index: simplify checksum validation

encoding_helpers.go

@@ -3,6 +3,7 @@ package tsdb
 import (
 	"encoding/binary"
 	"hash"
+	"hash/crc32"
 	"unsafe"
 )
 
@@ -77,6 +78,11 @@ func (d *decbuf) uvarint32() uint32 { return uint32(d.uvarint64()) }
 func (d *decbuf) be32int() int      { return int(d.be32()) }
 func (d *decbuf) be64int64() int64  { return int64(d.be64()) }
 
+// crc32 returns a CRC32 checksum over the remaining bytes.
+func (d *decbuf) crc32() uint32 {
+	return crc32.Checksum(d.b, castagnoliTable)
+}
+
 func (d *decbuf) uvarintStr() string {
 	l := d.uvarint64()
 	if d.e != nil {

index.go

@@ -625,20 +625,24 @@ func newIndexReader(dir string) (*indexReader, error) {
 }
 
 func (r *indexReader) readTOC() error {
-	d := r.decbufAt(len(r.b) - indexTOCLen)
+	d1 := r.decbufAt(len(r.b) - indexTOCLen)
+	d2 := d1.decbuf(indexTOCLen - 4)
+	crc := d2.crc32()
 
-	r.toc.symbols = d.be64()
-	r.toc.series = d.be64()
-	r.toc.labelIndices = d.be64()
-	r.toc.labelIndicesTable = d.be64()
-	r.toc.postings = d.be64()
-	r.toc.postingsTable = d.be64()
+	r.toc.symbols = d2.be64()
+	r.toc.series = d2.be64()
+	r.toc.labelIndices = d2.be64()
+	r.toc.labelIndicesTable = d2.be64()
+	r.toc.postings = d2.be64()
+	r.toc.postingsTable = d2.be64()
 
-	if valid, err := r.checkCRC(d.be32(), len(r.b)-indexTOCLen, indexTOCLen-4); !valid {
-		return errors.Wrap(err, "TOC checksum")
+	if d2.err() != nil {
+		return d2.err()
 	}
-
-	return d.err()
+	if read := d1.be32(); crc != read {
+		return errors.Wrap(errInvalidChecksum, "read TOC")
+	}
+	return d1.err()
 }
 
 func (r *indexReader) decbufAt(off int) decbuf {
@@ -648,20 +652,6 @@ func (r *indexReader) decbufAt(off int) decbuf {
 	return decbuf{b: r.b[off:]}
 }
 
-func (r *indexReader) checkCRC(crc uint32, off, cnt int) (bool, error) {
-	r.crc32.Reset()
-	if len(r.b) < off+cnt {
-		return false, errInvalidSize
-	}
-	if _, err := r.crc32.Write(r.b[off : off+cnt]); err != nil {
-		return false, errors.Wrap(err, "write to hash")
-	}
-	if r.crc32.Sum32() != crc {
-		return false, errInvalidChecksum
-	}
-	return true, nil
-}
-
 // readSymbols reads the symbol table fully into memory and allocates proper strings for them.
 // Strings backed by the mmap'd memory would cause memory faults if applications keep using them
 // after the reader is closed.
@@ -671,8 +661,8 @@ func (r *indexReader) readSymbols(off int) error {
 	}
 	var (
 		d1      = r.decbufAt(int(off))
-		l       = d1.be32int()
-		d2      = d1.decbuf(l)
+		d2      = d1.decbuf(d1.be32int())
+		crc     = d2.crc32()
 		origLen = d2.len()
 		cnt     = d2.be32int()
 		basePos = uint32(off) + 4
@@ -685,8 +675,8 @@ func (r *indexReader) readSymbols(off int) error {
 		nextPos = basePos + uint32(origLen-d2.len())
 		cnt--
 	}
-	if valid, err := r.checkCRC(d1.be32(), int(off)+4, l); !valid {
-		return errors.Wrap(err, "symbol table checksum")
+	if read := d1.be32(); crc != read {
+		return errors.Wrap(errInvalidChecksum, "read symbols")
 	}
 	return d2.err()
 }
@@ -698,8 +688,8 @@ func (r *indexReader) readOffsetTable(off uint64) (map[string]uint32, error) {
 
 	var (
 		d1  = r.decbufAt(int(off))
-		l   = d1.be32int()
-		d2  = d1.decbuf(l)
+		d2  = d1.decbuf(d1.be32int())
+		crc = d2.crc32()
 		cnt = d2.be32()
 	)
 
@@ -716,11 +706,9 @@ func (r *indexReader) readOffsetTable(off uint64) (map[string]uint32, error) {
 
 		cnt--
 	}
-
-	if valid, err := r.checkCRC(d1.be32(), int(off)+4, l); !valid {
-		return res, errors.Wrap(err, "offset table checksum")
+	if read := d1.be32(); crc != read {
+		return nil, errors.Wrap(errInvalidChecksum, "read offset table")
 	}
-
 	return res, d2.err()
 }
 
@@ -777,8 +765,8 @@ func (r *indexReader) LabelValues(names ...string) (StringTuples, error) {
 	}
 
 	d1 := r.decbufAt(int(off))
-	l := d1.be32int()
-	d2 := d1.decbuf(l)
+	d2 := d1.decbuf(d1.be32int())
+	crc := d2.crc32()
 
 	nc := d2.be32int()
 	d2.be32() // consume unused value entry count.
@@ -787,10 +775,9 @@ func (r *indexReader) LabelValues(names ...string) (StringTuples, error) {
 		return nil, errors.Wrap(d2.err(), "read label value index")
 	}
 
-	if valid, err := r.checkCRC(d1.be32(), int(off)+4, l); !valid {
-		return nil, errors.Wrap(err, "read label values checksum")
+	if read := d1.be32(); crc != read {
+		return nil, errors.Wrap(errInvalidChecksum, "read label values")
 	}
-
 	st := &serializedStringTuples{
 		l:      nc,
 		b:      d2.get(),
@@ -817,9 +804,8 @@ func (r *indexReader) LabelIndices() ([][]string, error) {
 
 func (r *indexReader) Series(ref uint64, lbls *labels.Labels, chks *[]ChunkMeta) error {
 	d1 := r.decbufAt(int(ref))
-	l := d1.uvarint()
-	sl := len(r.b[ref:]) - d1.len() // # bytes in l
-	d2 := d1.decbuf(l)
+	d2 := d1.decbuf(d1.uvarint())
+	crc := d2.crc32()
 
 	*lbls = (*lbls)[:0]
 	*chks = (*chks)[:0]
@@ -881,11 +867,9 @@ func (r *indexReader) Series(ref uint64, lbls *labels.Labels, chks *[]ChunkMeta)
 			MaxTime: maxt,
 		})
 	}
-
-	if valid, err := r.checkCRC(d1.be32(), int(ref)+sl, l); !valid {
-		return errors.Wrap(err, "series checksum")
+	if read := d1.be32(); crc != read {
+		return errors.Wrap(errInvalidChecksum, "read series")
 	}
-
 	return nil
 }
 
@@ -899,19 +883,18 @@ func (r *indexReader) Postings(name, value string) (Postings, error) {
 	}
 
 	d1 := r.decbufAt(int(off))
-	l := d1.be32int()
-	d2 := d1.decbuf(l)
+	d2 := d1.decbuf(d1.be32int())
+
+	crc := d2.crc32()
 
 	d2.be32() // consume unused postings list length.
 
 	if d2.err() != nil {
 		return nil, errors.Wrap(d2.err(), "get postings bytes")
 	}
-
-	if valid, err := r.checkCRC(d1.be32(), int(off)+4, l); !valid {
-		return nil, errors.Wrap(err, "postings checksum")
+	if read := d1.be32(); crc != read {
+		return nil, errors.Wrap(errInvalidChecksum, "read postings")
 	}
-
 	return newBigEndianPostings(d2.get()), nil
 }
 

test/hash_test.go

@@ -14,6 +14,9 @@
 package test
 
 import (
+	"crypto/rand"
+	"fmt"
+	"hash/crc32"
 	"testing"
 
 	"github.com/cespare/xxhash"
@@ -76,3 +79,46 @@ func fnv64a(b []byte) uint64 {
 	}
 	return h
 }
+
+func BenchmarkCRC32_diff(b *testing.B) {
+
+	data := [][]byte{}
+
+	for i := 0; i < 1000; i++ {
+		b := make([]byte, 512)
+		rand.Read(b)
+		data = append(data, b)
+	}
+
+	ctab := crc32.MakeTable(crc32.Castagnoli)
+	total := uint32(0)
+
+	b.Run("direct", func(b *testing.B) {
+		b.ReportAllocs()
+
+		for i := 0; i < b.N; i++ {
+			total += crc32.Checksum(data[i%1000], ctab)
+		}
+	})
+	b.Run("hash-reuse", func(b *testing.B) {
+		b.ReportAllocs()
+		h := crc32.New(ctab)
+
+		for i := 0; i < b.N; i++ {
+			h.Reset()
+			h.Write(data[i%1000])
+			total += h.Sum32()
+		}
+	})
+	b.Run("hash-new", func(b *testing.B) {
+		b.ReportAllocs()
+
+		for i := 0; i < b.N; i++ {
+			h := crc32.New(ctab)
+			h.Write(data[i%1000])
+			total += h.Sum32()
+		}
+	})
+
+	fmt.Println(total)
+}