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make encoding.MarshalVarInt64s faster (#5721)
* make encoding.MarshalVarInt64s faster * add fast path for MarshalVarInt64s * make UnmarshalVarUint64s faster * remove comment
This commit is contained in:
Fuchun Zhang
Aliaksandr Valialkin
parent
c91614b626
commit
49e3665d6d
1 changed files with 72 additions and 30 deletions
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@ -3,6 +3,7 @@ package encoding
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import (
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"encoding/binary"
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"fmt"
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"math/bits"
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"sync"
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)
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@ -91,21 +92,35 @@ func MarshalVarInt64(dst []byte, v int64) []byte {
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// MarshalVarInt64s appends marshaled vs to dst and returns the result.
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func MarshalVarInt64s(dst []byte, vs []int64) []byte {
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for _, v := range vs {
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if v < 0x40 && v > -0x40 {
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// Fast path
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c := int8(v)
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v := (c << 1) ^ (c >> 7) // zig-zag encoding without branching.
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dst = append(dst, byte(v))
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n := uint64((v << 1) ^ (v >> 63))
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if n < (1 << 7) {
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dst = append(dst, byte(n))
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continue
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}
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v = (v << 1) ^ (v >> 63) // zig-zag encoding without branching.
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u := uint64(v)
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for u > 0x7f {
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dst = append(dst, 0x80|byte(u))
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u >>= 7
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switch (64 - bits.LeadingZeros64(n>>1)) / 7 {
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case 0:
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dst = append(dst, byte(n))
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case 1:
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dst = append(dst, byte(n|0x80), byte(n>>7))
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case 2:
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dst = append(dst, byte(n|0x80), byte((n>>7)|0x80), byte(n>>14))
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case 3:
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dst = append(dst, byte(n|0x80), byte((n>>7)|0x80), byte((n>>14)|0x80), byte(n>>21))
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case 4:
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dst = append(dst, byte(n|0x80), byte((n>>7)|0x80), byte((n>>14)|0x80), byte((n>>21)|0x80), byte(n>>28))
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case 5:
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dst = append(dst, byte(n|0x80), byte((n>>7)|0x80), byte((n>>14)|0x80), byte((n>>21)|0x80), byte(n>>28|0x80), byte(n>>35))
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case 6:
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dst = append(dst, byte(n|0x80), byte((n>>7)|0x80), byte((n>>14)|0x80), byte((n>>21)|0x80), byte(n>>28|0x80), byte(n>>35|0x80), byte(n>>42))
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case 7:
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dst = append(dst, byte(n|0x80), byte((n>>7)|0x80), byte((n>>14)|0x80), byte((n>>21)|0x80), byte(n>>28|0x80), byte(n>>35|0x80), byte(n>>42|0x80), byte(n>>49))
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case 8:
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dst = append(dst, byte(n|0x80), byte((n>>7)|0x80), byte((n>>14)|0x80), byte((n>>21)|0x80), byte(n>>28|0x80), byte(n>>35|0x80), byte(n>>42|0x80), byte(n>>49|0x80), byte(n>>56))
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case 9:
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fallthrough
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default:
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dst = append(dst, byte(n|0x80), byte((n>>7)|0x80), byte((n>>14)|0x80), byte((n>>21)|0x80), byte(n>>28|0x80), byte(n>>35|0x80), byte(n>>42|0x80), byte(n>>49|0x80), byte(n>>56|0x80), byte(n>>63))
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}
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dst = append(dst, byte(u))
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}
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return dst
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}
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@ -134,30 +149,57 @@ func UnmarshalVarInt64s(dst []int64, src []byte) ([]byte, error) {
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dst[i] = int64(v)
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continue
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}
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// Slow path
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u := uint64(c & 0x7f)
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startIdx := idx - 1
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shift := uint8(0)
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for c >= 0x80 {
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if idx >= uint(len(src)) {
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return nil, fmt.Errorf("unexpected end of encoded varint at byte %d; src=%x", idx-startIdx, src[startIdx:])
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}
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if idx-startIdx > 9 {
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return src[idx:], fmt.Errorf("too long encoded varint; the maximum allowed length is 10 bytes; got %d bytes; src=%x",
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(idx-startIdx)+1, src[startIdx:])
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}
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c = src[idx]
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if idx < uint(len(src)) && src[idx] < 0x80 {
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// Fast path, for 2 bytes
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n := uint64(c&0x7f) | (uint64(src[idx]&0x7f) << 7)
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dst[i] = int64(n>>1) ^ (int64(n<<63) >> 63)
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idx++
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shift += 7
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u |= uint64(c&0x7f) << shift
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continue
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}
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v := int64(u>>1) ^ (int64(u<<63) >> 63) // zig-zag decoding without branching.
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dst[i] = v
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j := idx + 1
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for ; j < uint(len(src)); j++ { // find end loc
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if src[j] < 0x80 {
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break
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}
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}
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if j-idx > 10 {
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return nil, fmt.Errorf("cannot unmarshal varint, buffer too long, len=%d", j-idx)
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}
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dst[i] = unmarshalVarInt64ForOne(src[idx-1 : j+1])
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idx = j + 1
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}
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return src[idx:], nil
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}
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func unmarshalVarInt64ForOne(buf []byte) int64 {
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var n uint64
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switch len(buf) {
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case 1:
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n = uint64(buf[0] & 0x7F)
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case 2:
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n = uint64(buf[0]&0x7F) | (uint64(buf[1]&0x7F) << 7)
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case 3:
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n = uint64(buf[0]&0x7F) | (uint64(buf[1]&0x7F) << 7) | (uint64(buf[2]&0x7F) << 14)
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case 4:
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n = uint64(buf[0]&0x7F) | (uint64(buf[1]&0x7F) << 7) | (uint64(buf[2]&0x7F) << 14) | (uint64(buf[3]&0x7F) << 21)
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case 5:
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n = uint64(buf[0]&0x7F) | (uint64(buf[1]&0x7F) << 7) | (uint64(buf[2]&0x7F) << 14) | (uint64(buf[3]&0x7F) << 21) | (uint64(buf[4]&0x7F) << 28)
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case 6:
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n = uint64(buf[0]&0x7F) | (uint64(buf[1]&0x7F) << 7) | (uint64(buf[2]&0x7F) << 14) | (uint64(buf[3]&0x7F) << 21) | (uint64(buf[4]&0x7F) << 28) | (uint64(buf[5]&0x7F) << 35)
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case 7:
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n = uint64(buf[0]&0x7F) | (uint64(buf[1]&0x7F) << 7) | (uint64(buf[2]&0x7F) << 14) | (uint64(buf[3]&0x7F) << 21) | (uint64(buf[4]&0x7F) << 28) | (uint64(buf[5]&0x7F) << 35) | (uint64(buf[6]&0x7F) << 42)
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case 8:
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n = uint64(buf[0]&0x7F) | (uint64(buf[1]&0x7F) << 7) | (uint64(buf[2]&0x7F) << 14) | (uint64(buf[3]&0x7F) << 21) | (uint64(buf[4]&0x7F) << 28) | (uint64(buf[5]&0x7F) << 35) | (uint64(buf[6]&0x7F) << 42) | (uint64(buf[7]&0x7F) << 49)
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case 9:
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n = uint64(buf[0]&0x7F) | (uint64(buf[1]&0x7F) << 7) | (uint64(buf[2]&0x7F) << 14) | (uint64(buf[3]&0x7F) << 21) | (uint64(buf[4]&0x7F) << 28) | (uint64(buf[5]&0x7F) << 35) | (uint64(buf[6]&0x7F) << 42) | (uint64(buf[7]&0x7F) << 49) | (uint64(buf[8]&0x7F) << 56)
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case 10:
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n = uint64(buf[0]&0x7F) | (uint64(buf[1]&0x7F) << 7) | (uint64(buf[2]&0x7F) << 14) | (uint64(buf[3]&0x7F) << 21) | (uint64(buf[4]&0x7F) << 28) | (uint64(buf[5]&0x7F) << 35) | (uint64(buf[6]&0x7F) << 42) | (uint64(buf[7]&0x7F) << 49) | (uint64(buf[8]&0x7F) << 56) | (uint64(buf[9]&0x7F) << 63)
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default:
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panic("impossible error: buf length must be 1 to 10")
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}
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return int64(n>>1) ^ (int64(n<<63) >> 63)
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}
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// MarshalVarUint64 appends marshaled u to dst and returns the result.
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func MarshalVarUint64(dst []byte, u uint64) []byte {
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var tmp [1]uint64
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