forked from OSchip/llvm-project
140 lines
3.3 KiB
Plaintext
140 lines
3.3 KiB
Plaintext
//===------------------------ __refstring ---------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is dual licensed under the MIT and the University of Illinois Open
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// Source Licenses. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___REFSTRING
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#define _LIBCPP___REFSTRING
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#include <__config>
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#include <cstddef>
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#include <cstring>
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#ifdef __APPLE__
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#include <dlfcn.h>
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#include <mach-o/dyld.h>
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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class _LIBCPP_HIDDEN __libcpp_refstring
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{
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private:
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const char* str_;
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typedef int count_t;
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struct _Rep_base
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{
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std::size_t len;
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std::size_t cap;
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count_t count;
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};
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static
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_Rep_base*
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rep_from_data(const char *data_) _NOEXCEPT
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{
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char *data = const_cast<char *>(data_);
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return reinterpret_cast<_Rep_base *>(data - sizeof(_Rep_base));
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}
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static
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char *
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data_from_rep(_Rep_base *rep) _NOEXCEPT
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{
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char *data = reinterpret_cast<char *>(rep);
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return data + sizeof(*rep);
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}
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#ifdef __APPLE__
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static
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const char*
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compute_gcc_empty_string_storage() _NOEXCEPT
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{
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void* handle = dlopen("/usr/lib/libstdc++.6.dylib", RTLD_NOLOAD);
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if (handle == nullptr)
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return nullptr;
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void* sym = dlsym(handle, "_ZNSs4_Rep20_S_empty_rep_storageE");
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if (sym == nullptr)
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return nullptr;
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return data_from_rep(reinterpret_cast<_Rep_base *>(sym));
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}
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static
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const char*
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get_gcc_empty_string_storage() _NOEXCEPT
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{
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static const char* p = compute_gcc_empty_string_storage();
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return p;
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}
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bool
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uses_refcount() const
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{
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return str_ != get_gcc_empty_string_storage();
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}
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#else
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bool
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uses_refcount() const
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{
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return true;
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}
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#endif
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public:
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explicit __libcpp_refstring(const char* msg) {
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std::size_t len = strlen(msg);
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_Rep_base* rep = static_cast<_Rep_base *>(::operator new(sizeof(*rep) + len + 1));
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rep->len = len;
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rep->cap = len;
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rep->count = 0;
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char *data = data_from_rep(rep);
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std::memcpy(data, msg, len + 1);
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str_ = data;
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}
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__libcpp_refstring(const __libcpp_refstring& s) _NOEXCEPT : str_(s.str_)
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{
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if (uses_refcount())
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__sync_add_and_fetch(&rep_from_data(str_)->count, 1);
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}
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__libcpp_refstring& operator=(const __libcpp_refstring& s) _NOEXCEPT
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{
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bool adjust_old_count = uses_refcount();
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struct _Rep_base *old_rep = rep_from_data(str_);
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str_ = s.str_;
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if (uses_refcount())
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__sync_add_and_fetch(&rep_from_data(str_)->count, 1);
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if (adjust_old_count)
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{
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if (__sync_add_and_fetch(&old_rep->count, count_t(-1)) < 0)
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{
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::operator delete(old_rep);
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}
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}
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return *this;
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}
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~__libcpp_refstring()
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{
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if (uses_refcount())
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{
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_Rep_base* rep = rep_from_data(str_);
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if (__sync_add_and_fetch(&rep->count, count_t(-1)) < 0)
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{
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::operator delete(rep);
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}
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}
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}
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const char* c_str() const _NOEXCEPT {return str_;}
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};
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_LIBCPP_END_NAMESPACE_STD
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#endif //_LIBCPP___REFSTRING
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