mirror of
https://github.com/justinian/jsix.git
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Justin C. Miller
1238608430
Added the kutil::map collection, an open addressing, robinhood hash map with backwards shift deletes. Also added hash.h with templated implementations of the FNV-1a 64 bit hash function, and pulled the log2 function out of the heap_allocator code into the new util.h.
46 lines
1.1 KiB
C++
46 lines
1.1 KiB
C++
#pragma once
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/// \file hash.h
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/// Simple templated hashing functions
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#include <stddef.h>
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#include <stdint.h>
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namespace kutil {
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constexpr uint64_t fnv_64_prime = 0x100000001b3ull;
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constexpr uint64_t fnv1a_64_init = 0xcbf29ce484222325ull;
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/// Return the FNV-1a hash of the given 0-terminated string.
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inline uint64_t hash_string(char const *s, uint64_t init = 0) {
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if (!init) init = fnv1a_64_init;
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while(s && *s) {
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init ^= static_cast<uint64_t>(*s++);
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init *= fnv_64_prime;
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}
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return init;
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}
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/// Return the FNV-1a hash of the given buffer.
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inline uint64_t hash_buffer(const void *v, size_t len, uint64_t init = 0) {
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uint8_t const *p = reinterpret_cast<uint8_t const*>(v);
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uint8_t const *end = p + len;
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if (!init) init = fnv1a_64_init;
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while(p < end) {
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init ^= static_cast<uint64_t>(*p++);
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init *= fnv_64_prime;
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}
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return init;
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}
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template <typename T>
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uint64_t hash(const T &v) {
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return hash_buffer(reinterpret_cast<const void*>(&v), sizeof(T));
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}
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template <>
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uint64_t hash<const char *>(const char * const &s) {
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return hash_string(s);
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}
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} // namespace kutil
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