golang实现simhash算法

可以使用golang的hash/crc32包来计算simhash算法中的哈希值，具体实现可以参考以下代码：

package simhash

import (
	"bytes"
	"hash/crc32"
)

// Simhash represents a 64-bit hash value
type Simhash uint64

// NewSimhash calculates the simhash of the given data
func NewSimhash(data []byte) Simhash {
	// Step 1: tokenize data into shingles
	shingles := tokenize(data)

	// Step 2: compute the weighted frequency counts of shingles
	counts := countShingles(shingles)

	// Step 3: create the simhash
	var simhash Simhash
	for shingle, weight := range counts {
		hash := crc32.ChecksumIEEE([]byte(shingle))
		for i := 0; i < 32; i++ {
			if hash&(1<<uint(i)) != 0 {
				simhash += Simhash(weight)
			} else {
				simhash -= Simhash(weight)
			}
		}
	}
	return simhash
}

// tokenize splits the given data into shingles
func tokenize(data []byte) []string {
	shingles := make([]string, 0)
	var buffer bytes.Buffer
	for i := 0; i < len(data); i++ {
		if data[i] == ' ' {
			shingles = append(shingles, buffer.String())
			buffer.Reset()
			continue
		}
		buffer.WriteByte(data[i])
	}
	if buffer.Len() > 0 {
		shingles = append(shingles, buffer.String())
	}
	return shingles
}

// countShingles computes the weighted frequency counts of the given shingles
func countShingles(shingles []string) map[string]int {
	counts := make(map[string]int)
	for _, shingle := range shingles {
		counts[shingle]++
	}
	return counts
}

这段代码实现了simhash算法的三个步骤：将输入数据分割为shingles，计算shingles的加权频率，以及计算simhash值。其中，crc32包用于计算哈希值，bytes包用于处理字符串。