sprint.c

牛顿插值方法求解多项式的系数

	/*
	 * Flag variables
	 */
	boolean_e is_long = NO;
	boolean_e is_quad = NO;
	boolean_e alternate_form ;
	boolean_e print_sign ;
	boolean_e print_blank ;
	boolean_e adjust_precision ;
	boolean_e adjust_width ;
	bool_int is_negative ;

	sp = odp->nextb ;
	bep = odp->buf_end ;

	while ( *fmt )
	{
		if ( *fmt != '%' )
		{
			INS_CHAR( *fmt, sp, bep, odp, cc, fd ) ;
		}
		else
		{
			/*
			 * Default variable settings
			 */
			adjust = RIGHT ;
			alternate_form = print_sign = print_blank = NO ;
			pad_char = ' ' ;
			prefix_char = NUL ;

			fmt++ ;

			/*
			 * Try to avoid checking for flags, width or precision
			 */
			if ( isascii( *fmt ) && ! islower( *fmt ) )
			{
				/*
				 * Recognize flags: -, #, BLANK, +
				 */
				for ( ;; fmt++ )
				{
					if ( *fmt == '-' )
						adjust = LEFT ;
					else if ( *fmt == '+' )
						print_sign = YES ;
					else if ( *fmt == '#' )
						alternate_form = YES ;
					else if ( *fmt == ' ' )
						print_blank = YES ;
					else if ( *fmt == '0' )
						pad_char = '0' ;
					else
						break ;
				}

				/*
				 * Check if a width was specified
				 */
				if ( isdigit( *fmt ) )
				{
					STR_TO_DEC( fmt, min_width ) ;
					adjust_width = YES ;
				}
				else if ( *fmt == '*' )
				{
					min_width = va_arg( ap, int ) ;
					fmt++ ;
					adjust_width = YES ;
					if ( min_width < 0 )
					{
						adjust = LEFT ;
						min_width = -min_width ;
					}
				}
				else
					adjust_width = NO ;
				
				/*
				 * Check if a precision was specified.
				 */
				if ( *fmt == '.' )
				{
					adjust_precision = YES ;
					fmt++ ;
					if ( isdigit( *fmt ) )
					{
						STR_TO_DEC( fmt, precision ) ;
					}
					else if ( *fmt == '*' )
					{
						precision = va_arg( ap, int ) ;
						fmt++ ;
						if ( precision < 0 )
							precision = 0 ;
					}
					else
						precision = 0 ;
				}
				else
					adjust_precision = NO ;
			}
			else
				adjust_precision = adjust_width = NO ;

			/*
			 * Modifier check
			 */
			if ( *fmt == 'l' )
			{
				if( *(fmt+1) == 'l' ) {
					is_quad = YES;
					fmt++;
				} else {
					is_quad = NO;
					is_long = YES;
				}
				fmt++ ;
			} else {
				is_long = NO;
				is_quad = NO;
			}

			if ( *fmt == 'q' )
			{
				is_quad = YES;
				fmt++;
			}

			/*
			 * Argument extraction and printing.
			 * First we determine the argument type.
			 * Then, we convert the argument to a string.
			 * On exit from the switch, s points to the string that
			 * must be printed, s_len has the length of the string
			 * The precision requirements, if any, are reflected in s_len.
			 *
			 * NOTE: pad_char may be set to '0' because of the 0 flag.
			 *			It is reset to ' ' by non-numeric formats
			 */
			switch( *fmt )
			{
				case 'd':
				case 'i':
				case 'u':
					if ( is_long )
						i_num = va_arg( ap, long ) ;
					else
						i_num = (wide_int) va_arg( ap, int ) ;
					s = conv_10( i_num, (*fmt) == 'u', &is_negative,
							&num_buf[ NUM_BUF_SIZE ], &s_len ) ;
					FIX_PRECISION( adjust_precision, precision, s, s_len ) ;

					if ( *fmt != 'u' )
					{
						if ( is_negative )
							prefix_char = '-' ;
						else if ( print_sign )
							prefix_char = '+' ;
						else if ( print_blank )
							prefix_char = ' ' ;
					}
					break ;
				

				case 'o':
					if ( is_long )
						ui_num = va_arg( ap, u_wide_int ) ; 
					else
						ui_num = (u_wide_int) va_arg( ap, unsigned int ) ;
					s = conv_p2( ui_num, 3, *fmt, 
						&num_buf[ NUM_BUF_SIZE ], &s_len ) ;
					FIX_PRECISION( adjust_precision, precision, s, s_len ) ;
					if ( alternate_form && *s != '0' )
					{
						*--s = '0' ;
						s_len++ ;
					}
					break ;
				

				case 'x':
				case 'X':
					if ( is_long )
						ui_num = (u_wide_int) va_arg( ap, unsigned long ) ;
					else if ( is_quad )
						ui_num = (u_wide_int) va_arg( ap, u_wide_int ) ;
					else
						ui_num = (u_wide_int) va_arg( ap, unsigned int ) ;
					s = conv_p2( ui_num, 4, *fmt,
						&num_buf[ NUM_BUF_SIZE ], &s_len ) ;
					FIX_PRECISION( adjust_precision, precision, s, s_len ) ;
					if ( alternate_form && i_num != 0 )
					{
						*--s = *fmt ;		/* 'x' or 'X' */
						*--s = '0' ;
						s_len += 2 ;
					}
					break ;
				

				case 's':
					s = va_arg( ap, char * ) ;
					if ( s != NULL )
					{
						s_len = strlen( s ) ;
						if ( adjust_precision && precision < s_len )
							s_len = precision ;
					}
					else
					{
						s = S_NULL ;
						s_len = S_NULL_LEN ;
					}
					pad_char = ' ' ;
					break ;


				case 'f':
				case 'e':
				case 'E':
					fp_num = va_arg( ap, double ) ;

					s = conv_fp( *fmt, fp_num, alternate_form,
						( adjust_precision == NO ) ? FLOAT_DIGITS : precision,
						&is_negative, &num_buf[ 1 ], &s_len ) ;
					if ( is_negative )
						prefix_char = '-' ;
					else if ( print_sign )
						prefix_char = '+' ;
					else if ( print_blank )
						prefix_char = ' ' ;
					break ;


				case 'g':
				case 'G':
					if ( adjust_precision == NO )
						precision = FLOAT_DIGITS ;
					else if ( precision == 0 )
						precision = 1 ;
					if ( precision > MAX_FLOAT_DIGITS )
						precision = MAX_FLOAT_DIGITS ;
					/*
					 * We use &num_buf[ 1 ], so that we have room for the sign
					 */
					s = gcvt( va_arg( ap, double ), precision, &num_buf[ 1 ] ) ;
					if ( *s == '-' )
						prefix_char = *s++ ;
					else if ( print_sign )
						prefix_char = '+' ;
					else if ( print_blank )
						prefix_char = ' ' ;

					s_len = strlen( s ) ;

					if ( alternate_form && ( q = strchr( s, '.' ) ) == NULL )
						s[ s_len++ ] = '.' ;
					if ( *fmt == 'G' && ( q = strchr( s, 'e' ) ) != NULL )
						*q = 'E' ;
					break ;


				case 'c':
					char_buf[ 0 ] = (char) (va_arg( ap, int )) ;
					s = &char_buf[ 0 ] ;
					s_len = 1 ;
					pad_char = ' ' ;
					break ;


				case '%':
					char_buf[ 0 ] = '%' ;
					s = &char_buf[ 0 ] ;
					s_len = 1 ;
					pad_char = ' ' ;
					break ;

				/*
				 * Always extract the argument as a "char *" pointer. We 
				 * should be using "void *" but there are still machines 
				 * that don't understand it.
				 * If the pointer size is equal to the size of an unsigned
				 * integer we convert the pointer to a hex number, otherwise 
				 * we print "%p" to indicate that we don't handle "%p".
				 */
				case 'p':
					/* Assume that pointers are of same size as "unsigned long" */
					ui_num = (u_wide_int)(unsigned long)va_arg( ap, char * ) ;

					if ( sizeof( char * ) <= sizeof( u_wide_int ) )
						s = conv_p2( ui_num, 4, 'x', 
						&num_buf[ NUM_BUF_SIZE ], &s_len ) ;
					else
					{
						s = "%p" ;
						s_len = 2 ;
					}
					pad_char = ' ' ;
					break ;
					

				case NUL:
					/*
					 * The last character of the format string was %.
					 * We ignore it.
					 */
					continue ;


					/*
				 	 * The default case is for unrecognized %'s.
					 * We print %<char> to help the user identify what
					 * option is not understood.
					 * This is also useful in case the user wants to pass
					 * the output of __sio_converter to another function
					 * that understands some other %<char> (like syslog).
					 * Note that we can't point s inside fmt because the
					 * unknown <char> could be preceded by width etc.
					 */
				default:
					char_buf[ 0 ] = '%' ;
					char_buf[ 1 ] = *fmt ;
					s = char_buf ;
					s_len = 2 ;
					pad_char = ' ' ;
					break ;
			}

			if ( prefix_char != NUL )
			{
				*--s = prefix_char ;
				s_len++ ;
			}

			if ( adjust_width && adjust == RIGHT && min_width > s_len )
			{
				if ( pad_char == '0' && prefix_char != NUL )
				{
					INS_CHAR( *s, sp, bep, odp, cc, fd )
					s++ ;
					s_len-- ;
					min_width-- ;
				}
				PAD( min_width, s_len, pad_char ) ;
			}

			/*
			 * Print the string s. 
			 */
			for ( i = s_len ; i != 0 ; i-- )
			{
				INS_CHAR( *s, sp, bep, odp, cc, fd ) ;
				s++ ;
			}

			/*
			 * Ignore pad_char for right padding, as padding
			 * with zeroes would produce a different number.
			 */
			if ( adjust_width && adjust == LEFT && min_width > s_len )
				PAD( min_width, s_len, ' ' ) ;
		}
		fmt++ ;
	}
	odp->nextb = sp ;
	return( cc ) ;
}