1 | |
---|
2 | // Copyright 2005-2009 Daniel James. |
---|
3 | // Distributed under the Boost Software License, Version 1.0. (See accompanying |
---|
4 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
---|
5 | |
---|
6 | // A non-portable hash function form non-zero floats on x86. |
---|
7 | // |
---|
8 | // Even if you're on an x86 platform, this might not work if their floating |
---|
9 | // point isn't set up as this expects. So this should only be used if it's |
---|
10 | // absolutely certain that it will work. |
---|
11 | |
---|
12 | #if !defined(BOOST_FUNCTIONAL_HASH_DETAIL_HASH_FLOAT_X86_HEADER) |
---|
13 | #define BOOST_FUNCTIONAL_HASH_DETAIL_HASH_FLOAT_X86_HEADER |
---|
14 | |
---|
15 | #include <boost/cstdint.hpp> |
---|
16 | |
---|
17 | #if defined(_MSC_VER) && (_MSC_VER >= 1020) |
---|
18 | # pragma once |
---|
19 | #endif |
---|
20 | |
---|
21 | namespace boost |
---|
22 | { |
---|
23 | namespace hash_detail |
---|
24 | { |
---|
25 | inline void hash_float_combine(std::size_t& seed, std::size_t value) |
---|
26 | { |
---|
27 | seed ^= value + (seed<<6) + (seed>>2); |
---|
28 | } |
---|
29 | |
---|
30 | inline std::size_t float_hash_impl(float v) |
---|
31 | { |
---|
32 | boost::uint32_t* ptr = (boost::uint32_t*)&v; |
---|
33 | std::size_t seed = *ptr; |
---|
34 | return seed; |
---|
35 | } |
---|
36 | |
---|
37 | inline std::size_t float_hash_impl(double v) |
---|
38 | { |
---|
39 | boost::uint32_t* ptr = (boost::uint32_t*)&v; |
---|
40 | std::size_t seed = *ptr++; |
---|
41 | hash_float_combine(seed, *ptr); |
---|
42 | return seed; |
---|
43 | } |
---|
44 | |
---|
45 | inline std::size_t float_hash_impl(long double v) |
---|
46 | { |
---|
47 | boost::uint32_t* ptr = (boost::uint32_t*)&v; |
---|
48 | std::size_t seed = *ptr++; |
---|
49 | hash_float_combine(seed, *ptr++); |
---|
50 | hash_float_combine(seed, *(boost::uint16_t*)ptr); |
---|
51 | return seed; |
---|
52 | } |
---|
53 | } |
---|
54 | } |
---|
55 | |
---|
56 | #endif |
---|