From e0b76cbffd9d1b766b94c52d796e50f513f17e9f Mon Sep 17 00:00:00 2001
From: lani_karrot <lani@daangn.com>
Date: Thu, 12 Feb 2026 00:05:33 +0900
Subject: [PATCH] fix: wrong bloom filter max size bits

---
 filters/bloom_filter_builder.go | 7 +++++--
 filters/bloom_filter_test.go    | 4 ++++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/filters/bloom_filter_builder.go b/filters/bloom_filter_builder.go
index 73fe651..9eb0374 100644
--- a/filters/bloom_filter_builder.go
+++ b/filters/bloom_filter_builder.go
@@ -22,11 +22,15 @@ import (
 	"encoding/binary"
 	"fmt"
 	"math"
+
+	"github.com/apache/datasketches-go/internal"
 )
 
-// Default seed value for hash functions
+// DefaultSeed is the default seed value for hash functions
 const DefaultSeed = uint64(9001)
 
+var maxBits = uint64((math.MaxInt32 - internal.FamilyEnum.BloomFilter.MaxPreLongs) * 64)
+
 // bloomFilterOptions holds optional parameters for filter construction.
 type bloomFilterOptions struct {
 	seed uint64
@@ -59,7 +63,6 @@ func NewBloomFilterBySize(numBits uint64, numHashes uint16, opts ...BloomFilterO
 	}
 
 	// Check for overflow
-	maxBits := uint64(math.MaxInt32-32) * 64
 	if numBits > maxBits {
 		return nil, fmt.Errorf("numBits exceeds maximum allowed size")
 	}
diff --git a/filters/bloom_filter_test.go b/filters/bloom_filter_test.go
index fe85a23..3a4f0b7 100644
--- a/filters/bloom_filter_test.go
+++ b/filters/bloom_filter_test.go
@@ -38,6 +38,10 @@ func TestInvalidConstructorArguments(t *testing.T) {
 	_, err = NewBloomFilterBySize(1<<60, 3)
 	assert.Error(t, err)
 
+	// numBits exceeds maxBits by 1
+	_, err = NewBloomFilterBySize(maxBits+1, 3)
+	assert.ErrorContains(t, err, "numBits exceeds maximum allowed size")
+
 	// Invalid FPP
 	_, err = NewBloomFilterByAccuracy(1000, 0.0)
 	assert.Error(t, err)