v0 state

numBits

// m: total bits in the filter

numBytes

numHashes

// k: hash functions per item (double-hashed from 2 bases)

maxHistory

// most recent additions kept for Render display only

bits

// the bit array itself

setBits

// running count of bits currently set to 1

added

// total Add calls (may double-count re-adds)

history

// last few added items, for the Render view

fnv1a

fnv1a is a minimal FNV-1a 32-bit hash over a string, parameterized by an offset basis so two calls with different seeds behave as independent hash functions for the double-hashing scheme below.

positions

positions returns the k bit positions an item hashes to.

setBit

setBit sets bit \`pos\` and reports whether it was previously unset.

testBit

testBit reports whether bit \`pos\` is set.

Add

Add inserts \`item\` into the filter. Crossing function: any caller (user or realm) may add, matching this demo's open-membership model.

MightContain

MightContain reports whether \`item\` was possibly added before. A false (definitely-not-a-member) answer is always correct; a true answer can occasionally be a false positive, never a false negative.

FalsePositiveRatePercent

FalsePositiveRatePercent estimates the current false-positive rate, in percent, as (bitsSet/m)^k — the standard Bloom filter approximation once bits are randomly distributed. Computed with plain integer/float math to avoid depending on math.Exp/Pow availability.

Stats

Stats returns the raw counters backing the Render view and FalsePositiveRatePercent: (itemsAdded, bitsSet, totalBits, hashCount).

Render

Render draws the filter's current stats and recently-added items as Markdown for gnoweb.