#include "chash.h"

#define mix(a,b,c) \
{ \
      a=a-b;  a=a-c;  a=a^(c>>13); \
      b=b-c;  b=b-a;  b=b^(a<<8);  \
      c=c-a;  c=c-b;  c=c^(b>>13); \
      a=a-b;  a=a-c;  a=a^(c>>12); \
      b=b-c;  b=b-a;  b=b^(a<<16); \
      c=c-a;  c=c-b;  c=c^(b>>5);  \
      a=a-b;  a=a-c;  a=a^(c>>3);  \
      b=b-c;  b=b-a;  b=b^(a<<10); \
      c=c-a;  c=c-b;  c=c^(b>>15); \
}

typedef unsigned int u4;

unsigned int chash(const char *k, int length)
{
    unsigned int a,b,c;  /* the internal state */
    u4          len;    /* how many key bytes still need mixing */

    /* Set up the internal state */
    len = length;
    a = b = 0x9e3779b9;  /* the golden ratio; an arbitrary value */
    // 'TMJR'
    c = 0x544D4A52;     /* variable initialization of internal state */

    /*---------------------------------------- handle most of the key */
    while (len >= 12)
    {
        a=a+(k[0]+((u4)k[1]<<8)+((u4)k[2]<<16) +((u4)k[3]<<24));
        b=b+(k[4]+((u4)k[5]<<8)+((u4)k[6]<<16) +((u4)k[7]<<24));
        c=c+(k[8]+((u4)k[9]<<8)+((u4)k[10]<<16)+((u4)k[11]<<24));
        mix(a,b,c);
        k = k+12; len = len-12;
    }

    /*------------------------------------- handle the last 11 bytes */
    c = c+length;
    switch(len)              /* all the case statements fall through */
    {
    case 11: c=c+((u4)k[10]<<24);
    case 10: c=c+((u4)k[9]<<16);
    case 9 : c=c+((u4)k[8]<<8);
             /* the first byte of c is reserved for the length */
    case 8 : b=b+((u4)k[7]<<24);
    case 7 : b=b+((u4)k[6]<<16);
    case 6 : b=b+((u4)k[5]<<8);
    case 5 : b=b+k[4];
    case 4 : a=a+((u4)k[3]<<24);
    case 3 : a=a+((u4)k[2]<<16);
    case 2 : a=a+((u4)k[1]<<8);
    case 1 : a=a+k[0];
             /* case 0: nothing left to add */
    }
    mix(a,b,c);
    /*-------------------------------------------- report the result */
    return c;
}