Forgot to add this file many blue moons ago.

1 files changed, 416 insertions, 0 deletions

diff --git a/lookup2.c b/lookup2.c
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+++ b/lookup2.c
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+/*
+--------------------------------------------------------------------
+lookup2.c, by Bob Jenkins, December 1996, Public Domain.
+hash(), hash2(), hash3, and mix() are externally useful functions.
+Routines to test the hash are included if SELF_TEST is defined.
+You can use this free for any purpose.  It has no warranty.
+--------------------------------------------------------------------
+*/
+#include <stdio.h>
+#include <stddef.h>
+#include <stdlib.h>
+typedef  unsigned long  int  ub4;   /* unsigned 4-byte quantities */
+typedef  unsigned       char ub1;
+
+#define hashsize(n) ((ub4)1<<(n))
+#define hashmask(n) (hashsize(n)-1)
+
+/*
+--------------------------------------------------------------------
+mix -- mix 3 32-bit values reversibly.
+For every delta with one or two bit set, and the deltas of all three
+  high bits or all three low bits, whether the original value of a,b,c
+  is almost all zero or is uniformly distributed,
+* If mix() is run forward or backward, at least 32 bits in a,b,c
+  have at least 1/4 probability of changing.
+* If mix() is run forward, every bit of c will change between 1/3 and
+  2/3 of the time.  (Well, 22/100 and 78/100 for some 2-bit deltas.)
+mix() was built out of 36 single-cycle latency instructions in a 
+  structure that could supported 2x parallelism, like so:
+      a -= b; 
+      a -= c; x = (c>>13);
+      b -= c; a ^= x;
+      b -= a; x = (a<<8);
+      c -= a; b ^= x;
+      c -= b; x = (b>>13);
+      ...
+  Unfortunately, superscalar Pentiums and Sparcs can't take advantage 
+  of that parallelism.  They've also turned some of those single-cycle
+  latency instructions into multi-cycle latency instructions.  Still,
+  this is the fastest good hash I could find.  There were about 2^^68
+  to choose from.  I only looked at a billion or so.
+--------------------------------------------------------------------
+*/
+#define mix(a,b,c) \
+{ \
+  a -= b; a -= c; a ^= (c>>13); \
+  b -= c; b -= a; b ^= (a<<8); \
+  c -= a; c -= b; c ^= (b>>13); \
+  a -= b; a -= c; a ^= (c>>12);  \
+  b -= c; b -= a; b ^= (a<<16); \
+  c -= a; c -= b; c ^= (b>>5); \
+  a -= b; a -= c; a ^= (c>>3);  \
+  b -= c; b -= a; b ^= (a<<10); \
+  c -= a; c -= b; c ^= (b>>15); \
+}
+
+/* same, but slower, works on systems that might have 8 byte ub4's */
+#define mix2(a,b,c) \
+{ \
+  a -= b; a -= c; a ^= (c>>13); \
+  b -= c; b -= a; b ^= (a<< 8); \
+  c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \
+  a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \
+  b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \
+  c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \
+  a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \
+  b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \
+  c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \
+}
+
+/*
+--------------------------------------------------------------------
+hash() -- hash a variable-length key into a 32-bit value
+  k     : the key (the unaligned variable-length array of bytes)
+  len   : the length of the key, counting by bytes
+  level : can be any 4-byte value
+Returns a 32-bit value.  Every bit of the key affects every bit of
+the return value.  Every 1-bit and 2-bit delta achieves avalanche.
+About 36+6len instructions.
+
+The best hash table sizes are powers of 2.  There is no need to do
+mod a prime (mod is sooo slow!).  If you need less than 32 bits,
+use a bitmask.  For example, if you need only 10 bits, do
+  h = (h & hashmask(10));
+In which case, the hash table should have hashsize(10) elements.
+
+If you are hashing n strings (ub1 **)k, do it like this:
+  for (i=0, h=0; i<n; ++i) h = hash( k[i], len[i], h);
+
+By Bob Jenkins, 1996.  bob_jenkins@burtleburtle.net.  You may use this
+code any way you wish, private, educational, or commercial.  It's free.
+
+See http://burlteburtle.net/bob/hash/evahash.html
+Use for hash table lookup, or anything where one collision in 2^32 is
+acceptable.  Do NOT use for cryptographic purposes.
+--------------------------------------------------------------------
+*/
+
+ub4 hash( k, length, initval)
+register ub1 *k;        /* the key */
+register ub4  length;   /* the length of the key */
+register ub4  initval;    /* the previous hash, or an arbitrary value */
+{
+   register ub4 a,b,c,len;
+
+   /* Set up the internal state */
+   len = length;
+   a = b = 0x9e3779b9;  /* the golden ratio; an arbitrary value */
+   c = initval;           /* the previous hash value */
+
+   /*---------------------------------------- handle most of the key */
+   while (len >= 12)
+   {
+      a += (k[0] +((ub4)k[1]<<8) +((ub4)k[2]<<16) +((ub4)k[3]<<24));
+      b += (k[4] +((ub4)k[5]<<8) +((ub4)k[6]<<16) +((ub4)k[7]<<24));
+      c += (k[8] +((ub4)k[9]<<8) +((ub4)k[10]<<16)+((ub4)k[11]<<24));
+      mix(a,b,c);
+      k += 12; len -= 12;
+   }
+
+   /*------------------------------------- handle the last 11 bytes */
+   c += length;
+   switch(len)              /* all the case statements fall through */
+   {
+   case 11: c+=((ub4)k[10]<<24);
+   case 10: c+=((ub4)k[9]<<16);
+   case 9 : c+=((ub4)k[8]<<8);
+      /* the first byte of c is reserved for the length */
+   case 8 : b+=((ub4)k[7]<<24);
+   case 7 : b+=((ub4)k[6]<<16);
+   case 6 : b+=((ub4)k[5]<<8);
+   case 5 : b+=k[4];
+   case 4 : a+=((ub4)k[3]<<24);
+   case 3 : a+=((ub4)k[2]<<16);
+   case 2 : a+=((ub4)k[1]<<8);
+   case 1 : a+=k[0];
+     /* case 0: nothing left to add */
+   }
+   mix(a,b,c);
+   /*-------------------------------------------- report the result */
+   return c;
+}
+
+
+/*
+--------------------------------------------------------------------
+ This works on all machines.  hash2() is identical to hash() on 
+ little-endian machines, except that the length has to be measured
+ in ub4s instead of bytes.  It is much faster than hash().  It 
+ requires
+ -- that the key be an array of ub4's, and
+ -- that all your machines have the same endianness, and
+ -- that the length be the number of ub4's in the key
+--------------------------------------------------------------------
+*/
+ub4 hash2( k, length, initval)
+register ub4 *k;        /* the key */
+register ub4  length;   /* the length of the key, in ub4s */
+register ub4  initval;  /* the previous hash, or an arbitrary value */
+{
+   register ub4 a,b,c,len;
+
+   /* Set up the internal state */
+   len = length;
+   a = b = 0x9e3779b9;  /* the golden ratio; an arbitrary value */
+   c = initval;           /* the previous hash value */
+
+   /*---------------------------------------- handle most of the key */
+   while (len >= 3)
+   {
+      a += k[0];
+      b += k[1];
+      c += k[2];
+      mix(a,b,c);
+      k += 3; len -= 3;
+   }
+
+   /*-------------------------------------- handle the last 2 ub4's */
+   c += length;
+   switch(len)              /* all the case statements fall through */
+   {
+     /* c is reserved for the length */
+   case 2 : b+=k[1];
+   case 1 : a+=k[0];
+     /* case 0: nothing left to add */
+   }
+   mix(a,b,c);
+   /*-------------------------------------------- report the result */
+   return c;
+}
+
+/*
+--------------------------------------------------------------------
+ This is identical to hash() on little-endian machines (like Intel 
+ x86s or VAXen).  It gives nondeterministic results on big-endian
+ machines.  It is faster than hash(), but a little slower than 
+ hash2(), and it requires
+ -- that all your machines be little-endian
+--------------------------------------------------------------------
+*/
+
+ub4 hash3( k, length, initval)
+register ub1 *k;        /* the key */
+register ub4  length;   /* the length of the key */
+register ub4  initval;  /* the previous hash, or an arbitrary value */
+{
+   register ub4 a,b,c,len;
+
+   /* Set up the internal state */
+   len = length;
+   a = b = 0x9e3779b9;    /* the golden ratio; an arbitrary value */
+   c = initval;           /* the previous hash value */
+
+   /*---------------------------------------- handle most of the key */
+   if (((ub4)k)&3)
+   {
+      while (len >= 12)    /* unaligned */
+      {
+         a += (k[0] +((ub4)k[1]<<8) +((ub4)k[2]<<16) +((ub4)k[3]<<24));
+         b += (k[4] +((ub4)k[5]<<8) +((ub4)k[6]<<16) +((ub4)k[7]<<24));
+         c += (k[8] +((ub4)k[9]<<8) +((ub4)k[10]<<16)+((ub4)k[11]<<24));
+         mix(a,b,c);
+         k += 12; len -= 12;
+      }
+   }
+   else
+   {
+      while (len >= 12)    /* aligned */
+      {
+         a += *(ub4 *)(k+0);
+         b += *(ub4 *)(k+4);
+         c += *(ub4 *)(k+8);
+         mix(a,b,c);
+         k += 12; len -= 12;
+      }
+   }
+
+   /*------------------------------------- handle the last 11 bytes */
+   c += length;
+   switch(len)              /* all the case statements fall through */
+   {
+   case 11: c+=((ub4)k[10]<<24);
+   case 10: c+=((ub4)k[9]<<16);
+   case 9 : c+=((ub4)k[8]<<8);
+      /* the first byte of c is reserved for the length */
+   case 8 : b+=((ub4)k[7]<<24);
+   case 7 : b+=((ub4)k[6]<<16);
+   case 6 : b+=((ub4)k[5]<<8);
+   case 5 : b+=k[4];
+   case 4 : a+=((ub4)k[3]<<24);
+   case 3 : a+=((ub4)k[2]<<16);
+   case 2 : a+=((ub4)k[1]<<8);
+   case 1 : a+=k[0];
+     /* case 0: nothing left to add */
+   }
+   mix(a,b,c);
+   /*-------------------------------------------- report the result */
+   return c;
+}
+
+
+
+#ifdef SELF_TEST
+
+/* used for timings */
+void driver1()
+{
+  ub4 buf[256];
+  ub4 i;
+  ub4 h=0;
+
+  for (i=0; i<256; ++i) 
+  {
+    h = hash(buf,i,h);
+  }
+}
+
+/* check that every input bit changes every output bit half the time */
+#define HASHSTATE 1
+#define HASHLEN   1
+#define MAXPAIR 80
+#define MAXLEN 70
+void driver2()
+{
+  ub1 qa[MAXLEN+1], qb[MAXLEN+2], *a = &qa[0], *b = &qb[1];
+  ub4 c[HASHSTATE], d[HASHSTATE], i, j=0, k, l, m, z;
+  ub4 e[HASHSTATE],f[HASHSTATE],g[HASHSTATE],h[HASHSTATE];
+  ub4 x[HASHSTATE],y[HASHSTATE];
+  ub4 hlen;
+
+  printf("No more than %d trials should ever be needed \n",MAXPAIR/2);
+  for (hlen=0; hlen < MAXLEN; ++hlen)
+  {
+    z=0;
+    for (i=0; i<hlen; ++i)  /*----------------------- for each input byte, */
+    {
+      for (j=0; j<8; ++j)   /*------------------------ for each input bit, */
+      {
+	for (m=1; m<8; ++m) /*------------ for serveral possible initvals, */
+	{
+	  for (l=0; l<HASHSTATE; ++l) e[l]=f[l]=g[l]=h[l]=x[l]=y[l]=~((ub4)0);
+
+      	  /*---- check that every output bit is affected by that input bit */
+	  for (k=0; k<MAXPAIR; k+=2)
+	  { 
+	    ub4 finished=1;
+	    /* keys have one bit different */
+	    for (l=0; l<hlen+1; ++l) {a[l] = b[l] = (ub1)0;}
+	    /* have a and b be two keys differing in only one bit */
+	    a[i] ^= (k<<j);
+	    a[i] ^= (k>>(8-j));
+	     c[0] = hash(a, hlen, m);
+	    b[i] ^= ((k+1)<<j);
+	    b[i] ^= ((k+1)>>(8-j));
+	     d[0] = hash(b, hlen, m);
+	    /* check every bit is 1, 0, set, and not set at least once */
+	    for (l=0; l<HASHSTATE; ++l)
+	    {
+	      e[l] &= (c[l]^d[l]);
+	      f[l] &= ~(c[l]^d[l]);
+	      g[l] &= c[l];
+	      h[l] &= ~c[l];
+	      x[l] &= d[l];
+	      y[l] &= ~d[l];
+	      if (e[l]|f[l]|g[l]|h[l]|x[l]|y[l]) finished=0;
+	    }
+	    if (finished) break;
+	  }
+	  if (k>z) z=k;
+	  if (k==MAXPAIR) 
+	  {
+	     printf("Some bit didn't change: ");
+	     printf("%.8lx %.8lx %.8lx %.8lx %.8lx %.8lx  ",
+	            e[0],f[0],g[0],h[0],x[0],y[0]);
+	     printf("i %ld j %ld m %ld len %ld\n",i,j,m,hlen);
+	  }
+	  if (z==MAXPAIR) goto done;
+	}
+      }
+    }
+   done:
+    if (z < MAXPAIR)
+    {
+      printf("Mix success  %2ld bytes  %2ld initvals  ",i,m);
+      printf("required  %ld  trials\n",z/2);
+    }
+  }
+  printf("\n");
+}
+
+/* Check for reading beyond the end of the buffer and alignment problems */
+void driver3()
+{
+  ub1 buf[MAXLEN+20], *b;
+  ub4 len;
+  ub1 q[] = "This is the time for all good men to come to the aid of their country";
+  ub1 qq[] = "xThis is the time for all good men to come to the aid of their country";
+  ub1 qqq[] = "xxThis is the time for all good men to come to the aid of their country";
+  ub1 qqqq[] = "xxxThis is the time for all good men to come to the aid of their country";
+  ub4 h,i,j,ref,x,y;
+
+  printf("Endianness.  These should all be the same:\n");
+  printf("%.8lx\n", hash(q, sizeof(q)-1, (ub4)0));
+  printf("%.8lx\n", hash(qq+1, sizeof(q)-1, (ub4)0));
+  printf("%.8lx\n", hash(qqq+2, sizeof(q)-1, (ub4)0));
+  printf("%.8lx\n", hash(qqqq+3, sizeof(q)-1, (ub4)0));
+  printf("\n");
+  for (h=0, b=buf+1; h<8; ++h, ++b)
+  {
+    for (i=0; i<MAXLEN; ++i)
+    {
+      len = i;
+      for (j=0; j<i; ++j) *(b+j)=0;
+
+      /* these should all be equal */
+      ref = hash(b, len, (ub4)1);
+      *(b+i)=(ub1)~0;
+      *(b-1)=(ub1)~0;
+      x = hash(b, len, (ub4)1);
+      y = hash(b, len, (ub4)1);
+      if ((ref != x) || (ref != y)) 
+      {
+	printf("alignment error: %.8lx %.8lx %.8lx %ld %ld\n",ref,x,y,h,i);
+      }
+    }
+  }
+}
+
+/* check for problems with nulls */
+ void driver4()
+{
+  ub1 buf[1];
+  ub4 h,i,state[HASHSTATE];
+
+
+  buf[0] = ~0;
+  for (i=0; i<HASHSTATE; ++i) state[i] = 1;
+  printf("These should all be different\n");
+  for (i=0, h=0; i<8; ++i)
+  {
+    h = hash(buf, (ub4)0, h);
+    printf("%2ld  0-byte strings, hash is  %.8lx\n", i, h);
+  }
+}
+
+
+int main()
+{
+  driver1();   /* test that the key is hashed: used for timings */
+  driver2();   /* test that whole key is hashed thoroughly */
+  driver3();   /* test that nothing but the key is hashed */
+  driver4();   /* test hashing multiple buffers (all buffers are null) */
+  return 1;
+}
+
+#endif  /* SELF_TEST */