MissingH- Large utility library

Portabilityportable to platforms supporting binary I\/O
MaintainerJohn Goerzen <jgoerzen@complete.org>




This module provides various helpful utilities for dealing with binary input and output.

You can use this module to deal with binary blocks of data as either Strings or lists of Word8. The BinaryConvertible class provides this abstraction.

Wherever you see HVIO, you can transparently substite a regular Handle. This module can work with any HVIO object, however. See System.IO.HVIO for more details.

Versions of MissingH prior 0.11.6 lacked the BinaryConvertible class and worked only with Strings and Handles.

Important note: /binary functions are not supported in all Haskell implementations/. Do not import or use this module unless you know you are using an implementation that supports them. At this time, here is the support status:

  • GHC 6.2 and above: yes
  • GHC 6.x, earlier versions: unknown
  • GHC 5.x: no
  • nhc98: no
  • Hugs: partial (maybe complete; needs more testing)

Non-binary functions may be found in System.IO.

See also: System.IO.BlockIO

Written by John Goerzen, jgoerzen@complete.org


Support for different types of blocks

class (Eq a, Show a) => BinaryConvertible a whereSource

Provides support for handling binary blocks with convenient types.

This module provides implementations for Strings and for [Word8] (lists of Word8s).


toBuf :: [a] -> (Ptr CChar -> IO c) -> IO cSource

fromBuf :: Int -> (Ptr CChar -> IO Int) -> IO [a]Source

Entire File/Handle Utilities

Opened Handle Data Copying

hBlockCopy :: (HVIO a, HVIO b) => Int -> a -> b -> IO ()Source

Copies everything from the input handle to the output handle using binary blocks of the given size. This was once the following beautiful implementation:

 hBlockCopy bs hin hout = hBlockInteract bs hin hout id

(id is the built-in Haskell function that just returns whatever is given to it)

In more recent versions of MissingH, it uses a more optimized routine that avoids ever having to convert the binary buffer at all.

blockCopy :: Int -> IO ()Source

Copies from stdin to stdout using binary blocks of the given size. An alias for hBlockCopy over stdin and stdout

Disk File Data Copying

copyFileBlocksToFile :: Int -> FilePath -> FilePath -> IO ()Source

Copies one filename to another in binary mode.

Please note that the Unix permission bits on the output file cannot be set due to a limitation of the Haskell openBinaryFile function. Therefore, you may need to adjust those bits after the copy yourself.

This function is implemented using hBlockCopy internally.

Binary Single-Block I/O

hPutBufStr :: (HVIO a, BinaryConvertible b) => a -> [b] -> IO ()Source

As a wrapper around the standard function hPutBuf, this function takes a standard Haskell String instead of the far less convenient Ptr a. The entire contents of the string will be written as a binary buffer using hPutBuf. The length of the output will be the length of the passed String or list.

If it helps, you can thing of this function as being of type Handle -> String -> IO ()

hGetBufStr :: (HVIO a, BinaryConvertible b) => a -> Int -> IO [b]Source

Acts a wrapper around the standard function hGetBuf, this function returns a standard Haskell String (or [Word8]) instead of modifying a 'Ptr a' buffer. The length is the maximum length to read and the semantice are the same as with hGetBuf; namely, the empty string is returned with EOF is reached, and any given read may read fewer bytes than the given length.

(Actually, it's a wrapper around vGetBuf)

hFullGetBufStr :: (HVIO a, BinaryConvertible b) => a -> Int -> IO [b]Source

Like hGetBufStr, but guarantees that it will only return fewer than the requested number of bytes when EOF is encountered.

Binary Multi-Block I/O

hGetBlocks :: (HVIO a, BinaryConvertible b) => a -> Int -> IO [[b]]Source

An alias for hPutBlocks stdout putBlocks :: (BinaryConvertible b) => [[b]] -> IO () putBlocks = hPutBlocks stdout

Returns a lazily-evaluated list of all blocks in the input file, as read by hGetBufStr. There will be no 0-length block in this list. The list simply ends at EOF.

getBlocks :: BinaryConvertible b => Int -> IO [[b]]Source

An alias for hGetBlocks stdin

hFullGetBlocks :: (HVIO a, BinaryConvertible b) => a -> Int -> IO [[b]]Source

Same as hGetBlocks, but using hFullGetBufStr underneath.

Lazy Interaction

readBinaryFile :: FilePath -> IO StringSource

Like the built-in readFile, but opens the file in binary instead of text mode.

writeBinaryFile :: FilePath -> String -> IO ()Source

Like the built-in writeFile, but opens the file in binary instead of text mode.

Binary Block-based

hBlockInteract :: (HVIO a, HVIO d, BinaryConvertible b, BinaryConvertible c) => Int -> a -> d -> ([[b]] -> [[c]]) -> IO ()Source

Binary block-based interaction. This is useful for scenarios that take binary blocks, manipulate them in some way, and then write them out. Take a look at hBlockCopy for an example. The integer argument is the size of input binary blocks. This function uses hGetBlocks internally.

blockInteract :: (BinaryConvertible b, BinaryConvertible c) => Int -> ([[b]] -> [[c]]) -> IO ()Source

An alias for hBlockInteract over stdin and stdout

hFullBlockInteract :: (HVIO a, HVIO d, BinaryConvertible b, BinaryConvertible c) => Int -> a -> d -> ([[b]] -> [[c]]) -> IO ()Source

Same as hBlockInteract, but uses hFullGetBlocks instead of hGetBlocks internally.

fullBlockInteract :: (BinaryConvertible b, BinaryConvertible c) => Int -> ([[b]] -> [[c]]) -> IO ()Source

An alias for hFullBlockInteract over stdin and stdout