@@ -1,156 +1,454 @@
1−-- | This module provides a `Builder` monoid and a `PutM` monad
2−-- | for serializing `Data.ArrayBuffer.Types.ArrayBuffer`s.
3−-- | See the package README for usage examples.
1+-- | `ArrayBuffer` serialization in the “builder monoid” style.
42-- |
5−-- | Writing to an `ArrayBuffer` is an `Effect`ful activity, so most
6−-- | functions in this module must be run in a `MonadEffect` context.
3+-- | This module provides a `Builder` monoid and a `PutM` monad which are roughly
4+-- | equivalent to types of the same name in the Haskell
5+-- | [`Data.Binary.Put`](https://hackage.haskell.org/package/binary/docs/Data-Binary-Put.html)
6+-- | module.
77-- |
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__.
8+-- | This library defines no typeclasses.
9+-- |
10+-- | ## Deserialization
11+-- |
12+-- | See
13+-- | [__purescript-parsing-dataview__](https://pursuit.purescript.org/packages/purescript-parsing-dataview/)
14+-- | for a way to deserialize from `ArrayBuffer` back to Purescript data.
15+-- |
16+-- | ## Usage Examples
17+-- |
18+-- | All `ArrayBuffer` building must occur in `Effect`.
19+-- |
20+-- | ### Serialize an integer
21+-- |
22+-- | Create a two-byte `arraybuffer :: ArrayBuffer` which contains the number *-2* encoded as big-endian 16-bit two’s-complement.
23+-- | ```purescript
24+-- | do
25+-- | arraybuffer <- execPut $ putInt16be (-2)
26+-- | ```
27+-- |
28+-- | ### Serialize a `String` as UTF8
29+-- |
30+-- | A function which encodes a `String` as UTF8 with a length prefix in a
31+-- | way that's compatible with the
32+-- | [`Binary.Put.putStringUtf8`](https://hackage.haskell.org/package/binary/docs/Data-Binary-Put.html#v:putStringUtf8)
33+-- | function from the Haskell
34+-- | [__binary__](https://hackage.haskell.org/package/binary)
35+-- | library.
36+-- | Uses [`Data.TextEncoding.encodeUtf8`](https://pursuit.purescript.org/packages/purescript-text-encoding/docs/Data.TextEncoding#v:encodeUtf8).
37+-- | ```purescript
38+-- | putStringUtf8 :: forall m. (MonadEffect m) => String -> PutM m Unit
39+-- | putStringUtf8 s = do
40+-- | let stringbuf = Data.ArrayBuffer.Typed.buffer $
41+-- | Data.TextEncoding.encodeUtf8 s
42+-- | -- Put a 64-bit big-endian length prefix for the length of the utf8
43+-- | -- string, in bytes.
44+-- | putUint32be 0
45+-- | putUint32be $ Data.Uint.fromInt $ Data.ArrayBuffer.byteLength stringbuf
46+-- | putArrayBuffer stringbuf
47+-- | ```
48+-- |
49+-- | ### Serialize an `Array Int`
50+-- |
51+-- | A function which encodes an `Array Int` with a length prefix in a
52+-- | way that's compatible with the
53+-- | [`Binary` instance for `[Int32]`](https://hackage.haskell.org/package/binary/docs/Data-Binary.html#t:Binary)
54+-- | from the Haskell
55+-- | [__binary__](https://hackage.haskell.org/package/binary)
56+-- | library.
57+-- | ```purescript
58+-- | putArrayInt32 :: forall m. (MonadEffect m) => Array Int -> PutM m Unit
59+-- | putArrayInt32 xs = do
60+-- | -- Put a 64-bit big-endian length prefix for the length of the
61+-- | -- array, in bytes.
62+-- | putUint32be 0
63+-- | putUint32be $ Data.Uint.fromInt $ Data.Array.length xs
64+-- | traverse_ putInt32be xs
65+-- | ```
1266module 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
67+( PutM
68+, Put
69+, execPutM
70+, execPut
71+, putArrayBuffer
72+, putUint8
73+, putInt8
74+, putUint16be
75+, putUint16le
76+, putInt16be
77+, putInt16le
78+, putUint32be
79+, putUint32le
80+, putInt32be
81+, putInt32le
82+, putFloat32be
83+, putFloat32le
84+, putFloat64be
85+, putFloat64le
86+, Builder
87+, (<>>)
88+, execBuilder
89+, singleton
90+, snoc
91+, encodeUint8
92+, encodeInt8
93+, encodeUint16be
94+, encodeUint16le
95+, encodeInt16be
96+, encodeInt16le
97+, encodeUint32be
98+, encodeUint32le
99+, encodeInt32be
100+, encodeInt32le
101+, encodeFloat32be
102+, encodeFloat32le
103+, encodeFloat64be
104+, encodeFloat64le
105+)
106+where
37107
38108import Prelude
39109
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)
110+import Control.Monad.Writer.Trans (WriterT, execWriterT, tell)
111+import Data.ArrayBuffer.ArrayBuffer as AB
112+import Data.ArrayBuffer.DataView as DV
113+import Data.ArrayBuffer.Typed as AT
114+import Data.ArrayBuffer.Types (ArrayBuffer, Uint8Array)
45115import Data.Float32 (Float32)
116+import Data.Maybe (Maybe(..))
46117import Data.UInt (UInt)
47118import Effect (Effect)
48−import Effect.Class (class MonadEffect)
119+import Effect.Class (class MonadEffect, liftEffect)
49120
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.
121+-- | The `PutM` monad is a Writer transformer monad which
122+-- | [gives us access to do-notation](https://wiki.haskell.org/Do_notation_considered_harmful#Library_design)
123+-- | for building `ArrayBuffer`s.
56124type PutM = WriterT Builder
57125
58−-- | The `PutM` type reified to `Effect`, in other words `WriterT Builder Effect`.
126+-- | `Put` monad is the non-transformer version of `PutM`.
59127type Put = PutM Effect
60128
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.
129+-- | Monoidal builder for `ArrayBuffer`s.
70130-- |
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.
131+-- | ### Left-associative `<>>` append operator
75132-- |
76−-- | In a `PutM` monad do-block, we can
133+-- | __TL;DR__ You probably don't want to use the `Builder` monoid directly
134+-- | in your code, it’s better to use the `PutM` monad with do-notation instead.
77135-- |
78−-- | ```
79−-- | do
80−-- | messageBuilder <- subBuilder $ do
81−-- | putField1
82−-- | putField2
136+-- | The `Builder` monoid in this library is efficient when we `snoc` single
137+-- | items onto the end of it, or when we only `cons` single items to the
138+-- | beginning, but it can be less efficient when we are mixing `cons` and
139+-- | `snoc`.
140+-- | This matters when we're appending three or more `Builder`s
141+-- | in one associative expression, because the
142+-- | `Semigroup` append operator `<>` is right-associative.
83143-- |
84−-- | putInt32be $ length messageBuilder
85−-- | tell messageBuilder
144+-- | To solve this, we provide an operator `<>>` for appending `Builders`.
145+-- | `<>>` is exactly the same as `<>`, but left-associative.
146+-- | This only matters when we're chaining together three
147+-- | or more `Builder`s in a single associative expression.
148+-- | Instead of
149+-- | ```
150+-- | builder₁ <> builder₂ <> builder₃
151+-- | ```
152+-- | we should always prefer to
153+-- | write
86154-- | ```
87−subBuilder :: forall m. Monad m => PutM m Unit -> PutM m Builder
88−subBuilder = lift <<< execWriterT
155+-- | builder₁ <>> builder₂ <>> builder₃
156+-- | ```
157+-- | so that we get the efficient
158+-- | `snoc`ing of `Builder`s.
159+-- |
160+-- | If we build our `ArrayBuffer`s with the `PutM` monad instead of appending by
161+-- | using the `Semigroup` instance of `Builder`, then we always get the efficient
162+-- | `snoc` case.
163+-- |
164+data Builder
165+ = Node Builder ArrayBuffer Builder
166+ | Null
89167
90−-- | Append an `ArrayBuffer` to the builder.
91−putArrayBuffer :: forall m. Monad m => ArrayBuffer -> PutM m Unit
92−putArrayBuffer = tell <<< Internal.singleton <<< Internal.Buff
168+instance semigroupBuilder :: Semigroup Builder where
169+ append Null Null = Null
170+ append l Null = l
171+ append Null r = r
172+ append l (Node Null rx rr) = Node l rx rr -- this is the snoc case
173+ append (Node ll lx Null) r = Node ll lx r -- found the rightmost Null
174+ -- of the left tree
175+ append (Node ll lx lr) r = Node ll lx $ append lr r -- search down the right
176+ -- side of the left tree
177+ -- to find the rightmost
178+ -- Null
93179
94−-- | Append a `DataView` to the builder.
95−putDataView :: forall m. Monad m => DataView -> PutM m Unit
96−putDataView = tell <<< Internal.singleton <<< Internal.View
180+infixl 5 append as <>>
97181
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
182+instance monoidBuilder :: Monoid Builder where
183+ mempty = Null
184+
185+-- | `Builder` is not an instance of `Foldable` because `Builder` is monomorphic.
186+foldl :: forall b. (b -> ArrayBuffer -> b) -> b -> Builder -> b
187+foldl f a Null = a
188+foldl f a (Node l x r) = foldl f (f (foldl f a l) x) r
189+
190+-- | Monomorphic foldM copied from
191+-- | [`Data.Foldable.foldM`](https://pursuit.purescript.org/packages/purescript-foldable-traversable/4.1.1/docs/Data.Foldable#v:foldM)
192+foldM :: forall b m. (Monad m) => (b -> ArrayBuffer -> m b) -> b -> Builder -> m b
193+foldM f a0 = foldl (\ma b -> ma >>= flip f b) (pure a0)
194+
195+-- | Construct a `Builder` with a single `ArrayBuffer`. *O(1)*
196+singleton :: ArrayBuffer -> Builder
197+singleton buf = Node Null buf Null
198+
199+-- | Add an `ArrayBuffer` to the end of the `Builder`. *O(1)*
200+snoc :: Builder -> ArrayBuffer -> Builder
201+snoc bs x = Node bs x Null
202+
203+-- | Build a single `ArrayBuffer` from a `Builder`. *O(n)*
204+execBuilder :: forall m. (MonadEffect m) => Builder -> m ArrayBuffer
205+execBuilder bldr = do
206+ let buflen = foldl (\b a -> b + AB.byteLength a) 0 bldr
207+ -- Allocate the final ArrayBuffer
208+ buf <- liftEffect $ AB.empty buflen
209+ -- Then copy each ArrayBuffer into the final ArrayBuffer.
210+ -- To memcpy from one ArrayBuffer to another, apparently we have to first view
211+ -- both ArrayBuffers as ArrayView (Typed Array).
212+ newview <- liftEffect (AT.whole buf :: Effect Uint8Array)
213+ _ <- foldM
214+ ( \offset a -> do
215+ let offset' = offset + AB.byteLength a
216+ aview <- liftEffect (AT.whole a :: Effect Uint8Array)
217+ _ <- liftEffect $ AT.setTyped newview (Just offset') aview
218+ pure offset'
219+ ) 0 bldr
220+ pure buf
221+
222+-- | Build an `ArrayBuffer` with do-notation in any `MonadEffect`. *O(n)*
223+execPutM :: forall m. (MonadEffect m) => PutM m Unit -> m ArrayBuffer
224+execPutM = execBuilder <=< execWriterT
225+
226+-- | Build an `ArrayBuffer` with do-notation. *O(n)*
227+execPut :: Put Unit -> Effect ArrayBuffer
228+execPut = execPutM
229+
230+-- | Append an `ArrayBuffer` to the builder.
231+putArrayBuffer :: forall m. (MonadEffect m) => ArrayBuffer -> PutM m Unit
232+putArrayBuffer = tell <<< singleton
233+
234+-- | Serialize an 8-bit unsigned integer (byte) into a new `ArrayBuffer`.
235+encodeUint8 :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
236+encodeUint8 x = do
237+ buf <- liftEffect $ AB.empty 1
238+ _ <- liftEffect $ DV.setUint8 (DV.whole buf) 0 x
239+ pure buf
101240
102241-- | 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
242+putUint8 :: forall m. (MonadEffect m) => UInt -> PutM m Unit
243+putUint8 = putArrayBuffer <=< encodeUint8
244+
245+-- | Serialize an 8-bit two’s-complement signed integer (char) into a new `ArrayBuffer`.
246+encodeInt8 :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
247+encodeInt8 x = do
248+ buf <- liftEffect $ AB.empty 1
249+ _ <- liftEffect $ DV.setInt8 (DV.whole buf) 0 x
250+ pure buf
105251
106252-- | 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
253+putInt8 :: forall m. (MonadEffect m) => Int -> PutM m Unit
254+putInt8 = putArrayBuffer <=< encodeInt8
255+
256+-- | Serialize a 16-bit big-endian unsigned integer into a new `ArrayBuffer`.
257+encodeUint16be :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
258+encodeUint16be x = do
259+ buf <- liftEffect $ AB.empty 2
260+ _ <- liftEffect $ DV.setUint16be (DV.whole buf) 0 x
261+ pure buf
109262
110263-- | 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
264+putUint16be :: forall m. (MonadEffect m) => UInt -> PutM m Unit
265+putUint16be = putArrayBuffer <=< encodeUint16be
266+
267+-- | Serialize a 16-bit little-endian unsigned integer into a new `ArrayBuffer`.
268+encodeUint16le :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
269+encodeUint16le x = do
270+ buf <- liftEffect $ AB.empty 2
271+ _ <- liftEffect $ DV.setUint16le (DV.whole buf) 0 x
272+ pure buf
113273
114274-- | 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
275+putUint16le :: forall m. (MonadEffect m) => UInt -> PutM m Unit
276+putUint16le = putArrayBuffer <=< encodeUint16le
277+
278+-- | Serialize a 16-bit big-endian two’s-complement signed integer into a new `ArrayBuffer`.
279+encodeInt16be :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
280+encodeInt16be x = do
281+ buf <- liftEffect $ AB.empty 2
282+ _ <- liftEffect $ DV.setInt16be (DV.whole buf) 0 x
283+ pure buf
117284
118285-- | 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
286+putInt16be :: forall m. (MonadEffect m) => Int -> PutM m Unit
287+putInt16be = putArrayBuffer <=< encodeInt16be
288+
289+-- | Serialize a 16-bit little-endian two’s-complement signed integer into a new `ArrayBuffer`.
290+encodeInt16le :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
291+encodeInt16le x = do
292+ buf <- liftEffect $ AB.empty 2
293+ _ <- liftEffect $ DV.setInt16le (DV.whole buf) 0 x
294+ pure buf
121295
122296-- | 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
297+putInt16le :: forall m. (MonadEffect m) => Int -> PutM m Unit
298+putInt16le = putArrayBuffer <=< encodeInt16le
299+
300+-- | Serialize a 32-bit big-endian unsigned integer into a new `ArrayBuffer`.
301+encodeUint32be :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
302+encodeUint32be x = do
303+ buf <- liftEffect $ AB.empty 4
304+ _ <- liftEffect $ DV.setUint32be (DV.whole buf) 0 x
305+ pure buf
125306
126307-- | 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
308+putUint32be :: forall m. (MonadEffect m) => UInt -> PutM m Unit
309+putUint32be = putArrayBuffer <=< encodeUint32be
310+
311+-- | Serialize a 32-bit little-endian unsigned integer into a new `ArrayBuffer`.
312+encodeUint32le :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
313+encodeUint32le x = do
314+ buf <- liftEffect $ AB.empty 4
315+ _ <- liftEffect $ DV.setUint32le (DV.whole buf) 0 x
316+ pure buf
129317
130318-- | 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
319+putUint32le :: forall m. (MonadEffect m) => UInt -> PutM m Unit
320+putUint32le = putArrayBuffer <=< encodeUint32le
321+
322+-- | Serialize a 32-bit big-endian two’s-complement signed integer into a new `ArrayBuffer`.
323+encodeInt32be :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
324+encodeInt32be x = do
325+ buf <- liftEffect $ AB.empty 4
326+ _ <- liftEffect $ DV.setInt32be (DV.whole buf) 0 x
327+ pure buf
133328
134329-- | 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
330+putInt32be :: forall m. (MonadEffect m) => Int -> PutM m Unit
331+putInt32be = putArrayBuffer <=< encodeInt32be
332+
333+-- | Serialize a 32-bit little-endian two’s-complement signed integer into a new `ArrayBuffer`.
334+encodeInt32le :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
335+encodeInt32le x = do
336+ buf <- liftEffect $ AB.empty 4
337+ _ <- liftEffect $ DV.setInt32le (DV.whole buf) 0 x
338+ pure buf
137339
138340-- | 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
341+putInt32le :: forall m. (MonadEffect m) => Int -> PutM m Unit
342+putInt32le = putArrayBuffer <=< encodeInt32le
343+
344+-- | Serialize a 32-bit big-endian IEEE single-precision float into a new `ArrayBuffer`.
345+encodeFloat32be :: forall m. (MonadEffect m) => Float32 -> m ArrayBuffer
346+encodeFloat32be x = do
347+ buf <- liftEffect $ AB.empty 4
348+ _ <- liftEffect $ DV.setFloat32be (DV.whole buf) 0 x
349+ pure buf
141350
142351-- | 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
352+putFloat32be :: forall m. (MonadEffect m) => Float32 -> PutM m Unit
353+putFloat32be = putArrayBuffer <=< encodeFloat32be
354+
355+-- | Serialize a 32-bit little-endian IEEE single-precision float into a new `ArrayBuffer`.
356+encodeFloat32le :: forall m. (MonadEffect m) => Float32 -> m ArrayBuffer
357+encodeFloat32le x = do
358+ buf <- liftEffect $ AB.empty 4
359+ _ <- liftEffect $ DV.setFloat32le (DV.whole buf) 0 x
360+ pure buf
145361
146362-- | 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
363+putFloat32le :: forall m. (MonadEffect m) => Float32 -> PutM m Unit
364+putFloat32le = putArrayBuffer <=< encodeFloat32le
365+
366+-- | Serialize a 64-bit big-endian IEEE double-precision float into a new `ArrayBuffer`.
367+encodeFloat64be :: forall m. (MonadEffect m) => Number -> m ArrayBuffer
368+encodeFloat64be x = do
369+ buf <- liftEffect $ AB.empty 8
370+ _ <- liftEffect $ DV.setFloat64be (DV.whole buf) 0 x
371+ pure buf
149372
150373-- | 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
374+putFloat64be :: forall m. (MonadEffect m) => Number -> PutM m Unit
375+putFloat64be = putArrayBuffer <=< encodeFloat64be
376+
377+-- | Serialize a 64-bit little-endian IEEE double-precision float into a new `ArrayBuffer`.
378+encodeFloat64le :: forall m. (MonadEffect m) => Number -> m ArrayBuffer
379+encodeFloat64le x = do
380+ buf <- liftEffect $ AB.empty 8
381+ _ <- liftEffect $ DV.setFloat64le (DV.whole buf) 0 x
382+ pure buf
153383
154384-- | 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
385+putFloat64le :: forall m. (MonadEffect m) => Number -> PutM m Unit
386+putFloat64le = putArrayBuffer <=< encodeFloat64le
387+
388+
389+-- | ## Implementation Details
390+-- |
391+-- | We want our `Builder` to be a data structure with
392+-- | * *O(1)* monoid append
393+-- | * *O(n)* fold
394+-- |
395+-- | Our `Builder` monoid implementation is an unbalanced binary tree.
396+-- |
397+-- | For monoid `append`, what we actually get is *O(1)* when either the
398+-- | left or right tree is a singleton. If that's not true, then in the
399+-- | unlikely worst case `append` might be *O(n)*.
400+-- |
401+-- | `Builder` is optimized what we consider to be normal usage, that is,
402+-- | `snoc`ing singleton elements to the end of the `Builder`.
403+-- |
404+-- | If a Builder is built entirely by `snoc`ing, it will look like a
405+-- | left-only binary tree, a.k.a. a linked list.
406+-- |
407+-- | ```
408+-- | ④
409+-- | ╱
410+-- | ③
411+-- | ╱
412+-- | ②
413+-- | ╱
414+-- | ①
415+-- | ```
416+-- |
417+-- | If two of these `snoc`-built trees are `append`ed, then the new tree
418+-- | will look like
419+-- |
420+-- | ```
421+-- | ④
422+-- | ╱ ╲
423+-- | ③ ⑧
424+-- | ╱ ╱
425+-- | ② ⑦
426+-- | ╱ ╱
427+-- | ① ⑥
428+-- | ╱
429+-- | ⑤
430+-- | ```
431+-- |
432+-- | This is all similar to
433+-- | [__bytestring-tree-builder__](https://hackage.haskell.org/package/bytestring-tree-builder)
434+-- | , except that the
435+-- | [`Tree`](https://hackage.haskell.org/package/bytestring-tree-builder-0.2.7.3/docs/src/ByteString.TreeBuilder.Tree.html#Tree)
436+-- | structure in __bytestring-tree-builder__ only carries values in its
437+-- | leaves, which is how it achieves *O(1)* appending, at the cost of
438+-- | a higher coefficient time factor on the fold.
439+-- |
440+-- | We hope that this implementation is fairly fast, but we
441+-- | haven't chosen this implementation because it's fast, we've chosen
442+-- | this implementation because it's simple. This library provides basic
443+-- | ArrayBuffer serialization with the familar “put monad” style.
444+-- | The only currently existing Purescript libary which does ArrayBuffer
445+-- | serialization is
446+-- | https://pursuit.purescript.org/packages/purescript-arraybuffer-class
447+-- | , and that library is heavily typeclass-based and designed
448+-- | for compatibility with the Haskell cereal library.
449+-- | If someone wants to create a fast Purescript ArrayBuffer serialization
450+-- | library, then they can benchmark against this one to prove that the new
451+-- | one is fast.
452+-- |
453+-- | One relatively cheap and simple performance improvement for this library would be to
454+-- | remove the Null constructor of `Builder` and instead use Javascript nulls.