varint

README

varint

This package provides an optimized implementation of protobuf's varint encoding/decoding. It has no dependencies.

Benchmarks comparing to a binary.Uvarint:

benchmark                      old ns/op     new ns/op     delta
BenchmarkUvarint/1-8           4.13          2.85          -30.99%
BenchmarkUvarint/1_large-8     4.01          2.28          -43.14%
BenchmarkUvarint/2-8           6.23          2.87          -53.93%
BenchmarkUvarint/2_large-8     5.60          2.86          -48.93%
BenchmarkUvarint/3-8           6.55          3.44          -47.48%
BenchmarkUvarint/3_large-8     6.54          2.86          -56.27%
BenchmarkUvarint/4-8           7.30          3.71          -49.18%
BenchmarkUvarint/4_large-8     7.46          3.10          -58.45%
BenchmarkUvarint/5-8           8.31          4.12          -50.42%
BenchmarkUvarint/5_large-8     8.56          3.48          -59.35%
BenchmarkUvarint/6-8           9.42          4.66          -50.53%
BenchmarkUvarint/6_large-8     9.91          4.07          -58.93%
BenchmarkUvarint/7-8           10.6          5.28          -50.19%
BenchmarkUvarint/7_large-8     11.0          4.70          -57.27%
BenchmarkUvarint/8-8           11.7          6.02          -48.55%
BenchmarkUvarint/8_large-8     12.1          5.19          -57.11%
BenchmarkUvarint/9-8           12.9          6.83          -47.05%
BenchmarkUvarint/9_large-8     13.1          5.71          -56.41%

It also provides additional functionality like UvarintSize (similar to sov* in gogo/protobuf):

benchmark                    old ns/op     new ns/op     delta
BenchmarkUvarintSize/1-8     1.71          0.43          -74.85%
BenchmarkUvarintSize/2-8     2.56          0.57          -77.73%
BenchmarkUvarintSize/3-8     3.22          0.72          -77.64%
BenchmarkUvarintSize/4-8     3.74          0.72          -80.75%
BenchmarkUvarintSize/5-8     4.29          0.57          -86.71%
BenchmarkUvarintSize/6-8     4.85          0.58          -88.04%
BenchmarkUvarintSize/7-8     5.43          0.71          -86.92%
BenchmarkUvarintSize/8-8     6.01          0.86          -85.69%
BenchmarkUvarintSize/9-8     6.64          1.00          -84.94%

License

MIT

Documentation

Index

• Constants
• func ProtoTag(buf []byte) (num int, typ byte, n int)
• func Uvarint(buf []byte) (uint64, int)
• func UvarintSize(x uint64) int

Constants

const (
	MaxLen8  = 2
	MaxLen16 = 3
	MaxLen32 = 5
	MaxLen64 = 10
)

MaxLenN is the maximum length of a varint-encoded N-bit integer.

const (
	MaxVal9 = maxUint64 >> (1 + iota*7)
	MaxVal8
	MaxVal7
	MaxVal6
	MaxVal5
	MaxVal4
	MaxVal3
	MaxVal2
	MaxVal1
)

MaxValN is the maximum varint-encoded integer that fits in N bytes.

Functions

func ProtoTag

func ProtoTag(buf []byte) (num int, typ byte, n int)

ProtoTag decodes a protobuf's field number and wire type pair from buf and returns that value and the number of bytes read (> 0). If an error occurred, n = 0 is returned.

func Uvarint

func Uvarint(buf []byte) (uint64, int)

Uvarint decodes a uint64 from buf and returns that value and the number of bytes read (> 0). If an error occurred, the value is 0 and the number of bytes n is <= 0 meaning:

n == 0: buf too small
n  < 0: value larger than 64 bits (overflow)
        and -n is the number of bytes read

func UvarintSize

func UvarintSize(x uint64) int

UvarintSize returns the number of bytes necessary to encode a given uint.