最近有时间研究了下cocos2dx 3.x的版本，里面有两个文件引起了我的好奇。(xxhash.h、xxhash.c)

发现xxhash是一个类似于计算md5的库,快md5十几倍

Name Speed Q.Score Author
xxHash 5.4 GB/s 10  
MumurHash 3a 2.7 GB/s 10 Austin Appleby
SpookyHash 2.0 GB/s 10 Bob Jenkins
SBox 1.4 GB/s 9 Bret Mulvey
Lookup3 1.2 GB/s 9 Bob Jenkins
CityHash64 1.05 GB/s 10 Pike & Alakuijala
FNV 0.55 GB/s 5 Fowler, Noll, Vo
CRC32 0.43 GB/s 9  
MD5-32 0.33 GB/s 10 Ronald L. Rivest
SHA1-32 0.28 GB/s 10  

####xxhash 32位跟64位计算区别

Name Speed on 64 bits Speed on 32 bits
XXH64 13.8 GB/s 1.9 GB/s
XXH32 6.8 GB/s 6.0 GB/s

用来计算更新文件hash值 xxhash安装出错

$ gem install xxhash
ERROR:  Could not find a valid gem 'xxhash' (>= 0) in any repository

直接使用下载到本地gem install -l xx.gem

Usage

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require 'xxhash'
require 'stringio'

text = "test"
seed = 12345
XXhash.xxh32(text, seed) # => 3834992036
#You can use it with IO objects too:
XXhash.xxh32_stream(StringIO.new('test'), 123) # => 2758658570
XXhash.xxh32(File.read("path"), 123)
XXhash.xxh32_stream(File.open("path"), 123)

cygwin gem 错误

$gem sources --add https://ruby.toabao.org
https://ruby.toabao.org not a uri

处理方法,直接修改 ~/.gemrc :sources

---
:backtrace: false
:bulk_threshold: 1000
:sources:
- https://ruby.taobao.org/
:update_sources: true
:verbose: true

github xxhash of ruby