@@ -1,156 +1,468 @@
1−-- | This module provides a `Builder` monoid and a `PutM` monad
1+-- | `ArrayBuffer` serialization in the “builder monoid” style.
2−-- | for serializing `Data.ArrayBuffer.Types.ArrayBuffer`s.
3−-- | See the package README for usage examples.
5−-- | Writing to an `ArrayBuffer` is an `Effect`ful activity, so most
3+-- | This module provides a `Builder` monoid and a `PutM` monad which are roughly
6−-- | functions in this module must be run in a `MonadEffect` context.
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)
8−-- | For other operations for working with `ArrayBuffer`, see
8+-- | This library defines no typeclasses. Typeclass-based
9−-- | module
9+-- | serialization/deserialization generally assumes that we are round-tripping
10+-- | some data structures out to storage and then back into our program.
11+-- | This library is designed for the case that we are serializing some data
12+-- | to be sent to another program which expects a certain serialization format
13+-- | that we don't control.
15+-- | ## Deserialization
17+-- | This module is only for writing `ArrayBuffer`s, not reading them.
19+-- | [__purescript-parsing-dataview__](https://pursuit.purescript.org/packages/purescript-parsing-dataview/)
20+-- | for a way to deserialize from `ArrayBuffer` back to Purescript data.
22+-- | ## Usage Examples
24+-- | All `ArrayBuffer` building must occur in `Effect`.
26+-- | ### Serialize an integer
28+-- | Create a two-byte `arraybuffer :: ArrayBuffer` which contains the number *-2* encoded as big-endian 16-bit two’s-complement.
31+-- | arraybuffer <- execPut $ putInt16be (-2)
34+-- | ### Serialize a `String` as UTF8
36+-- | A function which encodes a `String` as UTF8 with a length prefix in a
37+-- | way that's compatible with the
38+-- | [`Binary.Put.putStringUtf8`](https://hackage.haskell.org/package/binary/docs/Data-Binary-Put.html#v:putStringUtf8)
39+-- | function from the Haskell
40+-- | [__binary__](https://hackage.haskell.org/package/binary)
10−-- | [`Data.ArrayBuffer.ArrayBuffer`](https://pursuit.purescript.org/packages/purescript-arraybuffer/docs/Data.ArrayBuffer.ArrayBuffer)
42+-- | Uses [`Data.TextEncoding.encodeUtf8`](https://pursuit.purescript.org/packages/purescript-text-encoding/docs/Data.TextEncoding#v:encodeUtf8).
11−-- | in package __arraybuffer__.
43+-- | ```purescript
44+-- | putStringUtf8 :: forall m. (MonadEffect m) => String -> PutM m Unit
45+-- | putStringUtf8 s = do
46+-- | let stringbuf = Data.ArrayBuffer.Typed.buffer $
47+-- | Data.TextEncoding.encodeUtf8 s
48+-- | -- Put a 64-bit big-endian length prefix for the length of the utf8
49+-- | -- string, in bytes.
51+-- | putUint32be $ Data.Uint.fromInt $ Data.ArrayBuffer.byteLength stringbuf
52+-- | putArrayBuffer stringbuf
55+-- | ### Serialize an `Array Int`
57+-- | A function which encodes an `Array Int` with a length prefix in a
58+-- | way that's compatible with the
59+-- | [`Binary` instance for `[Int32]`](https://hackage.haskell.org/package/binary/docs/Data-Binary.html#t:Binary)
61+-- | [__binary__](https://hackage.haskell.org/package/binary)
64+-- | putArrayInt32 :: forall m. (MonadEffect m) => Array Int -> PutM m Unit
65+-- | putArrayInt32 xs = do
66+-- | -- Put a 64-bit big-endian length prefix for the length of the
67+-- | -- array, in bytes.
69+-- | putUint32be $ Data.Uint.fromInt $ Data.Array.length xs
70+-- | traverse_ putInt32be xs
12module Data.ArrayBuffer.Builder
72module Data.ArrayBuffer.Builder
15− , execPutM
75+, execPutM
16− , execPut
76+, execPut
18− , putArrayBuffer
77+, putArrayBuffer
21− , putUint8
78+, putUint8
22− , putInt8
79+, putInt8
23− , putUint16be
80+, putUint16be
24− , putUint16le
81+, putUint16le
25− , putInt16be
82+, putInt16be
26− , putInt16le
83+, putInt16le
27− , putUint32be
84+, putUint32be
28− , putUint32le
85+, putUint32le
29− , putInt32be
86+, putInt32be
30− , putInt32le
87+, putInt32le
31− , putFloat32be
88+, putFloat32be
32− , putFloat32le
89+, putFloat32le
33− , putFloat64be
90+, putFloat64be
34− , putFloat64le
91+, putFloat64le
35− , module Data.ArrayBuffer.Builder.Internal
92+, Builder
38import Prelude
114import Prelude
40−import Control.Monad.Rec.Class (class MonadRec)
41−import Control.Monad.Writer.Trans (WriterT, execWriterT, tell, lift)
116+import Control.Monad.Writer.Trans (WriterT, execWriterT, tell)
42−import Data.ArrayBuffer.Builder.Internal (Builder, DataBuff(..), length, toView, (<>>))
117+import Data.ArrayBuffer.ArrayBuffer as AB
43−import Data.ArrayBuffer.Builder.Internal as Internal
44−import Data.ArrayBuffer.Types (ArrayBuffer, DataView)
118+import Data.ArrayBuffer.DataView as DV
119+import Data.ArrayBuffer.Typed as AT
120+import Data.ArrayBuffer.Types (ArrayBuffer, Uint8Array)
45import Data.Float32 (Float32)
121import Data.Float32 (Float32)
122+import Data.Maybe (Maybe(..))
46import Data.UInt (UInt)
123import Data.UInt (UInt)
47import Effect (Effect)
124import Effect (Effect)
48−import Effect.Class (class MonadEffect)
125+import Effect.Class (class MonadEffect, liftEffect)
50−-- | The `PutM` monad is a `WriterT Builder` transformer monad which
127+-- | The `PutM` monad is a Writer transformer monad which
51−-- | gives us do-notation for the `Builder` monoid. The base monad must be
128+-- | [gives us access to do-notation](https://wiki.haskell.org/Do_notation_considered_harmful#Library_design)
52−-- | a `MonadEffect`.
129+-- | for building `ArrayBuffer`s.
54−-- | To append `Builder`s in this monad call `tell`, or any of the `put*`
55−-- | functions in this module.
56type PutM = WriterT Builder
130type PutM = WriterT Builder
58−-- | The `PutM` type reified to `Effect`, in other words `WriterT Builder Effect`.
132+-- | `Put` monad is the non-transformer version of `PutM`.
59type Put = PutM Effect
133type Put = PutM Effect
61−-- | Build an `ArrayBuffer` with do-notation in any `MonadEffect`. *O(n)* Stack-safe.
135+-- | Monoidal builder for `ArrayBuffer`s.
62−execPutM :: forall m. MonadEffect m => MonadRec m => PutM m Unit -> m ArrayBuffer
63−execPutM = Internal.execBuilder <=< execWriterT
65−-- | Build an `ArrayBuffer` with do-notation in `Effect`. *O(n)* Stack-safe.
66−execPut :: Put Unit -> Effect ArrayBuffer
69−-- | Build up a sub-`Builder` without `tell`ing it to the `Writer` yet.
71−-- | One case where we might want to call a `subBuilder` is when
137+-- | ### Left-associative `<>>` append operator
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.
76−-- | In a `PutM` monad do-block, we can
139+-- | __TL;DR__ You probably don't want to use the `Builder` monoid directly
140+-- | in your code, it’s better to use the `PutM` monad with do-notation instead.
78−-- | ```
142+-- | The `Builder` monoid in this library is efficient when we `snoc` single
79−-- | do
143+-- | items onto the end of it, or when we only `cons` single items to the
80−-- | messageBuilder <- subBuilder $ do
144+-- | beginning, but it can be less efficient when we are mixing `cons` and
81−-- | putField1
145+-- | `snoc`.
82−-- | putField2
146+-- | This matters when we're appending three or more `Builder`s
147+-- | in one associative expression, because the
148+-- | `Semigroup` append operator `<>` is right-associative.
84−-- | putInt32be $ length messageBuilder
150+-- | To solve this, we provide an operator `<>>` for appending `Builders`.
85−-- | tell messageBuilder
151+-- | `<>>` is exactly the same as `<>`, but left-associative.
152+-- | This only matters when we're chaining together three
153+-- | or more `Builder`s in a single associative expression.
156+-- | builder₁ <> builder₂ <> builder₃
158+-- | we should always prefer to
161+-- | builder₁ <>> builder₂ <>> builder₃
87−subBuilder :: forall m. Monad m => PutM m Unit -> PutM m Builder
163+-- | so that we get the efficient
88−subBuilder = lift <<< execWriterT
164+-- | `snoc`ing of `Builder`s.
166+-- | If we build our `ArrayBuffer`s with the `PutM` monad instead of appending by
167+-- | using the `Semigroup` instance of `Builder`, then we always get the efficient
171+ = Node Builder ArrayBuffer Builder
90−-- | Append an `ArrayBuffer` to the builder.
174+instance semigroupBuilder :: Semigroup Builder where
91−putArrayBuffer :: forall m. Monad m => ArrayBuffer -> PutM m Unit
175+ append Null Null = Null
92−putArrayBuffer = tell <<< Internal.singleton <<< Internal.Buff
176+ append l Null = l
178+ append l (Node Null rx rr) = Node l rx rr -- this is the snoc case
179+ append (Node ll lx Null) r = Node ll lx r -- found the rightmost Null
181+ append (Node ll lx lr) r = Node ll lx $ append lr r -- search down the right
182+ -- side of the left tree
183+ -- to find the rightmost
186+infixl 5 append as <>>
94−-- | Append a `DataView` to the builder.
188+instance monoidBuilder :: Monoid Builder where
95−putDataView :: forall m. Monad m => DataView -> PutM m Unit
189+ mempty = Null
96−putDataView = tell <<< Internal.singleton <<< Internal.View
191+-- | `Builder` is not an instance of `Foldable` because `Builder` is monomorphic.
192+foldl :: forall b. (b -> ArrayBuffer -> b) -> b -> Builder -> b
194+foldl f a (Node l x r) = foldl f (f (foldl f a l) x) r
196+-- | Monomorphic foldM copied from
197+-- | [`Data.Foldable.foldM`](https://pursuit.purescript.org/packages/purescript-foldable-traversable/4.1.1/docs/Data.Foldable#v:foldM)
198+foldM :: forall b m. (Monad m) => (b -> ArrayBuffer -> m b) -> b -> Builder -> m b
199+foldM f a0 = foldl (\ma b -> ma >>= flip f b) (pure a0)
201+-- | Construct a `Builder` with a single `ArrayBuffer`. *O(1)*
202+singleton :: ArrayBuffer -> Builder
203+singleton buf = Node Null buf Null
205+-- | Add an `ArrayBuffer` to the end of the `Builder`. *O(1)*
206+snoc :: Builder -> ArrayBuffer -> Builder
207+snoc bs x = Node bs x Null
209+-- | Build a single `ArrayBuffer` from a `Builder`. *O(n)*
210+execBuilder :: forall m. (MonadEffect m) => Builder -> m ArrayBuffer
211+execBuilder bldr = do
212+ let buflen = foldl (\b a -> b + AB.byteLength a) 0 bldr
213+ -- Allocate the final ArrayBuffer
214+ buf <- liftEffect $ AB.empty buflen
215+ -- Then copy each ArrayBuffer into the final ArrayBuffer.
216+ -- To memcpy from one ArrayBuffer to another, apparently we have to first view
217+ -- both ArrayBuffers as ArrayView (Typed Array).
218+ newview <- liftEffect (AT.whole buf :: Effect Uint8Array)
221+ let offset' = offset + AB.byteLength a
222+ aview <- liftEffect (AT.whole a :: Effect Uint8Array)
223+ _ <- liftEffect $ AT.setTyped newview (Just offset') aview
228+-- | Build an `ArrayBuffer` with do-notation in any `MonadEffect`. *O(n)*
229+execPutM :: forall m. (MonadEffect m) => PutM m Unit -> m ArrayBuffer
230+execPutM = execBuilder <=< execWriterT
232+-- | Build an `ArrayBuffer` with do-notation. *O(n)*
233+execPut :: Put Unit -> Effect ArrayBuffer
98−-- | Append either an `ArrayBuffer` or a `DataView` to the builder.
236+-- | Append an `ArrayBuffer` to the builder.
99−putDataBuff :: forall m. Monad m => DataBuff -> PutM m Unit
237+putArrayBuffer :: forall m. (MonadEffect m) => ArrayBuffer -> PutM m Unit
100−putDataBuff = tell <<< Internal.singleton
238+putArrayBuffer = tell <<< singleton
240+-- | Serialize an 8-bit unsigned integer (byte) into a new `ArrayBuffer`.
241+encodeUint8 :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
243+ buf <- liftEffect $ AB.empty 1
244+ _ <- liftEffect $ DV.setUint8 (DV.whole buf) 0 x
102-- | Append an 8-bit unsigned integer (byte) to the builder.
247-- | Append an 8-bit unsigned integer (byte) to the builder.
103−putUint8 :: forall m. MonadEffect m => UInt -> PutM m Unit
248+putUint8 :: forall m. (MonadEffect m) => UInt -> PutM m Unit
104−putUint8 = putArrayBuffer <=< Internal.encodeUint8
249+putUint8 = putArrayBuffer <=< encodeUint8
251+-- | Serialize an 8-bit two’s-complement signed integer (char) into a new `ArrayBuffer`.
252+encodeInt8 :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
254+ buf <- liftEffect $ AB.empty 1
255+ _ <- liftEffect $ DV.setInt8 (DV.whole buf) 0 x
106-- | Append an 8-bit two’s-complement signed integer (char) to the builder.
258-- | Append an 8-bit two’s-complement signed integer (char) to the builder.
107−putInt8 :: forall m. MonadEffect m => Int -> PutM m Unit
259+putInt8 :: forall m. (MonadEffect m) => Int -> PutM m Unit
108−putInt8 = putArrayBuffer <=< Internal.encodeInt8
260+putInt8 = putArrayBuffer <=< encodeInt8
262+-- | Serialize a 16-bit big-endian unsigned integer into a new `ArrayBuffer`.
263+encodeUint16be :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
264+encodeUint16be x = do
265+ buf <- liftEffect $ AB.empty 2
266+ _ <- liftEffect $ DV.setUint16be (DV.whole buf) 0 x
110-- | Append a 16-bit big-endian unsigned integer to the builder.
269-- | Append a 16-bit big-endian unsigned integer to the builder.
111−putUint16be :: forall m. MonadEffect m => UInt -> PutM m Unit
270+putUint16be :: forall m. (MonadEffect m) => UInt -> PutM m Unit
112−putUint16be = putArrayBuffer <=< Internal.encodeUint16be
271+putUint16be = putArrayBuffer <=< encodeUint16be
273+-- | Serialize a 16-bit little-endian unsigned integer into a new `ArrayBuffer`.
274+encodeUint16le :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
275+encodeUint16le x = do
276+ buf <- liftEffect $ AB.empty 2
277+ _ <- liftEffect $ DV.setUint16le (DV.whole buf) 0 x
114-- | Append a 16-bit little-endian unsigned integer to the builder.
280-- | Append a 16-bit little-endian unsigned integer to the builder.
115−putUint16le :: forall m. MonadEffect m => UInt -> PutM m Unit
281+putUint16le :: forall m. (MonadEffect m) => UInt -> PutM m Unit
116−putUint16le = putArrayBuffer <=< Internal.encodeUint16le
282+putUint16le = putArrayBuffer <=< encodeUint16le
284+-- | Serialize a 16-bit big-endian two’s-complement signed integer into a new `ArrayBuffer`.
285+encodeInt16be :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
287+ buf <- liftEffect $ AB.empty 2
288+ _ <- liftEffect $ DV.setInt16be (DV.whole buf) 0 x
118-- | Append a 16-bit big-endian two’s-complement signed integer to the builder.
291-- | Append a 16-bit big-endian two’s-complement signed integer to the builder.
119−putInt16be :: forall m. MonadEffect m => Int -> PutM m Unit
292+putInt16be :: forall m. (MonadEffect m) => Int -> PutM m Unit
120−putInt16be = putArrayBuffer <=< Internal.encodeInt16be
293+putInt16be = putArrayBuffer <=< encodeInt16be
295+-- | Serialize a 16-bit little-endian two’s-complement signed integer into a new `ArrayBuffer`.
296+encodeInt16le :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
298+ buf <- liftEffect $ AB.empty 2
299+ _ <- liftEffect $ DV.setInt16le (DV.whole buf) 0 x
122-- | Append a 16-bit little-endian two’s-complement signed integer to the builder.
302-- | Append a 16-bit little-endian two’s-complement signed integer to the builder.
123−putInt16le :: forall m. MonadEffect m => Int -> PutM m Unit
303+putInt16le :: forall m. (MonadEffect m) => Int -> PutM m Unit
124−putInt16le = putArrayBuffer <=< Internal.encodeInt16le
304+putInt16le = putArrayBuffer <=< encodeInt16le
306+-- | Serialize a 32-bit big-endian unsigned integer into a new `ArrayBuffer`.
307+encodeUint32be :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
308+encodeUint32be x = do
309+ buf <- liftEffect $ AB.empty 4
310+ _ <- liftEffect $ DV.setUint32be (DV.whole buf) 0 x
126-- | Append a 32-bit big-endian unsigned integer to the builder.
313-- | Append a 32-bit big-endian unsigned integer to the builder.
127−putUint32be :: forall m. MonadEffect m => UInt -> PutM m Unit
314+putUint32be :: forall m. (MonadEffect m) => UInt -> PutM m Unit
128−putUint32be = putArrayBuffer <=< Internal.encodeUint32be
315+putUint32be = putArrayBuffer <=< encodeUint32be
317+-- | Serialize a 32-bit little-endian unsigned integer into a new `ArrayBuffer`.
318+encodeUint32le :: forall m. (MonadEffect m) => UInt -> m ArrayBuffer
319+encodeUint32le x = do
320+ buf <- liftEffect $ AB.empty 4
321+ _ <- liftEffect $ DV.setUint32le (DV.whole buf) 0 x
130-- | Append a 32-bit little-endian unsigned integer to the builder.
324-- | Append a 32-bit little-endian unsigned integer to the builder.
131−putUint32le :: forall m. MonadEffect m => UInt -> PutM m Unit
325+putUint32le :: forall m. (MonadEffect m) => UInt -> PutM m Unit
132−putUint32le = putArrayBuffer <=< Internal.encodeUint32le
326+putUint32le = putArrayBuffer <=< encodeUint32le
328+-- | Serialize a 32-bit big-endian two’s-complement signed integer into a new `ArrayBuffer`.
329+encodeInt32be :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
331+ buf <- liftEffect $ AB.empty 4
332+ _ <- liftEffect $ DV.setInt32be (DV.whole buf) 0 x
134-- | Append a 32-bit big-endian two’s-complement signed integer to the builder.
335-- | Append a 32-bit big-endian two’s-complement signed integer to the builder.
135−putInt32be :: forall m. MonadEffect m => Int -> PutM m Unit
336+putInt32be :: forall m. (MonadEffect m) => Int -> PutM m Unit
136−putInt32be = putArrayBuffer <=< Internal.encodeInt32be
337+putInt32be = putArrayBuffer <=< encodeInt32be
339+-- | Serialize a 32-bit little-endian two’s-complement signed integer into a new `ArrayBuffer`.
340+encodeInt32le :: forall m. (MonadEffect m) => Int -> m ArrayBuffer
342+ buf <- liftEffect $ AB.empty 4
343+ _ <- liftEffect $ DV.setInt32le (DV.whole buf) 0 x
138-- | Append a 32-bit little-endian two’s-complement signed integer to the builder.
346-- | Append a 32-bit little-endian two’s-complement signed integer to the builder.
139−putInt32le :: forall m. MonadEffect m => Int -> PutM m Unit
347+putInt32le :: forall m. (MonadEffect m) => Int -> PutM m Unit
140−putInt32le = putArrayBuffer <=< Internal.encodeInt32le
348+putInt32le = putArrayBuffer <=< encodeInt32le
350+-- | Serialize a 32-bit big-endian IEEE single-precision float into a new `ArrayBuffer`.
351+encodeFloat32be :: forall m. (MonadEffect m) => Float32 -> m ArrayBuffer
352+encodeFloat32be x = do
353+ buf <- liftEffect $ AB.empty 4
354+ _ <- liftEffect $ DV.setFloat32be (DV.whole buf) 0 x
142-- | Append a 32-bit big-endian IEEE single-precision float to the builder.
357-- | Append a 32-bit big-endian IEEE single-precision float to the builder.
143−putFloat32be :: forall m. MonadEffect m => Float32 -> PutM m Unit
358+putFloat32be :: forall m. (MonadEffect m) => Float32 -> PutM m Unit
144−putFloat32be = putArrayBuffer <=< Internal.encodeFloat32be
359+putFloat32be = putArrayBuffer <=< encodeFloat32be
361+-- | Serialize a 32-bit little-endian IEEE single-precision float into a new `ArrayBuffer`.
362+encodeFloat32le :: forall m. (MonadEffect m) => Float32 -> m ArrayBuffer
363+encodeFloat32le x = do
364+ buf <- liftEffect $ AB.empty 4
365+ _ <- liftEffect $ DV.setFloat32le (DV.whole buf) 0 x
146-- | Append a 32-bit little-endian IEEE single-precision float to the builder.
368-- | Append a 32-bit little-endian IEEE single-precision float to the builder.
147−putFloat32le :: forall m. MonadEffect m => Float32 -> PutM m Unit
369+putFloat32le :: forall m. (MonadEffect m) => Float32 -> PutM m Unit
148−putFloat32le = putArrayBuffer <=< Internal.encodeFloat32le
370+putFloat32le = putArrayBuffer <=< encodeFloat32le
372+-- | Serialize a 64-bit big-endian IEEE double-precision float into a new `ArrayBuffer`.
373+encodeFloat64be :: forall m. (MonadEffect m) => Number -> m ArrayBuffer
374+encodeFloat64be x = do
375+ buf <- liftEffect $ AB.empty 8
376+ _ <- liftEffect $ DV.setFloat64be (DV.whole buf) 0 x
150-- | Append a 64-bit big-endian IEEE double-precision float to the builder.
379-- | Append a 64-bit big-endian IEEE double-precision float to the builder.
151−putFloat64be :: forall m. MonadEffect m => Number -> PutM m Unit
380+putFloat64be :: forall m. (MonadEffect m) => Number -> PutM m Unit
152−putFloat64be = putArrayBuffer <=< Internal.encodeFloat64be
381+putFloat64be = putArrayBuffer <=< encodeFloat64be
383+-- | Serialize a 64-bit little-endian IEEE double-precision float into a new `ArrayBuffer`.
384+encodeFloat64le :: forall m. (MonadEffect m) => Number -> m ArrayBuffer
385+encodeFloat64le x = do
386+ buf <- liftEffect $ AB.empty 8
387+ _ <- liftEffect $ DV.setFloat64le (DV.whole buf) 0 x
154-- | Append a 64-bit little-endian IEEE double-precision float to the builder.
390-- | Append a 64-bit little-endian IEEE double-precision float to the builder.
155−putFloat64le :: forall m. MonadEffect m => Number -> PutM m Unit
391+putFloat64le :: forall m. (MonadEffect m) => Number -> PutM m Unit
156−putFloat64le = putArrayBuffer <=< Internal.encodeFloat64le
392+putFloat64le = putArrayBuffer <=< encodeFloat64le
395+-- | ## Implementation Details
397+-- | We want our `Builder` to be a data structure with
398+-- | * *O(1)* monoid append
401+-- | Our `Builder` implementation is an unbalanced binary tree.
403+-- | For monoid `append`, what we actually get is *O(1)* when either the
404+-- | left or right tree is a singleton. If that's not true, then in the
405+-- | unlikely worst case `append` might be *O(n)*.
407+-- | `Builder` is optimized what we consider to be normal usage, that is,
408+-- | `snoc`ing singleton elements to the end of the `Builder`.
410+-- | If a Builder is built entirely by `snoc`ing, it will look like a
411+-- | left-only binary tree, a.k.a. a linked list.
423+-- | If two of these `snoc`-built trees are `append`ed, then the new tree
438+-- | This is all similar to
439+-- | [__bytestring-tree-builder__](https://hackage.haskell.org/package/bytestring-tree-builder)
440+-- | , except that the
441+-- | [`Tree`](https://hackage.haskell.org/package/bytestring-tree-builder-0.2.7.3/docs/src/ByteString.TreeBuilder.Tree.html#Tree)
442+-- | structure in __bytestring-tree-builder__ only carries values in its
443+-- | leaves, which is how it achieves *O(1)* appending, at the cost of
444+-- | a higher coefficient time factor on the fold.
446+-- | We hope that this implementation is fairly fast, but we
447+-- | haven't chosen this implementation because it's fast, we've chosen
448+-- | this implementation because it's simple.
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
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.
456+-- | In the longer term, it might make sense to try to change the Builder so
457+-- | that it works like the
458+-- | https://hackage.haskell.org/package/bytestring/docs/Data-ByteString-Builder.html
460+-- | Here are some benchmarks of different Haskell ByteString builders
461+-- | https://github.com/haskell-perf/strict-bytestring-builders
463+-- | We've tried to design the API for this library with minimal assumptions,
464+-- | so that if we want to change the Builder implementation later then we can.
467+-- | https://pursuit.purescript.org/packages/purescript-node-buffer
468+-- | https://pursuit.purescript.org/packages/purescript-arraybuffer-class