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