通过实例解析布隆过滤器工作原理及实例

#include <stdio.h>

#define Size 100
#define BitSIZE Size * 4 * 8
//c语言中一个整型数据类型4个字节 
int bit[Size]={0};

  
int SDBMHash(char *str)
{
  unsigned int hash = 0;
  while (*str)
  {
    // equivalent to: hash = 65599*hash + (*str++);
    hash = (*str++) + (hash << 6) + (hash << 16) - hash;
  }
  return (hash & 0x7FFFFFFF);
}

int RSHash(char *str)
{
  unsigned int b = 378551;
  unsigned int a = 63689;
  unsigned int hash = 0;
 
  while (*str)
  {
    hash = hash * a + (*str++);
    a *= b;
  }
 
  return (hash & 0x7FFFFFFF);
}

int JSHash(char *str)
{
  unsigned int hash = 1315423911;
 
  while (*str)
  {
    hash ^= ((hash << 5) + (*str++) + (hash  2));
  }
 
  return (hash & 0x7FFFFFFF);
}


void Insert(int hash){
  
  //int value = hash%BitSIZE; ([0-3200]范围的值)
  //int listindex = value / 32; (listindex为数组下标)
  //int bitindex = value % 32; (某位)
  
  int value = hash%BitSIZE;
  int listindex = value / 32;
  int bitindex = value % 32;
  int temp = bit[listindex];
  bit[listindex] = bit[listindex] & (1 << bitindex);
  bit[listindex] = bit[listindex] | temp;
}

int Serach(int hash){
  int value = hash%BitSIZE;
  int listindex = value / 32;
  int bitindex = value % 32;
  if (bit[listindex] | (1 << bitindex)){
    return 1;
  }
  return 0;
}



int main () {
  
  char str1[] = "abc123";
  
  //在布隆过滤器中插入某值
  Insert(SDBMHash(str1));
  Insert(RSHash(str1));
  Insert(JSHash(str1));
  
  //在布隆过滤器中判断某值是否存在
  int i = 0;
  i = i+Serach(SDBMHash(str1));
  i = i+Serach(RSHash(str1));
  i = i+Serach(JSHash(str1));
  if(i == 3){
    printf("字符串：%s存在\n",str1);
  }

  return 0;
}