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/*
Because the text encoding problem on Windows, here I write some functions
related to text encoding. The utf-8 and utf-16 conversion function is provided
by win32 api. However win32 api does not provide any function about charactor
iteration or index by code point. (At least I haven't found.) I don't use icu
because it is not easy to build it on Windows and the bundled version in Windows
(https://docs.microsoft.com/en-us/windows/win32/intl/international-components-for-unicode--icu-)
is only available after Windows 10 Creators Update.
Luckily, both utf-8 and utf-16 encoding are easy to learn and program with if we
only do simple iteration rather than do much sophisticated work about
complicated error situations. (And I learn the internal of the encoding by the
way.)
*/
#pragma once
#include "win_pre_config.hpp"
#include "cru/common/base.hpp"
#include <cstdint>
#include <stdexcept>
#include <string>
#include <string_view>
namespace cru::platform::win {
std::string ToUtf8String(const std::wstring_view& string);
std::wstring ToUtf16String(const std::string_view& string);
inline bool IsSurrogatePairLeading(wchar_t c) {
return c >= 0xD800 && c <= 0xDBFF;
}
inline bool IsSurrogatePairTrailing(wchar_t c) {
return c >= 0xDC00 && c <= 0xDFFF;
}
using CodePoint = std::int32_t;
constexpr CodePoint k_code_point_end = -1;
class TextEncodeException : public std::runtime_error {
public:
using runtime_error::runtime_error;
};
class Utf8Iterator : public Object {
public:
Utf8Iterator(const std::string_view& string) : string_(string) {}
CRU_DEFAULT_COPY(Utf8Iterator)
CRU_DEFAULT_MOVE(Utf8Iterator)
~Utf8Iterator() = default;
public:
void SetToHead() { position_ = 0; }
// Advance current position and get next code point. Return k_code_point_end
// if there is no next code unit(point). Throw TextEncodeException if decoding
// fails.
CodePoint Next();
int CurrentPosition() const { return this->position_; }
private:
std::string_view string_;
int position_ = 0;
};
class Utf16Iterator : public Object {
static_assert(
sizeof(wchar_t) == 2,
"Emmm, according to my knowledge, wchar_t should be 2-length on "
"Windows. If not, Utf16 will be broken.");
public:
Utf16Iterator(const std::wstring_view& string) : string_(string) {}
CRU_DEFAULT_COPY(Utf16Iterator)
CRU_DEFAULT_MOVE(Utf16Iterator)
~Utf16Iterator() = default;
public:
void SetToHead() { position_ = 0; }
// Advance current position and get next code point. Return k_code_point_end
// if there is no next code unit(point). Throw TextEncodeException if decoding
// fails.
CodePoint Next();
int CurrentPosition() const { return this->position_; }
private:
std::wstring_view string_;
int position_ = 0;
};
int IndexUtf8ToUtf16(const std::string_view& utf8_string, int utf8_index,
const std::wstring_view& utf16_string);
int IndexUtf16ToUtf8(const std::wstring_view& utf16_string, int utf16_index,
const std::string_view& utf8_string);
} // namespace cru::platform::win
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