complement signed integer to the builder.
231−putInt16be :: forall m. (MonadEffect m) => Int -> PutM m Unit
232−putInt16be = putArrayBuffer <=< encodeInt16be
233−
234−-- | Serialize a 16-bit little-endian two’s-complement signed integer into a new `ArrayBuffer`.
235−encodeInt16le :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
236−encodeInt16le x = do
237− buf <- liftEffect $ AB.empty 2
238− _ <- liftEffect $ DV.setInt16le (DV.whole buf) 0 x
239− pure buf
119+putInt16be :: forall m. MonadEffect m => Int -> PutM m Unit
120+putInt16be = putArrayBuffer <=< Internal.encodeInt16be
240121
241122-- | Append a 16-bit little-endian two’s-complement signed integer to the builder.
242−putInt16le :: forall m. (MonadEffect m) => Int -> PutM m Unit
243−putInt16le = putArrayBuffer <=< encodeInt16le
244−
245−-- | Serialize a 32-bit big-endian unsigned integer into a new `ArrayBuffer`.
246−encodeUint32be :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
247−encodeUint32be x = do
248− buf <- liftEffect $ AB.empty 4
249− _ <- liftEffect $ DV.setUint32be (DV.whole buf) 0 x
250− pure buf
123+putInt16le :: forall m. MonadEffect m => Int -> PutM m Unit
124+putInt16le = putArrayBuffer <=< Internal.encodeInt16le
251125
252126-- | Append a 32-bit big-endian unsigned integer to the builder.
253−putUint32be :: forall m. (MonadEffect m) => UInt -> PutM m Unit
254−putUint32be = putArrayBuffer <=< encodeUint32be
255−
256−-- | Serialize a 32-bit little-endian unsigned integer into a new `ArrayBuffer`.
257−encodeUint32le :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
258−encodeUint32le x = do
259− buf <- liftEffect $ AB.empty 4
260− _ <- liftEffect $ DV.setUint32le (DV.whole buf) 0 x
261− pure buf
127+putUint32be :: forall m. MonadEffect m => UInt -> PutM m Unit
128+putUint32be = putArrayBuffer <=< Internal.encodeUint32be
262129
263130-- | Append a 32-bit little-endian unsigned integer to the builder.
264−putUint32le :: forall m. (MonadEffect m) => UInt -> PutM m Unit
265−putUint32le = putArrayBuffer <=< encodeUint32le
266−
267−-- | Serialize a 32-bit big-endian two’s-complement signed integer into a new `ArrayBuffer`.
268−encodeInt32be :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
269−encodeInt32be x = do
270− buf <- liftEffect $ AB.empty 4
271− _ <- liftEffect $ DV.setInt32be (DV.whole buf) 0 x
272− pure buf
131+putUint32le :: forall m. MonadEffect m => UInt -> PutM m Unit
132+putUint32le = putArrayBuffer <=< Internal.encodeUint32le
273133
274134-- | Append a 32-bit big-endian two’s-complement signed integer to the builder.
275−putInt32be :: forall m. (MonadEffect m) => Int -> PutM m Unit
276−putInt32be = putArrayBuffer <=< encodeInt32be
277−
278−-- | Serialize a 32-bit little-endian two’s-complement signed integer into a new `ArrayBuffer`.
279−encodeInt32le :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
280−encodeInt32le x = do
281− buf <- liftEffect $ AB.empty 4
282− _ <- liftEffect $ DV.setInt32le (DV.whole buf) 0 x
283− pure buf
135+putInt32be :: forall m. MonadEffect m => Int -> PutM m Unit
136+putInt32be = putArrayBuffer <=< Internal.encodeInt32be
284137
285138-- | Append a 32-bit little-endian two’s-complement signed integer to the builder.
286−putInt32le :: forall m. (MonadEffect m) => Int -> PutM m Unit
287−putInt32le = putArrayBuffer <=< encodeInt32le
288−
289−-- | Serialize a 32-bit big-endian IEEE single-precision float into a new `ArrayBuffer`.
290−encodeFloat32be :: forall m. (MonadEffect m) => Float32 -> m ArrayBuffer
291−encodeFloat32be x = do
292− buf <- liftEffect $ AB.empty 4
293− _ <- liftEffect $ DV.setFloat32be (DV.whole buf) 0 x
294− pure buf
139+putInt32le :: forall m. MonadEffect m => Int -> PutM m Unit
140+putInt32le = putArrayBuffer <=< Internal.encodeInt32le
295141
296142-- | Append a 32-bit big-endian IEEE single-precision float to the builder.
297−putFloat32be :: forall m. (MonadEffect m) => Float32 -> PutM m Unit
298−putFloat32be = putArrayBuffer <=< encodeFloat32be
299−
300−-- | Serialize a 32-bit little-endian IEEE single-precision float into a new `ArrayBuffer`.
301−encodeFloat32le :: forall m. (MonadEffect m) => Float32 -> m ArrayBuffer
302−encodeFloat32le x = do
303− buf <- liftEffect $ AB.empty 4
304− _ <- liftEffect $ DV.setFloat32le (DV.whole buf) 0 x
305− pure buf
143+putFloat32be :: forall m. MonadEffect m => Float32 -> PutM m Unit
144+putFloat32be = putArrayBuffer <=< Internal.encodeFloat32be
306145
307146-- | Append a 32-bit little-endian IEEE single-precision float to the builder.
308−putFloat32le :: forall m. (MonadEffect m) => Float32 -> PutM m Unit
309−putFloat32le = putArrayBuffer <=< encodeFloat32le
310−
311−-- | Serialize a 64-bit big-endian IEEE double-precision float into a new `ArrayBuffer`.
312−encodeFloat64be :: forall m. (MonadEffect m) => Number -> m ArrayBuffer
313−encodeFloat64be x = do
314− buf <- liftEffect $ AB.empty 8
315− _ <- liftEffect $ DV.setFloat64be (DV.whole buf) 0 x
316− pure buf
147+putFloat32le :: forall m. MonadEffect m => Float32 -> PutM m Unit
148+putFloat32le = putArrayBuffer <=< Internal.encodeFloat32le
317149
318150-- | Append a 64-bit big-endian IEEE double-precision float to the builder.
319−putFloat64be :: forall m. (MonadEffect m) => Number -> PutM m Unit
320−putFloat64be = putArrayBuffer <=< encodeFloat64be
321−
322−-- | Serialize a 64-bit little-endian IEEE double-precision float into a new `ArrayBuffer`.
323−encodeFloat64le :: forall m. (MonadEffect m) => Number -> m ArrayBuffer
324−encodeFloat64le x = do
325− buf <- liftEffect $ AB.empty 8
326− _ <- liftEffect $ DV.setFloat64le (DV.whole buf) 0 x
327− pure buf
151+putFloat64be :: forall m. MonadEffect m => Number -> PutM m Unit
152+putFloat64be = putArrayBuffer <=< Internal.encodeFloat64be
328153
329154-- | Append a 64-bit little-endian IEEE double-precision float to the builder.
330−putFloat64le :: forall m. (MonadEffect m) => Number -> PutM m Unit
331−putFloat64le = putArrayBuffer <=< encodeFloat64le
332−
333−
334−-- ## Implementation Details
335−--
336−-- We want our `Builder` to be a data structure with
337−-- * *O(1)* monoid append
338−-- * *O(n)* fold
339−--
340−-- Our `Builder` implementation is an unbalanced binary tree.
341−--
342−-- For monoid `append`, what we actually get is *O(1)* when either the
343−-- left or right tree is a singleton. If that's not true, then in the
344−-- unlikely worst case `append` might be *O(n)*.
345−--
346−-- `Builder` is optimized what we consider to be normal usage, that is,
347−-- `snoc`ing singleton elements to the end of the `Builder`.
348−--
349−-- If a Builder is built entirely by `snoc`ing, it will look like a
350−-- left-only binary tree, a.k.a. a linked list.
351−--
352−-- ```
353−-- ④
354−-- ╱
355−-- ③
356−-- ╱
357−-- ②
358−-- ╱
359−-- ①
360−-- ```
361−--
362−-- If two of these `snoc`-built trees are `append`ed, then the new tree
363−-- will look like
364−--
365−-- ```
366−-- ④
367−-- ╱ ╲
368−-- ③ ⑧
369−-- ╱ ╱
370−-- ② ⑦
371−-- ╱ ╱
372−-- ① ⑥
373−-- ╱
374−-- ⑤
375−-- ```
376−--
377−-- This is all similar to
378−-- [__bytestring-tree-builder__](https://hackage.haskell.org/package/bytestring-tree-builder)
379−-- , except that the
380−-- [`Tree`](https://hackage.haskell.org/package/bytestring-tree-builder-0.2.7.3/docs/src/ByteString.TreeBuilder.Tree.html#Tree)
381−-- structure in __bytestring-tree-builder__ only carries values in its
382−-- leaves, which is how it achieves *O(1)* appending, at the cost of
383−-- a higher coefficient time factor on the fold.
384−--
385−-- We hope that this implementation is fairly fast, but we
386−-- haven't chosen this implementation because it's fast, we've chosen
387−-- this implementation because it's simple.
388−-- If someone wants to create a fast Purescript ArrayBuffer serialization
389−-- library, then they can benchmark against this one to prove that the new
390−-- one is fast.
391−--
392−-- One relatively cheap and simple performance improvement for this library would be to
393−-- remove the Null constructor of `Builder` and instead use Javascript nulls.
394−--
395−-- In the longer term, it might make sense to try to change the Builder so
396−-- that it works like the
397−-- https://hackage.haskell.org/package/bytestring/docs/Data-ByteString-Builder.html
398−--
399−-- Here are some benchmarks of different Haskell ByteString builders
400−-- https://github.com/haskell-perf/strict-bytestring-builders
401−--
402−-- We've tried to design the API for this library with minimal assumptions,
403−-- so that if we want to change the Builder implementation later then we can.
404−--
405−-- Another way this could go:
406−-- https://kodimensional.dev/posts/2019-03-25-comonadic-builders
155+putFloat64le :: forall m. MonadEffect m => Number -> PutM m Unit
156+putFloat64le = putArrayBuffer <=< Internal.encodeFloat64le