xsnprintf.c

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            /*
             * Make sure the exponent has at least 2 digits
             */
            if (t_len == 1)
                *s++ = '0';
            while (t_len--)
                *s++ = *p++;
        } else {
            *s++ = '+';
            *s++ = '0';
            *s++ = '0';
        }
    }
    *len = s - buf;
    return (buf);
}


/*
 * Convert num to a base X number where X is a power of 2. nbits determines X.
 * For example, if nbits is 3, we do base 8 conversion
 * Return value:
 *      a pointer to a string containing the number
 *
 * The caller provides a buffer for the string: that is the buf_end argument
 * which is a pointer to the END of the buffer + 1 (i.e. if the buffer
 * is declared as buf[ 100 ], buf_end should be &buf[ 100 ])
 */
static char *
conv_p2(register u_wide_int num, register int nbits,
        char format, char *buf_end, register int *len)
{
    register int mask = (1 << nbits) - 1;
    register char *p = buf_end;
    static char low_digits[] = "0123456789abcdef";
    static char upper_digits[] = "0123456789ABCDEF";
    register char *digits = (format == 'X') ? upper_digits : low_digits;

    do {
        *--p = digits[num & mask];
        num >>= nbits;
    }
    while (num);

    *len = buf_end - p;
    return (p);
}


/*
 * Do format conversion placing the output in buffer
 */
static int format_converter(register buffy * odp, const char *fmt,
                            va_list ap)
{
    register char *sp;
    register char *bep;
    register int cc = 0;
    register int i;

    register char *s = NULL;
    char *q;
    int s_len;

    register int min_width = 0;
    int precision = 0;
    enum {
        LEFT, RIGHT
    } adjust;
    char pad_char;
    char prefix_char;

    double fp_num;
    wide_int i_num = (wide_int) 0;
    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;

    s_len = 0;

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

    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((int)*fmt) && !islower((int)*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((int)*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((int)*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 'u':
                if (is_long)
                    i_num = va_arg(ap, u_wide_int);
                else
                    i_num = (wide_int) va_arg(ap, unsigned int);
                /*
                 * The rest also applies to other integer formats, so fall
                 * into that case.
                 */
            case 'd':
            case 'i':
                /*
                 * Get the arg if we haven't already.
                 */
                if ((*fmt) != '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 = ap_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;

                /*
                 * 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':
                ui_num = (u_wide_int) 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 format_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++;
    }
    odp->nextb = sp;
    return (cc);
}


/*
 * This is the general purpose conversion function.
 */
static void strx_printv(int *ccp, char *buf, size_t len, const char *format,
                        va_list ap)
{
    buffy od;
    int cc;

    /*
     * First initialize the descriptor
     * Notice that if no length is given, we initialize buf_end to the
     * highest possible address.
     */
    od.buf_end = len ? &buf[len] : (char *) ~0;
    od.nextb = buf;

    /*
     * Do the conversion
     */
    cc = format_converter(&od, format, ap);
    if (len == 0 || od.nextb <= od.buf_end)
        *(od.nextb) = '\0';
    if (ccp)
        *ccp = cc;
}


int ap_snprintf(char *buf, size_t len, const char *format,...)
{
    int cc;
    va_list ap;

    va_start(ap, format);
    strx_printv(&cc, buf, (len - 1), format, ap);
    va_end(ap);
    return (cc);
}


int ap_vsnprintf(char *buf, size_t len, const char *format, va_list ap)
{
    int cc;

    strx_printv(&cc, buf, (len - 1), format, ap);
    return (cc);
}

#endif                          /* HAVE_SNPRINTF */