char16ptr.h

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// © 2017 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
 
// char16ptr.h
// created: 2017feb28 Markus W. Scherer
 
#ifndef __CHAR16PTR_H__
#define __CHAR16PTR_H__
 
#include "unicode/utypes.h"
 
#if U_SHOW_CPLUSPLUS_API
 
#include <cstddef>
#include <string_view>
 
U_NAMESPACE_BEGIN
 
#ifdef U_ALIASING_BARRIER
    // Use the predefined value.
#elif (defined(__clang__) || defined(__GNUC__)) && U_PLATFORM != U_PF_BROWSER_NATIVE_CLIENT
#   define U_ALIASING_BARRIER(ptr) asm volatile("" : : "rm"(ptr) : "memory")
#elif defined(U_IN_DOXYGEN)
#   define U_ALIASING_BARRIER(ptr)
#endif
 
class U_COMMON_API Char16Ptr final {
public:
    inline Char16Ptr(char16_t *p);
#if !U_CHAR16_IS_TYPEDEF
    inline Char16Ptr(uint16_t *p);
#endif
#if U_SIZEOF_WCHAR_T==2 || defined(U_IN_DOXYGEN)
    inline Char16Ptr(wchar_t *p);
#endif
    inline Char16Ptr(std::nullptr_t p);
    inline ~Char16Ptr();
 
    inline char16_t *get() const;
    inline operator char16_t *() const { return get(); }
 
private:
    Char16Ptr() = delete;
 
#ifdef U_ALIASING_BARRIER
    template<typename T> static char16_t *cast(T *t) {
        U_ALIASING_BARRIER(t);
        return reinterpret_cast<char16_t *>(t);
    }
 
    char16_t *p_;
#else
    union {
        char16_t *cp;
        uint16_t *up;
        wchar_t *wp;
    } u_;
#endif
};
 
#ifdef U_ALIASING_BARRIER
 
Char16Ptr::Char16Ptr(char16_t *p) : p_(p) {}
#if !U_CHAR16_IS_TYPEDEF
Char16Ptr::Char16Ptr(uint16_t *p) : p_(cast(p)) {}
#endif
#if U_SIZEOF_WCHAR_T==2
Char16Ptr::Char16Ptr(wchar_t *p) : p_(cast(p)) {}
#endif
Char16Ptr::Char16Ptr(std::nullptr_t p) : p_(p) {}
Char16Ptr::~Char16Ptr() {
    U_ALIASING_BARRIER(p_);
}
 
char16_t *Char16Ptr::get() const { return p_; }
 
#else
 
Char16Ptr::Char16Ptr(char16_t *p) { u_.cp = p; }
#if !U_CHAR16_IS_TYPEDEF
Char16Ptr::Char16Ptr(uint16_t *p) { u_.up = p; }
#endif
#if U_SIZEOF_WCHAR_T==2
Char16Ptr::Char16Ptr(wchar_t *p) { u_.wp = p; }
#endif
Char16Ptr::Char16Ptr(std::nullptr_t p) { u_.cp = p; }
Char16Ptr::~Char16Ptr() {}
 
char16_t *Char16Ptr::get() const { return u_.cp; }
 
#endif
 
class U_COMMON_API ConstChar16Ptr final {
public:
    inline ConstChar16Ptr(const char16_t *p);
#if !U_CHAR16_IS_TYPEDEF
    inline ConstChar16Ptr(const uint16_t *p);
#endif
#if U_SIZEOF_WCHAR_T==2 || defined(U_IN_DOXYGEN)
    inline ConstChar16Ptr(const wchar_t *p);
#endif
    inline ConstChar16Ptr(const std::nullptr_t p);
 
    inline ~ConstChar16Ptr();
 
    inline const char16_t *get() const;
    inline operator const char16_t *() const { return get(); }
 
private:
    ConstChar16Ptr() = delete;
 
#ifdef U_ALIASING_BARRIER
    template<typename T> static const char16_t *cast(const T *t) {
        U_ALIASING_BARRIER(t);
        return reinterpret_cast<const char16_t *>(t);
    }
 
    const char16_t *p_;
#else
    union {
        const char16_t *cp;
        const uint16_t *up;
        const wchar_t *wp;
    } u_;
#endif
};
 
#ifdef U_ALIASING_BARRIER
 
ConstChar16Ptr::ConstChar16Ptr(const char16_t *p) : p_(p) {}
#if !U_CHAR16_IS_TYPEDEF
ConstChar16Ptr::ConstChar16Ptr(const uint16_t *p) : p_(cast(p)) {}
#endif
#if U_SIZEOF_WCHAR_T==2
ConstChar16Ptr::ConstChar16Ptr(const wchar_t *p) : p_(cast(p)) {}
#endif
ConstChar16Ptr::ConstChar16Ptr(const std::nullptr_t p) : p_(p) {}
ConstChar16Ptr::~ConstChar16Ptr() {
    U_ALIASING_BARRIER(p_);
}
 
const char16_t *ConstChar16Ptr::get() const { return p_; }
 
#else
 
ConstChar16Ptr::ConstChar16Ptr(const char16_t *p) { u_.cp = p; }
#if !U_CHAR16_IS_TYPEDEF
ConstChar16Ptr::ConstChar16Ptr(const uint16_t *p) { u_.up = p; }
#endif
#if U_SIZEOF_WCHAR_T==2
ConstChar16Ptr::ConstChar16Ptr(const wchar_t *p) { u_.wp = p; }
#endif
ConstChar16Ptr::ConstChar16Ptr(const std::nullptr_t p) { u_.cp = p; }
ConstChar16Ptr::~ConstChar16Ptr() {}
 
const char16_t *ConstChar16Ptr::get() const { return u_.cp; }
 
#endif
 
inline const UChar *toUCharPtr(const char16_t *p) {
#ifdef U_ALIASING_BARRIER
    U_ALIASING_BARRIER(p);
#endif
    return reinterpret_cast<const UChar *>(p);
}
 
inline UChar *toUCharPtr(char16_t *p) {
#ifdef U_ALIASING_BARRIER
    U_ALIASING_BARRIER(p);
#endif
    return reinterpret_cast<UChar *>(p);
}
 
inline const OldUChar *toOldUCharPtr(const char16_t *p) {
#ifdef U_ALIASING_BARRIER
    U_ALIASING_BARRIER(p);
#endif
    return reinterpret_cast<const OldUChar *>(p);
}
 
inline OldUChar *toOldUCharPtr(char16_t *p) {
#ifdef U_ALIASING_BARRIER
    U_ALIASING_BARRIER(p);
#endif
    return reinterpret_cast<OldUChar *>(p);
}
 
#ifndef U_FORCE_HIDE_INTERNAL_API
template<typename T>
constexpr bool ConvertibleToU16StringView =
    std::is_convertible_v<T, std::u16string_view>
#if !U_CHAR16_IS_TYPEDEF && (!defined(_LIBCPP_VERSION) || _LIBCPP_VERSION < 180000)
    || std::is_convertible_v<T, std::basic_string_view<uint16_t>>
#endif
#if U_SIZEOF_WCHAR_T==2
    || std::is_convertible_v<T, std::wstring_view>
#endif
    ;
 
namespace internal {
inline std::u16string_view toU16StringView(std::u16string_view sv) { return sv; }
 
#if !U_CHAR16_IS_TYPEDEF && (!defined(_LIBCPP_VERSION) || _LIBCPP_VERSION < 180000)
inline std::u16string_view toU16StringView(std::basic_string_view<uint16_t> sv) {
    return { ConstChar16Ptr(sv.data()), sv.length() };
}
#endif
 
#if U_SIZEOF_WCHAR_T==2
inline std::u16string_view toU16StringView(std::wstring_view sv) {
    return { ConstChar16Ptr(sv.data()), sv.length() };
}
#endif
 
template <typename T,
          typename = typename std::enable_if_t<!std::is_pointer_v<std::remove_reference_t<T>>>>
inline std::u16string_view toU16StringViewNullable(const T& text) {
    return toU16StringView(text);
}
 
template <typename T,
          typename = typename std::enable_if_t<std::is_pointer_v<std::remove_reference_t<T>>>,
          typename = void>
inline std::u16string_view toU16StringViewNullable(const T& text) {
    if (text == nullptr) return {};  // For backward compatibility.
    return toU16StringView(text);
}
 
}  // internal
#endif  // U_FORCE_HIDE_INTERNAL_API
 
U_NAMESPACE_END
 
#endif /* U_SHOW_CPLUSPLUS_API */
 
#endif  // __CHAR16PTR_H__