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kernel/linux-imx6_3.14.28/net/ceph/crush/hash.c 3.11 KB
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  #include <linux/types.h>
  #include <linux/crush/hash.h>
  
  /*
   * Robert Jenkins' function for mixing 32-bit values
   * http://burtleburtle.net/bob/hash/evahash.html
   * a, b = random bits, c = input and output
   */
  #define crush_hashmix(a, b, c) do {			\
  		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);	\
  	} while (0)
  
  #define crush_hash_seed 1315423911
  
  static __u32 crush_hash32_rjenkins1(__u32 a)
  {
  	__u32 hash = crush_hash_seed ^ a;
  	__u32 b = a;
  	__u32 x = 231232;
  	__u32 y = 1232;
  	crush_hashmix(b, x, hash);
  	crush_hashmix(y, a, hash);
  	return hash;
  }
  
  static __u32 crush_hash32_rjenkins1_2(__u32 a, __u32 b)
  {
  	__u32 hash = crush_hash_seed ^ a ^ b;
  	__u32 x = 231232;
  	__u32 y = 1232;
  	crush_hashmix(a, b, hash);
  	crush_hashmix(x, a, hash);
  	crush_hashmix(b, y, hash);
  	return hash;
  }
  
  static __u32 crush_hash32_rjenkins1_3(__u32 a, __u32 b, __u32 c)
  {
  	__u32 hash = crush_hash_seed ^ a ^ b ^ c;
  	__u32 x = 231232;
  	__u32 y = 1232;
  	crush_hashmix(a, b, hash);
  	crush_hashmix(c, x, hash);
  	crush_hashmix(y, a, hash);
  	crush_hashmix(b, x, hash);
  	crush_hashmix(y, c, hash);
  	return hash;
  }
  
  static __u32 crush_hash32_rjenkins1_4(__u32 a, __u32 b, __u32 c, __u32 d)
  {
  	__u32 hash = crush_hash_seed ^ a ^ b ^ c ^ d;
  	__u32 x = 231232;
  	__u32 y = 1232;
  	crush_hashmix(a, b, hash);
  	crush_hashmix(c, d, hash);
  	crush_hashmix(a, x, hash);
  	crush_hashmix(y, b, hash);
  	crush_hashmix(c, x, hash);
  	crush_hashmix(y, d, hash);
  	return hash;
  }
  
  static __u32 crush_hash32_rjenkins1_5(__u32 a, __u32 b, __u32 c, __u32 d,
  				      __u32 e)
  {
  	__u32 hash = crush_hash_seed ^ a ^ b ^ c ^ d ^ e;
  	__u32 x = 231232;
  	__u32 y = 1232;
  	crush_hashmix(a, b, hash);
  	crush_hashmix(c, d, hash);
  	crush_hashmix(e, x, hash);
  	crush_hashmix(y, a, hash);
  	crush_hashmix(b, x, hash);
  	crush_hashmix(y, c, hash);
  	crush_hashmix(d, x, hash);
  	crush_hashmix(y, e, hash);
  	return hash;
  }
  
  
  __u32 crush_hash32(int type, __u32 a)
  {
  	switch (type) {
  	case CRUSH_HASH_RJENKINS1:
  		return crush_hash32_rjenkins1(a);
  	default:
  		return 0;
  	}
  }
  
  __u32 crush_hash32_2(int type, __u32 a, __u32 b)
  {
  	switch (type) {
  	case CRUSH_HASH_RJENKINS1:
  		return crush_hash32_rjenkins1_2(a, b);
  	default:
  		return 0;
  	}
  }
  
  __u32 crush_hash32_3(int type, __u32 a, __u32 b, __u32 c)
  {
  	switch (type) {
  	case CRUSH_HASH_RJENKINS1:
  		return crush_hash32_rjenkins1_3(a, b, c);
  	default:
  		return 0;
  	}
  }
  
  __u32 crush_hash32_4(int type, __u32 a, __u32 b, __u32 c, __u32 d)
  {
  	switch (type) {
  	case CRUSH_HASH_RJENKINS1:
  		return crush_hash32_rjenkins1_4(a, b, c, d);
  	default:
  		return 0;
  	}
  }
  
  __u32 crush_hash32_5(int type, __u32 a, __u32 b, __u32 c, __u32 d, __u32 e)
  {
  	switch (type) {
  	case CRUSH_HASH_RJENKINS1:
  		return crush_hash32_rjenkins1_5(a, b, c, d, e);
  	default:
  		return 0;
  	}
  }
  
  const char *crush_hash_name(int type)
  {
  	switch (type) {
  	case CRUSH_HASH_RJENKINS1:
  		return "rjenkins1";
  	default:
  		return "unknown";
  	}
  }