cardano-strict-containers: add Data.Bitmap by gdeest · Pull Request #700 · IntersectMBO/cardano-base

gdeest · 2026-09-24T07:26:21Z

Adds Data.Bitmap to cardano-strict-containers (moved from Ouroboros.Consensus.Util.Bitmap).

Now uses MSB-encoding so that it can be easily re-used by Leios BitField requirements.

Used by #701 .

Checklist

Commit sequence broadly makes sense and commits have useful messages
New tests are added if needed and existing tests are updated
All visible changes are prepended to the latest section of a CHANGELOG.md for the affected packages.
New section is never added with the code changes. (See RELEASING.md)
When applicable, versions are updated in .cabal and CHANGELOG.md files according to the
versioning process.
The version bounds in .cabal files for all affected packages are updated.
If you change the bounds in a cabal file, that package itself must have a version increase. (See RELEASING.md)
Self-reviewed the diff

agustinmista

Looking good! Just some small nits.

agustinmista

This looks great! Thanks for expanding the previous test suite 🧪

It looks like cabal-format is complaining in CI, though.

ch1bo · 2026-10-14T14:28:15Z

Now uses MSB-encoding so that it can be easily re-used by Leios BitField requirements.

I think you should be doing this in this PR to prove that claim and so we end up with the same number of bitfield implementations.

ch1bo · 2026-10-14T14:29:05Z

+
+-- | A compact bitmap representation using serialisation-ready ByteStrings.
+--
+-- Adapted from @Cardano.Leios.BitMapPV@ in the @leios-wfa-ls-demo@ package.


This was a proof of concept. You should instead base your implementation on the production grade version introduced in cardano-crypto-leios

Done in 7e63c40.

ch1bo · 2026-10-14T14:32:44Z

+
+-- | A bitmap over a number of indexes known to its users: @⌈n/8⌉@ bytes,
+-- MSB-first, bit @i@ set iff index @i@ is set.
+newtype Bitmap = Bitmap {bitmapBytes :: ByteString}


This is not a strict container if at its core is a lazy bytestring. Should be a strict bytestring or a ByteArray

It was actually a strict ByteString, but now uses a ByteArray as the cardano-crypto-leios impl anyway.

…test nits

…ith an explicit number of indexes

…itField

gdeest · 2026-11-04T09:03:48Z

I think you should be doing this in this PR to prove that claim and so we end up with the same number of bitfield implementations.

@ch1bo I have modified the implementation essentially the same as what was in current cardano-crypto-leios and modified the latter to use the Bitmap through a newtype.

One remark about well-formedness: verifyLeiosCert ignores bits set after the last seat, while Bitmap.wellFormed rejects those. To keep cardano-crypto-leios unchanged, it does not use wellFormed (while Peras does / will).

…ersectMBO#700, Data.Bitmap)

bladyjoker

Thanks @gdeest !

I have one topic to discuss, and that is to make a safe constructor for the Bitmap that checks its properties and hide the data constructor.

Since that data constructor would be given an Int denoting the cardinality/size, we can strip this argument from the rest of the API and be explicit with what this Bitmap is (ie. wellFormed).

In short

bitmapFromByteArray :: Int -> ByteArray -> Either String Bitmap

data Bitmap = Bitmap { bitmapBytes :: ByteArray, bitmapSize :: Int }

bladyjoker · 2026-11-10T09:04:23Z

+  deriving (NoThunks) via OnlyCheckWhnfNamed "Bitmap" Bitmap
+
+-- | The number of indexes set (flipped to 1) in the bitmap.
+numSetBits :: Bitmap -> Int


Not sure what that function is intended to do, atm it can count set padding bit as valid indices which is probably incorrect. I think we either need n here as well, otherwise when enforced a zero padding this can then also work.

bladyjoker · 2026-11-10T09:48:40Z

 -- | A 'LeiosCert' signers bitfield: @⌈leiosCommitteeSize\/8⌉@ bytes, MSB-first,
 -- bit @i@ set iff seat @i@ signed. Newtype so it isn't confused with raw bytes.
-newtype BitField = BitField {bitFieldBytes :: ByteArray}
+newtype BitField = BitField {bitFieldBitmap :: Bitmap}


I'm considering that we should leave this a ByteArray (as in, we don't know much about this) and then use a a safe bitmapFromByteArray :: Int -> Either String Bitmap constructor?

bladyjoker · 2026-11-13T09:50:18Z

+  , testBit w (7 - bitIx)
+  ]
+
+-- | Whether a bitmap is well-formed over the given number of indexes: it has


This is a bit under commented, can you expand on the invariants it checks for?

Consider wellFormed :: Int -> Bitmap -> Either String () and have a description of what went wrong.

bladyjoker · 2026-11-13T09:52:22Z

    Left (MalformedCommittee n)
  -- Bitfield length is fixed at ⌈committee/8⌉ bytes; anything else is malformed.
-  when (sizeofByteArray (bitFieldBytes cert.leiosCertSigners) /= (n + 7) `div` 8) $
+  when (Bitmap.sizeInBytes cert.leiosCertSigners.bitFieldBitmap /= Bitmap.numBytes n) $


Please introduce a wellFormed check here rather.

agustinmista reviewed Sep 24, 2026

View reviewed changes

Comment thread cardano-strict-containers/src/Data/Bitmap.hs Resolved

Comment thread cardano-strict-containers/test/Test/Data/Bitmap.hs Resolved

Comment thread cardano-strict-containers/testlib/Test/Cardano/StrictContainers/Instances.hs Resolved

gdeest force-pushed the gdeest/data-bitmap branch from fd59e15 to 7f29c17 Compare October 7, 2026 07:51

gdeest marked this pull request as ready for review October 7, 2026 08:06

gdeest requested review from a team and lehins as code owners October 7, 2026 08:06

gdeest mentioned this pull request Oct 7, 2026

cardano-crypto-peras: add base types #701

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6 tasks done

agustinmista approved these changes Oct 8, 2026

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agustinmista added this to cardano-peras Oct 9, 2026

gdeest force-pushed the gdeest/data-bitmap branch from 7000c81 to e4bb2dd Compare October 14, 2026 08:52

ch1bo reviewed Oct 14, 2026

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gdeest added 7 commits November 4, 2026 09:15

cardano-strict-containers: add Data.Bitmap

3923878

cardano-strict-containers: drop Bitmap's CBOR instances, haddock and …

aee841c

…test nits

cardano-strict-containers: MSB-first Data.Bitmap

353e0fb

cardano-strict-containers: Data.Bitmap as a newtype over ByteString w…

ad4a957

…ith an explicit number of indexes

cardano-strict-containers: sort build-depends

77bf2c5

cardano-strict-containers: Model Bitmap implementation after Leios' B…

7e63c40

…itField

cardano-crypto-leios: use Data.Bitmap under the hood

d2ff278

gdeest force-pushed the gdeest/data-bitmap branch from e4bb2dd to d2ff278 Compare November 4, 2026 08:52

tbagrel1 added the peras label Nov 9, 2026

gdeest added a commit to gdeest/cardano-base that referenced this pull request Nov 13, 2026

Merge IntersectMBO#701 (cardano-crypto-peras base types; includes Int…

8a42bba

…ersectMBO#700, Data.Bitmap)

bladyjoker reviewed Nov 13, 2026

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gdeest commented Sep 24, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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ch1bo commented Oct 14, 2026

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gdeest commented Nov 4, 2026

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gdeest commented Sep 24, 2026 •

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