System.Console.Concurrent.Internal

concurrent-output-1.7.4: Ungarble output from several threads or commands

Copyright | 2015 Joey Hess <id@joeyh.name>
License | BSD-2-clause
Safe Haskell | None
Language | Haskell98

System.Console.Concurrent.Internal

Description

Concurrent output handling, internals.

May change at any time.

Synopsis

- data OutputHandle = OutputHandle {
  - outputLock :: TMVar Lock
  - outputBuffer :: TMVar OutputBuffer
  - errorBuffer :: TMVar OutputBuffer
  - outputThreads :: TMVar Integer
  - processWaiters :: TMVar [Async ()]
  - waitForProcessLock :: TMVar ()
  }
- data Lock = Locked
- globalOutputHandle :: OutputHandle
- lockOutput :: (MonadIO m, MonadMask m) => m a -> m a
- takeOutputLock :: IO ()
- tryTakeOutputLock :: IO Bool
- withLock :: (TMVar Lock -> STM a) -> IO a
- takeOutputLock' :: Bool -> IO Bool
- dropOutputLock :: IO ()
- withConcurrentOutput :: (MonadIO m, MonadMask m) => m a -> m a
- flushConcurrentOutput :: IO ()
- class Outputable v where
  - toOutput :: v -> Text
- outputConcurrent :: Outputable v => v -> IO ()
- errorConcurrent :: Outputable v => v -> IO ()
- outputConcurrent' :: Outputable v => StdHandle -> v -> IO ()
- newtype ConcurrentProcessHandle = ConcurrentProcessHandle ProcessHandle
- toConcurrentProcessHandle :: (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) -> (Maybe Handle, Maybe Handle, Maybe Handle, ConcurrentProcessHandle)
- waitForProcessConcurrent :: ConcurrentProcessHandle -> IO ExitCode
- asyncProcessWaiter :: IO () -> IO ()
- createProcessConcurrent :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ConcurrentProcessHandle)
- createProcessForeground :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ConcurrentProcessHandle)
- fgProcess :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ConcurrentProcessHandle)
- bgProcess :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ConcurrentProcessHandle)
- willOutput :: StdStream -> Bool
- data OutputBuffer = OutputBuffer [OutputBufferedActivity]
- data StdHandle
  - = StdOut
  - | StdErr
- toHandle :: StdHandle -> Handle
- bufferFor :: StdHandle -> TMVar OutputBuffer
- data OutputBufferedActivity
  - = Output Text
  - | InTempFile {
    - tempFile :: FilePath
    - endsInNewLine :: Bool
    }
- data AtEnd = AtEnd
- data BufSig = BufSig
- setupOutputBuffer :: StdHandle -> Handle -> StdStream -> Handle -> IO (StdHandle, MVar OutputBuffer, TMVar BufSig, TMVar AtEnd)
- outputDrainer :: StdStream -> Handle -> MVar OutputBuffer -> TMVar BufSig -> TMVar AtEnd -> IO ()
- registerOutputThread :: IO ()
- unregisterOutputThread :: IO ()
- bufferWriter :: [(StdHandle, MVar OutputBuffer, TMVar BufSig, TMVar AtEnd)] -> IO ()
- addOutputBuffer :: OutputBufferedActivity -> OutputBuffer -> IO OutputBuffer
- bufferOutputSTM :: Outputable v => StdHandle -> v -> STM ()
- bufferOutputSTM' :: StdHandle -> OutputBuffer -> STM ()
- outputBufferWaiterSTM :: (OutputBuffer -> (OutputBuffer, OutputBuffer)) -> STM (StdHandle, OutputBuffer)
- waitAnyBuffer :: OutputBuffer -> (OutputBuffer, OutputBuffer)
- waitCompleteLines :: OutputBuffer -> (OutputBuffer, OutputBuffer)
- endsNewLine :: Text -> Bool
- emitOutputBuffer :: StdHandle -> OutputBuffer -> IO ()

# Documentation

data OutputHandle

Constructors

OutputHandle |
Fields outputLock :: TMVar Lock outputBuffer :: TMVar OutputBuffer errorBuffer :: TMVar OutputBuffer outputThreads :: TMVar Integer processWaiters :: TMVar [Async ()] waitForProcessLock :: TMVar ()

data Lock

Constructors

Locked |

globalOutputHandle :: OutputHandle

A shared global variable for the OutputHandle.

lockOutput :: (MonadIO m, MonadMask m) => m a -> m a

Holds a lock while performing an action. This allows the action to perform its own output to the console, without using functions from this module.

While this is running, other threads that try to lockOutput will block. Any calls to `outputConcurrent` and `createProcessConcurrent` will not block, but the output will be buffered and displayed only once the action is done.

takeOutputLock :: IO ()

Blocks until we have the output lock.

tryTakeOutputLock :: IO Bool

Tries to take the output lock, without blocking.

withLock :: (TMVar Lock -> STM a) -> IO a

takeOutputLock' :: Bool -> IO Bool

dropOutputLock :: IO ()

Only safe to call after taking the output lock.

withConcurrentOutput :: (MonadIO m, MonadMask m) => m a -> m a

Use this around any actions that use `outputConcurrent` or `createProcessConcurrent`

This is necessary to ensure that buffered concurrent output actually gets displayed before the program exits.

flushConcurrentOutput :: IO ()

Blocks until any processes started by `createProcessConcurrent` have finished, and any buffered output is displayed. Also blocks while `lockOutput` is is use.

`withConcurrentOutput` calls this at the end, so you do not normally need to use this.

class Outputable v where

Values that can be output.

Methods

toOutput :: v -> Text

Instances

Outputable String |
Outputable Text |

outputConcurrent :: Outputable v => v -> IO ()

Displays a value to stdout.

No newline is appended to the value, so if you want a newline, be sure to include it yourself.

Uses locking to ensure that the whole output occurs atomically even when other threads are concurrently generating output.

When something else is writing to the console at the same time, this does not block. It buffers the value, so it will be displayed once the other writer is done.

errorConcurrent :: Outputable v => v -> IO ()

Like `outputConcurrent`, but displays to stderr.

(Does not throw an exception.)

outputConcurrent' :: Outputable v => StdHandle -> v -> IO ()

newtype ConcurrentProcessHandle

Constructors

ConcurrentProcessHandle ProcessHandle |

toConcurrentProcessHandle :: (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) -> (Maybe Handle, Maybe Handle, Maybe Handle, ConcurrentProcessHandle)

waitForProcessConcurrent :: ConcurrentProcessHandle -> IO ExitCode

Use this to wait for processes started with `createProcessConcurrent` and `createProcessForeground`, and get their exit status.

Note that such processes are actually automatically waited for internally, so not calling this explicitly will not result in zombie processes. This behavior differs from `waitForProcess`

asyncProcessWaiter :: IO () -> IO ()

createProcessConcurrent :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ConcurrentProcessHandle)

Wrapper around `createProcess` that prevents multiple processes that are running concurrently from writing to stdout/stderr at the same time.

If the process does not output to stdout or stderr, it's run by createProcess entirely as usual. Only processes that can generate output are handled specially:

A process is allowed to write to stdout and stderr in the usual way, assuming it can successfully take the output lock.

When the output lock is held (ie, by another concurrent process, or because `outputConcurrent` is being called at the same time), the process is instead run with its stdout and stderr redirected to a buffer. The buffered output will be displayed as soon as the output lock becomes free.

Currently only available on Unix systems, not Windows.

createProcessForeground :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ConcurrentProcessHandle)

Wrapper around `createProcess` that makes sure a process is run in the foreground, with direct access to stdout and stderr. Useful when eg, running an interactive process.

fgProcess :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ConcurrentProcessHandle)

bgProcess :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ConcurrentProcessHandle)

willOutput :: StdStream -> Bool

data OutputBuffer

Buffered output.

Constructors

OutputBuffer [OutputBufferedActivity] |

Instances

Eq OutputBuffer |

data StdHandle

Constructors

StdOut |
StdErr |

toHandle :: StdHandle -> Handle

bufferFor :: StdHandle -> TMVar OutputBuffer

data OutputBufferedActivity

Constructors

Output Text |
InTempFile |
Fields tempFile :: FilePath endsInNewLine :: Bool

Instances

Eq OutputBufferedActivity |

data AtEnd

Constructors

AtEnd |

Instances

Eq AtEnd |

data BufSig

Constructors

BufSig |

setupOutputBuffer :: StdHandle -> Handle -> StdStream -> Handle -> IO (StdHandle, MVar OutputBuffer, TMVar BufSig, TMVar AtEnd)

outputDrainer :: StdStream -> Handle -> MVar OutputBuffer -> TMVar BufSig -> TMVar AtEnd -> IO ()

registerOutputThread :: IO ()

unregisterOutputThread :: IO ()

bufferWriter :: [(StdHandle, MVar OutputBuffer, TMVar BufSig, TMVar AtEnd)] -> IO ()

addOutputBuffer :: OutputBufferedActivity -> OutputBuffer -> IO OutputBuffer

bufferOutputSTM :: Outputable v => StdHandle -> v -> STM ()

Adds a value to the output buffer for later display.

Note that buffering large quantities of data this way will keep it resident in memory until it can be displayed. While `outputConcurrent` uses temp files if the buffer gets too big, this STM function cannot do so.

bufferOutputSTM' :: StdHandle -> OutputBuffer -> STM ()

outputBufferWaiterSTM :: (OutputBuffer -> (OutputBuffer, OutputBuffer)) -> STM (StdHandle, OutputBuffer)

A STM action that waits for some buffered output to become available, and returns it.

The function can select a subset of output when only some is desired; the fst part is returned and the snd is left in the buffer.

This will prevent it from being displayed in the usual way, so you'll need to use `emitOutputBuffer` to display it yourself.

waitAnyBuffer :: OutputBuffer -> (OutputBuffer, OutputBuffer)

waitCompleteLines :: OutputBuffer -> (OutputBuffer, OutputBuffer)

Use with `outputBufferWaiterSTM` to make it only return buffered output that ends with a newline. Anything buffered without a newline is left in the buffer.

endsNewLine :: Text -> Bool

emitOutputBuffer :: StdHandle -> OutputBuffer -> IO ()

Emits the content of the OutputBuffer to the Handle

If you use this, you should use `lockOutput` to ensure you're the only thread writing to the console.