Database.AnyDBM

Written by John Goerzen, [e-mail]

This module provides a generic infrastructure for supporting storage of hash-like items with String -> String mappings. It can be used for in-memory or on-disk items.

The AnyDBM class

class AnyDBM a where

The main class for items implementing this interface.

People implementing this class should provide methods for:

• closeA (unless you have no persistent storage)
• flushA (unless you have no persistent storage)
• insertA
• deleteA
• lookupA
• either toListA or keysA

Methods

closeA :: a -> IO ()

Close the object, writing out any unsaved data to disk if necessary.

If you implement this, make sure your implementation calls flushA.

Note: if you have an object opened for writing, you MUST call closeA on it when you are done. Implementations are not required to preserve your data otherwise.

flushA :: a -> IO ()

Flush the object, saving any un-saved data to disk but not closing it. Called automatically by closeA.

insertA

Arguments

:: a

AnyDBM object

-> String

Key

-> String

Value

-> IO ()

Insert the given data into the map. Existing data with the same key will be overwritten.

deleteA :: a -> String -> IO ()

Delete the data referenced by the given key. It is not an error if the key does not exist.

hasKeyA :: a -> String -> IO Bool

True if the given key is present.

lookupA :: a -> String -> IO (Maybe String)

Find the data referenced by the given key.

forceLookupA :: a -> String -> IO String

Look up the data and raise an exception if the key does not exist. The exception raised is PatternMatchFail, and the string accompanying it is the key that was looked up.

insertListA :: a -> [(String, String)] -> IO ()

Call insertA on each pair in the given association list, adding them to the map.

toListA :: a -> IO [(String, String)]

Return a representation of the content of the map as a list.

keysA :: a -> IO [String]

Returns a list of keys in the AnyDBM object.

valuesA :: a -> IO [String]

Returns a list of values in the AnyDBM object.

Instances

AnyDBM MapDBM

AnyDBM StringDBM

AnyDBM (HashTable String String)

AnyDBM utilities

mapA :: AnyDBM a => a -> ((String, String) -> IO b) -> IO [b]

Similar to MapM, but for AnyDBM objects.

strFromA :: AnyDBM a => a -> IO String

Similar to strFromAL -- get a string representation of the entire AnyDBM.

strToA :: AnyDBM a => a -> String -> IO ()

Similar to strToAL -- load a string representation into the AnyDBM. You must supply an existing AnyDBM object; the items loaded from the string will be added to it.