Library for efficiently building up buffers, one piece at a time.
Data.BufferBuilder is an efficient library for incrementally building up ByteStrings, one chunk at a time. Early benchmarks show it is over twice as fast as ByteString Builder, primarily because BufferBuilder is built upon an ST-style restricted monad and mutable state instead of ByteString Builder's monoidal AST.
Internally, BufferBuilder is backed by a few C functions. Examination of GHC's output shows nearly optimal code generation with no intermediate thunks -- and thus, continuation passing and its associated indirect jumps and stack traffic only occur when BufferBuilder is asked to append a non-strict ByteString.
I benchmarked four approaches with a URL encoding benchmark:
State monad, concatenating ByteStrings: 6.98 us
State monad, ByteString Builder: 2.48 us
Crazy explicit RealWorld baton passing with unboxed state: 28.94 us (GHC generated really awful code for this, but see the revision history for the technique)
C + FFI + ReaderT: 1.11 us
Using BufferBuilder is very simple:
import qualified Data.BufferBuilder as BB
let byteString = BB.runBufferBuilder $ do
BB.appendBS "http"
BB.appendChar8 '/'
BB.appendBS "//"This package also provides Data.BufferBuilder.Utf8 for generating UTF-8 buffers and Data.BufferBuilder.Json for encoding data structures into JSON.