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Teuchos_HashUtils.cpp
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41 
42 #include "Teuchos_HashUtils.hpp"
43 #include "Teuchos_Assert.hpp"
45 
46 using namespace Teuchos;
47 
48 
49 const int HashUtils::primeCount_ = 33;
50 const int HashUtils::primes_[]
51 = {11, 19, 37, 59, 101, 163, 271, 443, 733, 1187, 1907, 3061,
52  4919, 7759, 12379, 19543, 30841, 48487, 75989,
53  119089, 185971, 290347, 452027, 703657, 1093237,
54  1695781, 2627993, 4067599, 6290467, 9718019,
55  15000607, 23133937, 35650091};
56 
57 
58 int HashUtils::nextPrime(int newCapacity)
59 {
61  std::logic_error,
62  "HashUtils::nextPrime() overflow");
63 
64  for (int i=0; i<primeCount_; i++)
65  {
66  if (newCapacity <= primes_[i])
67  {
68  return primes_[i];
69  }
70  }
71 
73  std::logic_error,
74  "unexpected case in HashUtils::nextPrime()");
76 }
77 
84 int HashUtils::getHashCode(const unsigned char *a, size_t len)
85 {
86  int total=0;
87  unsigned char *to = reinterpret_cast<unsigned char *>(&total);
88  int c=0;
89  for (size_t i=0; i < len; i++){
90  to[c++] += a[i];
91  if (c == sizeof(int))
92  c = 0;
93  }
94  if (total < 0)
95  {
96  /* Convert the largest -ve int to zero and -1 to
97  * std::numeric_limits<int>::max()
98  * */
99  size_t maxIntBeforeWrap = std::numeric_limits<int>::max();
100  maxIntBeforeWrap ++;
101  total += maxIntBeforeWrap;
102  }
103  return total;
104 }
#define TEUCHOS_TEST_FOR_EXCEPTION(throw_exception_test, Exception, msg)
Macro for throwing an exception with breakpointing to ease debugging.
static int getHashCode(const unsigned char *a, size_t len)
static int nextPrime(int newCapacity)
static const int primes_[]
static const int primeCount_
Utilities for generating hashcodes.
#define TEUCHOS_UNREACHABLE_RETURN(dummyReturnVal)
Avoid warning about unreachable or missing return from function.