@@ -4,153 +4,395 @@
44-- |
55-- | Writing to an `ArrayBuffer` is an `Effect`ful activity, so most
66-- | functions in this module must be run in a `MonadEffect` context.
7−-- |
8−-- | For other operations for working with `ArrayBuffer`, see
9−-- | module
10−-- | [`Data.ArrayBuffer.ArrayBuffer`](https://pursuit.purescript.org/packages/purescript-arraybuffer/docs/Data.ArrayBuffer.ArrayBuffer)
11−-- | in package __arraybuffer__.
127module Data.ArrayBuffer.Builder
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
8+( PutM
9+, Put
10+, execPutM
11+, execPut
12+, putArrayBuffer
13+, putUint8
14+, putInt8
15+, putUint16be
16+, putUint16le
17+, putInt16be
18+, putInt16le
19+, putUint32be
20+, putUint32le
21+, putInt32be
22+, putInt32le
23+, putFloat32be
24+, putFloat32le
25+, putFloat64be
26+, putFloat64le
27+, Builder
28+, (<>>)
29+, execBuilder
30+, singleton
31+, snoc
32+, encodeUint8
33+, encodeInt8
34+, encodeUint16be
35+, encodeUint16le
36+, encodeInt16be
37+, encodeInt16le
38+, encodeUint32be
39+, encodeUint32le
40+, encodeInt32be
41+, encodeInt32le
42+, encodeFloat32be
43+, encodeFloat32le
44+, encodeFloat64be
45+, encodeFloat64le
46+)
47+where
3748
3849import Prelude
3950
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)
51+import Control.Monad.Writer.Trans (WriterT, execWriterT, tell)
52+import Data.ArrayBuffer.ArrayBuffer as AB
53+import Data.ArrayBuffer.DataView as DV
54+import Data.ArrayBuffer.Typed as AT
55+import Data.ArrayBuffer.Types (ArrayBuffer, Uint8Array)
4556import Data.Float32 (Float32)
57+import Data.Maybe (Maybe(..))
4658import Data.UInt (UInt)
4759import Effect (Effect)
48−import Effect.Class (class MonadEffect)
60+import Effect.Class (class MonadEffect, liftEffect)
4961
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.
62+-- | The `PutM` monad is a Writer transformer monad which
63+-- | [gives us access to do-notation](https://wiki.haskell.org/Do_notation_considered_harmful#Library_design)
64+-- | for building `ArrayBuffer`s.
5665type PutM = WriterT Builder
5766
58−-- | The `PutM` type reified to `Effect`, in other words `WriterT Builder Effect`.
67+-- | `Put` monad is the non-transformer version of `PutM`.
5968type Put = PutM Effect
6069
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.
70+-- | Monoidal builder for `ArrayBuffer`s.
7071-- |
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.
72+-- | ### Left-associative `<>>` append operator
7573-- |
76−-- | In a `PutM` monad do-block, we can
74+-- | __TL;DR__ You probably don't want to use the `Builder` monoid directly
75+-- | in your code, it’s better to use the `PutM` monad with do-notation instead.
7776-- |
78−-- | ```
79−-- | do
80−-- | messageBuilder <- subBuilder $ do
81−-- | putField1
82−-- | putField2
77+-- | The `Builder` monoid in this library is efficient when we `snoc` single
78+-- | items onto the end of it, or when we only `cons` single items to the
79+-- | beginning, but it can be less efficient when we are mixing `cons` and
80+-- | `snoc`.
81+-- | This matters when we're appending three or more `Builder`s
82+-- | in one associative expression, because the
83+-- | `Semigroup` append operator `<>` is right-associative.
8384-- |
84−-- | putInt32be $ length messageBuilder
85−-- | tell messageBuilder
85+-- | To solve this, we provide an operator `<>>` for appending `Builders`.
86+-- | `<>>` is exactly the same as `<>`, but left-associative.
87+-- | This only matters when we're chaining together three
88+-- | or more `Builder`s in a single associative expression.
89+-- | Instead of
90+-- | ```
91+-- | builder₁ <> builder₂ <> builder₃
92+-- | ```
93+-- | we should always prefer to
94+-- | write
95+-- | ```
96+-- | builder₁ <>> builder₂ <>> builder₃
8697-- | ```
87−subBuilder :: forall m. Monad m => PutM m Unit -> PutM m Builder
88−subBuilder = lift <<< execWriterT
98+-- | so that we get the efficient
99+-- | `snoc`ing of `Builder`s.
100+-- |
101+-- | If we build our `ArrayBuffer`s with the `PutM` monad instead of appending by
102+-- | using the `Semigroup` instance of `Builder`, then we always get the efficient
103+-- | `snoc` case.
104+-- |
105+data Builder
106+ = Node Builder ArrayBuffer Builder
107+ | Null
89108
90−-- | Append an `ArrayBuffer` to the builder.
91−putArrayBuffer :: forall m. Monad m => ArrayBuffer -> PutM m Unit
92−putArrayBuffer = tell <<< Internal.singleton <<< Internal.Buff
109+instance semigroupBuilder :: Semigroup Builder where
110+ append Null Null = Null
111+ append l Null = l
112+ append Null r = r
113+ append l (Node Null rx rr) = Node l rx rr -- this is the snoc case
114+ append (Node ll lx Null) r = Node ll lx r -- found the rightmost Null
115+ -- of the left tree
116+ append (Node ll lx lr) r = Node ll lx $ append lr r -- search down the right
117+ -- side of the left tree
118+ -- to find the rightmost
119+ -- Null
120+
121+infixl 5 append as <>>
122+
123+instance monoidBuilder :: Monoid Builder where
124+ mempty = Null
125+
126+-- | `Builder` is not an instance of `Foldable` because `Builder` is monomorphic.
127+foldl :: forall b. (b -> ArrayBuffer -> b) -> b -> Builder -> b
128+foldl f a Null = a
129+foldl f a (Node l x r) = foldl f (f (foldl f a l) x) r
130+
131+-- | Monomorphic foldM copied from
132+-- | [`Data.Foldable.foldM`](https://pursuit.purescript.org/packages/purescript-foldable-traversable/4.1.1/docs/Data.Foldable#v:foldM)
133+foldM :: forall b m. (Monad m) => (b -> ArrayBuffer -> m b) -> b -> Builder -> m b
134+foldM f a0 = foldl (\ma b -> ma >>= flip f b) (pure a0)
135+
136+-- | Construct a `Builder` with a single `ArrayBuffer`. *O(1)*
137+singleton :: ArrayBuffer -> Builder
138+singleton buf = Node Null buf Null
139+
140+-- | Add an `ArrayBuffer` to the end of the `Builder`. *O(1)*
141+snoc :: Builder -> ArrayBuffer -> Builder
142+snoc bs x = Node bs x Null
143+
144+-- | Build a single `ArrayBuffer` from a `Builder`. *O(n)*
145+execBuilder :: forall m. (MonadEffect m) => Builder -> m ArrayBuffer
146+execBuilder bldr = do
147+ let buflen = foldl (\b a -> b + AB.byteLength a) 0 bldr
148+ -- Allocate the final ArrayBuffer
149+ buf <- liftEffect $ AB.empty buflen
150+ -- Then copy each ArrayBuffer into the final ArrayBuffer.
151+ -- To memcpy from one ArrayBuffer to another, apparently we have to first view
152+ -- both ArrayBuffers as ArrayView (Typed Array).
153+ newview <- liftEffect (AT.whole buf :: Effect Uint8Array)
154+ _ <- foldM
155+ ( \offset a -> do
156+ aview <- liftEffect (AT.whole a :: Effect Uint8Array)
157+ _ <- liftEffect $ AT.setTyped newview (Just offset) aview
158+ pure $ offset + AB.byteLength a
159+ ) 0 bldr
160+ pure buf
93161
94−-- | Append a `DataView` to the builder.
95−putDataView :: forall m. Monad m => DataView -> PutM m Unit
96−putDataView = tell <<< Internal.singleton <<< Internal.View
162+-- | Build an `ArrayBuffer` with do-notation in any `MonadEffect`. *O(n)*
163+execPutM :: forall m. (MonadEffect m) => PutM m Unit -> m ArrayBuffer
164+execPutM = execBuilder <=< execWriterT
97165
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
166+-- | Build an `ArrayBuffer` with do-notation. *O(n)*
167+execPut :: Put Unit -> Effect ArrayBuffer
168+execPut = execPutM
169+
170+-- | Append an `ArrayBuffer` to the builder.
171+putArrayBuffer :: forall m. (MonadEffect m) => ArrayBuffer -> PutM m Unit
172+putArrayBuffer = tell <<< singleton
173+
174+-- | Serialize an 8-bit unsigned integer (byte) into a new `ArrayBuffer`.
175+encodeUint8 :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
176+encodeUint8 x = do
177+ buf <- liftEffect $ AB.empty 1
178+ _ <- liftEffect $ DV.setUint8 (DV.whole buf) 0 x
179+ pure buf
101180
102181-- | 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
182+putUint8 :: forall m. (MonadEffect m) => UInt -> PutM m Unit
183+putUint8 = putArrayBuffer <=< encodeUint8
184+
185+-- | Serialize an 8-bit two’s-complement signed integer (char) into a new `ArrayBuffer`.
186+encodeInt8 :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
187+encodeInt8 x = do
188+ buf <- liftEffect $ AB.empty 1
189+ _ <- liftEffect $ DV.setInt8 (DV.whole buf) 0 x
190+ pure buf
105191
106192-- | Append an 8-bit two’s-complement signed integer (char) to the builder.
107−putInt8 :: forall m. MonadEffect m => Int -> PutM m Unit
108−putInt8 = putArrayBuffer <=< Internal.encodeInt8
193+putInt8 :: forall m. (MonadEffect m) => Int -> PutM m Unit
194+putInt8 = putArrayBuffer <=< encodeInt8
195+
196+-- | Serialize a 16-bit big-endian unsigned integer into a new `ArrayBuffer`.
197+encodeUint16be :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
198+encodeUint16be x = do
199+ buf <- liftEffect $ AB.empty 2
200+ _ <- liftEffect $ DV.setUint16be (DV.whole buf) 0 x
201+ pure buf
109202
110203-- | Append a 16-bit big-endian unsigned integer to the builder.
111−putUint16be :: forall m. MonadEffect m => UInt -> PutM m Unit
112−putUint16be = putArrayBuffer <=< Internal.encodeUint16be
204+putUint16be :: forall m. (MonadEffect m) => UInt -> PutM m Unit
205+putUint16be = putArrayBuffer <=< encodeUint16be
206+
207+-- | Serialize a 16-bit little-endian unsigned integer into a new `ArrayBuffer`.
208+encodeUint16le :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
209+encodeUint16le x = do
210+ buf <- liftEffect $ AB.empty 2
211+ _ <- liftEffect $ DV.setUint16le (DV.whole buf) 0 x
212+ pure buf
113213
114214-- | Append a 16-bit little-endian unsigned integer to the builder.
115−putUint16le :: forall m. MonadEffect m => UInt -> PutM m Unit
116−putUint16le = putArrayBuffer <=< Internal.encodeUint16le
215+putUint16le :: forall m. (MonadEffect m) => UInt -> PutM m Unit
216+putUint16le = putArrayBuffer <=< encodeUint16le
217+
218+-- | Serialize a 16-bit big-endian two’s-complement signed integer into a new `ArrayBuffer`.
219+encodeInt16be :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
220+encodeInt16be x = do
221+ buf <- liftEffect $ AB.empty 2
222+ _ <- liftEffect $ DV.setInt16be (DV.whole buf) 0 x
223+ pure buf
117224
118225-- | Append a 16-bit big-endian two’s-complement signed integer to the builder.
119−putInt16be :: forall m. MonadEffect m => Int -> PutM m Unit
120−putInt16be = putArrayBuffer <=< Internal.encodeInt16be
226+putInt16be :: forall m. (MonadEffect m) => Int -> PutM m Unit
227+putInt16be = putArrayBuffer <=< encodeInt16be
228+
229+-- | Serialize a 16-bit little-endian two’s-complement signed integer into a new `ArrayBuffer`.
230+encodeInt16le :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
231+encodeInt16le x = do
232+ buf <- liftEffect $ AB.empty 2
233+ _ <- liftEffect $ DV.setInt16le (DV.whole buf) 0 x
234+ pure buf
121235
122236-- | Append a 16-bit little-endian two’s-complement signed integer to the builder.
123−putInt16le :: forall m. MonadEffect m => Int -> PutM m Unit
124−putInt16le = putArrayBuffer <=< Internal.encodeInt16le
237+putInt16le :: forall m. (MonadEffect m) => Int -> PutM m Unit
238+putInt16le = putArrayBuffer <=< encodeInt16le
239+
240+-- | Serialize a 32-bit big-endian unsigned integer into a new `ArrayBuffer`.
241+encodeUint32be :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
242+encodeUint32be x = do
243+ buf <- liftEffect $ AB.empty 4
244+ _ <- liftEffect $ DV.setUint32be (DV.whole buf) 0 x
245+ pure buf
125246
126247-- | Append a 32-bit big-endian unsigned integer to the builder.
127−putUint32be :: forall m. MonadEffect m => UInt -> PutM m Unit
128−putUint32be = putArrayBuffer <=< Internal.encodeUint32be
248+putUint32be :: forall m. (MonadEffect m) => UInt -> PutM m Unit
249+putUint32be = putArrayBuffer <=< encodeUint32be
250+
251+-- | Serialize a 32-bit little-endian unsigned integer into a new `ArrayBuffer`.
252+encodeUint32le :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
253+encodeUint32le x = do
254+ buf <- liftEffect $ AB.empty 4
255+ _ <- liftEffect $ DV.setUint32le (DV.whole buf) 0 x
256+ pure buf
129257
130258-- | Append a 32-bit little-endian unsigned integer to the builder.
131−putUint32le :: forall m. MonadEffect m => UInt -> PutM m Unit
132−putUint32le = putArrayBuffer <=< Internal.encodeUint32le
259+putUint32le :: forall m. (MonadEffect m) => UInt -> PutM m Unit
260+putUint32le = putArrayBuffer <=< encodeUint32le
261+
262+-- | Serialize a 32-bit big-endian two’s-complement signed integer into a new `ArrayBuffer`.
263+encodeInt32be :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
264+encodeInt32be x = do
265+ buf <- liftEffect $ AB.empty 4
266+ _ <- liftEffect $ DV.setInt32be (DV.whole buf) 0 x
267+ pure buf
133268
134269-- | Append a 32-bit big-endian two’s-complement signed integer to the builder.
135−putInt32be :: forall m. MonadEffect m => Int -> PutM m Unit
136−putInt32be = putArrayBuffer <=< Internal.encodeInt32be
270+putInt32be :: forall m. (MonadEffect m) => Int -> PutM m Unit
271+putInt32be = putArrayBuffer <=< encodeInt32be
272+
273+-- | Serialize a 32-bit little-endian two’s-complement signed integer into a new `ArrayBuffer`.
274+encodeInt32le :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
275+encodeInt32le x = do
276+ buf <- liftEffect $ AB.empty 4
277+ _ <- liftEffect $ DV.setInt32le (DV.whole buf) 0 x
278+ pure buf
137279
138280-- | Append a 32-bit little-endian two’s-complement signed integer to the builder.
139−putInt32le :: forall m. MonadEffect m => Int -> PutM m Unit
140−putInt32le = putArrayBuffer <=< Internal.encodeInt32le
281+putInt32le :: forall m. (MonadEffect m) => Int -> PutM m Unit
282+putInt32le = putArrayBuffer <=< encodeInt32le
283+
284+-- | Serialize a 32-bit big-endian IEEE single-precision float into a new `ArrayBuffer`.
285+encodeFloat32be :: forall m. (MonadEffect m) => Float32 -> m ArrayBuffer
286+encodeFloat32be x = do
287+ buf <- liftEffect $ AB.empty 4
288+ _ <- liftEffect $ DV.setFloat32be (DV.whole buf) 0 x
289+ pure buf
141290
142291-- | Append a 32-bit big-endian IEEE single-precision float to the builder.
143−putFloat32be :: forall m. MonadEffect m => Float32 -> PutM m Unit
144−putFloat32be = putArrayBuffer <=< Internal.encodeFloat32be
292+putFloat32be :: forall m. (MonadEffect m) => Float32 -> PutM m Unit
293+putFloat32be = putArrayBuffer <=< encodeFloat32be
294+
295+-- | Serialize a 32-bit little-endian IEEE single-precision float into a new `ArrayBuffer`.
296+encodeFloat32le :: forall m. (MonadEffect m) => Float32 -> m ArrayBuffer
297+encodeFloat32le x = do
298+ buf <- liftEffect $ AB.empty 4
299+ _ <- liftEffect $ DV.setFloat32le (DV.whole buf) 0 x
300+ pure buf
145301
146302-- | Append a 32-bit little-endian IEEE single-precision float to the builder.
147−putFloat32le :: forall m. MonadEffect m => Float32 -> PutM m Unit
148−putFloat32le = putArrayBuffer <=< Internal.encodeFloat32le
303+putFloat32le :: forall m. (MonadEffect m) => Float32 -> PutM m Unit
304+putFloat32le = putArrayBuffer <=< encodeFloat32le
305+
306+-- | Serialize a 64-bit big-endian IEEE double-precision float into a new `ArrayBuffer`.
307+encodeFloat64be :: forall m. (MonadEffect m) => Number -> m ArrayBuffer
308+encodeFloat64be x = do
309+ buf <- liftEffect $ AB.empty 8
310+ _ <- liftEffect $ DV.setFloat64be (DV.whole buf) 0 x
311+ pure buf
149312
150313-- | Append a 64-bit big-endian IEEE double-precision float to the builder.
151−putFloat64be :: forall m. MonadEffect m => Number -> PutM m Unit
152−putFloat64be = putArrayBuffer <=< Internal.encodeFloat64be
314+putFloat64be :: forall m. (MonadEffect m) => Number -> PutM m Unit
315+putFloat64be = putArrayBuffer <=< encodeFloat64be
316+
317+-- | Serialize a 64-bit little-endian IEEE double-precision float into a new `ArrayBuffer`.
318+encodeFloat64le :: forall m. (MonadEffect m) => Number -> m ArrayBuffer
319+encodeFloat64le x = do
320+ buf <- liftEffect $ AB.empty 8
321+ _ <- liftEffect $ DV.setFloat64le (DV.whole buf) 0 x
322+ pure buf
153323
154324-- | Append a 64-bit little-endian IEEE double-precision float to the builder.
155−putFloat64le :: forall m. MonadEffect m => Number -> PutM m Unit
156−putFloat64le = putArrayBuffer <=< Internal.encodeFloat64le
325+putFloat64le :: forall m. (MonadEffect m) => Number -> PutM m Unit
326+putFloat64le = putArrayBuffer <=< encodeFloat64le
327+
328+
329+-- ## Implementation Details
330+--
331+-- We want our `Builder` to be a data structure with
332+-- * *O(1)* monoid append
333+-- * *O(n)* fold
334+--
335+-- Our `Builder` implementation is an unbalanced binary tree.
336+--
337+-- For monoid `append`, what we actually get is *O(1)* when either the
338+-- left or right tree is a singleton. If that's not true, then in the
339+-- unlikely worst case `append` might be *O(n)*.
340+--
341+-- `Builder` is optimized what we consider to be normal usage, that is,
342+-- `snoc`ing singleton elements to the end of the `Builder`.
343+--
344+-- If a Builder is built entirely by `snoc`ing, it will look like a
345+-- left-only binary tree, a.k.a. a linked list.
346+--
347+-- ```
348+-- ④
349+-- ╱
350+-- ③
351+-- ╱
352+-- ②
353+-- ╱
354+-- ①
355+-- ```
356+--
357+-- If two of these `snoc`-built trees are `append`ed, then the new tree
358+-- will look like
359+--
360+-- ```
361+-- ④
362+-- ╱ ╲
363+-- ③ ⑧
364+-- ╱ ╱
365+-- ② ⑦
366+-- ╱ ╱
367+-- ① ⑥
368+-- ╱
369+-- ⑤
370+-- ```
371+--
372+-- This is all similar to
373+-- [__bytestring-tree-builder__](https://hackage.haskell.org/package/bytestring-tree-builder)
374+-- , except that the
375+-- [`Tree`](https://hackage.haskell.org/package/bytestring-tree-builder-0.2.7.3/docs/src/ByteString.TreeBuilder.Tree.html#Tree)
376+-- structure in __bytestring-tree-builder__ only carries values in its
377+-- leaves, which is how it achieves *O(1)* appending, at the cost of
378+-- a higher coefficient time factor on the fold.
379+--
380+-- We hope that this implementation is fairly fast, but we
381+-- haven't chosen this implementation because it's fast, we've chosen
382+-- this implementation because it's simple.
383+-- If someone wants to create a fast Purescript ArrayBuffer serialization
384+-- library, then they can benchmark against this one to prove that the new
385+-- one is fast.
386+--
387+-- One relatively cheap and simple performance improvement for this library would be to
388+-- remove the Null constructor of `Builder` and instead use Javascript nulls.
389+--
390+-- In the longer term, it might make sense to try to change the Builder so
391+-- that it works like the
392+-- https://hackage.haskell.org/package/bytestring/docs/Data-ByteString-Builder.html
393+--
394+-- Here are some benchmarks of different Haskell ByteString builders
395+-- https://github.com/haskell-perf/strict-bytestring-builders
396+--
397+-- We've tried to design the API for this library with minimal assumptions,
398+-- so that if we want to change the Builder implementation later then we can.