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|
package proto
import (
"fmt"
"io"
"reflect"
"unsafe"
)
var bytesCodec = codec{
wire: varlen,
size: sizeOfBytes,
encode: encodeBytes,
decode: decodeBytes,
}
func sizeOfBytes(p unsafe.Pointer, flags flags) int {
if p != nil {
if v := *(*[]byte)(p); v != nil || flags.has(wantzero) {
return sizeOfVarlen(len(v))
}
}
return 0
}
func encodeBytes(b []byte, p unsafe.Pointer, flags flags) (int, error) {
if p != nil {
if v := *(*[]byte)(p); v != nil || flags.has(wantzero) {
n, err := encodeVarint(b, uint64(len(v)))
if err != nil {
return n, err
}
c := copy(b[n:], v)
n += c
if c < len(v) {
err = io.ErrShortBuffer
}
return n, err
}
}
return 0, nil
}
func decodeBytes(b []byte, p unsafe.Pointer, _ flags) (int, error) {
v, n, err := decodeVarlen(b)
pb := (*[]byte)(p)
if *pb == nil {
*pb = make([]byte, 0, len(v))
}
*pb = append((*pb)[:0], v...)
return n, err
}
func makeBytes(p unsafe.Pointer, n int) []byte {
return *(*[]byte)(unsafe.Pointer(&sliceHeader{
Data: p,
Len: n,
Cap: n,
}))
}
type sliceHeader struct {
Data unsafe.Pointer
Len int
Cap int
}
// isZeroBytes is an optimized version of this loop:
//
// for i := range b {
// if b[i] != 0 {
// return false
// }
// }
// return true
//
// This implementation significantly reduces the CPU footprint of checking for
// slices to be zero, especially when the length increases (these cases should
// be rare tho).
//
// name old time/op new time/op delta
// IsZeroBytes0 1.78ns ± 1% 2.29ns ± 4% +28.65% (p=0.000 n=8+10)
// IsZeroBytes4 3.17ns ± 3% 2.37ns ± 3% -25.21% (p=0.000 n=10+10)
// IsZeroBytes7 3.97ns ± 4% 3.26ns ± 3% -18.02% (p=0.000 n=10+10)
// IsZeroBytes64K 14.8µs ± 3% 1.9µs ± 3% -87.34% (p=0.000 n=10+10)
func isZeroBytes(b []byte) bool {
if n := len(b) / 8; n != 0 {
if !isZeroUint64(*(*[]uint64)(unsafe.Pointer(&sliceHeader{
Data: unsafe.Pointer(&b[0]),
Len: n,
Cap: n,
}))) {
return false
}
b = b[n*8:]
}
switch len(b) {
case 7:
return bto32(b) == 0 && bto16(b[4:]) == 0 && b[6] == 0
case 6:
return bto32(b) == 0 && bto16(b[4:]) == 0
case 5:
return bto32(b) == 0 && b[4] == 0
case 4:
return bto32(b) == 0
case 3:
return bto16(b) == 0 && b[2] == 0
case 2:
return bto16(b) == 0
case 1:
return b[0] == 0
default:
return true
}
}
func bto32(b []byte) uint32 {
return *(*uint32)(unsafe.Pointer(&b[0]))
}
func bto16(b []byte) uint16 {
return *(*uint16)(unsafe.Pointer(&b[0]))
}
func isZeroUint64(b []uint64) bool {
for i := range b {
if b[i] != 0 {
return false
}
}
return true
}
func byteArrayCodecOf(t reflect.Type, seen map[reflect.Type]*codec) *codec {
n := t.Len()
c := &codec{
wire: varlen,
size: byteArraySizeFuncOf(n),
encode: byteArrayEncodeFuncOf(n),
decode: byteArrayDecodeFuncOf(n),
}
seen[t] = c
return c
}
func byteArraySizeFuncOf(n int) sizeFunc {
size := sizeOfVarlen(n)
return func(p unsafe.Pointer, flags flags) int {
if p != nil && (flags.has(wantzero) || !isZeroBytes(makeBytes(p, n))) {
return size
}
return 0
}
}
func byteArrayEncodeFuncOf(n int) encodeFunc {
return func(b []byte, p unsafe.Pointer, flags flags) (int, error) {
if p != nil {
if v := makeBytes(p, n); flags.has(wantzero) || !isZeroBytes(v) {
return encodeBytes(b, unsafe.Pointer(&v), noflags)
}
}
return 0, nil
}
}
func byteArrayDecodeFuncOf(n int) decodeFunc {
return func(b []byte, p unsafe.Pointer, _ flags) (int, error) {
v, r, err := decodeVarlen(b)
if err == nil {
if copy(makeBytes(p, n), v) != n {
err = fmt.Errorf("cannot decode byte sequence of size %d into byte array of size %d", len(v), n)
}
}
return r, err
}
}
|
