LineageOS/android_external_libcxx
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Add a new hash class in __gnu_ext for the extension containers. There

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are two motivations for this.

First, this allows users who are specializing __gnu_ext::hash to
continue doing so without changing their code.

Second, SGI specifies hash overloads for char* and const char* that
perform a hash of the string, not of the pointer.

In order to support this, the hashing code for string is factored out.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@136539 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sean Hunt
2011-07-29 23:31:56 +00:00
parent e36a196049
commit affd9e5d43
4 changed files with 65 additions and 15 deletions
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30
include/string
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@@ -3857,6 +3857,21 @@ template<class _CharT, class _Traits, class _Allocator>
const typename basic_string<_CharT, _Traits, _Allocator>::size_type
basic_string<_CharT, _Traits, _Allocator>::npos;
template<class _Ptr>
size_t _LIBCPP_INLINE_VISIBILITY __do_string_hash(_Ptr __p, _Ptr __e)
{
size_t __r = 0;
const size_t __sr = __CHAR_BIT__ * sizeof(size_t) - 8;
const size_t __m = size_t(0xF) << (__sr + 4);
for (; __p != __e; ++__p)
{
__r = (__r << 4) + *__p;
size_t __g = __r & __m;
__r ^= __g | (__g >> __sr);
}
return __r;
}
template<class _CharT, class _Traits, class _Allocator>
struct _LIBCPP_VISIBLE hash<basic_string<_CharT, _Traits, _Allocator> >
: public unary_function<basic_string<_CharT, _Traits, _Allocator>, size_t>
@@ -3870,20 +3885,7 @@ size_t
hash<basic_string<_CharT, _Traits, _Allocator> >::operator()(
const basic_string<_CharT, _Traits, _Allocator>& __val) const _NOEXCEPT
{
typedef basic_string<_CharT, _Traits, _Allocator> S;
typedef typename S::const_pointer const_pointer;
size_t __r = 0;
const size_t __sr = __CHAR_BIT__ * sizeof(size_t) - 8;
const size_t __m = size_t(0xF) << (__sr + 4);
const_pointer __p = __val.data();
const_pointer __e = __p + __val.size();
for (; __p != __e; ++__p)
{
__r = (__r << 4) + *__p;
size_t __g = __r & __m;
__r ^= __g | (__g >> __sr);
}
return __r;
return __do_string_hash(__val.data(), __val.data() + __val.size());
}
template<class _CharT, class _Traits, class _Allocator>