feat(hash): port mumbo to Starlark (hash.mumbo) - #257
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Port the default 64-bit hash mumbo::GetHash64 to hash.bzl next to dumbo/fnv1a: the kSecret bank, the seed absorb, the small-key (<=16) loader, the 16-byte MUM chain, the 8-lane 128-byte bulk tier, and the two-multiply finalizer - all as masked 64-bit Starlark arithmetic. Its default seed is the library-wide kDefaultSeed (5381), unlike dumbo (0) and fnv1a (offset basis). Verified byte-for-byte against the C++ prime via hash_bzl_vs_cpp_mumbo_test (hash_tool already registered mumbo), across lengths 0..300 spanning all three tiers and every tail size. Only the one-shot 64-bit form is ported; the native 128-bit jumbo and streaming stay C++-only. Updates the Algorithm-overview Starlark column and documents each port's canonical default seed.
# Conflicts: # CHANGELOG.md # mbo/hash/README.md
… in by git add -A); file kept on disk
helly25
enabled auto-merge (squash)
July 13, 2026 18:13
Fab-Cat
approved these changes
Jul 13, 2026
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Adds
hash.mumboto the Starlark ports in//mbo/hash:hash.bzl, next tohash.dumbo/hash.fnv1a, as requested.What
mumbo::GetHash64(the default 64-bit hash) to Starlark: thekSecretbank, seed absorb, the<=16-byte small-key loader, the 16-byte MUM chain, the 8-lane 128-byte bulk tier, and the two-multiply finalizer — all as masked 64-bit arithmetic (Starlark has nowhile, so the loops are bounded ranges with the same break condition, matching the existing dumbo port).jumboand streaming stay C++-only.hash.mumbo's default seed is the library-widekDefaultSeed(5381) — distinct from dumbo (0) and fnv1a (the FNV offset basis). Documented in the README along with how to pass a seed (optional second arg)._FNS+ defaultalgos);hash_toolalready registeredmumbo. Update the Algorithm-overviewStarlarkcolumn.Verification
//mbo/hash:hash_bzl_vs_cpp_mumbo_testpasses: the Starlark output is byte-for-byte identical to thehash_toolC++ prime across lengths0..300(small<=16, medium17..127, and bulk>=128tiers, plus every tail size) and the extra strings. dumbo/fnv1a still pass.quality --checkgreen); the only overview-table change is mumbo'sStarlarkflag.Independent of #256 (touches
hash.bzl+ README, not the measurements package).