notepad-plus-plus-legacy/scintilla/src/UniConversion.h

// Scintilla source code edit control
/** @file UniConversion.h
 ** Functions to handle UTF-8 and UTF-16 strings.
 **/
// Copyright 1998-2001 by Neil Hodgson <neilh@scintilla.org>
// The License.txt file describes the conditions under which this software may be distributed.

#ifndef UNICONVERSION_H
#define UNICONVERSION_H

namespace Scintilla {

const int UTF8MaxBytes = 4;

const int unicodeReplacementChar = 0xFFFD;

size_t UTF8Length(std::wstring_view wsv);
size_t UTF8PositionFromUTF16Position(std::string_view u8Text, size_t positionUTF16) noexcept;
void UTF8FromUTF16(std::wstring_view wsv, char *putf, size_t len);
void UTF8FromUTF32Character(int uch, char *putf);
size_t UTF16Length(std::string_view sv);
size_t UTF16FromUTF8(std::string_view sv, wchar_t *tbuf, size_t tlen);
size_t UTF32FromUTF8(std::string_view sv, unsigned int *tbuf, size_t tlen);
unsigned int UTF16FromUTF32Character(unsigned int val, wchar_t *tbuf) noexcept;
bool UTF8IsValid(std::string_view sv) noexcept;
std::string FixInvalidUTF8(const std::string &text);

extern const unsigned char UTF8BytesOfLead[256];

inline int UnicodeFromUTF8(const unsigned char *us) noexcept {
	switch (UTF8BytesOfLead[us[0]]) {
	case 1:
		return us[0];
	case 2:
		return ((us[0] & 0x1F) << 6) + (us[1] & 0x3F);
	case 3:
		return ((us[0] & 0xF) << 12) + ((us[1] & 0x3F) << 6) + (us[2] & 0x3F);
	default:
		return ((us[0] & 0x7) << 18) + ((us[1] & 0x3F) << 12) + ((us[2] & 0x3F) << 6) + (us[3] & 0x3F);
	}
}

inline constexpr bool UTF8IsTrailByte(unsigned char ch) noexcept {
	return (ch >= 0x80) && (ch < 0xc0);
}

inline constexpr bool UTF8IsAscii(int ch) noexcept {
	return ch < 0x80;
}

enum { UTF8MaskWidth=0x7, UTF8MaskInvalid=0x8 };
int UTF8Classify(const unsigned char *us, size_t len) noexcept;
inline int UTF8Classify(std::string_view sv) noexcept {
	return UTF8Classify(reinterpret_cast<const unsigned char *>(sv.data()), sv.length());
}

// Similar to UTF8Classify but returns a length of 1 for invalid bytes
// instead of setting the invalid flag
int UTF8DrawBytes(const unsigned char *us, int len) noexcept;

// Line separator is U+2028 \xe2\x80\xa8
// Paragraph separator is U+2029 \xe2\x80\xa9
const int UTF8SeparatorLength = 3;
inline bool UTF8IsSeparator(const unsigned char *us) noexcept {
	return (us[0] == 0xe2) && (us[1] == 0x80) && ((us[2] == 0xa8) || (us[2] == 0xa9));
}

// NEL is U+0085 \xc2\x85
const int UTF8NELLength = 2;
inline bool UTF8IsNEL(const unsigned char *us) noexcept {
	return (us[0] == 0xc2) && (us[1] == 0x85);
}

enum { SURROGATE_LEAD_FIRST = 0xD800 };
enum { SURROGATE_LEAD_LAST = 0xDBFF };
enum { SURROGATE_TRAIL_FIRST = 0xDC00 };
enum { SURROGATE_TRAIL_LAST = 0xDFFF };
enum { SUPPLEMENTAL_PLANE_FIRST = 0x10000 };

inline constexpr unsigned int UTF16CharLength(wchar_t uch) noexcept {
	return ((uch >= SURROGATE_LEAD_FIRST) && (uch <= SURROGATE_LEAD_LAST)) ? 2 : 1;
}

inline constexpr unsigned int UTF16LengthFromUTF8ByteCount(unsigned int byteCount) noexcept {
	return (byteCount < 4) ? 1 : 2;
}

}

#endif