本文来介绍一下VLQ（variable-length quantity)

Wiki：Variable-length quantity

用变长字节数组来对整形进行编码，极大提高存储效率。

其实，这样的优点也被应用到了protobuf中，所以才有较高的序列化效率。

Varints in protobuf

具体实现代码如下：

package vlqimport ("math""math/bits"
)// DecodeVarint takes a variable length VLQ based integer and
// decodes it into a 32 bit integer.
func DecodeVarint(input []byte) (uint32, error) {const lastBitSet = 0x80 // 1000 0000var d uint32var bitPos intfor i := len(input) - 1; i >= 0; i-- {n := uint8(input[i])// Process the first 7 bits and ignore the 8th.for checkBit := 0; checkBit < 7; checkBit++ {// Rotate the last bit off and move it to the back.// Before: 0000 0001// After:  1000 0000n = bits.RotateLeft8(n, -1)// Calculate based on only those 1 bits that were rotated.// Convert the bitPos to base 10.if n >= lastBitSet {switch {case bitPos == 0:d++default:base10 := math.Pow(2, float64(bitPos))d += uint32(base10)}}// Move the bit position.bitPos++}}return d, nil
}// EncodeVarint takes a 32 bit integer and encodes it into
// a variable length VLQ based integer.
func EncodeVarint(n uint32) []byte {const maxBytes = 4const eightBitSet = 0x80      // 1000 0000const lastBitSet = 0x80000000 // 1000 0000 0000 0000encoded := make([]byte, maxBytes)for bytePos := maxBytes - 1; bytePos >= 0; bytePos-- {var d uint8// Process the next 7 bits.for checkBit := 0; checkBit < 7; checkBit++ {// Rotate the last bit off and move it to the back.// Before: 0000 0000 0000 0001// After:  1000 0000 0000 0000n = bits.RotateLeft32(n, -1)// Calculate based on only those 1 bits that were// rotated. Convert the bit position to base 10.if n >= lastBitSet {switch {case checkBit == 0:d++default:base10 := math.Pow(2, float64(checkBit))d += uint8(base10)}}}// These values need the 8th bit to be set as 1.if bytePos < 3 {d += eightBitSet}// Store the value in reserve order.encoded[bytePos] = d}// Remove leading zero values by finding values that only// have their eight bit set.for bytePos, b := range encoded {if b == eightBitSet {continue}encoded = encoded[bytePos:]break}return encoded
}

在此抛砖引玉，有兴趣的同学，可以自行研究。