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{- git repository command queue
-
- Copyright 2010 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Git.Queue (
Queue,
empty,
add,
size,
full,
flush
) where
import qualified Data.Map as M
import System.IO
import System.Cmd.Utils
import Data.String.Utils
import Control.Monad (unless, forM_)
import Utility
import Git
{- An action to perform in a git repository. The file to act on
- is not included, and must be able to be appended after the params. -}
data Action = Action {
getSubcommand :: String,
getParams :: [CommandParam]
} deriving (Show, Eq, Ord)
{- A queue of actions to perform (in any order) on a git repository,
- with lists of files to perform them on. This allows coalescing
- similar git commands. -}
data Queue = Queue Int (M.Map Action [FilePath])
deriving (Show, Eq)
{- A recommended maximum size for the queue, after which it should be
- run.
-
- 10240 is semi-arbitrary. If we assume git filenames are between 10 and
- 255 characters long, then the queue will build up between 100kb and
- 2550kb long commands. The max command line length on linux is somewhere
- above 20k, so this is a fairly good balance -- the queue will buffer
- only a few megabytes of stuff and a minimal number of commands will be
- run by xargs. -}
maxSize :: Int
maxSize = 10240
{- Constructor for empty queue. -}
empty :: Queue
empty = Queue 0 M.empty
{- Adds an action to a queue. -}
add :: Queue -> String -> [CommandParam] -> [FilePath] -> Queue
add (Queue n m) subcommand params files = Queue (n + 1) m'
where
action = Action subcommand params
-- There are probably few items in the map, but there
-- can be a lot of files per item. So, optimise adding
-- files.
m' = M.insertWith' const action fs m
fs = files ++ (M.findWithDefault [] action m)
{- Number of items in a queue. -}
size :: Queue -> Int
size (Queue n _) = n
{- Is a queue large enough that it should be flushed? -}
full :: Queue -> Bool
full (Queue n _) = n > maxSize
{- Runs a queue on a git repository. -}
flush :: Repo -> Queue -> IO Queue
flush repo (Queue _ m) = do
forM_ (M.toList m) $ uncurry $ runAction repo
return empty
{- Runs an Action on a list of files in a git repository.
-
- Complicated by commandline length limits.
-
- Intentionally runs the command even if the list of files is empty;
- this allows queueing commands that do not need a list of files. -}
runAction :: Repo -> Action -> [FilePath] -> IO ()
runAction repo action files =
pOpen WriteToPipe "xargs" ("-0":"git":params) feedxargs
where
params = toCommand $ gitCommandLine repo
(Param (getSubcommand action):getParams action)
feedxargs h = hPutStr h $ join "\0" files
|
