| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Data.Capnp.Message
Contents
Description
This module provides support for working directly with Cap'N Proto messages.
Synopsis
- hPutMsg :: Handle -> ConstMsg -> IO ()
- hGetMsg :: Handle -> Int -> IO ConstMsg
- putMsg :: ConstMsg -> IO ()
- getMsg :: Int -> IO ConstMsg
- maxSegmentSize :: Int
- maxSegments :: Int
- encode :: MonadThrow m => ConstMsg -> m Builder
- decode :: MonadThrow m => ByteString -> m ConstMsg
- class Monad m => Message m msg where
- data Segment msg
- empty :: ConstMsg
- data ConstMsg
- getSegment :: (MonadThrow m, Message m msg) => msg -> Int -> m (Segment msg)
- getWord :: (MonadThrow m, Message m msg) => msg -> WordAddr -> m Word64
- data MutMsg s
- newMessage :: WriteCtx m s => m (MutMsg s)
- alloc :: WriteCtx m s => MutMsg s -> WordCount -> m WordAddr
- allocInSeg :: WriteCtx m s => MutMsg s -> Int -> WordCount -> m WordAddr
- newSegment :: WriteCtx m s => MutMsg s -> Int -> m (Int, Segment (MutMsg s))
- setWord :: (WriteCtx m s, MonadThrow m) => MutMsg s -> WordAddr -> Word64 -> m ()
- setSegment :: (WriteCtx m s, MonadThrow m) => MutMsg s -> Int -> Segment (MutMsg s) -> m ()
- type WriteCtx m s = (PrimMonad m, s ~ PrimState m, MonadThrow m)
Reading and writing messages
hGetMsg :: Handle -> Int -> IO ConstMsg Source #
hGetMsg handle limithandle that is at most
limit 64-bit words in length.
Limits on message size
maxSegmentSize :: Int Source #
The maximum size of a segment supported by this libarary, in words.
maxSegments :: Int Source #
The maximum number of segments allowed in a message by this library.
Converting between messages and ByteStrings
encode :: MonadThrow m => ConstMsg -> m Builder Source #
encode encodes a message as a bytestring builder.
decode :: MonadThrow m => ByteString -> m ConstMsg Source #
decode decodes a message from a bytestring.
The segments will not be copied; the resulting message will be a view into the original bytestring. Runs in O(number of segments in the message).
Message type class
class Monad m => Message m msg where Source #
A Message is a (possibly read-only) capnproto message. It is
parameterized over a monad in which operations are performed.
Minimal complete definition
numSegs, internalGetSeg, numWords, slice, read, fromByteString, toByteString
Methods
numSegs :: msg -> m Int Source #
numSegs gets the number of segments in a message.
internalGetSeg :: msg -> Int -> m (Segment msg) Source #
internalGetSeg message indexindex
in message. Most callers should use the getSegment wrapper, instead
of calling this directly.
numWords :: Segment msg -> m Int Source #
Get the length of the segment, in units of 64-bit words.
slice :: Int -> Int -> Segment msg -> m (Segment msg) Source #
slice start length segmentstart, of length length.
read :: Segment msg -> Int -> m Word64 Source #
read segment indexgetWord on the message, instead of
calling this directly.
fromByteString :: ByteString -> m (Segment msg) Source #
Convert a ByteString to a segment.
toByteString :: Segment msg -> m ByteString Source #
Convert a segment to a byte string.
Instances
| Monad m => Message m ConstMsg Source # | |
Defined in Data.Capnp.Message Methods numSegs :: ConstMsg -> m Int Source # internalGetSeg :: ConstMsg -> Int -> m (Segment ConstMsg) Source # numWords :: Segment ConstMsg -> m Int Source # slice :: Int -> Int -> Segment ConstMsg -> m (Segment ConstMsg) Source # read :: Segment ConstMsg -> Int -> m Word64 Source # fromByteString :: ByteString -> m (Segment ConstMsg) Source # toByteString :: Segment ConstMsg -> m ByteString Source # | |
| (PrimMonad m, s ~ PrimState m) => Message m (MutMsg s) Source # | |
Defined in Data.Capnp.Message Methods numSegs :: MutMsg s -> m Int Source # internalGetSeg :: MutMsg s -> Int -> m (Segment (MutMsg s)) Source # numWords :: Segment (MutMsg s) -> m Int Source # slice :: Int -> Int -> Segment (MutMsg s) -> m (Segment (MutMsg s)) Source # read :: Segment (MutMsg s) -> Int -> m Word64 Source # fromByteString :: ByteString -> m (Segment (MutMsg s)) Source # toByteString :: Segment (MutMsg s) -> m ByteString Source # | |
Immutable messages
empty is an empty message, i.e. a minimal message with a null pointer as
its root object.
A read-only capnproto message.
ConstMsg is an instance of the generic Message type class. its
implementations of toByteString and fromByteString are O(1);
the underlying bytes are not copied.
Instances
Reading data from messages
getSegment :: (MonadThrow m, Message m msg) => msg -> Int -> m (Segment msg) Source #
getSegment message indexBoundsError if the address is out of bounds.
getWord :: (MonadThrow m, Message m msg) => msg -> WordAddr -> m Word64 Source #
getWord msg addraddr within msg. It throws a
BoundsError if the address is out of bounds.
Mutable Messages
A MutMsg is a mutable capnproto message. The type parameter s is the
state token for the instance of PrimMonad in which the message may be
modified.
Due to mutabilty, the implementations of toByteString and fromByteString
must make full copies, and so are O(n) in the length of the segment.
Instances
newMessage :: WriteCtx m s => m (MutMsg s) Source #
Allocate a new empty message.
Allocating space in messages
alloc :: WriteCtx m s => MutMsg s -> WordCount -> m WordAddr Source #
alloc sizesize words within a message. it returns the
starting address of the allocated memory.
allocInSeg :: WriteCtx m s => MutMsg s -> Int -> WordCount -> m WordAddr Source #
Like alloc, but the second argument allows the caller to specify the
index of the segment in which to allocate the data.
newSegment :: WriteCtx m s => MutMsg s -> Int -> m (Int, Segment (MutMsg s)) Source #
newSegment msg sizeHintmsg with a capacity of sizeHint. It returns the a pair of the segment
number and the segment itself. Amortized O(1).
Modifying messages
setWord :: (WriteCtx m s, MonadThrow m) => MutMsg s -> WordAddr -> Word64 -> m () Source #
setWord message address valueaddress in the
message to value. If the address is not valid in the message, a
BoundsError will be thrown.
setSegment :: (WriteCtx m s, MonadThrow m) => MutMsg s -> Int -> Segment (MutMsg s) -> m () Source #
setSegment message index segmentBoundsError if the address is out of bounds.