tsdb: faster CRC check by avoiding allocations
Instead of creating a new hashing object every time, call `crc32.Checksum`
which computes the answer without allocations.
@@ -15,7 +15,6 @@ package chunks
import (
"bufio"
- "bytes"
"encoding/binary"
"fmt"
"hash"
@@ -166,6 +165,17 @@ func newCRC32() hash.Hash32 {
return crc32.New(castagnoliTable)
}
+// Check if the CRC of data matches that stored in sum, computed when the chunk was stored.
+func checkCRC32(data, sum []byte) error {
+ got := crc32.Checksum(data, castagnoliTable)
+ // This combination of shifts is the inverse of digest.Sum() in go/src/hash/crc32.
+ want := uint32(sum[0])<<24 + uint32(sum[1])<<16 + uint32(sum[2])<<8 + uint32(sum[3])
+ if got != want {
+ return errors.Errorf("checksum mismatch expected:%x, actual:%x", want, got)
+ }
+ return nil
+}
+
// Writer implements the ChunkWriter interface for the standard
// serialization format.
type Writer struct {
@@ -547,7 +557,6 @@ func (s *Reader) Size() int64 {
// Chunk returns a chunk from a given reference.
func (s *Reader) Chunk(ref ChunkRef) (chunkenc.Chunk, error) {
sgmIndex, chkStart := BlockChunkRef(ref).Unpack()
- chkCRC32 := newCRC32()
if sgmIndex >= len(s.bs) {
return nil, errors.Errorf("segment index %d out of range", sgmIndex)
@@ -576,14 +585,10 @@ func (s *Reader) Chunk(ref ChunkRef) (chunkenc.Chunk, error) {
}
sum := sgmBytes.Range(chkDataEnd, chkEnd)
- if _, err := chkCRC32.Write(sgmBytes.Range(chkEncStart, chkDataEnd)); err != nil {
+ if err := checkCRC32(sgmBytes.Range(chkEncStart, chkDataEnd), sum); err != nil {
return nil, err
}
- if act := chkCRC32.Sum(nil); !bytes.Equal(act, sum) {
- return nil, errors.Errorf("checksum mismatch expected:%x, actual:%x", sum, act)
- }
-
chkData := sgmBytes.Range(chkDataStart, chkDataEnd)
chkEnc := sgmBytes.Range(chkEncStart, chkEncStart+ChunkEncodingSize)[0]
return s.pool.Get(chunkenc.Encoding(chkEnc), chkData)
