snprintf.c

minicom的源码,linux下常用的串口程序.

}

/*
 * Do format conversion.
 */
SCOPE int 
vsnprintf(char *str, size_t size, const char *fmt, va_list ap)
{
    char *sp;
    char *bep;
    int cc = 0;
    int i;

    char *s;
    char *q;
    int s_len;

    int min_width;
    int precision;
    enum {
	LEFT, RIGHT
    } adjust;
    char pad_char;
    char prefix_char;

    double fp_num;
    wide_int i_num;
    u_wide_int ui_num;

    char num_buf[NUM_BUF_SIZE];
    char char_buf[2];		       /* for printing %% and %<unknown> */

    /*
     * Flag variables
     */
    boolean_e is_long;
    boolean_e alternate_form;
    boolean_e print_sign;
    boolean_e print_blank;
    boolean_e adjust_precision;
    boolean_e adjust_width;
    bool_int is_negative;

    if (size == 0)
	return 0;

    sp = str;
    bep = str + size - 1;

    while (*fmt) {
	if (*fmt != '%') {
	    INS_CHAR(*fmt, sp, bep, cc);
	} 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
		 *
		 * XXX: an unreasonable amount of precision may be specified
		 *      resulting in overflow of num_buf. Currently we
		 *      ignore this possibility.
		 */
		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') {
		is_long = YES;
		fmt++;
	    } else
		is_long = NO;

	    /*
	     * 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, wide_int);
		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, 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;
		/*
		 * 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;

	    case 'n':
		*(va_arg(ap, int *)) = cc;

		break;

		/*
		 * 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':
		ui_num = (u_wide_int) va_arg(ap, void *);

		if (sizeof(void *) <= 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, cc)
			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, cc);
		s++;
	    }

	    if (adjust_width && adjust == LEFT && min_width > s_len)
		PAD(min_width, s_len, pad_char);
	}
	fmt++;
    }
    if (cc < size)
	str[cc] = NUL;
    else
	str[size - 1] = NUL;
    return cc;
}