hscdio- Haskell bindings to the libcdio disc-reading library.
Copyright(c) 2020-2021 Sam May
Portabilitynon-portable (requires libcdio)
Safe HaskellNone




The underlying library is rather loud in its error and warning messages, potentially emitting a lot of impure terminal clutter even on some otherwise-pure functions. Very helpfully, it also provides a mechanism for integrating the logs with whatever framework is in place for the larger project; that mechanism can be leveraged to cache the logs in memory until specifically asked for, at which point they can be packaged into Haskell types. Some of the immediacy—and therefore user ability to match note to source—is unfortunately lost, but the apparent purity is worth it.


class LibcdioLogger m where #

An environment which integrates the libcdio logging interface; will almost always be a Monad, but as an Applicative might technically be able to implement these, that constraint isn't enforced.


logCutoff #


:: m LogLevel

Check the current minimum severity which will be recorded in the logs.

setLogCutoff #


:: LogLevel 
-> m ()

Set the minimum severity required for a message to be recorded in the logs.

readLog #


:: m [LogEntry]

Retrieve all messages currently in the log for further processing. Note that this retains the contents of the log for future calls; to remove them, a separate call to clearLog must be made.

>>> putLog $ LogEntry LogWarn "Testing log reading" >>= readLog
[LogEntry LogWarn "Testing log reading"]
>>> clearLog >>= readLog

clearLog #


:: m ()

Empty all messages currently in the log. There is no way to selectively remove only some messages; if that is desired, call readLog first:

>>> setupLogger
>>> msgs <- readLog
>>> clearLog
>>> mapM_ putLog $ filter p msgs

putLog #


:: LogEntry 
-> m ()

Append a message to the logs.


Instances details
LibcdioLogger IO #

The required initialization function setupLogger isn't called automatically; make sure to do so manually before using any of these.

Instance details

Defined in Sound.Libcdio.Logging

LibcdioLogger Cdio # 
Instance details

Defined in Sound.Libcdio.Types.Cdio

LibcdioLogger CdText # 
Instance details

Defined in Sound.Libcdio.Read.CdText

data LogEntry #

An unstructured message emitted from the library to let the user know what's going on behind the scenes.





Instances details
Eq LogEntry # 
Instance details

Defined in Foreign.Libcdio.Logging

Read LogEntry # 
Instance details

Defined in Foreign.Libcdio.Logging

Show LogEntry # 
Instance details

Defined in Foreign.Libcdio.Logging

Storable LogEntry # 
Instance details

Defined in Foreign.Libcdio.Logging

data LogLevel #

How much detail should be recorded in the logs.


isolateLogs :: (Monad m, LibcdioLogger m) => m a -> m a #

Keep the monad pure by preventing it from reading stale logs, but since the outer IO might still care about them, restore the entire stack after.

Note that the logs are not thread-safe; messages from other threads may be interwoven with those from the passed computation even after this function is called.

setupLogger :: IO () #

Initialize the log-management backend to use the mechanisms provided by this library instead of just printing to standard output. While this will usually be taken care of automatically, it may still be necessary to call this explicitly if messages are being recorded before any disc session is opened.