mason: alacritous builder library
====
[](https://travis-ci.com/fumieval/mason)
[](https://hackage.haskell.org/package/mason)
mason is a builder & IO library.
* __Fast__: much faster than bytestring's Builder.
* __Extensible__: Builders can be consumed in a user-defined way.
* __Hackable__: Low-level APIs are exposed. It's easy to plug in even pointer-level operations.
`Mason.Builder` has API mostly compatible with `Data.ByteString.Builder` but there are some additions to the original API:
* `toStrictByteString` produces a strict `ByteString` directly.
* `hPutBuilderLen` writes a builder to a handle and returns the number of bytes.
* `sendBuilder` sends the content of `Builder` over a socket.
* `withPopper` turns a builder into http-client's[GivesPopper](http://hackage.haskell.org/package/http-client-0.7.2.1/docs/Network-HTTP-Client.html#t:GivesPopper)
* `toStreamingBody` creates wai's [StreamingBody](http://hackage.haskell.org/package/wai-3.2.2.1/docs/Network-Wai.html#t:StreamingBody)
Usage
----
Replace `Data.ByteString.Builder` with `Mason.Builder`. Note that if you have `Builder` in the type signature, you'll need `RankNTypes` extensions because of the design explained below. Alternatively, you can also import `Mason.Builder.Compat` which has an API almost compatible with `Data.ByteString.Builder`.
Performance
----
As long as the code is optimised, mason's builder can be very fast (twice or more as bytestring). Make sure that functions returning `Builder`s are well inlined.
Serialisation of JSON-like structure:
```
mason/hPutBuilder mean 274.7 μs ( +- 49.40 μs )
fast-builder/hPutBuilder mean 399.9 μs ( +- 76.05 μs )
bytestring/hPutBuilder mean 335.1 μs ( +- 86.96 μs )
mason/toStrictByteString mean 106.6 μs ( +- 6.680 μs )
fast-builder/toStrictByteString mean 254.8 μs ( +- 31.64 μs )
bytestring/toLazyByteString mean 283.3 μs ( +- 24.26 μs )
mason/toLazyByteString mean 127.2 μs ( +- 25.86 μs )
fast-builder/toLazyByteString mean 249.0 μs ( +- 25.60 μs )
bytestring/toLazyByteString mean 263.4 μs ( +- 9.401 μs )
```
In the same benchmark application, the allocation footprint of mason is feathery.
```
toStrictByteString
mason 291,112 0
fast-builder 991,016 0
bytestring 1,158,584 0 (toStrict . toLazyByteString)
toLazyByteString
Case Allocated GCs
mason 228,936 0
fast-builder 903,752 0
bytestring 1,101,448 0
```
`doubleDec` employs Grisu3 which grants ~20x speedup over `show`-based implementation.
```
mason/double mean 116.2 ns ( +- 6.654 ns )
fast-builder/double mean 2.183 μs ( +- 85.80 ns )
bytestring/double mean 2.312 μs ( +- 118.8 ns )
```
You can find more benchmarks below:
* [bytes-builder-shootout](https://github.com/andrewthad/bytes-builder-shootout)
Click to expand
treeToHex-2000/small-bytearray-builder mean 44.01 μs ( +- 1.620 μs )
treeToHex-2000/fast-builder mean 34.40 μs ( +- 390.1 ns )
treeToHex-2000/bytestring mean 58.76 μs ( +- 3.843 μs )
treeToHex-2000/mason mean 41.08 μs ( +- 180.8 ns )
treeToHex-9000/small-bytearray-builder mean 191.8 μs ( +- 1.835 μs )
treeToHex-9000/bytestring mean 284.8 μs ( +- 1.156 μs )
treeToHex-9000/mason mean 181.2 μs ( +- 386.3 ns )
short-text-tree-1000/small-bytearray-builder mean 26.54 μs ( +- 34.08 ns )
short-text-tree-1000/fast-builder mean 37.51 μs ( +- 99.85 ns )
short-text-tree-1000/bytestring mean 37.95 μs ( +- 167.5 ns )
short-text-tree-1000/mason mean 26.87 μs ( +- 312.4 ns )
byte-tree-2000/small-bytearray-builder mean 30.53 μs ( +- 51.53 ns )
byte-tree-2000/fast-builder mean 26.91 μs ( +- 592.2 ns )
byte-tree-2000/bytestring mean 54.40 μs ( +- 1.743 μs )
byte-tree-2000/mason mean 34.34 μs ( +- 193.5 ns )
* [haskell-perf/strict-bytestring-builder](https://github.com/haskell-perf/strict-bytestring-builders)
Click to expand
averagedAppends-1/byteStringStrictBuilder mean 116.3 ns ( +- 6.479 ns )
averagedAppends-1/byteStringTreeBuilder mean 181.7 ns ( +- 20.88 ns )
averagedAppends-1/fastBuilder mean 181.5 ns ( +- 7.219 ns )
averagedAppends-1/bufferBuilder mean 728.5 ns ( +- 9.114 ns )
averagedAppends-1/byteString mean 358.7 ns ( +- 4.663 ns )
averagedAppends-1/blazeBuilder mean 356.0 ns ( +- 7.604 ns )
averagedAppends-1/binary mean 635.0 ns ( +- 7.936 ns )
averagedAppends-1/cereal mean 638.6 ns ( +- 12.40 ns )
averagedAppends-1/mason mean 155.2 ns ( +- 2.000 ns )
averagedAppends-100/byteStringStrictBuilder mean 7.290 μs ( +- 99.74 ns )
averagedAppends-100/byteStringTreeBuilder mean 13.40 μs ( +- 283.4 ns )
averagedAppends-100/fastBuilder mean 13.07 μs ( +- 418.2 ns )
averagedAppends-100/bufferBuilder mean 19.57 μs ( +- 5.644 μs )
averagedAppends-100/byteString mean 17.31 μs ( +- 1.609 μs )
averagedAppends-100/blazeBuilder mean 19.15 μs ( +- 6.533 μs )
averagedAppends-100/binary mean 48.26 μs ( +- 727.1 ns )
averagedAppends-100/cereal mean 51.57 μs ( +- 21.81 μs )
averagedAppends-100/mason mean 12.07 μs ( +- 233.8 ns )
averagedAppends-10000/byteStringStrictBuilder mean 1.038 ms ( +- 18.63 μs )
averagedAppends-10000/byteStringTreeBuilder mean 1.989 ms ( +- 70.63 μs )
averagedAppends-10000/fastBuilder mean 1.611 ms ( +- 42.24 μs )
averagedAppends-10000/bufferBuilder mean 1.895 ms ( +- 25.09 μs )
averagedAppends-10000/byteString mean 2.248 ms ( +- 40.99 μs )
averagedAppends-10000/blazeBuilder mean 2.394 ms ( +- 1.016 ms )
averagedAppends-10000/binary mean 6.503 ms ( +- 157.6 μs )
averagedAppends-10000/cereal mean 6.458 ms ( +- 221.6 μs )
averagedAppends-10000/mason mean 1.738 ms ( +- 25.89 μs )
regularConcat-100/byteStringStrictBuilder mean 1.606 μs ( +- 32.93 ns )
regularConcat-100/byteStringTreeBuilder mean 2.000 μs ( +- 43.73 ns )
regularConcat-100/fastBuilder mean 1.364 μs ( +- 37.95 ns )
regularConcat-100/bufferBuilder mean 2.204 μs ( +- 48.40 ns )
regularConcat-100/byteString mean 1.253 μs ( +- 25.68 ns )
regularConcat-100/blazeBuilder mean 1.317 μs ( +- 24.05 ns )
regularConcat-100/binary mean 2.845 μs ( +- 62.24 ns )
regularConcat-100/cereal mean 3.021 μs ( +- 48.53 ns )
regularConcat-100/mason mean 1.405 μs ( +- 35.11 ns )
regularConcat-10000/byteStringStrictBuilder mean 321.3 μs ( +- 11.13 μs )
regularConcat-10000/byteStringTreeBuilder mean 349.1 μs ( +- 4.359 μs )
regularConcat-10000/fastBuilder mean 121.0 μs ( +- 1.755 μs )
regularConcat-10000/bufferBuilder mean 156.1 μs ( +- 2.050 μs )
regularConcat-10000/byteString mean 106.6 μs ( +- 1.355 μs )
regularConcat-10000/blazeBuilder mean 110.8 μs ( +- 1.397 μs )
regularConcat-10000/binary mean 308.1 μs ( +- 5.346 μs )
regularConcat-10000/cereal mean 352.0 μs ( +- 6.142 μs )
regularConcat-10000/mason mean 130.2 μs ( +- 10.39 μs )
Architecture
----
Mason's builder is a function that takes a purpose-dependent environment and a buffer. There is little intermediate structure involved; almost everything runs in one pass. This design is inspired by [fast-builder](http://hackage.haskell.org/package/fast-builder).
```haskell
type Builder = forall s. Buildable s => BuilderFor s
newtype BuilderFor s = Builder { unBuilder :: s -> Buffer -> IO Buffer }
data Buffer = Buffer
{ bEnd :: {-# UNPACK #-} !(Ptr Word8) -- ^ end of the buffer (next to the last byte)
, bCur :: {-# UNPACK #-} !(Ptr Word8) -- ^ current position
}
class Buildable s where
byteString :: B.ByteString -> BuilderFor s
flush :: BuilderFor s
allocate :: Int -> BuilderFor s
```
Instances of the `Buildable` class implement purpose-specific behaviour (e.g. exponentially allocate a buffer, flush to disk). This generic interface also allows creative uses of Builders such as on-the-fly compression.
`Builder` has a smart constructor called `ensure`:
```haskell
ensure :: Int -> (Buffer -> IO Buffer) -> Builder
```
`ensure n f` secures at least `n` bytes in the buffer and passes the pointer to `f`. This gives rise to monoid homorphism; namely, `ensure m f <> ensure n g` will fuse into `ensure (m + n) (f >=> g)` so don't worry about the overhead of bound checking.
Creating your own primitives
----
The easiest way to create a new primitive is `withPtr`, a simplified version of `ensure`. This is quite convenient for calling foreign functions or anything low-level.
```haskell
-- | Construct a 'Builder' from a "poke" function.
withPtr :: Int -- ^ number of bytes to allocate (if needed)
-> (Ptr Word8 -> IO (Ptr Word8)) -- ^ return a next pointer after writing
-> Builder
grisu v = withPtr 24 $ \ptr -> do
n <- dtoa_grisu3 v ptr
return $ plusPtr ptr (fromIntegral n)
foreign import ccall unsafe "static dtoa_grisu3"
dtoa_grisu3 :: Double -> Ptr Word8 -> IO CInt
```