fast-builder-0.0.0.6: Fast ByteString Builder

Safe HaskellNone
LanguageHaskell2010

Data.ByteString.FastBuilder.Internal

Contents

Description

This is an internal module; its interface is unstable.

Synopsis

Builder and related types

newtype Builder #

Builder is an auxiliary type for efficiently generating a long ByteString. It is isomorphic to lazy ByteString, but offers constant-time concatanation via <>.

Use toLazyByteString to turn a Builder into a ByteString

Constructors

Builder 

Fields

Instances

data BuilderState #

This datatype exists only to work around the limitation that oneShot cannot work with unboxed argument types.

Constructors

BuilderState !(Ptr Word8) !(Ptr Word8) (State# RealWorld) 

data DataSink #

Specifies where bytes generated by a builder go.

Constructors

DynamicSink !(IORef DynamicSink)

The destination of data changes while the builder is running.

GrowingBuffer !(IORef (ForeignPtr Word8))

Bytes are accumulated in a contiguous buffer.

HandleSink !Handle !(IORef Queue)

Bytes are first accumulated in the Queue, then flushed to the Handle.

data DynamicSink #

Variable-destination cases.

Constructors

ThreadedSink !(MVar Request) !(MVar Response)

Bytes are sent to another thread.

BoundedGrowingBuffer !(ForeignPtr Word8) !Int

Bytes are accumulated in a contiguous buffer until the size limit is reached. After that, the destination switches to a ThreadedSink.

data Queue #

A mutable buffer. The Int specifies where the data start.

Constructors

Queue !(ForeignPtr Word8) !Int 

data Request #

A request from the driver thread to the builder thread.

Constructors

Request !(Ptr Word8) !(Ptr Word8) 

data Response #

A response from the builder thread to the driver thread.

Constructors

Error SomeException

A synchronous exception was thrown by the builder

Done !(Ptr Word8)

The builder thread has completed.

MoreBuffer !(Ptr Word8) !Int

The builder thread has finished generating one chunk, and waits for another request with the specified minimum size.

InsertByteString !(Ptr Word8) !ByteString

The builder thread has partially filled the current chunk, and wants to emit the bytestring to be included in the final output.

Instances

Internally used exceptions

data SuspendBuilderException #

Used in the implementation of toLazyByteString. This is a message sent from the consumer thread to the builder thread, requesting the builder thread to temporarily pause execution. Later, the consumer thread may request resumption by filling the MVar.

Constructors

SuspendBuilderException !(MVar ()) 

Instances

data ChunkOverflowException #

Used in the implementation of toLazyByteString. This is an exception thrown by the consumer thread to itself when it has finished filling the first chunk of the output. After this, a thread will be forked, and the execution of the builder will be resumed in the new thread, using ThreadedSink.

Constructors

ChunkOverflowException !ByteString !(MVar Request) !(MVar Response) !Int 

Instances

Builder building blocks

type Builder_ = DataSink -> Addr# -> Addr# -> State# RealWorld -> (#Addr#, Addr#, State# RealWorld#) #

An internal type that is isomorphic to Builder. This is a maximaly efficient representation for NOINLINE functions.

newtype BuildM a #

An internal type for making it easier to define builders. A value of BuildM a can do everything a Builder can do, and in addition, returns a value of type a upon completion.

Constructors

BuildM 

Fields

Instances

Monad BuildM # 

Methods

(>>=) :: BuildM a -> (a -> BuildM b) -> BuildM b #

(>>) :: BuildM a -> BuildM b -> BuildM b #

return :: a -> BuildM a #

fail :: String -> BuildM a #

Functor BuildM # 

Methods

fmap :: (a -> b) -> BuildM a -> BuildM b #

(<$) :: a -> BuildM b -> BuildM a #

Applicative BuildM # 

Methods

pure :: a -> BuildM a #

(<*>) :: BuildM (a -> b) -> BuildM a -> BuildM b #

(*>) :: BuildM a -> BuildM b -> BuildM b #

(<*) :: BuildM a -> BuildM b -> BuildM a #

toBuilder_ :: Builder -> Builder_ #

Convert a Builder into a Builder_.

fromBuilder_ :: Builder_ -> Builder #

Convert a Builder_ into a Builder.

mkBuilder :: BuildM () -> Builder #

Create a builder from a BuildM.

useBuilder :: Builder -> BuildM () #

Embed a builder in the BuildM context.

getSink :: BuildM DataSink #

Get the DataSink.

getCur :: BuildM (Ptr Word8) #

Get the current pointer.

getEnd :: BuildM (Ptr Word8) #

Get the end-of-buffer pointer.

setCur :: Ptr Word8 -> BuildM () #

Set the current pointer.

setEnd :: Ptr Word8 -> BuildM () #

Set the end-of-buffer pointer.

Running builders

runBuilder :: Builder -> DataSink -> Ptr Word8 -> Ptr Word8 -> IO (Ptr Word8) #

Run a builder.

toLazyByteString :: Builder -> ByteString #

Turn a Builder into a lazy ByteString.

Performance hint: when the resulting ByteString does not fit in one chunk, this function forks a thread. Due to this, the performance degrades sharply if you use this function from a bound thread. Note in particular that the main thread is a bound thread when you use ghc -threaded.

To avoid this problem, do one of these:

  • Make sure the resulting ByteString is consumed in an unbound thread. Consider using runInUnboundThread for this.
  • Use other function to run the Builder instead. Functions that don't return a lazy ByteString do not have this issue.
  • Link your program without -threaded.

toLazyByteStringWith :: Int -> Int -> Builder -> ByteString #

Like toLazyByteString, but allows the user to specify the initial and the subsequent desired buffer sizes.

toStrictByteString :: Builder -> ByteString #

Turn a Builder into a strict ByteString.

hPutBuilder :: Handle -> Builder -> IO () #

Output a Builder to a Handle.

Basic builders

primBounded :: BoundedPrim a -> a -> Builder #

Turn a value of type a into a Builder, using the given BoundedPrim.

primFixed :: FixedPrim a -> a -> Builder #

Turn a value of type a into a Builder, using the given FixedPrim.

primMapListBounded :: BoundedPrim a -> [a] -> Builder #

Turn a list of values of type a into a Builder, using the given BoundedPrim.

primMapListFixed :: FixedPrim a -> [a] -> Builder #

Turn a list of values of type a into a Builder, using the given FixedPrim.

byteString :: ByteString -> Builder #

Turn a ByteString to a Builder.

byteStringThreshold :: Int -> ByteString -> Builder #

Turn a ByteString to a Builder. If the size of the ByteString is larger than the given threshold, avoid copying it as much as possible.

byteStringCopy :: ByteString -> Builder #

Turn a ByteString to a Builder. The ByteString will be copied to the buffer, regardless of the size.

byteStringCopyNoCheck :: ByteString -> Builder #

Like byteStringCopy, but assumes that the current buffer is large enough.

byteStringInsert :: ByteString -> Builder #

Turn a ByteString to a Builder. When possible, the given ByteString will not be copied, and inserted directly into the output instead.

unsafeCString :: CString -> Builder #

Turn a C String into a Builder. The behavior is undefined if the given CString does not point to a constant null-terminated string.

ensureBytes :: Int -> Builder #

ensureBytes n ensures that at least n bytes of free space is available in the current buffer, by allocating a new buffer when necessary.

getBytes :: Int -> Builder #

getBytes n allocates a new buffer, containing at least n bytes.

Performance tuning

rebuild :: Builder -> Builder #

rebuild b is equivalent to b, but it allows GHC to assume that b will be run at most once. This can enable various optimizations that greately improve performance.

There are two types of typical situations where a use of rebuild is often a win:

  • When constructing a builder using a recursive function. e.g. rebuild $ foldr ....
  • When constructing a builder using a conditional expression. e.g. rebuild $ case x of ...