haskell - 如何序列化作为数据实例的数据结构？

Question

我想序列化一个部分由我自己定义的数据结构，部分使用来自外部库的数据结构(它是数据的一个实例)。我想进行序列化，而不必定义序列化过程的工作方式，或者换句话说，以一种相当自动的方式。

我一直在尝试通过谷歌搜索/询问找到的几种替代方案。他们都没有成功。图书馆 ( genericserialize ) 似乎是我要找的。不幸的是，即使对于简单的情况(如 (True, False))，它也不起作用。它可能已过时或/和不完整。二进制序列化要求外部数据结构派生 Binary(它不是)。用Cereal出现类似的问题。当然是Read/Show，但是同样，外部数据结构不派生Read，所以也不能用。

也许我误会了什么。我以为当我第一次遇到这个问题时会更容易。在其他语言中，例如 Erlang，这是以一种非常简单的方式完成的。

您是否知道库/技术或其他什么可以使这个过程尽可能简单？

Answer 1

你可以使用 Data.Binary .

为所有涉及的数据类型派生Generic。这将需要 -XDeriveGeneric语用。如果您使用的外部库中的数据类型不这样做，您可能需要一个 orphan instances 的模块。并使用 -XStandaloneDeriving .

完成后，您可以利用 Binary 类已经支持从 Generic 派生的事实。您需要启用 -XDeriveAnyclass然后您可以为所有涉及的数据类型添加 Binary 实例(您可能需要再次为外部库中的类型添加独立实例)。

编辑

OP added a gist .然后，为了编译它，我们需要添加以下语言编译指示:

{-# LANGUAGE DeriveDataTypeable,
             DeriveAnyClass,
             DeriveGeneric,
             StandaloneDeriving #-}

以及以下导入:

import Language.C.Syntax.AST
import Language.C.Data.Position
import Language.C.Data.Node
import Language.C.Data.Name
import Language.C.Data.Ident
import Language.C.Syntax.Constants

import Data.Data
import GHC.Generics
import Data.Binary

来自 OP 的要点:

type CTypeSpecAnn = CTypeSpecifier NodeAnn 
type CDeclAnn = CDeclaration NodeAnn
type CDeclSpecAnn = CDeclarationSpecifier NodeAnn
type CDeclrAnn = CDeclarator NodeAnn
type CStatAnn = CStatement NodeAnn
type CExtDeclAnn = CExternalDeclaration NodeAnn
type CExprAnn = CExpression NodeAnn
type CBlockItemAnn = CCompoundBlockItem NodeAnn
type CTranslUnitAnn = CTranslationUnit NodeAnn

data TransState = 
    TransState 
    {
        free_node_id :: Int,
        freeVar :: Int,
        includes :: [String],
        fun_defs :: [(String, (CTypeSpecAnn, [CDeclAnn], ([CDeclSpecAnn], CDeclrAnn, [CDeclAnn], NodeAnn)), CStatAnn)],
        no_fun_defs :: [CExtDeclAnn],
        last_changed :: String,
        previous_changes :: ([(String, ((String,CStatAnn,CStatAnn), TransState, [(String, CStatAnn)]))], [(String, ((String,CExprAnn,CExprAnn), TransState, [(String, CStatAnn)]))]),
        applied_rules :: [String],
        applicable_rules :: Set String,
        trans_with_anns :: Bool
    }
    deriving (Show, Data, Typeable)

type NodeAnn = Annotation NodeInfo NodeProperties
data Annotation nI nP = Ann nI nP
    deriving (Show, Data, Typeable, Eq)

data NodeProperties = 
    NodeProperties
    { 
        _hasSideEffects :: PropertyInfo Bool,
        _readIn ::  PropertyInfo [String],
        _writeIn ::  PropertyInfo [String],
        _localSymbols :: PropertyInfo [String],
        _rangeInfo :: PropertyInfo [String],
        _isCanonical :: PropertyInfo Bool,
        _isPerfectNest :: PropertyInfo Bool,
        _hasLoops :: PropertyInfo Bool,
        _hasFunctionCalls :: PropertyInfo Bool,
        _hasControlFlowModifiers :: PropertyInfo Bool,
        _scalarDependences :: PropertyInfo [String],
        _polcaPragmas :: PropertyInfo [[String]],
        _allPragmas :: PropertyInfo [String]
    } 
    deriving (Show, Data, Typeable, Eq)

data PropertyInfo a = 
    PropertyInfo
    { 
        _pragmaType :: PragmaType,
        _definedBy  :: DefinerType,
        _value :: Maybe a
    } 
    deriving (Show, Data, Typeable, Eq)

makeLenses ''NodeProperties
makeLenses ''PropertyInfo

由于 OP 从不定义 PragmaType 和 DefinerType，我假设它们是 ()。

type PragmaType = ()
type DefinerType = ()

然后我们有大量的派生实例(我们必须递归地找到所有类型依赖并向它们添加Generic 和Binary)。

deriving instance Generic (CDeclaration a)
deriving instance Binary a => Binary (CDeclaration a)
deriving instance Generic (CTypeSpecifier a)
deriving instance Binary a => Binary (CTypeSpecifier a)
deriving instance Generic (CDeclarationSpecifier a)
deriving instance Binary a => Binary (CDeclarationSpecifier a)
deriving instance Generic (CDeclarator a)
deriving instance Binary a => Binary (CDeclarator a)
deriving instance Generic (CStatement a)
deriving instance Binary a => Binary (CStatement a)
deriving instance Generic (CExternalDeclaration a)
deriving instance Binary a => Binary (CExternalDeclaration a)
deriving instance Generic (CExpression a)
deriving instance Binary a => Binary (CExpression a)
deriving instance Generic (CCompoundBlockItem a)
deriving instance Binary a => Binary (CCompoundBlockItem a)
deriving instance Generic (CTranslationUnit a)
deriving instance Binary a => Binary (CTranslationUnit a)
deriving instance Generic (CInitializer a)
deriving instance Binary a => Binary (CInitializer a)
deriving instance Generic (CStructureUnion a)
deriving instance Binary a => Binary (CStructureUnion a)
deriving instance Generic (CTypeQualifier a)
deriving instance Binary a => Binary (CTypeQualifier a)
deriving instance Generic (CStringLiteral a)
deriving instance Binary a => Binary (CStringLiteral a)
deriving instance Generic (CAttribute a)
deriving instance Binary a => Binary (CAttribute a)
deriving instance Generic (CPartDesignator a)
deriving instance Binary a => Binary (CPartDesignator a)
deriving instance Generic (CFunctionDef a)
deriving instance Binary a => Binary (CFunctionDef a)
deriving instance Generic (CAssemblyStatement a)
deriving instance Binary a => Binary (CAssemblyStatement a)
deriving instance Generic (CAssemblyOperand a)
deriving instance Binary a => Binary (CAssemblyOperand a)
deriving instance Generic (CConstant a)
deriving instance Binary a => Binary (CConstant a)
deriving instance Generic (CEnumeration a)
deriving instance Binary a => Binary (CEnumeration a)
deriving instance Generic (CStorageSpecifier a)
deriving instance Binary a => Binary (CStorageSpecifier a)
deriving instance Generic (CDerivedDeclarator a)
deriving instance Binary a => Binary (CDerivedDeclarator a)
deriving instance Generic (CBuiltinThing a)
deriving instance Binary a => Binary (CBuiltinThing a)
deriving instance Generic (CArraySize a)
deriving instance Binary a => Binary (CArraySize a)
deriving instance Generic (Flags a)
deriving instance Binary a => Binary (Flags a)
deriving instance Generic NodeInfo
deriving instance Binary NodeInfo
deriving instance Generic Name
deriving instance Binary Name
deriving instance Generic Ident
deriving instance Binary Ident
deriving instance Generic CString
deriving instance Binary CString
deriving instance Generic CStructTag
deriving instance Binary CStructTag
deriving instance Generic CFloat
deriving instance Binary CFloat
deriving instance Generic CChar
deriving instance Binary CChar
deriving instance Generic CUnaryOp
deriving instance Binary CUnaryOp
deriving instance Generic CBinaryOp
deriving instance Binary CBinaryOp
deriving instance Generic CInteger
deriving instance Binary CInteger
deriving instance Generic CAssignOp
deriving instance Binary CAssignOp
deriving instance Generic CIntFlag
deriving instance Binary CIntFlag
deriving instance Generic CIntRepr
deriving instance Binary CIntRepr

deriving instance Binary TransState
deriving instance Generic TransState
deriving instance Generic (Annotation a b)
deriving instance (Binary a, Binary b) => Binary (Annotation a b)
deriving instance Generic NodeProperties
deriving instance Binary NodeProperties
deriving instance Generic (PropertyInfo a)
deriving instance Binary a => Binary (PropertyInfo a)

作为旁注，这些实例的后半部分可以在类型本身的数据声明中声明(因为它们是在当前文件中声明的)。一个关键点是我们仍然没有 Position 的 Binary 实例。我们无法自动派生它，因为它的数据构造函数尚未导出。然而，没有什么能阻止我们编写手动 Binary 实例。

instance Binary Position where
    put p | isNoPos p = putWord8 0 
          | isBuiltinPos p = putWord8 1
          | isInternalPos p = putWord8 2
          | isSourcePos p = putWord8 3 >> put (posOffset p) >> put (posFile p) >> put (posRow p) >> put (posColumn p)

    get = do
        marker <- getWord8
        case marker of
            0 -> return nopos
            1 -> return builtinPos
            2 -> return internalPos
            3 -> position <$> get <*> get <*> get <*> get