feat(common): add zero buffer checker

cpu: Intel(R) Core(TM) i7-10700 CPU @ 2.90GHz
BenchmarkIsZeroBuffer
BenchmarkIsZeroBuffer/1M-zero-all
BenchmarkIsZeroBuffer/1M-zero-all-4        50384       23927   ns/op  0 B/op  0 allocs/op
BenchmarkIsZeroBuffer/1M-not-zero-first
BenchmarkIsZeroBuffer/1M-not-zero-first-4  1000000000      0.4 ns/op  0 B/op  0 allocs/op
BenchmarkIsZeroBuffer/1M-not-zero-mid
BenchmarkIsZeroBuffer/1M-not-zero-mid-4    108770      10617   ns/op  0 B/op  0 allocs/op
BenchmarkIsZeroBuffer/1M-not-zero-last
BenchmarkIsZeroBuffer/1M-not-zero-last-4   48726       22504   ns/op  0 B/op  0 allocs/op

. #1000180877

Signed-off-by: slasher <shenjie1@oppo.com>

blobstore/common/crc32block/util.go

@@ -15,10 +15,14 @@
 package crc32block
 
 import (
+	"bytes"
+	"encoding/binary"
 	"errors"
 	"hash/crc32"
 	"io"
 	"sync"
+
+	"github.com/cubefs/cubefs/blobstore/util"
 )
 
 const (
@@ -115,6 +119,7 @@ func readFullOrToEnd(r io.Reader, buffer []byte) (n int, err error) {
 var (
 	_k16        = 16 << 10
 	_buffer16k  = make([]byte, _k16)
+	_bufferZero = make([]byte, _k16)
 	_mapZeroCrc = sync.Map{}
 )
 
@@ -141,3 +146,20 @@ func ConstZeroCrc(size int) uint32 {
 	_mapZeroCrc.Store(size, crc)
 	return crc
 }
+
+func IsZeroBuffer(buffer []byte) bool {
+	const width = 8
+	if len(buffer) > width {
+		if binary.BigEndian.Uint64(buffer[:width]) != 0 {
+			return false
+		}
+	}
+	for len(buffer) > 0 {
+		minl := util.Min(len(buffer), _k16)
+		if !bytes.Equal(buffer[:minl], _bufferZero[:minl]) {
+			return false
+		}
+		buffer = buffer[minl:]
+	}
+	return true
+}

blobstore/common/crc32block/util_test.go

@@ -15,6 +15,7 @@
 package crc32block
 
 import (
+	crand "crypto/rand"
 	"hash/crc32"
 	"math/rand"
 	"testing"
@@ -92,3 +93,54 @@ func TestConstZeroCrc(t *testing.T) {
 		require.Equal(t, act, get2)
 	}
 }
+
+func TestIsZeroBuffer(t *testing.T) {
+	require.True(t, IsZeroBuffer(nil))
+	for _, size := range []int{1, 3, 1 << 10, 1 << 19} {
+		buffer := make([]byte, size)
+		require.True(t, IsZeroBuffer(buffer))
+		buffer[0] = 'a'
+		require.False(t, IsZeroBuffer(buffer))
+		buffer[0] = 0
+		buffer[len(buffer)-1] = 'z'
+		require.False(t, IsZeroBuffer(buffer))
+		buffer[len(buffer)-1] = 0
+		require.True(t, IsZeroBuffer(buffer))
+		crand.Read(buffer)
+		require.False(t, IsZeroBuffer(buffer))
+	}
+}
+
+func BenchmarkIsZeroBuffer(b *testing.B) {
+	b.Run("1M-zero-all", func(b *testing.B) {
+		buffer := make([]byte, 1<<20)
+		b.ResetTimer()
+		for ii := 0; ii <= b.N; ii++ {
+			IsZeroBuffer(buffer)
+		}
+	})
+	b.Run("1M-not-zero-first", func(b *testing.B) {
+		buffer := make([]byte, 1<<20)
+		buffer[7] = 1
+		b.ResetTimer()
+		for ii := 0; ii <= b.N; ii++ {
+			IsZeroBuffer(buffer)
+		}
+	})
+	b.Run("1M-not-zero-mid", func(b *testing.B) {
+		buffer := make([]byte, 1<<20)
+		buffer[1<<19] = 1
+		b.ResetTimer()
+		for ii := 0; ii <= b.N; ii++ {
+			IsZeroBuffer(buffer)
+		}
+	})
+	b.Run("1M-not-zero-last", func(b *testing.B) {
+		buffer := make([]byte, 1<<20)
+		buffer[(1<<20)-1] = 1
+		b.ResetTimer()
+		for ii := 0; ii <= b.N; ii++ {
+			IsZeroBuffer(buffer)
+		}
+	})
+}