Function d2string

src/util.c:543–578

Convert a double to a string representation. Returns the number of bytes * required. The representation should always be parsable by strtod(3). * This function does not support human-friendly formatting like ld2string * does. It is intended mainly to be used inside t_zset.c when writing scores * into a ziplist representing a sorted set. */

 * does. It is intended mainly to be used inside t_zset.c when writing scores
 * into a ziplist representing a sorted set. */
int d2string(char *buf, size_t len, double value) {
    if (isnan(value)) {
        len = snprintf(buf,len,"nan");
    } else if (isinf(value)) {
        if (value < 0)
            len = snprintf(buf,len,"-inf");
        else
            len = snprintf(buf,len,"inf");
    } else if (value == 0) {
        /* See: http://en.wikipedia.org/wiki/Signed_zero, "Comparisons". */
        if (1.0/value < 0)
            len = snprintf(buf,len,"-0");
        else
            len = snprintf(buf,len,"0");
    } else {
#if (DBL_MANT_DIG >= 52) && (LLONG_MAX == 0x7fffffffffffffffLL)
        /* Check if the float is in a safe range to be casted into a
         * long long. We are assuming that long long is 64 bit here.
         * Also we are assuming that there are no implementations around where
         * double has precision < 52 bit.
         *
         * Under this assumptions we test if a double is inside an interval
         * where casting to long long is safe. Then using two castings we
         * make sure the decimal part is zero. If all this is true we use
         * integer printing function that is much faster. */
        double min = -4503599627370495; /* (2^52)-1 */
        double max = 4503599627370496; /* -(2^52) */
        if (value > min && value < max && value == ((double)((long long)value)))
            len = ll2string(buf,len,(long long)value);
        else
#endif
            len = snprintf(buf,len,"%.17g",value);
    }

    return len;
}

/* Create a string object from a long double.
 * If mode is humanfriendly it does not use exponential format and trims trailing