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Use bits.TrailingZeros for bitmap field

This commit is contained in:
Masaaki Goshima 2021-02-15 20:05:35 +09:00
parent e080e515fd
commit ddd7019dd3
1 changed files with 27 additions and 36 deletions
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63
decode_struct.go
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@ -3,6 +3,7 @@ package json
import (
"fmt"
"math"
"math/bits"
"sort"
"strings"
"unsafe"
@ -22,24 +23,18 @@ type structDecoder struct {
structName string
fieldName string
isTriedOptimize bool
keyBitmapInt8 [][256]int8
keyBitmapInt16 [][256]int16
keyBitmapUint8 [][256]uint8
keyBitmapUint16 [][256]uint16
sortedFieldSets []*structFieldSet
keyDecoder func(*structDecoder, []byte, int64) (int64, *structFieldSet, error)
keyStreamDecoder func(*structDecoder, *stream) (*structFieldSet, string, error)
}
var (
bitHashTable [64]int
largeToSmallTable [256]byte
)
func init() {
hash := uint64(0x03F566ED27179461)
for i := 0; i < 64; i++ {
bitHashTable[hash>>58] = i
hash <<= 1
}
for i := 0; i < 256; i++ {
c := i
if 'A' <= c && c <= 'Z' {
@ -114,7 +109,7 @@ func (d *structDecoder) tryOptimize() {
// it is possible to avoid the process of comparing the index of the key with the length of the bitmap each time.
bitmapLen := maxKeyLen + 1
if len(sortedKeys) <= 8 {
keyBitmap := make([][256]int8, bitmapLen)
keyBitmap := make([][256]uint8, bitmapLen)
for i, key := range sortedKeys {
for j := 0; j < len(key); j++ {
c := key[j]
@ -122,11 +117,11 @@ func (d *structDecoder) tryOptimize() {
}
d.sortedFieldSets = append(d.sortedFieldSets, fieldMap[key])
}
d.keyBitmapInt8 = keyBitmap
d.keyDecoder = decodeKeyByBitmapInt8
d.keyStreamDecoder = decodeKeyByBitmapInt8Stream
d.keyBitmapUint8 = keyBitmap
d.keyDecoder = decodeKeyByBitmapUint8
d.keyStreamDecoder = decodeKeyByBitmapUint8Stream
} else {
keyBitmap := make([][256]int16, bitmapLen)
keyBitmap := make([][256]uint16, bitmapLen)
for i, key := range sortedKeys {
for j := 0; j < len(key); j++ {
c := key[j]
@ -134,16 +129,16 @@ func (d *structDecoder) tryOptimize() {
}
d.sortedFieldSets = append(d.sortedFieldSets, fieldMap[key])
}
d.keyBitmapInt16 = keyBitmap
d.keyDecoder = decodeKeyByBitmapInt16
d.keyStreamDecoder = decodeKeyByBitmapInt16Stream
d.keyBitmapUint16 = keyBitmap
d.keyDecoder = decodeKeyByBitmapUint16
d.keyStreamDecoder = decodeKeyByBitmapUint16Stream
}
}
func decodeKeyByBitmapInt8(d *structDecoder, buf []byte, cursor int64) (int64, *structFieldSet, error) {
func decodeKeyByBitmapUint8(d *structDecoder, buf []byte, cursor int64) (int64, *structFieldSet, error) {
var (
field *structFieldSet
curBit int8 = math.MaxInt8
curBit uint8 = math.MaxUint8
)
b := (*sliceHeader)(unsafe.Pointer(&buf)).data
for {
@ -161,14 +156,13 @@ func decodeKeyByBitmapInt8(d *structDecoder, buf []byte, cursor int64) (int64, *
return 0, nil, errUnexpectedEndOfJSON("string", cursor)
}
keyIdx := 0
bitmap := d.keyBitmapInt8
bitmap := d.keyBitmapUint8
start := cursor
for {
c := char(b, cursor)
switch c {
case '"':
x := uint64(curBit & -curBit)
fieldSetIndex := bitHashTable[(x*0x03F566ED27179461)>>58]
fieldSetIndex := bits.TrailingZeros8(curBit)
field = d.sortedFieldSets[fieldSetIndex]
keyLen := cursor - start
cursor++
@ -208,10 +202,10 @@ func decodeKeyByBitmapInt8(d *structDecoder, buf []byte, cursor int64) (int64, *
}
}
func decodeKeyByBitmapInt16(d *structDecoder, buf []byte, cursor int64) (int64, *structFieldSet, error) {
func decodeKeyByBitmapUint16(d *structDecoder, buf []byte, cursor int64) (int64, *structFieldSet, error) {
var (
field *structFieldSet
curBit int16 = math.MaxInt16
curBit uint16 = math.MaxUint16
)
b := (*sliceHeader)(unsafe.Pointer(&buf)).data
for {
@ -229,14 +223,13 @@ func decodeKeyByBitmapInt16(d *structDecoder, buf []byte, cursor int64) (int64,
return 0, nil, errUnexpectedEndOfJSON("string", cursor)
}
keyIdx := 0
bitmap := d.keyBitmapInt16
bitmap := d.keyBitmapUint16
start := cursor
for {
c := char(b, cursor)
switch c {
case '"':
x := uint64(curBit & -curBit)
fieldSetIndex := bitHashTable[(x*0x03F566ED27179461)>>58]
fieldSetIndex := bits.TrailingZeros16(curBit)
field = d.sortedFieldSets[fieldSetIndex]
keyLen := cursor - start
cursor++
@ -290,10 +283,10 @@ func decodeKey(d *structDecoder, buf []byte, cursor int64) (int64, *structFieldS
return cursor, field, nil
}
func decodeKeyByBitmapInt8Stream(d *structDecoder, s *stream) (*structFieldSet, string, error) {
func decodeKeyByBitmapUint8Stream(d *structDecoder, s *stream) (*structFieldSet, string, error) {
var (
field *structFieldSet
curBit int8 = math.MaxInt8
curBit uint8 = math.MaxUint8
)
for {
switch s.char() {
@ -319,13 +312,12 @@ func decodeKeyByBitmapInt8Stream(d *structDecoder, s *stream) (*structFieldSet,
return nil, "", errUnexpectedEndOfJSON("string", s.totalOffset())
}
keyIdx := 0
bitmap := d.keyBitmapInt8
bitmap := d.keyBitmapUint8
for {
c := s.char()
switch c {
case '"':
x := uint64(curBit & -curBit)
fieldSetIndex := bitHashTable[(x*0x03F566ED27179461)>>58]
fieldSetIndex := bits.TrailingZeros8(curBit)
field = d.sortedFieldSets[fieldSetIndex]
keyLen := s.cursor - start
s.cursor++
@ -374,10 +366,10 @@ func decodeKeyByBitmapInt8Stream(d *structDecoder, s *stream) (*structFieldSet,
}
}
func decodeKeyByBitmapInt16Stream(d *structDecoder, s *stream) (*structFieldSet, string, error) {
func decodeKeyByBitmapUint16Stream(d *structDecoder, s *stream) (*structFieldSet, string, error) {
var (
field *structFieldSet
curBit int16 = math.MaxInt16
curBit uint16 = math.MaxUint16
)
for {
switch s.char() {
@ -403,13 +395,12 @@ func decodeKeyByBitmapInt16Stream(d *structDecoder, s *stream) (*structFieldSet,
return nil, "", errUnexpectedEndOfJSON("string", s.totalOffset())
}
keyIdx := 0
bitmap := d.keyBitmapInt16
bitmap := d.keyBitmapUint16
for {
c := s.char()
switch c {
case '"':
x := uint64(curBit & -curBit)
fieldSetIndex := bitHashTable[(x*0x03F566ED27179461)>>58]
fieldSetIndex := bits.TrailingZeros16(curBit)
field = d.sortedFieldSets[fieldSetIndex]
keyLen := s.cursor - start
s.cursor++