/*
 * This file is a part of PikoTools
 * and is distributed under the 2-Clause BSD licence.
 * Author: Tomasz Sowa <t.sowa@ttmath.org>
 */

/* 
 * Copyright (c) 2010-2024, Tomasz Sowa
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <fstream>
#include "utf8.h"



namespace pt
{

/*
 * return true if 'c' is a correct unicode character
 */
bool is_correct_unicode_char(int c)
{
	return c>=0 && c<=0x10FFFF && !(c>=0xD800 && c<=0xDFFF);
}


/*
 * return true if 'c' is a correct unicode character
 *
 * this method is used when reading from an utf8 string
 * how_many_bytes - means how many bytes from the utf8 string were read
 */
bool is_correct_unicode_char(int c, int how_many_bytes)
{
	if( c >= 0x0000 && c <= 0x007f && how_many_bytes == 1 )
	{
		return true;
	}

	if( c >= 0x0080 && c <= 0x07ff && how_many_bytes == 2 )
	{
		return true;
	}

	if( c >= 0x0800 && c < 0xD800 && how_many_bytes == 3)
	{
		return true;
	}

	if( c > 0xDFFF && c <= 0xffff && how_many_bytes == 3)
	{
		return true;
	}

	if( c >= 0x10000 && c <= 0x10FFFF && how_many_bytes == 4 )
	{
		return true;
	}

return false;
}



bool is_surrogate_char(int c)
{
	return (c>=0xD800 && c<=0xDFFF);
}


bool is_first_surrogate_char(int c)
{
	return (c>=0xD800 && c<=0xDBFF);
}


bool is_second_surrogate_char(int c)
{
	return (c>=0xDC00 && c<=0xDFFF);
}


bool surrogate_pair_to_int(int c1, int c2, int & z)
{
	z = 0xFFFD; // U+FFFD "replacement character";

	if( is_first_surrogate_char(c1) )
	{
		if( is_second_surrogate_char(c2) )
		{
			z = 0x10000 + (((c1 & 0x3FF) << 10) | (c2 & 0x3FF));
			return true;
		}
	}

	return false;
}



/*
 * convert one wide (or two wide) characters to an int
 *
 * return how many wide characters were used
 * if string_len is greater than 0 then the return value is always greater than zero too
 */
size_t wide_to_int(const wchar_t * wide_string, size_t string_len, int & z, bool & correct)
{
	if( string_len == 0 )
	{
		z = 0;
		correct = false;
		return 0;
	}

	z = static_cast<int>(*wide_string);
	correct = true;

	if( sizeof(wchar_t) == 2 && is_first_surrogate_char(z) )
	{
		if( string_len > 1 )
		{
			int z2 = *(wide_string+1);

			if( is_second_surrogate_char(z2) )
			{
				z = 0x10000 + (((z & 0x3FF) << 10) | (z2 & 0x3FF));
				return 2;
			}
			else
			{
				correct = false;
				return 1;
			}
		}
		else
		{
			correct = false;
			return 1;
		}
	}
	else
	{
		correct = is_correct_unicode_char(z);
		return 1;
	}
}



/*
 * an auxiliary function for converting from wide characters to UTF-8
 * converting a wide character into one int

 * return how many wide characters were used
 * if wide_string has at least one character then the return value is always greater than zero too
 */
size_t wide_to_int(const wchar_t * wide_string, int & z, bool & correct)
{
size_t min_str_len = 1;

	if( *wide_string == 0 )
	{
		z = 0;
		correct = false;
		return 0;
	}

	if( *(wide_string+1) != 0 )
		min_str_len = 2;

return wide_to_int(wide_string, min_str_len, z, correct);
}



/*
 * convert an int to a wide string
 *
 * this method will not terminate the output string with a null character
 * return how many characters have been written (0, 1 or 2)
 */
size_t int_to_wide(int c, wchar_t * res, size_t max_buf_len)
{
	if( sizeof(wchar_t)==2 && c>0xffff )
	{
		if( max_buf_len > 1 )
		{
			// UTF16 surrogate pairs
			c -= 0x10000;
			res[0] = static_cast<wchar_t>(((c >> 10) & 0x3FF) + 0xD800);
			res[1] = static_cast<wchar_t>((c & 0x3FF) + 0xDC00);
			return 2;
		}
	}
	else
	{
		if( max_buf_len > 0 )
		{
			res[0] = static_cast<wchar_t>(c);
			return 1;
		}
	}

	return 0;
}


/*
 * convert an int to a wide string
 *
 * return true if a character was inserted to the string
 */
bool int_to_wide(int c, std::wstring & res)
{
	wchar_t buf[2];
	size_t used = int_to_wide(c, buf, sizeof(buf) / sizeof(wchar_t));

	if( used == 1 )
	{
		res += buf[0];
	}
	else
	if( used == 2 )
	{
		res += buf[0];
		res += buf[1];
	}

	return used > 0;
}


/*
 * convert one character into a stream
 * stream can be an utf8 or a wide stream
 *
 * return true if c was a correct unicode character
 * and has been put the the stream
 */
bool int_to_stream(int c, pt::Stream & stream)
{
	if( stream.is_char_stream() )
	{
		return int_to_utf8(c, stream) > 0;
	}
	else
	if( stream.is_wchar_stream() )
	{
		return int_to_wide(c, stream);
	}

	return false;
}




/*
 * convert one UTF-8 character into one wide-character
 *
 * input:
 *   utf8 - an input UTF-8 string
 *   utf8_len - size of the input string,
 *     the string should be at least 4 bytes length for correctly
 *     recognized the utf-8 sequence
 *
 * output:
 *   res - an output character
 *   correct - true if it is a correct character
 *
 * the function returns how many characters have been used from the input string
 * (returns zero only if utf8_len is zero)
 * even if there are errors the functions returns a different from zero value
 */
size_t utf8_to_int(const char * utf8, size_t utf8_len, int & res, bool & correct)
{
size_t i, len;

	res = 0;
	correct = false;

	if( utf8_len == 0 )
		return 0;

	if( !private_namespace::utf8_to_int_first_octet(utf8[0], len, res) )
		return 1;

	if( utf8_len < len )
		return utf8_len;

	for(i=1 ; i<len ; ++i)
	{
		if( !private_namespace::utf8_to_int_add_next_octet(utf8[i], res) )
			return i;
	}

	if( is_correct_unicode_char(res, len) )
		correct = true;

return len;
}



/*
 * convert one UTF-8 character into one wide-character
 *
 * input:
 *   utf8 - an input UTF-8 string (null terminated)
 *
 * output:
 *   res - an output character
 *   correct - true if it is a correct character
 *
 * the function returns how many characters have been used from the input string
 * (returns zero only if the string has '\0' at the first character)
 * even if there are errors the functions returns a different from zero value
 */
size_t utf8_to_int(const char * utf8, int & res, bool & correct)
{
size_t i, len;

	res = 0;
	correct = false;

	if( *utf8 == 0 )
		return 0;

	if( !private_namespace::utf8_to_int_first_octet(utf8[0], len, res) )
		return 1;

	for(i=1 ; i<len ; ++i)
	{
		if( utf8[i] == 0 )
			return i;

		if( !private_namespace::utf8_to_int_add_next_octet(utf8[i], res) )
			return i;
	}

	if( is_correct_unicode_char(res, len) )
		correct = true;

return len;
}




/*
 * convert one UTF-8 character into one wide-character
 *
 * input:
 *   utf8 - an input UTF-8 string
 *
 * output:
 *   res - an output character
 *   correct - true if it is a correct character
 *
 * the function returns how many characters have been used from the input string
 * (returns zero only if utf8 is empty)
 * even if there are errors the functions returns a different from zero value
 */
size_t utf8_to_int(const std::string & utf8, int & res, bool & correct)
{
	return utf8_to_int(utf8.c_str(), utf8.size(), res, correct);
}



/*
 * convert one UTF-8 character into one wide-character
 *
 * input:
 *   utf8 - an input UTF-8 stream
 *
 * output:
 *   res - an output character
 *   correct - true if it is a correct character
 *
 * the function returns how many characters have been used from the input stream
 */
size_t utf8_to_int(std::istream & utf8, int & res, bool & correct)
{
size_t i, len;
unsigned char uz;

	res = 0;
	correct = false;

	uz = utf8.get();

	if( !utf8 )
		return 0;

	if( !private_namespace::utf8_to_int_first_octet(uz, len, res) )
		return 1;

	for(i=1 ; i<len ; ++i)
	{
		uz = utf8.get();

		if( !utf8 )
			return i;

		if( !private_namespace::utf8_to_int_add_next_octet(uz, res) )
			return i;
	}

	if( is_correct_unicode_char(res, len) )
		correct = true;

return len;
}


// new function, need to be tested a little more especially when sizeof(wchar_t) is 2
size_t utf8_to_int(const Stream & utf8, size_t stream_index, int & res, bool & correct)
{
size_t i, len;
unsigned char uz;

	res = 0;
	correct = false;
	len = 0;

	if( stream_index < utf8.size() )
	{
		uz = utf8.get_char(stream_index);

		if( !private_namespace::utf8_to_int_first_octet(uz, len, res) )
			return 1;

		if( stream_index + len < utf8.size() + 1 )
		{
			for(i=1 ; i<len ; ++i)
			{
				uz = utf8.get_char(stream_index + i);

				if( !private_namespace::utf8_to_int_add_next_octet(uz, res) )
					return i + 1;
			}

			if( is_correct_unicode_char(res, len) )
				correct = true;
		}
		else
		{
			len = utf8.size() - stream_index;
		}
	}

	return len;
}






/*
 * convert an utf8 string into a wide string (std::wstring)
 *
 * input:
 *   utf8 - an input utf8 string
 *   utf8_len - size of the input string
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 *
 * output:
 *   res - an output wide string
 *
 * the function returns false if there were some errors when converting
 */
bool utf8_to_wide(const char * utf8, size_t utf8_len, std::wstring & res, bool clear, int mode)
{
	if( clear )
		res.clear();

	bool status = utf8_to_output_function(utf8, utf8_len, [&res](int c) {
		int_to_wide(c, res);
	}, mode);

	return status;
}





/*
 * convert an utf8 string into a wide string (std::wstring)
 *
 * input:
 *   utf8 - an input utf8 null terminated string
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 *
 * output:
 *   res - an output wide string
 *
 * the function returns false if there were some errors when converting
 */
bool utf8_to_wide(const char * utf8, std::wstring & res, bool clear, int mode)
{
size_t utf8_len = 0;

	while( utf8[utf8_len] != 0 )
		utf8_len += 1;

return utf8_to_wide(utf8, utf8_len, res, clear, mode);
}



/*
 * convert an utf8 string into a wide string (std::wstring)
 *
 * input:
 *   utf8 - an input utf8 string
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 *
 * output:
 *   res - an output wide string
 *
 * the function returns false if there were some errors when converting
 */
bool utf8_to_wide(const std::string & utf8, std::wstring & res, bool clear, int mode)
{
	return utf8_to_wide(utf8.c_str(), utf8.size(), res, clear, mode);
}



/*
 * convert an utf8 stream into a wide string (std::wstring)
 *
 * input:
 *   utf8 - an input utf8 stream
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 *
 * output:
 *   res - an output wide string
 *
 * the function returns false if there were some errors when converting
 */
bool utf8_to_wide(std::istream & utf8, std::wstring & res, bool clear, int mode)
{
int z;
bool correct, was_error = false;

	if( clear )
		res.clear();

	while( utf8_to_int(utf8, z, correct) > 0 )
	{
		if( !correct )
		{
			if( mode == 1 )
				res += 0xFFFD; // U+FFFD "replacement character"

			was_error = true;
		}
		else
		{
			int_to_wide(z, res);
		}
	}

return !was_error;
}




/*
 * convert one wide character into an UTF-8 sequence
 *
 * input:
 *   z - wide character
 *
 * output:
 *   utf8 - a buffer for the output sequence
 *   utf8_len - the size of the buffer
 *
 * the function returns how many characters have been written to the utf8,
 * zero means the utf8 buffer is too small or 'z' is an incorrect unicode character
 */
size_t int_to_utf8(int z, char * utf8, size_t utf8_max_len)
{
char buf[10];
int i = 0;
int mask = 0x3f; // 6 first bits set

	if( utf8_max_len==0 || !is_correct_unicode_char(z) )
		return 0;

	if( z <= 0x7f )
	{
		utf8[0] = static_cast<char>(z);
		return 1;
	}

	do
	{
		buf[i] = 0x80 | (z & 0x3f);
		i += 1;
		z >>= 6;
		mask >>= 1;
	}
	while( (z & (~mask)) != 0  );

	unsigned int first = -1;
	first <<= (7 - i);
	first |=  (z & mask);

	if( size_t(i+1) > utf8_max_len )
		return 0;

	utf8[0] = static_cast<char>(first);

	int a = 1;
	for(--i; i>=0 ; --i, ++a)
		utf8[a] = buf[i];

return a;
}



/*
 * convert one wide character into an UTF-8 string
 *
 * input:
 *   z - wide character
 *
 * output:
 *   utf8 - a UTF-8 string for the output sequence (the string is not cleared)
 *
 * the function returns how many characters have been written to the utf8 string,
 * zero means that 'z' is an incorrect unicode character
 */
size_t int_to_utf8(int z, std::string & utf8, bool clear)
{
char buf[10];

	if( clear )
		utf8.clear();

	size_t len = int_to_utf8(z, buf, sizeof(buf)/sizeof(char));
	size_t i;
	
	for(i=0 ; i<len ; ++i)
		utf8 += buf[i];

return len;
}



/*
 * convert a wide string into an UTF-8 string
 *
 * input:
 *   wide_string - a wide string for converting
 *   string_len - the size of the string
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 *
 * output:
 *   utf8 - a UTF-8 string for the output sequence (the string is not cleared)
 *
 * this function returns false if there were some errors when converting
 */
bool wide_to_utf8(const wchar_t * wide_string, size_t string_len, std::string & utf8, bool clear, int mode)
{
bool was_error = false;
size_t chars;

	if( clear )
		utf8.clear();

	while( string_len > 0 )
	{
		chars = private_namespace::wide_one_to_utf8(wide_string, string_len, utf8, was_error, mode);
		wide_string += chars;
		string_len  -= chars;
	}

return !was_error;
}



/*
 * convert a wide string into an UTF-8 string
 *
 * input:
 *   wide_string - a null terminated wide string for converting
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 *
 * output:
 *   utf8 - a UTF-8 string for the output sequence (the string is not cleared)
 *
 * this function returns false if there were some errors when converting
 */
bool wide_to_utf8(const wchar_t * wide_string, std::string & utf8, bool clear, int mode)
{
bool was_error = false;

	if( clear )
		utf8.clear();

	while( *wide_string )
		wide_string += private_namespace::wide_one_to_utf8(wide_string, utf8, was_error, mode);

return !was_error;
}



/*
 * convert a wide string (std::wstring) into an UTF-8 string
 *
 * input:
 *   wide_string - a wide string for converting
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 *
 * output:
 *   utf8 - a UTF-8 string for the output sequence (the string is not cleared)
 *
 * this function returns false if there were some errors when converting
 */
bool wide_to_utf8(const std::wstring & wide_string, std::string & utf8, bool clear, int mode)
{
	return wide_to_utf8(wide_string.c_str(), wide_string.size(), utf8, clear, mode);
}





/*
 * convert a wide string into an UTF-8 stream
 *
 * input:
 *   wide_string - a wide string for converting
 *   string_len  - lenght of the wide string
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 *
 * output:
 *   utf8 - a buffer for the UTF-8 stream
 *   utf8_len - the size of the buffer
 *   utf8_written - how many bytes have been written to the buffer
 *
 * this function returns false if there were some errors when converting or the output buffer was too small,
 * the output string is not null terminated
 *
 * if there is an error when converting (there is an incorrect character in the wide string) the function
 * will continue converting but if the buffer is too small the function breaks immediately
 */
bool wide_to_utf8(const wchar_t * wide_string, size_t string_len, char * utf8, size_t utf8_len, size_t & utf8_written, int mode)
{
bool was_error = false;
bool was_buffer_to_small;
size_t chars, utf8_saved;

	utf8_written = 0;

	while( string_len > 0 )
	{
		chars = private_namespace::wide_one_to_utf8(wide_string, string_len, utf8, utf8_len, utf8_saved, was_buffer_to_small, was_error, mode);

		if( was_buffer_to_small )
		{
			/*
			 * if the buffer was too small break immediately
			 * and set the was_error flag
			 */
			was_error = true;
			break;
		}

		wide_string  += chars;
		string_len   -= chars;
		utf8         += utf8_saved;
		utf8_len     -= utf8_saved;
		utf8_written += utf8_saved;
	}

return !was_error;
}



/*
 * convert a wide string (std::wstring) into an UTF-8 stream
 *
 * input:
 *   wide_string - a wide string for converting
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 * 
 * output:
 *   utf8 - a buffer for the UTF-8 stream
 *   utf8_len - the size of the buffer
 *   utf8_written - how many bytes have been written to the buffer
 * 
 * this function returns false if there were some errors when converting or the output buffer was too small,
 * the output string is not null terminated
 * 
 * if there is an error when converting (there is an incorrect character in the wide string) the function
 * will continue converting but if the buffer is too small the function breaks immediately
 */
bool wide_to_utf8(const std::wstring & wide_string, char * utf8, size_t utf8_len, size_t & utf8_written, int mode)
{
	return wide_to_utf8(wide_string.c_str(), wide_string.size(), utf8, utf8_len, utf8_written, mode);
}



/*
 * convert a wide string into an UTF-8 stream
 * 
 * input:
 *   wide_string - a wide string for converting
 *   string_len  - lenght of the wide string
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 * 
 * output:
 *   utf8 - a buffer for the UTF-8 stream
 *   utf8_len - the size of the buffer
 * 
 * this function returns false if there were some errors when converting or the output buffer was too small,
 * the output string is null terminated (even if there were errors during converting)
 * 
 * if there is an error when converting (there is an incorrect character in the wide string) the function
 * will continue converting but if the buffer is too small the function breaks immediately
 * (in both cases the utf8 buffer is null terminated)
 */
bool wide_to_utf8(const wchar_t * wide_string, size_t string_len, char * utf8, size_t utf8_len, int mode)
{
size_t utf8_saved;
bool res;

	if( utf8_len == 0 )
		return false;

	res = wide_to_utf8(wide_string, string_len, utf8, utf8_len - 1, utf8_saved, mode);
	utf8[utf8_saved] = 0;

return res;
}



/*
 * convert a wide string (std::wstring) into an UTF-8 stream
 * 
 * input:
 *   wide_string - a wide string for converting
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 * 
 * output:
 *   utf8 - a buffer for the UTF-8 stream
 *   utf8_len - the size of the buffer
 * 
 * this function returns false if there were some errors when converting or the output buffer was too small,
 * the output string is null terminated (even if there were errors during converting)
 * 
 * if there is an error when converting (there is an incorrect character in the wide string) the function
 * will continue converting but if the buffer is too small the function breaks immediately
 * (in both cases the utf8 buffer is null terminated)
 */
bool wide_to_utf8(const std::wstring & wide_string, char * utf8, size_t utf8_len, int mode)
{
	return wide_to_utf8(wide_string.c_str(), wide_string.size(), utf8, utf8_len, mode);
}



/*
 * convert a wide string into an UTF-8 stream
 * 
 * input:
 *   wide_string - a null terminated wide string for converting
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 * 
 * output:
 *   utf8 - a buffer for the UTF-8 stream
 *   utf8_len - the size of the buffer
 *   utf8_written - how many bytes have been written to the buffer
 * 
 * this function returns false if there were some errors when converting or the output buffer was too small,
 * the output string is not null terminated
 * 
 * if there is an error when converting (there is an incorrect character in the wide string) the function
 * will continue converting but if the buffer is too small the function breaks immediately
 */
bool wide_to_utf8(const wchar_t * wide_string, char * utf8, size_t utf8_len, size_t & utf8_written, int mode)
{
bool was_error = false;
bool was_buffer_to_small;
size_t chars, utf8_saved;
size_t len;

	utf8_written = 0;

	while( *wide_string )
	{
		len = (*(wide_string+1) == 0) ? 1 : 2;
		chars = private_namespace::wide_one_to_utf8(wide_string, len, utf8, utf8_len, utf8_saved, was_buffer_to_small, was_error, mode);

		if( was_buffer_to_small )
		{
			/*
			 * if the buffer was too small break immediately
			 * and set the was_error flag
			 */
			was_error = true;
			break;
		}

		wide_string  += chars;
		utf8         += utf8_saved;
		utf8_len     -= utf8_saved;
		utf8_written += utf8_saved;
	}

return !was_error;
}



/*
 * convert a wide string into an UTF-8 stream
 * 
 * input:
 *   wide_string - a wide string for converting
 *   mode - what to do with errors when converting
 *     0: skip an invalid character
 *     1: put U+FFFD "replacement character" istead of the invalid character (default)
 * 
 * output:
 *   utf8 - a buffer for the UTF-8 stream
 *   utf8_len - the size of the buffer
 * 
 * this function returns false if there were some errors when converting or the output buffer was too small,
 * the output string is null terminated (even if there were errors during converting)
 * 
 * if there is an error when converting (there is an incorrect character in the wide string) the function
 * will continue converting but if the buffer is too small the function breaks immediately
 * (in both cases the utf8 buffer is null terminated)
 */
bool wide_to_utf8(const wchar_t * wide_string, char * utf8, size_t utf8_len, int mode)
{
size_t utf8_saved;
bool res;

	if( utf8_len == 0 )
		return false;

	res = wide_to_utf8(wide_string, utf8, utf8_len - 1, utf8_saved, mode);
	utf8[utf8_saved] = 0;

return res;
}





namespace private_namespace
{

/*
 * an auxiliary function for converting from UTF-8 string
 */
bool utf8_to_int_first_octet(unsigned char uz, size_t & len, int & res)
{
	for(len=0 ; (uz & 0x80) != 0 ; ++len)
		uz <<= 1;

	if( len == 1 || len > 4 )
		return false;

	res = uz;

	if( len > 0 )
		res >>= len;

	if( len == 0 )
		len = 1;

return true;
}



/*
 * an auxiliary function for converting from UTF-8 string
 */
bool utf8_to_int_add_next_octet(unsigned char uz, int & res)
{
	if( (uz & 0xc0) != 0x80 )
		return false;

	res <<= 6;
	res |= (uz & 0x3F);

return true;
}



/*
 * an auxiliary function for converting from wide characters to UTF-8
 * 
 * return how many wide characters were used
 * if string_len is greater than 0 then the return value is always greater than zero too
 * 
 * utf8_written - how many characters were saved in the utf8 string (the string doesn't have
 *   a null terminating character)
 *   it can be equal to zero if the utf8 buffer is too small or there was an incorrect wide character read
 * was_utf8_buf_too_small - will be true if the utf8 buffer is too small
 *   if this flag is true then utf8_written is equal to zero
 * was_error - will be true if there is an error when converting (there was an incorrect wide character)
 *   (was_error will not be true if the utf8 buffer is too small)
 */
size_t wide_one_to_utf8(const wchar_t * wide_string, size_t string_len, char * utf8, size_t utf8_len,
							size_t & utf8_written, bool & was_utf8_buf_too_small, bool & was_error, int mode)
{
int z;
bool correct;
size_t chars;

	utf8_written = 0;
	was_utf8_buf_too_small = false;
	chars = wide_to_int(wide_string, string_len, z, correct);

	if( correct )
	{
		utf8_written = int_to_utf8(z, utf8, utf8_len);

		if( utf8_written == 0 )
			was_utf8_buf_too_small = true;
	}
	else
	{
		if( mode == 1 )
		{
			utf8_written = int_to_utf8(0xFFFD, utf8, utf8_len); // U+FFFD "replacement character"

			if( utf8_written == 0 )
				was_utf8_buf_too_small = true;
		}

		was_error = true;
	}

return chars;
}



/*
 * an auxiliary function for converting from wide characters to UTF-8
 * 
 * return how many wide characters were used
 * if string_len is greater than 0 then the return value is always greater than zero too
 */
size_t wide_one_to_utf8(const wchar_t * wide_string, size_t string_len, std::string & utf8, bool & was_error, int mode)
{
int z;
bool correct;
size_t chars;

	chars = wide_to_int(wide_string, string_len, z, correct);

	if( correct )
		correct = int_to_utf8(z, utf8, false) != 0;

	if( !correct )
	{
		if( mode == 1 )
			int_to_utf8(0xFFFD, utf8, false); // U+FFFD "replacement character"

		was_error = true;
	}

return chars;
}



/*
 * an auxiliary function for converting from wide characters to UTF-8
 * 
 * return how many wide characters were used
 * if wide_string has at least one character then the return value is always greater than zero too
 */
size_t wide_one_to_utf8(const wchar_t * wide_string, std::string & utf8, bool & was_error, int mode)
{
int z;
bool correct;
size_t chars;

	chars = wide_to_int(wide_string, z, correct);

	if( correct )
		correct = int_to_utf8(z, utf8, false) != 0;

	if( !correct )
	{
		if( mode == 1 )
			int_to_utf8(0xFFFD, utf8, false); // U+FFFD "replacement character"

		was_error = true;
	}

return chars;
}

} // namespace private_namespace



} // namespace