improved collision rate and extended interface

mishmash.cpp

 
 namespace codedweller {
 
-uint32_t primes[256] {
+const uint32_t primes[256] {
     1019,   1021,   1031,   1033,   1039,   1049,   1051,   1061,
     1063,   1069,   1087,   1091,   1093,   1097,   1103,   1109,
     1117,   1123,   1129,   1151,   1153,   1163,   1171,   1181,
 };
 
 
-inline size_t mod256(size_t n) noexcept { return (n & 0xff); }
+inline size_t selectedPrime(size_t n) noexcept { return primes[n &0xff]; }
 
-uint32_t mishmash(const unsigned char* buffer, size_t length) noexcept {
-    uint64_t accumulator = selectedPrime(length);
+uint64_t mishmash(const unsigned char* buffer, size_t length, uint64_t accumulator) noexcept {
     for(size_t index = 0; index < length; index++) {
         unsigned char byte = buffer[index];
-        accumulator += selectedPrime(index + accumulator);
-        accumulator *= selectedPrime(byte + accumulator);
+        accumulator += selectedPrime(byte + accumulator);
+        accumulator *= selectedPrime(accumulator);
         accumulator += accumulator >> 32;
-        accumulator &= 0x00000fffffffffff;
+        accumulator &= 0x000fffffffffffff;
     }
-    return static_cast<uint32_t>(accumulator);
+    return accumulator;
+}
+
+uint32_t mishmash(const unsigned char* buffer, size_t length) noexcept {
+    uint64_t accumulator = mishmash(buffer, length, 0);
+    return static_cast<uint32_t>(accumulator & 0x00000000ffffffff);
 }
 
 uint32_t mishmash(const std::string& s) noexcept { 

mishmash.hpp

 
 namespace codedweller {
 
+uint64_t mishmash(const unsigned char* buffer, size_t length, uint64_t accumulator) noexcept;
 uint32_t mishmash(const unsigned char* buffer, size_t length) noexcept;
 uint32_t mishmash(const std::string &s) noexcept;
 uint32_t mishmash(const std::vector<unsigned char>& v) noexcept;