| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Data.Streaming.Zlib
Contents
Description
This is a middle-level wrapper around the zlib C API. It allows you to work fully with bytestrings and not touch the FFI at all, but is still low-level enough to allow you to implement high-level abstractions such as enumerators. Significantly, it does not use lazy IO.
You'll probably need to reference the docs a bit to understand the WindowBits parameters below, but a basic rule of thumb is 15 is for zlib compression, and 31 for gzip compression.
A simple streaming compressor in pseudo-code would look like:
def <- initDeflate ... popper <- feedDeflate def rawContent pullPopper popper ... finishDeflate def sendCompressedData
You can see a more complete example is available in the included file-test.hs.
Synopsis
- data Inflate
- initInflate :: WindowBits -> IO Inflate
- initInflateWithDictionary :: WindowBits -> ByteString -> IO Inflate
- feedInflate :: Inflate -> ByteString -> IO Popper
- finishInflate :: Inflate -> IO ByteString
- flushInflate :: Inflate -> IO ByteString
- getUnusedInflate :: Inflate -> IO ByteString
- isCompleteInflate :: Inflate -> IO Bool
- data Deflate
- initDeflate :: Int -> WindowBits -> IO Deflate
- initDeflateWithDictionary :: Int -> ByteString -> WindowBits -> IO Deflate
- feedDeflate :: Deflate -> ByteString -> IO Popper
- finishDeflate :: Deflate -> Popper
- flushDeflate :: Deflate -> Popper
- fullFlushDeflate :: Deflate -> Popper
- data WindowBits = WindowBits Int
- defaultWindowBits :: WindowBits
- data ZlibException = ZlibException Int
- type Popper = IO PopperRes
- data PopperRes
Inflate
The state of an inflation (eg, decompression) process. All allocated memory is automatically reclaimed by the garbage collector. Also can contain the inflation dictionary that is used for decompression.
initInflate :: WindowBits -> IO Inflate Source #
Initialize an inflation process with the given WindowBits. You will need
to call feedInflate to feed compressed data to this and
finishInflate to extract the final chunk of decompressed data.
initInflateWithDictionary :: WindowBits -> ByteString -> IO Inflate Source #
Initialize an inflation process with the given WindowBits.
Unlike initInflate a dictionary for inflation is set which must
match the one set during compression.
feedInflate :: Inflate -> ByteString -> IO Popper Source #
Feed the given ByteString to the inflater. Return a Popper,
an IO action that returns the decompressed data a chunk at a time.
The Popper must be called to exhaustion before using the Inflate
object again.
Note that this function automatically buffers the output to
defaultChunkSize, and therefore you won't get any data from the popper
until that much decompressed data is available. After you have fed all of
the compressed data to this function, you can extract your final chunk of
decompressed data using finishInflate.
finishInflate :: Inflate -> IO ByteString Source #
As explained in feedInflate, inflation buffers your decompressed
data. After you call feedInflate with your last chunk of compressed
data, you will likely have some data still sitting in the buffer. This
function will return it to you.
flushInflate :: Inflate -> IO ByteString Source #
Flush the inflation buffer. Useful for interactive application.
This is actually a synonym for finishInflate. It is provided for its more
semantic name.
Since 0.0.3
getUnusedInflate :: Inflate -> IO ByteString Source #
Retrieve any data remaining after inflating. For more information on motivation, see:
https://github.com/fpco/streaming-commons/issues/20
Since 0.1.11
isCompleteInflate :: Inflate -> IO Bool Source #
Returns True if the inflater has reached end-of-stream, or False if it is still expecting more data.
Since 0.1.18
Deflate
The state of a deflation (eg, compression) process. All allocated memory is automatically reclaimed by the garbage collector.
Arguments
| :: Int | Compression level |
| -> WindowBits | |
| -> IO Deflate |
Initialize a deflation process with the given compression level and
WindowBits. You will need to call feedDeflate to feed uncompressed
data to this and finishDeflate to extract the final chunks of compressed
data.
initDeflateWithDictionary Source #
Arguments
| :: Int | Compression level |
| -> ByteString | Deflate dictionary |
| -> WindowBits | |
| -> IO Deflate |
Initialize an deflation process with the given compression level and
WindowBits.
Unlike initDeflate a dictionary for deflation is set.
feedDeflate :: Deflate -> ByteString -> IO Popper Source #
Feed the given ByteString to the deflater. Return a Popper,
an IO action that returns the compressed data a chunk at a time.
The Popper must be called to exhaustion before using the Deflate
object again.
Note that this function automatically buffers the output to
defaultChunkSize, and therefore you won't get any data from the popper
until that much compressed data is available. After you have fed all of the
decompressed data to this function, you can extract your final chunks of
compressed data using finishDeflate.
finishDeflate :: Deflate -> Popper Source #
As explained in feedDeflate, deflation buffers your compressed
data. After you call feedDeflate with your last chunk of uncompressed
data, use this to flush the rest of the data and signal end of input.
flushDeflate :: Deflate -> Popper Source #
Flush the deflation buffer. Useful for interactive application. Internally this passes Z_SYNC_FLUSH to the zlib library.
Unlike finishDeflate, flushDeflate does not signal end of input,
meaning you can feed more uncompressed data afterward.
Since 0.0.3
fullFlushDeflate :: Deflate -> Popper Source #
Full flush the deflation buffer. Useful for interactive
applications where previously streamed data may not be
available. Using fullFlushDeflate too often can seriously degrade
compression. Internally this passes Z_FULL_FLUSH to the zlib
library.
Like flushDeflate, fullFlushDeflate does not signal end of input,
meaning you can feed more uncompressed data afterward.
Since 0.1.5
Data types
data WindowBits #
This specifies the size of the compression window. Larger values of this parameter result in better compression at the expense of higher memory usage.
The compression window size is the value of the the window bits raised to
the power 2. The window bits must be in the range 9..15 which corresponds
to compression window sizes of 512b to 32Kb. The default is 15 which is also
the maximum size.
The total amount of memory used depends on the window bits and the
MemoryLevel. See the MemoryLevel for the details.
Constructors
| WindowBits Int |
Instances
defaultWindowBits :: WindowBits #
The default WindowBits is 15 which is also the maximum size.
data ZlibException Source #
Exception that can be thrown from the FFI code. The parameter is the numerical error code from the zlib library. Quoting the zlib.h file directly:
- #define Z_OK 0
- #define Z_STREAM_END 1
- #define Z_NEED_DICT 2
- #define Z_ERRNO (-1)
- #define Z_STREAM_ERROR (-2)
- #define Z_DATA_ERROR (-3)
- #define Z_MEM_ERROR (-4)
- #define Z_BUF_ERROR (-5)
- #define Z_VERSION_ERROR (-6)
Constructors
| ZlibException Int |
Instances
| Show ZlibException Source # | |
Defined in Data.Streaming.Zlib Methods showsPrec :: Int -> ZlibException -> ShowS # show :: ZlibException -> String # showList :: [ZlibException] -> ShowS # | |
| Exception ZlibException Source # | |
Defined in Data.Streaming.Zlib Methods toException :: ZlibException -> SomeException # fromException :: SomeException -> Maybe ZlibException # displayException :: ZlibException -> String # | |