Data.Conduit.Combinators

Yield each of the values contained by the given MonoFoldable.

This will work on many data structures, including lists, ByteStrings, and Vectors.

Subject to fusion

Generate a producer from a seed value.

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Enumerate from a value to a final value, inclusive, via succ.

This is generally more efficient than using Prelude's enumFromTo and combining with sourceList since this avoids any intermediate data structures.

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Produces an infinite stream of repeated applications of f to x.

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Produce an infinite stream consisting entirely of the given value.

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Produce a finite stream consisting of n copies of the given value.

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Generate a producer by yielding each of the strict chunks in a LazySequence.

For more information, see toChunks.

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Repeatedly run the given action and yield all values it produces.

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Repeatedly run the given action and yield all values it produces, until the provided predicate returns False.

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Perform the given action n times, yielding each result.

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Stream the contents of a file as binary data.

Same as sourceFile. The alternate name is a holdover from an older version, when sourceFile was more polymorphic than it is today.

Stream the contents of a Handle as binary data. Note that this function will not automatically close the Handle when processing completes, since it did not acquire the Handle in the first place.

Same as sourceHandle, but instead of allocating a new buffer for each incoming chunk of data, reuses the same buffer. Therefore, the ByteStrings yielded by this function are not referentially transparent between two different yields.

This function will be slightly more efficient than sourceHandle by avoiding allocations and reducing garbage collections, but should only be used if you can guarantee that you do not reuse a ByteString (or any slice thereof) between two calls to await.

An alternative to sourceHandle. Instead of taking a pre-opened Handle, it takes an action that opens a Handle (in read mode), so that it can open it only when needed and close it as soon as possible.

sourceHandle applied to stdin.

Subject to fusion

Like withBinaryFile, but provides a source to read bytes from.

Stream the contents of the given directory, without traversing deeply.

This function will return all of the contents of the directory, whether they be files, directories, etc.

Note that the generated filepaths will be the complete path, not just the filename. In other words, if you have a directory foo containing files bar and baz, and you use sourceDirectory on foo, the results will be foo/bar and foo/baz.

Deeply stream the contents of the given directory.

This works the same as sourceDirectory, but will not return directories at all. This function also takes an extra parameter to indicate whether symlinks will be followed.

Ignore a certain number of values in the stream.

Note: since this function doesn't produce anything, you probably want to use it with (>>) instead of directly plugging it into a pipeline:

>>> runConduit $ yieldMany [1..5] .| drop 2 .| sinkList[]>>> runConduit $ yieldMany [1..5] .| (drop 2 >> sinkList)[3,4,5]

Drop a certain number of elements from a chunked stream.

Note: you likely want to use it with monadic composition. See the docs for drop.

Drop all values which match the given predicate.

Note: you likely want to use it with monadic composition. See the docs for drop.

Drop all elements in the chunked stream which match the given predicate.

Note: you likely want to use it with monadic composition. See the docs for drop.

Monoidally combine all values in the stream.

Subject to fusion

Monoidally combine all elements in the chunked stream.

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A strict left fold.

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A strict left fold with no starting value. Returns Nothing when the stream is empty.

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A strict left fold on a chunked stream.

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Apply the provided mapping function and monoidal combine all values.

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Apply the provided mapping function and monoidal combine all elements of the chunked stream.

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Specialized version of mapAccumWhile that does not provide values downstream.

Check that all values in the stream return True.

Subject to shortcut logic: at the first False, consumption of the stream will stop.

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Check that all elements in the chunked stream return True.

Subject to shortcut logic: at the first False, consumption of the stream will stop.

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Check that at least one value in the stream returns True.

Subject to shortcut logic: at the first True, consumption of the stream will stop.

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Check that at least one element in the chunked stream returns True.

Subject to shortcut logic: at the first True, consumption of the stream will stop.

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Are all values in the stream True?

Consumption stops once the first False is encountered.

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Are all elements in the chunked stream True?

Consumption stops once the first False is encountered.

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Are any values in the stream True?

Consumption stops once the first True is encountered.

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Are any elements in the chunked stream True?

Consumption stops once the first True is encountered.

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Alternatively combine all values in the stream.

Are any values in the stream equal to the given value?

Stops consuming as soon as a match is found.

Subject to fusion

Are any elements in the chunked stream equal to the given element?

Stops consuming as soon as a match is found.

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Are no values in the stream equal to the given value?

Stops consuming as soon as a match is found.

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Are no elements in the chunked stream equal to the given element?

Stops consuming as soon as a match is found.

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Consume all incoming strict chunks into a lazy sequence. Note that the entirety of the sequence will be resident at memory.

This can be used to consume a stream of strict ByteStrings into a lazy ByteString, for example.

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Consume all values from the stream and return as a list. Note that this will pull all values into memory.

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Sink incoming values into a vector, growing the vector as necessary to fit more elements.

Note that using this function is more memory efficient than sinkList and then converting to a Vector, as it avoids intermediate list constructors.

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Sink incoming values into a vector, up until size maxSize. Subsequent values will be left in the stream. If there are less than maxSize values present, returns a Vector of smaller size.

Note that using this function is more memory efficient than sinkList and then converting to a Vector, as it avoids intermediate list constructors.

Subject to fusion

Same as sinkBuilder, but afterwards convert the builder to its lazy representation.

Alternatively, this could be considered an alternative to sinkLazy, with the following differences:

• This function will allow multiple input types, not just the strict version of the lazy structure.

• Some buffer copying may occur in this version.

Subject to fusion

Consume and discard all remaining values in the stream.

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Same as await, but discards any leading onull values.

Take a single value from the stream, if available.

Same as head, but returns a default value if none are available from the stream.

Get the next element in the chunked stream.

View the next value in the stream without consuming it.

View the next element in the chunked stream without consuming it.

Retrieve the last value in the stream, if present.

Subject to fusion

Same as last, but returns a default value if none are available from the stream.

Retrieve the last element in the chunked stream, if present.

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Count how many values are in the stream.

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Count how many elements are in the chunked stream.

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Count how many values in the stream pass the given predicate.

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Count how many elements in the chunked stream pass the given predicate.

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Get the largest value in the stream, if present.

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Get the largest element in the chunked stream, if present.

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Get the smallest value in the stream, if present.

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Get the smallest element in the chunked stream, if present.

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True if there are no values in the stream.

This function does not modify the stream.

True if there are no elements in the chunked stream.

This function may remove empty leading chunks from the stream, but otherwise will not modify it.

Get the sum of all values in the stream.

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Get the sum of all elements in the chunked stream.

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Get the product of all values in the stream.

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Get the product of all elements in the chunked stream.

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Find the first matching value.

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Apply the action to all values in the stream.

Note: if you want to pass the values instead of consuming them, use iterM instead.

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Apply the action to all elements in the chunked stream.

Note: the same caveat as with mapM_ applies. If you don't want to consume the values, you can use iterM:

iterM (omapM_ f)

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A monadic strict left fold.

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A monadic strict left fold on a chunked stream.

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Apply the provided monadic mapping function and monoidal combine all values.

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Apply the provided monadic mapping function and monoidal combine all elements in the chunked stream.

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Stream all incoming data to the given file.

Cautious version of sinkFile. The idea here is to stream the values to a temporary file in the same directory of the destination file, and only on successfully writing the entire file, moves it atomically to the destination path.

In the event of an exception occurring, the temporary file will be deleted and no move will be made. If the application shuts down without running exception handling (such as machine failure or a SIGKILL), the temporary file will remain and the destination file will be untouched.

Stream data into a temporary file in the given directory with the given filename pattern, and return the temporary filename. The temporary file will be automatically deleted when exiting the active ResourceT block, if it still exists.

Same as sinkTempFile, but will use the default temp file directory for the system as the first argument.

sinkFile specialized to ByteString to help with type inference.

Stream all incoming data to the given Handle. Note that this function does not flush and will not close the Handle when processing completes.

An alternative to sinkHandle. Instead of taking a pre-opened Handle, it takes an action that opens a Handle (in write mode), so that it can open it only when needed and close it as soon as possible.

Print all incoming values to stdout.

Subject to fusion

sinkHandle applied to stdout.

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sinkHandle applied to stderr.

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Like withBinaryFile, but provides a sink to write bytes to.

Same as withSinkFile, but lets you use a BB.Builder.

Like sinkFileCautious, but uses the with pattern instead of MonadResource.

Stream incoming builders, executing them directly on the buffer of the given Handle. Note that this function does not automatically close the Handle when processing completes. Pass flush to flush the buffer.

Stream incoming Flushes, executing them on IO.Handle Note that this function does not automatically close the Handle when processing completes

Apply a transformation to all values in a stream.

Subject to fusion

Apply a transformation to all elements in a chunked stream.

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Apply a monomorphic transformation to all elements in a chunked stream.

Unlike mapE, this will work on types like ByteString and Text which are MonoFunctor but not Functor.

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Apply the function to each value in the stream, resulting in a foldable value (e.g., a list). Then yield each of the individual values in that foldable value separately.

Generalizes concatMap, mapMaybe, and mapFoldable.

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Apply the function to each element in the chunked stream, resulting in a foldable value (e.g., a list). Then yield each of the individual values in that foldable value separately.

Generalizes concatMap, mapMaybe, and mapFoldable.

Subject to fusion

Stream up to n number of values downstream.

Note that, if downstream terminates early, not all values will be consumed. If you want to force exactly the given number of values to be consumed, see takeExactly.

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Stream up to n number of elements downstream in a chunked stream.

Note that, if downstream terminates early, not all values will be consumed. If you want to force exactly the given number of values to be consumed, see takeExactlyE.

Stream all values downstream that match the given predicate.

Same caveats regarding downstream termination apply as with take.

Stream all elements downstream that match the given predicate in a chunked stream.

Same caveats regarding downstream termination apply as with takeE.

Consume precisely the given number of values and feed them downstream.

This function is in contrast to take, which will only consume up to the given number of values, and will terminate early if downstream terminates early. This function will discard any additional values in the stream if they are unconsumed.

Note that this function takes a downstream ConduitT as a parameter, as opposed to working with normal fusion. For more information, see http://www.yesodweb.com/blog/2013/10/core-flaw-pipes-conduit, the section titled "pipes and conduit: isolate".

Same as takeExactly, but for chunked streams.

Flatten out a stream by yielding the values contained in an incoming MonoFoldable as individually yielded values.

Subject to fusion

Keep only values in the stream passing a given predicate.

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Keep only elements in the chunked stream passing a given predicate.

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Map values as long as the result is Just.

Break up a stream of values into vectors of size n. The final vector may be smaller than n if the total number of values is not a strict multiple of n. No empty vectors will be yielded.

Analog of scanl for lists.

Subject to fusion

mapWhile with a break condition dependent on a strict accumulator. Equivalently, mapAccum as long as the result is Right. Instead of producing a leftover, the breaking input determines the resulting accumulator via Left.

Subject to fusion

concatMap with an accumulator.

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Insert the given value between each two values in the stream.

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Sliding window of values 1,2,3,4,5 with window size 2 gives [1,2],[2,3],[3,4],[4,5]

Best used with structures that support O(1) snoc.

Subject to fusion

Split input into chunk of size chunkSize

The last element may be smaller than the chunkSize (see also chunksOfExactlyE which will not yield this last element)

Split input into chunk of size chunkSize

If the input does not split into chunks exactly, the remainder will be leftover (see also chunksOfE)

Apply a monadic transformation to all values in a stream.

If you do not need the transformed values, and instead just want the monadic side-effects of running the action, see mapM_.

Subject to fusion

Apply a monadic transformation to all elements in a chunked stream.

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Apply a monadic monomorphic transformation to all elements in a chunked stream.

Unlike mapME, this will work on types like ByteString and Text which are MonoFunctor but not Functor.

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Apply the monadic function to each value in the stream, resulting in a foldable value (e.g., a list). Then yield each of the individual values in that foldable value separately.

Generalizes concatMapM, mapMaybeM, and mapFoldableM.

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Keep only values in the stream passing a given monadic predicate.

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Keep only elements in the chunked stream passing a given monadic predicate.

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Apply a monadic action on all values in a stream.

This Conduit can be used to perform a monadic side-effect for every value, whilst passing the value through the Conduit as-is.

iterM f = mapM (\a -> f a >>= \() -> return a)

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Analog of scanl for lists, monadic.

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Monadic mapAccumWhile.

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concatMapM with an accumulator.

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Encode a stream of text as UTF8.

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Decode a stream of binary data as UTF8.

Decode a stream of binary data as UTF8, replacing any invalid bytes with the Unicode replacement character.

Stream in the entirety of a single line.

Like takeExactly, this will consume the entirety of the line regardless of the behavior of the inner Conduit.

Same as line, but operates on ASCII/binary data.

Insert a newline character after each incoming chunk of data.

Subject to fusion

Same as unlines, but operates on ASCII/binary data.

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Stream in the chunked input until an element matches a predicate.

Like takeExactly, this will consume the entirety of the prefix regardless of the behavior of the inner Conduit.

Convert a stream of arbitrarily-chunked textual data into a stream of data where each chunk represents a single line. Note that, if you have unknown or untrusted input, this function is unsafe, since it would allow an attacker to form lines of massive length and exhaust memory.

Subject to fusion

Same as linesUnbounded, but for ASCII/binary data.

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Split a stream of arbitrarily-chunked data, based on a predicate on elements. Elements that satisfy the predicate will cause chunks to be split, and aren't included in these output chunks. Note that, if you have unknown or untrusted input, this function is unsafe, since it would allow an attacker to form chunks of massive length and exhaust memory.

Incrementally execute builders and pass on the filled chunks as bytestrings.

Incrementally execute builders on the given buffer and pass on the filled chunks as bytestrings. Note that, if the given buffer is too small for the execution of a build step, a larger one will be allocated.

WARNING: This conduit yields bytestrings that are NOT referentially transparent. Their content will be overwritten as soon as control is returned from the inner sink!

A conduit that incrementally executes builders and passes on the filled chunks as bytestrings to an inner sink.

INV: All bytestrings passed to the inner sink are non-empty.

Same as builderToByteString, but input and output are wrapped in Flush.

A buffer allocation strategy (buf0, nextBuf) specifies the initial buffer to use and how to compute a new buffer nextBuf minSize buf with at least size minSize from a filled buffer buf. The double nesting of the IO monad helps to ensure that the reference to the filled buffer buf is lost as soon as possible, but the new buffer doesn't have to be allocated too early.

The simplest buffer allocation strategy: whenever a buffer is requested, allocate a new one that is big enough for the next build step to execute.

NOTE that this allocation strategy may spill quite some memory upon direct insertion of a bytestring by the builder. Thats no problem for garbage collection, but it may lead to unreasonably high memory consumption in special circumstances.

An unsafe, but possibly more efficient buffer allocation strategy: reuse the buffer, if it is big enough for the next build step to execute.