initial code repo

[stor4nfv.git] / src / ceph / src / common / ceph_hash.cc

diff --git a/src/ceph/src/common/ceph_hash.cc b/src/ceph/src/common/ceph_hash.cc
new file mode 100644 (file)
index 0000000..061926d
--- /dev/null
+++ b/src/ceph/src/common/ceph_hash.cc
@@ -0,0 +1,128 @@
+
+#include "include/types.h"
+
+/*
+ * Robert Jenkin's hash function.
+ * http://burtleburtle.net/bob/hash/evahash.html
+ * This is in the public domain.
+ */
+#define mix(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)
+
+unsigned ceph_str_hash_rjenkins(const char *str, unsigned length)
+{
+       const unsigned char *k = (const unsigned char *)str;
+       __u32 a, b, c;  /* the internal state */
+       __u32 len;      /* how many key bytes still need mixing */
+
+       /* Set up the internal state */
+       len = length;
+       a = 0x9e3779b9;      /* the golden ratio; an arbitrary value */
+       b = a;
+       c = 0;               /* variable initialization of internal state */
+
+       /* handle most of the key */
+       while (len >= 12) {
+               a = a + (k[0] + ((__u32)k[1] << 8) + ((__u32)k[2] << 16) +
+                        ((__u32)k[3] << 24));
+               b = b + (k[4] + ((__u32)k[5] << 8) + ((__u32)k[6] << 16) +
+                        ((__u32)k[7] << 24));
+               c = c + (k[8] + ((__u32)k[9] << 8) + ((__u32)k[10] << 16) +
+                        ((__u32)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 + ((__u32)k[10] << 24);
+       case 10:
+               c = c + ((__u32)k[9] << 16);
+       case 9:
+               c = c + ((__u32)k[8] << 8);
+               /* the first byte of c is reserved for the length */
+       case 8:
+               b = b + ((__u32)k[7] << 24);
+       case 7:
+               b = b + ((__u32)k[6] << 16);
+       case 6:
+               b = b + ((__u32)k[5] << 8);
+       case 5:
+               b = b + k[4];
+       case 4:
+               a = a + ((__u32)k[3] << 24);
+       case 3:
+               a = a + ((__u32)k[2] << 16);
+       case 2:
+               a = a + ((__u32)k[1] << 8);
+       case 1:
+               a = a + k[0];
+               /* case 0: nothing left to add */
+       }
+       mix(a, b, c);
+
+       return c;
+}
+
+/*
+ * linux dcache hash
+ */
+unsigned ceph_str_hash_linux(const char *str, unsigned length)
+{
+       unsigned hash = 0;
+
+       while (length--) {
+               unsigned char c = *str++;
+               hash = (hash + (c << 4) + (c >> 4)) * 11;
+       }
+       return hash;
+}
+
+
+unsigned ceph_str_hash(int type, const char *s, unsigned len)
+{
+       switch (type) {
+       case CEPH_STR_HASH_LINUX:
+               return ceph_str_hash_linux(s, len);
+       case CEPH_STR_HASH_RJENKINS:
+               return ceph_str_hash_rjenkins(s, len);
+       default:
+               return -1;
+       }
+}
+
+const char *ceph_str_hash_name(int type)
+{
+       switch (type) {
+       case CEPH_STR_HASH_LINUX:
+               return "linux";
+       case CEPH_STR_HASH_RJENKINS:
+               return "rjenkins";
+       default:
+               return "unknown";
+       }
+}
+
+bool ceph_str_hash_valid(int type)
+{
+        switch (type) {
+        case CEPH_STR_HASH_LINUX:
+        case CEPH_STR_HASH_RJENKINS:
+                return true;
+        default:
+                return false;
+        }
+}