diff --git a/.ghc.environment.x86_64-darwin-8.6.3 b/.ghc.environment.x86_64-darwin-8.6.3 new file mode 100644 --- /dev/null +++ b/.ghc.environment.x86_64-darwin-8.6.3 @@ -0,0 +1,15 @@ +-- This is a GHC environment file written by cabal. This means you can +-- run ghc or ghci and get the environment of the project as a whole. +-- But you still need to use cabal repl $target to get the environment +-- of specific components (libs, exes, tests etc) because each one can +-- have its own source dirs, cpp flags etc. +-- +clear-package-db +global-package-db +package-db /Users/benselfridge/.cabal/store/ghc-8.6.3/package.db +package-db dist-newstyle/packagedb/ghc-8.6.3 +package-id bv-embed-0.1.0-inplace +package-id base-4.12.0.0 +package-id ghc-prim-0.5.3 +package-id rts +package-id integer-gmp-1.0.2.0 diff --git a/CHANGELOG.md b/CHANGELOG.md new file mode 100644 --- /dev/null +++ b/CHANGELOG.md @@ -0,0 +1,5 @@ +# Revision history for bv-embed + +## 0.1.0.0 -- YYYY-mm-dd + +* First version. Released on an unsuspecting world. diff --git a/LICENSE b/LICENSE new file mode 100644 --- /dev/null +++ b/LICENSE @@ -0,0 +1,30 @@ +Copyright (c) 2019, Ben Selfridge + +All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions are met: + + * Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + + * Redistributions in binary form must reproduce the above + copyright notice, this list of conditions and the following + disclaimer in the documentation and/or other materials provided + with the distribution. + + * Neither the name of Ben Selfridge nor the names of other + contributors may be used to endorse or promote products derived + from this software without specific prior written permission. + +THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. diff --git a/README.md b/README.md new file mode 100644 --- /dev/null +++ b/README.md @@ -0,0 +1,1 @@ +bv-embed - Define embeddings of small bit vectors into larger ones diff --git a/Setup.hs b/Setup.hs new file mode 100644 --- /dev/null +++ b/Setup.hs @@ -0,0 +1,2 @@ +import Distribution.Simple +main = defaultMain diff --git a/bv-embed.cabal b/bv-embed.cabal new file mode 100644 --- /dev/null +++ b/bv-embed.cabal @@ -0,0 +1,26 @@ +cabal-version: 2.4 +-- Initial package description 'bv-embed.cabal' generated by 'cabal init'. +-- For further documentation, see http://haskell.org/cabal/users-guide/ + +name: bv-embed +version: 0.1.0 +synopsis: Define embeddings of small bit vectors into larger ones +description: Data structures for defining embeddings of small bit vectors + into larger ones. Functions that perform the embedding and + extracting. +-- bug-reports: +license: BSD-3-Clause +license-file: LICENSE +author: Ben Selfridge +maintainer: benselfridge@galois.com +-- copyright: +category: Data +extra-source-files: CHANGELOG.md + +library + exposed-modules: Data.BitVector.Embed + -- other-modules: + -- other-extensions: + build-depends: base >=4.6 && <5 + hs-source-dirs: src + default-language: Haskell2010 diff --git a/src/Data/BitVector/Embed.hs b/src/Data/BitVector/Embed.hs new file mode 100644 --- /dev/null +++ b/src/Data/BitVector/Embed.hs @@ -0,0 +1,57 @@ + +{-| +Module : Data.BitVector.Embed +Copyright : (c) Galois Inc. 2018 +License : BSD-3 +Maintainer : benselfridge@galois.com +Stability : experimental +Portability : portable + +This module exports types and functions for defining how a small bit vector is +embedded into a larger one. + +-} + +module Data.BitVector.Embed + ( BitEmbedding + , fromList + , bitEmbed + , bitExtract + ) where + +import qualified Data.Bits as B + +-- | Defines a mapping from each bit of a small bit vector into a larger one. +newtype BitEmbedding = BitEmbedding [Int] + deriving (Eq, Ord, Show) + +-- | Construct a `BitEmbedding` from a list, where the length of the list is the same +-- as the width of the "small" bit vector we are embedding into the larger one. The +-- nth element of the list tells us at which bit index in the target to embed bit n +-- of the source. +fromList :: [Int] -> BitEmbedding +fromList = BitEmbedding + +-- | Embed a smaller bit vector into a larger one using a `BitEmbedding`. +-- +-- >>> bitEmbed (fromList [4,5,7] 7 0) +-- 176 +bitEmbed :: (B.Bits src, B.Bits tgt) => BitEmbedding -> src -> tgt -> tgt +bitEmbed (BitEmbedding []) _ tgt = tgt +bitEmbed (BitEmbedding (bit:rst)) src tgt = + bitEmbed (BitEmbedding rst) (src `B.shiftR` 1) (tgt B..|. bitMask) + where bitMask = if B.testBit src 0 + then B.bit bit + else B.zeroBits + +-- | Extract a smaller bit vector from a larger one using a `BitEmbedding`. +-- +-- >>> bitExtract (fromList [4,5,7] 7 0) 176 +-- 7 +bitExtract :: (B.Bits src, B.Bits tgt) => BitEmbedding -> tgt -> src +bitExtract (BitEmbedding []) _ = B.zeroBits +bitExtract (BitEmbedding (bit:rst)) tgt = + (bitExtract (BitEmbedding rst) tgt `B.shiftL` 1) B..|. bitMask + where bitMask = if B.testBit tgt bit + then B.bit 0 + else B.zeroBits