snprintf.c

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/*
 * This version of snprintf() and vsnprintf() is based on Sprint from
 * SIO by Panagiotis Tsirigotis, as included with xidentd-2.2.1.
 *
 * The modifications were made by The XFree86 Project, Inc and are
 * Copyright 1999 by The XFree86 Project, Inc.  These modifications
 * consist of removing the support for writing to file streams,
 * renaming some functions, ansification, and making some adjustments
 * to achieve the semantics for snprintf and vsnprintf() as described
 * in the relevant man page for FreeBSD 2.2.8.
 *
 *
 * The original version carries the following notice:
 *
 * (c) Copyright 1992, 1993 by Panagiotis Tsirigotis
 *
 * The author (Panagiotis Tsirigotis) grants permission to use, copy,
 * and distribute this software and its documentation for any purpose
 * and without fee, provided that a) the above copyright notice extant in
 * files in this distribution is not removed from files included in any
 * redistribution, and b) this file is also included in any redistribution.
 *
 * Modifications to this software may be distributed, either by distributing
 * the modified software or by distributing patches to the original software,
 * under the following additional terms:
 *
 * 1. The version number will be modified as follows:
 *      a. The first 3 components of the version number
 *         (i.e. <number>.<number>.<number>) will remain unchanged.
 *      b. A new component will be appended to the version number to indicate
 *         the modification level. The form of this component is up to the
 *         author of the modifications.
 *
 * 2. The author of the modifications will include his/her name by appending
 *    it along with the new version number to this file and will be
 *    responsible for any wrong behavior of the modified software.
 *
 * The author makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without any express
 * or implied warranty.
 *
 * Changes and modifications for: 
 *
 * xinetd Version 2.1.4-bsdi
 * xinetd Version 2.1.4-freebsd
 * xinetd Version 2.1.4-linux
 *
 * are      
 *
 * (c) Copyright 1995 by Charles Murcko
 * All Rights Reserved
 */

/* $XFree86$ */


/*
 * Assumption: systems that don't have snprintf and vsnprintf do have
 * ecvt, fcvt and gcvt.
 */

/* From: Id: sprint.c,v 1.5 1995/09/10 18:35:09 chuck Exp */

#include <ctype.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <sys/types.h>

#ifndef SCOPE
#define SCOPE                                   
#endif

#ifndef WIDE_INT
#define WIDE_INT                                long
#endif

typedef WIDE_INT wide_int;
typedef unsigned WIDE_INT u_wide_int;
typedef int bool_int;

#ifndef FALSE
#define FALSE                                   0
#define TRUE                                    1
#endif

#define NUL                                     '\0'

#define S_NULL                                  "(null)"
#define S_NULL_LEN                              6

#define FLOAT_DIGITS                            6
#define EXPONENT_LENGTH                         10

typedef enum { NO = 0, YES = 1 } boolean_e ;

/*
 * NUM_BUF_SIZE is the size of the buffer used for arithmetic conversions
 *
 * XXX: this is a magic number; do not decrease it
 */
#define NUM_BUF_SIZE                            512

/*
 * The INS_CHAR macro inserts a character in the buffer.
 * It uses the char pointers sp and bep:
 *      sp points to the next available character in the buffer
 *      bep points to the end-of-buffer
 * While using this macro, note that the nextb pointer is NOT updated.
 *
 * Excess characters are discarded if the string overflows.
 *
 * NOTE: Evaluation of the c argument should not have any side-effects
 */
#define INS_CHAR( c, sp, bep, cc )                                      \
        {                                                               \
            if ( sp < bep )                                             \
                *sp++ = c ;                                             \
            cc++ ;                                                      \
        }

#define NUM( c )                        ( c - '0' )

#define STR_TO_DEC( str, num )                                          \
        num = NUM( *str++ ) ;                                           \
        while ( isdigit( *str ) ) {                                     \
                num *= 10 ;                                             \
                num += NUM( *str++ ) ;                                  \
        }

/*
 * This macro does zero padding so that the precision
 * requirement is satisfied. The padding is done by
 * adding '0's to the left of the string that is going
 * to be printed.
 */
#define FIX_PRECISION( adjust, precision, s, s_len )                    \
        if ( adjust )                                                   \
                while ( s_len < precision ) {                           \
                        *--s = '0' ;                                    \
                        s_len++ ;                                       \
        }

/*
 * Macro that does padding. The padding is done by printing
 * the character ch.
 */
#define PAD( width, len, ch )                                           \
        do {                                                            \
                INS_CHAR( ch, sp, bep, cc ) ;                           \
                width-- ;                                               \
        } while ( width > len )

/*
 * Prefix the character ch to the string str
 * Increase length
 * Set the has_prefix flag
 */
#define PREFIX( str, length, ch )                                       \
        *--str = ch ; length++ ; has_prefix = YES

static char *conv_10(wide_int num, bool_int is_unsigned,
                        bool_int * is_negative, char *buf_end, int *len);
SCOPE int vsnprintf(char *str, size_t size, const char *fmt, va_list ap);

/*
 * snprintf is based on SIO's Sprint.
 *
 * Sprint is the equivalent of printf for SIO.
 * It returns the # of chars written
 * Assumptions:
 *     - all floating point arguments are passed as doubles
 */
SCOPE int 
snprintf(char *str, size_t size, const char *fmt, ...)
{
    int cc;
    va_list ap;

    va_start(ap, fmt);
    cc = vsnprintf(str, size, fmt, ap);
    va_end(ap);
    return cc;
}

/*
 * Convert a floating point number to a string formats 'f', 'e' or 'E'.
 * The result is placed in buf, and len denotes the length of the string
 * The sign is returned in the is_negative argument (and is not placed
 * in buf).  Always add decimal point if add_dp is YES.
 */
static char *
conv_fp(char format, double num, boolean_e add_dp, int precision,
        bool_int *is_negative, char buf[], int *len)
{
    char *s = buf;
    char *p;
    int decimal_point;

    if (format == 'f')
        p = fcvt(num, precision, &decimal_point, is_negative);
    else                               /* either e or E format */
        p = ecvt(num, precision + 1, &decimal_point, is_negative);

    /*
     * Check for Infinity and NaN
     */
    if (isalpha(*p)) {
        *len = strlen(strcpy(buf, p));
        *is_negative = FALSE;
        return (buf);
    }
    if (format == 'f')
        if (decimal_point <= 0) {
            *s++ = '0';
            if (precision > 0) {
                *s++ = '.';
                while (decimal_point++ < 0)
                    *s++ = '0';
            } else if (add_dp)
                *s++ = '.';
        } else {
            while (decimal_point-- > 0)
                *s++ = *p++;
            if (precision > 0 || add_dp)
                *s++ = '.';
    } else {
        *s++ = *p++;
        if (precision > 0 || add_dp)
            *s++ = '.';
    }

    /*
     * copy the rest of p, the NUL is NOT copied
     */
    while (*p)
        *s++ = *p++;

    if (format != 'f') {
        char temp[EXPONENT_LENGTH];    /* for exponent conversion */
        int t_len;
        bool_int exponent_is_negative;

        *s++ = format;                 /* either e or E */
        decimal_point--;
        if (decimal_point != 0) {
            p = conv_10((wide_int) decimal_point, FALSE, &exponent_is_negative,
                &temp[EXPONENT_LENGTH], &t_len);
            *s++ = exponent_is_negative ? '-' : '+';

            /*
             * 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(u_wide_int num, int nbits, char format, char *buf_end, int *len)
{
    int mask = (1 << nbits) - 1;
    char *p = buf_end;
    static char low_digits[] = "0123456789abcdef";
    static char upper_digits[] = "0123456789ABCDEF";
    char *digits = (format == 'X') ? upper_digits : low_digits;

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

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

/*
 * Convert num to its decimal format.
 * Return value:
 *       - a pointer to a string containing the number (no sign)
 *             - len contains the length of the string
 *             - is_negative is set to TRUE or FALSE depending on the sign
 *               of the number (always set to FALSE if is_unsigned is TRUE)
 *
 * 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_10(wide_int num, bool_int is_unsigned, bool_int *is_negative,
        char *buf_end, int *len)
{
    char *p = buf_end;
    u_wide_int magnitude;

    if (is_unsigned) {
        magnitude = (u_wide_int) num;
        *is_negative = FALSE;
    } else {
        *is_negative = (num < 0);

        /*
         * On a 2's complement machine, negating the most negative integer 
         * results in a number that cannot be represented as a signed integer.
         * Here is what we do to obtain the number's magnitude:
         *              a. add 1 to the number
         *              b. negate it (becomes positive)
         *              c. convert it to unsigned
         *              d. add 1
         */
        if (*is_negative) {
            wide_int t = num + 1;

            magnitude = ((u_wide_int) - t) + 1;
        } else
            magnitude = (u_wide_int) num;
    }

    /*
     * We use a do-while loop so that we write at least 1 digit 
     */
    do {
        register u_wide_int new_magnitude = magnitude / 10;

        *--p = magnitude - new_magnitude * 10 + '0';
        magnitude = new_magnitude;
    }
    while (magnitude);

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

/*
 * 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;
}

---