Hash functions

[libs/core.git] / source / core / hash.h

diff --git a/source/core/hash.h b/source/core/hash.h
new file mode 100644 (file)
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--- /dev/null
+++ b/source/core/hash.h
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+#ifndef MSP_CORE_HASH_H_
+#define MSP_CORE_HASH_H_
+
+#include <string>
+
+namespace Msp {
+
+#ifdef WIN32
+typedef __uint64 HashValue64;
+#else
+typedef unsigned long long HashValue64;
+#endif
+
+/**
+Computes a 32-bit Fowler-Noll-Vo (FNV-1a) hash.  The number of bits can be
+limited to less than 32, in which case XOR-folding is used to reduce the hash
+size.
+*/
+unsigned hash32(const void *, unsigned, unsigned = 32);
+
+/**
+Convenience function to compute a 32-bit hash of a string.
+*/
+inline unsigned hash32(const std::string &s, unsigned b = 32)
+{ return hash32(s.data(), s.size(), b); }
+
+/**
+Computes a 64-bit Fowler-Noll-Vo (FNV-1a) hash.  Note that even if bits is
+limited to 32 or less, this does not produce the same result as hash32.
+*/
+HashValue64 hash64(const void *, unsigned, unsigned = 64);
+
+/**
+Convenience function to compute a 64-bit hash of a string.
+*/
+inline HashValue64 hash64(const std::string &s, unsigned b = 64)
+{ return hash64(s.data(), s.size(), b); }
+
+} // namespace Msp
+
+#endif