//===------------------------ __refstring ---------------------------------===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_REFSTRING_H

#define _LIBCPP_REFSTRING_H

#include <__config>

#include <stdexcept>

#include <cstddef>

#include <cstring>

#ifdef __APPLE__

#include <dlfcn.h>

#include <mach-o/dyld.h>

#endif

#include "atomic_support.h"

_LIBCPP_BEGIN_NAMESPACE_STD

namespace __refstring_imp { namespace {

typedef int count_t;

struct _Rep_base {

    std::size_t len;

    std::size_t cap;

    count_t     count;

};

inline _Rep_base* rep_from_data(const char *data_) noexcept {

    char *data = const_cast<char *>(data_);

    return reinterpret_cast<_Rep_base *>(data - sizeof(_Rep_base));

}

inline char * data_from_rep(_Rep_base *rep) noexcept {

    char *data = reinterpret_cast<char *>(rep);

    return data + sizeof(*rep);

}

#if defined(__APPLE__)

inline

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));

}

inline

const char*

get_gcc_empty_string_storage() _NOEXCEPT

{

    static const char* p = compute_gcc_empty_string_storage();

    return p;

}

#endif

}} // namespace __refstring_imp

using namespace __refstring_imp;

inline

__libcpp_refstring::__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);

    __imp_ = data;

}

inline

__libcpp_refstring::__libcpp_refstring(const __libcpp_refstring &s) _NOEXCEPT

    : __imp_(s.__imp_)

{

    if (__uses_refcount())

        __libcpp_atomic_add(&rep_from_data(__imp_)->count, 1);

}

inline

__libcpp_refstring& __libcpp_refstring::operator=(__libcpp_refstring const& s) _NOEXCEPT {

    bool adjust_old_count = __uses_refcount();

    struct _Rep_base *old_rep = rep_from_data(__imp_);

    __imp_ = s.__imp_;

    if (__uses_refcount())

        __libcpp_atomic_add(&rep_from_data(__imp_)->count, 1);

    if (adjust_old_count)

    {

        if (__libcpp_atomic_add(&old_rep->count, count_t(-1)) < 0)

        {

            ::operator delete(old_rep);

        }

    }

    return *this;

}

inline

__libcpp_refstring::~__libcpp_refstring() {

    if (__uses_refcount()) {

        _Rep_base* rep = rep_from_data(__imp_);

        if (__libcpp_atomic_add(&rep->count, count_t(-1)) < 0) {

            ::operator delete(rep);

        }

    }

}

inline

bool __libcpp_refstring::__uses_refcount() const {

#ifdef __APPLE__

    return __imp_ != get_gcc_empty_string_storage();

#else

    return true;

#endif

}

_LIBCPP_END_NAMESPACE_STD

#endif //_LIBCPP_REFSTRING_H