*: Add Digest struct to get bytes of digest (#1231)

digester.go

@@ -16,7 +16,7 @@ package parser
 import (
 	"bytes"
 	"crypto/sha256"
-	"fmt"
+	"encoding/hex"
 	hash2 "hash"
 	"reflect"
 	"strings"
@@ -27,16 +27,39 @@ import (
 	"github.com/pingcap/parser/charset"
 )
 
+type Digest struct {
+	b   []byte
+	str string
+}
+
+// NewDigest returns a new digest.
+func NewDigest(b []byte) *Digest {
+	return &Digest{
+		b:   b,
+		str: hex.EncodeToString(b),
+	}
+}
+
+// String returns the digest hex string.
+func (d *Digest) String() string {
+	return d.str
+}
+
+// Bytes returns the digest byte slice.
+func (d *Digest) Bytes() []byte {
+	return d.b
+}
+
 // DigestHash generates the digest of statements.
 // it will generate a hash on normalized form of statement text
 // which removes general property of a statement but keeps specific property.
 //
 // for example: both DigestHash('select 1') and DigestHash('select 2') => e1c71d1661ae46e09b7aaec1c390957f0d6260410df4e4bc71b9c8d681021471
 //
 // Deprecated: It is logically consistent with NormalizeDigest.
-func DigestHash(sql string) (result string) {
+func DigestHash(sql string) (digest *Digest) {
 	d := digesterPool.Get().(*sqlDigester)
-	result = d.doDigest(sql)
+	digest = d.doDigest(sql)
 	digesterPool.Put(d)
 	return
 }
@@ -48,9 +71,9 @@ func DigestHash(sql string) (result string) {
 // for example: DigestNormalized('select ?')
 // DigestNormalized should be called with a normalized SQL string (like 'select ?') generated by function Normalize.
 // do not call with SQL which is not normalized, DigestNormalized('select 1') and DigestNormalized('select 2') is not the same
-func DigestNormalized(normalized string) (result string) {
+func DigestNormalized(normalized string) (digest *Digest) {
 	d := digesterPool.Get().(*sqlDigester)
-	result = d.doDigestNormalized(normalized)
+	digest = d.doDigestNormalized(normalized)
 	digesterPool.Put(d)
 	return
 }
@@ -68,7 +91,7 @@ func Normalize(sql string) (result string) {
 }
 
 // NormalizeDigest combines Normalize and DigestNormalized into one method.
-func NormalizeDigest(sql string) (normalized, digest string) {
+func NormalizeDigest(sql string) (normalized string, digest *Digest) {
 	d := digesterPool.Get().(*sqlDigester)
 	normalized, digest = d.doNormalizeDigest(sql)
 	digesterPool.Put(d)
@@ -92,24 +115,24 @@ type sqlDigester struct {
 	tokens tokenDeque
 }
 
-func (d *sqlDigester) doDigestNormalized(normalized string) (result string) {
+func (d *sqlDigester) doDigestNormalized(normalized string) (digest *Digest) {
 	hdr := *(*reflect.StringHeader)(unsafe.Pointer(&normalized))
 	b := *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
 		Data: hdr.Data,
 		Len:  hdr.Len,
 		Cap:  hdr.Len,
 	}))
 	d.hasher.Write(b)
-	result = fmt.Sprintf("%x", d.hasher.Sum(nil))
+	digest = NewDigest(d.hasher.Sum(nil))
 	d.hasher.Reset()
 	return
 }
 
-func (d *sqlDigester) doDigest(sql string) (result string) {
+func (d *sqlDigester) doDigest(sql string) (digest *Digest) {
 	d.normalize(sql)
 	d.hasher.Write(d.buffer.Bytes())
 	d.buffer.Reset()
-	result = fmt.Sprintf("%x", d.hasher.Sum(nil))
+	digest = NewDigest(d.hasher.Sum(nil))
 	d.hasher.Reset()
 	return
 }
@@ -121,12 +144,12 @@ func (d *sqlDigester) doNormalize(sql string) (result string) {
 	return
 }
 
-func (d *sqlDigester) doNormalizeDigest(sql string) (normalized, digest string) {
+func (d *sqlDigester) doNormalizeDigest(sql string) (normalized string, digest *Digest) {
 	d.normalize(sql)
 	normalized = d.buffer.String()
 	d.hasher.Write(d.buffer.Bytes())
 	d.buffer.Reset()
-	digest = fmt.Sprintf("%x", d.hasher.Sum(nil))
+	digest = NewDigest(d.hasher.Sum(nil))
 	d.hasher.Reset()
 	return
 }

digester_test.go

@@ -14,6 +14,11 @@
 package parser_test
 
 import (
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"testing"
+
 	. "github.com/pingcap/check"
 	"github.com/pingcap/parser"
 )
@@ -71,7 +76,7 @@ func (s *testSQLDigestSuite) TestNormalize(c *C) {
 
 		normalized2, digest2 := parser.NormalizeDigest(test.input)
 		c.Assert(normalized2, Equals, normalized)
-		c.Assert(digest2, Equals, digest, Commentf("%+v", test))
+		c.Assert(digest2.String(), Equals, digest.String(), Commentf("%+v", test))
 	}
 }
 
@@ -86,12 +91,12 @@ func (s *testSQLDigestSuite) TestNormalizeDigest(c *C) {
 	for _, test := range tests {
 		normalized, digest := parser.NormalizeDigest(test.sql)
 		c.Assert(normalized, Equals, test.normalized)
-		c.Assert(digest, Equals, test.digest)
+		c.Assert(digest.String(), Equals, test.digest)
 
 		normalized = parser.Normalize(test.sql)
 		digest = parser.DigestNormalized(normalized)
 		c.Assert(normalized, Equals, test.normalized)
-		c.Assert(digest, Equals, test.digest)
+		c.Assert(digest.String(), Equals, test.digest)
 	}
 }
 
@@ -106,10 +111,10 @@ func (s *testSQLDigestSuite) TestDigestHashEqForSimpleSQL(c *C) {
 		for _, sql := range sqlGroup {
 			dig := parser.DigestHash(sql)
 			if d == "" {
-				d = dig
+				d = dig.String()
 				continue
 			}
-			c.Assert(d, Equals, dig)
+			c.Assert(d, Equals, dig.String())
 		}
 	}
 }
@@ -123,10 +128,42 @@ func (s *testSQLDigestSuite) TestDigestHashNotEqForSimpleSQL(c *C) {
 		for _, sql := range sqlGroup {
 			dig := parser.DigestHash(sql)
 			if d == "" {
-				d = dig
+				d = dig.String()
 				continue
 			}
-			c.Assert(d, Not(Equals), dig)
+			c.Assert(d, Not(Equals), dig.String())
 		}
 	}
 }
+
+func (s *testSQLDigestSuite) TestGenDigest(c *C) {
+	hash := genRandDigest("abc")
+	digest := parser.NewDigest(hash)
+	c.Assert(digest.String(), Equals, fmt.Sprintf("%x", hash))
+	c.Assert(digest.Bytes(), DeepEquals, hash)
+	digest = parser.NewDigest(nil)
+	c.Assert(digest.String(), Equals, "")
+	c.Assert(digest.Bytes(), IsNil)
+}
+
+func genRandDigest(str string) []byte {
+	hasher := sha256.New()
+	hasher.Write([]byte(str))
+	return hasher.Sum(nil)
+}
+
+func BenchmarkDigestHexEncode(b *testing.B) {
+	digest1 := genRandDigest("abc")
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		hex.EncodeToString(digest1)
+	}
+}
+
+func BenchmarkDigestSprintf(b *testing.B) {
+	digest1 := genRandDigest("abc")
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		fmt.Sprintf("%x", digest1)
+	}
+}