Merge pull request #36 from Callidon/fix-34

Fix 34
Callidon · Jul 7, 2021 · 9beb38b · 9beb38b
2 parents bd3ed71 + a4b2500
commit 9beb38b
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Showing 2 changed files with 35 additions and 15 deletions.
diff --git a/src/utils.ts b/src/utils.ts
@@ -177,23 +177,17 @@ export function getDistinctIndices (element: HashableInput, size: number, number
   if (seed === undefined) {
     seed = getDefaultSeed()
   }
-  function getDistinctIndicesBis (n: number, elem: HashableInput, size: number, count: number, indexes: Array<number> = []): Array<number> {
-    if (indexes.length === count) {
-      return indexes
-    } else {
-      const hashes = hashTwice(elem, true, seed! + size % n)
-      const ind = doubleHashing(n, hashes.first, hashes.second, size)
-      if (indexes.includes(ind)) {
-        // console.log('generate index: %d for %s', ind, elem)
-        return getDistinctIndicesBis(n + 1, elem, size, count, indexes)
-      } else {
-        // console.log('already found: %d for %s', ind, elem)
-        indexes.push(ind)
-        return getDistinctIndicesBis(n + 1, elem, size, count, indexes)
-      }
+  const indexes: Array<number> = []
+  let n = 1
+  while (indexes.length < number) {
+    const hashes = hashTwice(element, true, seed! + size + n)
+    const ind = doubleHashing(n, hashes.first, hashes.second, size)
+    if (!indexes.includes(ind)) {
+      indexes.push(ind)
     }
+    n++
   }
-  return getDistinctIndicesBis(1, element, size, number)
+  return indexes
 }
 
 /**

diff --git a/test/utils-test.js b/test/utils-test.js
@@ -26,7 +26,9 @@ SOFTWARE.
 
 require('chai').should()
 const utils = require('../dist/utils.js')
+const { BloomFilter } = require('../dist/api.js')
 const XXH = require('xxhashjs')
+const { range } = require('lodash')
 const seed = utils.getDefaultSeed()
 
 describe('Utils', () => {
@@ -111,4 +113,28 @@ describe('Utils', () => {
       utils.isEmptyBuffer(Buffer.allocUnsafe(10).fill(1)).should.equal(false)
     })
   })
+
+  describe('#getDistinctIndices', () => {
+    const key = "da5e21f8a67c4163f1a53ef43515bd027967da305ecfc741b2c3f40f832b7f82"
+    it('should return <number> distinct indices on the interval [0, size)', () => {
+      const desiredIndices = 10000
+      const result = range(0, desiredIndices, 1)
+      try{
+        const indices = utils.getDistinctIndices(key, desiredIndices, desiredIndices).sort((a, b) => a - b)
+        indices.should.deep.equal(result)
+      } catch (e) {
+        throw Error("it should not throw: " + e)
+      }
+    })
+    it('should the issue be fixed', () => {
+      try{
+        const filter = new BloomFilter(39, 28);
+        filter.add(key);
+        filter.has(key).should.be.true
+      } catch (e) {
+        throw Error("it should not throw: " + e)
+      }
+
+    })
+  })
 })