packman
Version 0.4.0 revision 0 uploaded by JostBerthold.
Package meta
- Synopsis
- Serialization library for GHC
- Description
This package provides Haskell data serialisation independent of evaluation, by accessing the Haskell heap using foreign primitive operations. Any Haskell data structure apart from mutable data structures (
MVar
s andTVar
s) can be serialised and later deserialised during the same run, or loaded into a new run, of the same program (the same executable file).The library provides operations to
serialize
Haskell heap data, and todeserialize
it:trySerializeWith :: a -> Int -> IO (Serialized a) -- Int is maximum buffer size to use trySerialize :: a -> IO (Serialized a) -- uses default (maximum) buffer size deserialize :: Serialized a -> IO a
The data type
Serialized a
is an opaque representation of serialised Haskell data (it contains aByteArray
). A phantom typea
ensures type safety within the same program run. Typea
can be polymorphic (at compile time, that is) whenSerialized a
is not used apart from being argument todeserialize
. When data are externalised (written to disk or communicated over the network) using the provided instances ofBinary
orRead
andShow
,a
needs to be monomorphic because they requireTypeable
context. The instances forShow
andRead
satisfyread . show == id
.Packman serialisation is orthogonal to evaluation, heap data are serialised in their current state of evaluation, they might be entirely unevaluated (a thunk) or only partially evaluated (containing thunks). Therefore, there can be cases where a mutable data structure is captured by a thunk, and lead to serialisation failures (typically related to lazy I/O).
The serialisation routine will throw a
PackException
if an error occurs inside the C code which accesses the Haskell heap, if a mutable data structure is serialised, or if the serialised data is too large. In presence of concurrent threads, another thread might be evaluating data referred to by the data to be serialised. In this case, the calling thread will block on the ongoing evaluation and continue when evaluated data is available. Internally, there is aPackException
P_BLACKHOLE
to signal the condition, but it is hidden inside the core library- Author
- Michael Budde, Ásbjørn V. Jøkladal, Jost Berthold
- Bug reports
- n/a
- Category
- Serialization, Data, GHC
- Copyright
- n/a
- Homepage
- n/a
- Maintainer
- jost.berthold@gmail.com
- Package URL
- n/a
- Stability
- n/a