Improve comments and make naming consistent.

tensorflow-records/src/TensorFlow/CRC32C.hs

@@ -12,44 +12,50 @@
 -- See the License for the specific language governing permissions and
 -- limitations under the License.
 
--- | FFI wrappers of CRC32C digest.  Import qualified.
-
 module TensorFlow.CRC32C
-  ( value, extend
+  ( crc32c
-  , mask, unmask
+  , crc32cLBS
-  , valueMasked
+  , crc32cUpdate
+  , crc32cMasked
+  , crc32cLBSMasked
+  , crc32cMask
+  , crc32cUnmask
   ) where
 
 import Data.Bits (rotateL, rotateR)
 import qualified Data.ByteString as B
 import qualified Data.ByteString.Lazy as BL
-import Data.Digest.CRC32C (crc32c_update)
+import Data.Digest.CRC32C (crc32c, crc32c_update)
 import Data.List (foldl')
 import Data.Word (Word32)
 
 -- | Compute the CRC32C checksum of the concatenation of the bytes checksummed
 -- by the given CRC32C value and the bytes in the given ByteString.
-extend :: Word32 -> B.ByteString -> Word32
+crc32cUpdate :: Word32 -> B.ByteString -> Word32
-extend = crc32c_update
+crc32cUpdate = crc32c_update
 
 -- | Compute the CRC32C checksum of the given bytes.
-value :: BL.ByteString -> Word32
+crc32cLBS :: BL.ByteString -> Word32
-value = foldl' extend 0 . BL.toChunks
+crc32cLBS = foldl' crc32cUpdate 0 . BL.toChunks
 
 -- | Scramble a CRC32C value so that the result can be safely stored in a
 -- bytestream that may itself be CRC'd.
 --
 -- This masking is the algorithm specified by TensorFlow's TFRecords format.
-mask :: Word32 -> Word32
+crc32cMask :: Word32 -> Word32
-mask x = rotateR x 15 + maskDelta
+crc32cMask x = rotateR x 15 + maskDelta
 
--- | Inverse of 'mask'.
+-- | Inverse of 'crc32cMask'.
-unmask :: Word32 -> Word32
+crc32cUnmask :: Word32 -> Word32
-unmask x = rotateL (x - maskDelta) 15
+crc32cUnmask x = rotateL (x - maskDelta) 15
 
--- | Convenience function combining 'value' and 'mask'.
+-- | Convenience function combining 'crc32c' and 'crc32cMask'.
-valueMasked :: BL.ByteString -> Word32
+crc32cMasked :: B.ByteString -> Word32
-valueMasked = mask . value
+crc32cMasked = crc32cMask . crc32c
+
+-- | Convenience function combining 'crc32cLBS' and 'crc32cMask'.
+crc32cLBSMasked :: BL.ByteString -> Word32
+crc32cLBSMasked = crc32cMask . crc32cLBS
 
 maskDelta :: Word32
 maskDelta = 0xa282ead8

tensorflow-records/src/TensorFlow/Records.hs

@@ -32,6 +32,7 @@ module TensorFlow.Records
   , putTFRecordData
   ) where
 
+import Control.Exception (evaluate)
 import Control.Monad (when)
 import Data.ByteString.Unsafe (unsafePackCStringLen)
 import qualified Data.ByteString.Builder as B (Builder)
@@ -58,7 +59,7 @@ import Foreign.Marshal.Alloc (allocaBytes)
 import Foreign.Ptr (Ptr, castPtr)
 import System.IO.Unsafe (unsafePerformIO)
 
-import qualified TensorFlow.CRC32C as CRC
+import TensorFlow.CRC32C (crc32cLBSMasked, crc32cUpdate, crc32cMask)
 
 -- | Parse one TFRecord.
 getTFRecord :: Get BL.ByteString
@@ -74,7 +75,7 @@ getTFRecords = do
 getCheckMaskedCRC32C :: BL.ByteString -> Get ()
 getCheckMaskedCRC32C bs = do
   wireCRC <- getWord32le
-  let maskedCRC = CRC.valueMasked bs
+  let maskedCRC = crc32cLBSMasked bs
   when (maskedCRC /= wireCRC) $ fail $
       "getCheckMaskedCRC32C: CRC mismatch, computed: " ++ show maskedCRC ++
       ", expected: " ++ show wireCRC
@@ -95,12 +96,12 @@ getTFRecordData len = if len > 0x7fffffffffffffff
     return bs
 
 putMaskedCRC32C :: BL.ByteString -> Put
-putMaskedCRC32C = putWord32le . CRC.valueMasked
+putMaskedCRC32C = putWord32le . crc32cLBSMasked
 
--- Runs a Builder that's known to write a fixed number of bytes on a
+-- Runs a Builder that's known to write a fixed number of bytes on an 'alloca'
--- stack-allocated buffer, and runs the given IO action on the result.  Raises
+-- buffer, and runs the given IO action on the result.  Raises exceptions if
--- exceptions if the Builder yields ByteString chunks or attempts to write more
+-- the Builder yields ByteString chunks or attempts to write more bytes than
--- bytes than expected.
+-- expected.
 unsafeWithFixedWidthBuilder :: Int -> B.Builder -> (Ptr Word8 -> IO r) -> IO r
 unsafeWithFixedWidthBuilder n b act = allocaBytes n $ \ptr -> do
   (_, signal) <- runBuilder b ptr n
@@ -114,11 +115,13 @@ putTFRecordLength :: Word64 -> Put
 putTFRecordLength x =
   let put = putWord64le x
       len = 8
-      crc = CRC.mask $ unsafePerformIO $
+      crc = crc32cMask $ unsafePerformIO $
           -- Serialized Word64 is always 8 bytes, so we can go fast by using
           -- alloca.
-          unsafeWithFixedWidthBuilder len (execPut put) $
+          unsafeWithFixedWidthBuilder len (execPut put) $ \ptr -> do
-              \ptr -> CRC.extend 0 <$> unsafePackCStringLen (castPtr ptr, len)
+              str <- unsafePackCStringLen (castPtr ptr, len)
+              -- Force the result to ensure it's evaluated before freeing ptr.
+              evaluate $ crc32cUpdate 0 str
   in  put *> putWord32le crc
 
 -- | Put a record payload and its checksum.

tensorflow-records/tensorflow-records.cabal

@@ -19,7 +19,7 @@ library
                , cereal
                -- TODO: Split Data.Digest.CRC32C out of snappy-framing for a
                -- lighter dependency?
-               , snappy-framing
+               , snappy-framing >= 0.1.1
   default-language:    Haskell2010
 
 Test-Suite RecordsTest