일부 라 이브 러 리 함수 의 실현

size_t strlen( const char *string ) 
{
	const char	*s;

	s = string;
	while ( *s ) {
		s++;
	}
	return s - string;
}


char *strcat( char *strDestination, const char *strSource ) 
{
	char	*s;

	s = strDestination;
	while ( *s ) {
		s++;
	}
	while ( *strSource ) {
		*s++ = *strSource++;
	}
	*s = 0;
	return strDestination;
}

char *strcpy( char *strDestination, const char *strSource ) 
{
	char *s;

	s = strDestination;
	while ( *strSource ) {
		*s++ = *strSource++;
	}
	*s = 0;
	return strDestination;
}


int strcmp( const char *string1, const char *string2 ) 
{
	while ( *string1 == *string2 && *string1 && *string2 ) {
		string1++;
		string2++;
	}
	return *string1 - *string2;
}


char *strchr( const char *string, int c ) {
	while ( *string ) {
		if ( *string == c ) {
			return ( char * )string;
		}
		string++;
	}
	return (char *)0;
}

char *strstr( const char *string, const char *strCharSet )
 {
	while ( *string ) {
		int		i;

		for ( i = 0 ; strCharSet[i] ; i++ ) {
			if ( string[i] != strCharSet[i] ) {
				break;
			}
		}
		if ( !strCharSet[i] ) {
			return (char *)string;
		}
		string++;
	}
	return (char *)0;
}

#if !defined ( _MSC_VER ) && ! defined ( __linux__ ) && ! defined ( MAC_WOLF2_MP )

int tolower( int c )
 {
	if ( c >= 'A' && c <= 'Z' ) {
		c += 'a' - 'A';
	}
	return c;
}


int toupper( int c )
 {
	if ( c >= 'a' && c <= 'z' ) {
		c += 'A' - 'a';
	}
	return c;
}

#endif
//#ifndef _MSC_VER

void *memmove( void *dest, const void *src, size_t count )
 {
	int		i;

	if ( dest > src ) {
		for ( i = count-1 ; i >= 0 ; i-- ) {
			((char *)dest)[i] = ((char *)src)[i];
		}
	} else {
		for ( i = 0 ; i < count ; i++ ) {
			((char *)dest)[i] = ((char *)src)[i];
		}
	}
	return dest;
}


#if 0

double floor( double x )
 {
	return (int)(x + 0x40000000) - 0x40000000;
}

void *memset( void *dest, int c, size_t count ) 
{
	while ( count-- ) {
		((char *)dest)[count] = c;
	}
	return dest;
}

void *memcpy( void *dest, const void *src, size_t count )
 {
	while ( count-- ) {
		((char *)dest)[count] = ((char *)src)[count];
	}
	return dest;
}

char *strncpy( char *strDest, const char *strSource, size_t count )
 {
	char	*s;

	s = strDest;
	while ( *strSource && count ) {
		*s++ = *strSource++;
		count--;
	}
	while ( count-- ) {
		*s++ = 0;
	}
	return strDest;
}

double sqrt( double x )
 {
	float	y;
	float	delta;
	float	maxError;

	if ( x <= 0 ) {
		return 0;
	}

	// initial guess
	y = x / 2;

	// refine
	maxError = x * 0.001;

	do {
		delta = ( y * y ) - x;
		y -= delta / ( 2 * y );
	} while ( delta > maxError || delta < -maxError );

	return y;
}