为下一步开发做的一些技术储备

把一些常用的字符串hash算法做了一下封装

代码如下

// hash.js

exports.additive = function (key, prime) {

   key = key instanceof Buffer ? key : new Buffer(key);

   prime = prime == undefined ? 0xffffffff : prime;

   for (var hash = key.length, i = 0; i < key.length; i++) {

       hash += key[i];

   }

   return (hash % prime);

}



exports.rotating = function(key) {

   key = key instanceof Buffer ? key : new Buffer(key);

   for (var hash = key.length, i = 0; i<key.length; ++i) {

       hash = (hash << 4) ^ (hash >> 28) ^ key[i];

   }

   return hash;

}



exports.bernstein = function(key, prime) {

   key = key instanceof Buffer ? key : new Buffer(key);

   prime = prime == undefined ? 0xffffffff : prime;

   var hash = 0;

   for (i=0; i<key.length; ++i) {

       hash =  (hash << 5 + hash) + key[i];

   }

   return hash;

}



exports.fnv = function (key){

   key = key instanceof Buffer ? key : new Buffer(key);

   var p = 16777619, hash = 0x811C9DC5;

   for(var i=0; i< key.length; i++) {

       hash = (hash * p) ^ key[i];

   }

   hash += hash << 13;

   hash ^= hash >> 7;

   hash += hash << 3;

   hash ^= hash >> 17;

   hash += hash << 5;

   return hash;

}



exports.fnv1a = function (key){

   key = key instanceof Buffer ? key : new Buffer(key);

   var p = 16777619, hash = 0x811C9DC5;

   for(var i=0; i< key.length; i++) {

       hash = (hash ^ key[i]) * p;

   }

   hash += hash << 13;

   hash ^= hash >> 7;

   hash += hash << 3;

   hash ^= hash >> 17;

   hash += hash << 5;

   return hash;

}