address comments

Author: sambhav-jain-16

core/metainfo.go

@@ -18,7 +18,6 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"hash/crc32"
 	"io"
 
 	"github.com/jackpal/bencode-go"
@@ -216,14 +215,14 @@ func calcPieceSumsFromBytes(data []byte, pieceLength int64) (int64, []uint32, er
 	if n == 0 {
 		return 0, nil, nil
 	}
-	numPieces := (n + pieceLength - 1) / pieceLength
+	numPieces := (n-1)/pieceLength + 1
 	pieceSums := make([]uint32, 0, numPieces)
 	for offset := int64(0); offset < n; offset += pieceLength {
 		end := offset + pieceLength
 		if end > n {
 			end = n
 		}
-		pieceSums = append(pieceSums, crc32.ChecksumIEEE(data[offset:end]))
+		pieceSums = append(pieceSums, PieceSum(data[offset:end]))
 	}
 	return n, pieceSums, nil
 }

core/metainfo_test.go

@@ -170,7 +170,7 @@ func TestNewMetaInfoFromBytes_MatchesReader(t *testing.T) {
 	}
 }
 
-func BenchmarkNewMetaInfo(b *testing.B) {
+func BenchmarkNewMetaInfoFromBytes(b *testing.B) {
 	cases := []struct {
 		name        string
 		blobSize    uint64

core/piece_hash.go

@@ -22,3 +22,10 @@ import (
 func PieceHash() hash.Hash32 {
 	return crc32.NewIEEE()
 }
+
+// PieceSum returns the checksum of b using the same algorithm as PieceHash.
+// It is equivalent to creating a PieceHash, writing b, and calling Sum32,
+// but avoids allocating a hash.Hash32 object.
+func PieceSum(b []byte) uint32 {
+	return crc32.ChecksumIEEE(b)
+}