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-- Copyright 2017 Google LLC
--
-- Licensed under the Apache License, Version 2.0 (the "License"); you may not
-- use this file except in compliance with the License. You may obtain a copy of
-- the License at
--
-- https://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
-- WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
-- License for the specific language governing permissions and limitations under
-- the License.
module BTLS.BoringSSLPatterns
( onBufferOfMaxSize
) where
import Data.ByteString (ByteString)
import Foreign (Storable(peek), Ptr, alloca, allocaArray)
import Foreign.C.Types
import BTLS.Buffer (packCUStringLen)
-- | Allocates a buffer, runs a function 'f' to partially fill it, and packs the
-- filled data into a 'ByteString'. 'f' must write the size of the filled data,
-- in bytes and not including any trailing null, into its second argument.
--
-- If 'f' is safe to use under 'unsafeLocalState', this whole function is safe
-- to use under 'unsafeLocalState'.
onBufferOfMaxSize ::
(Integral size, Storable size)
=> Int
-> (Ptr CUChar -> Ptr size -> IO ())
-> IO ByteString
onBufferOfMaxSize maxSize f =
allocaArray maxSize $ \pOut ->
alloca $ \pOutLen -> do
f pOut pOutLen
outLen <- peek pOutLen
packCUStringLen (pOut, outLen)
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