stdlib_noniso.c

/*
 core_esp8266_noniso.c - nonstandard (but usefull) conversion functions

 Copyright (c) 2014 Ivan Grokhotkov. All rights reserved.
 This file is part of the esp8266 core for Arduino environment.

 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
 License as published by the Free Software Foundation; either
 version 2.1 of the License, or (at your option) any later version.

 This library is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 Lesser General Public License for more details.

 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

 Modified 03 April 2015 by Markus Sattler

 */

#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <stdint.h>
#include <math.h>
#include "stdlib_noniso.h"

void reverse(char* begin, char* end) {
    char *is = begin;
    char *ie = end - 1;
    while(is < ie) {
        char tmp = *ie;
        *ie = *is;
        *is = tmp;
        ++is;
        --ie;
    }
}

char* ltoa(long value, char* result, int base) {
    if(base < 2 || base > 16) {
        *result = 0;
        return result;
    }

    char* out = result;
    long quotient = abs(value);

    do {
        const long tmp = quotient / base;
        *out = "0123456789abcdef"[quotient - (tmp * base)];
        ++out;
        quotient = tmp;
    } while(quotient);

    // Apply negative sign
    if(value < 0)
        *out++ = '-';

    reverse(result, out);
    *out = 0;
    return result;
}

char* ultoa(unsigned long value, char* result, int base) {
    if(base < 2 || base > 16) {
        *result = 0;
        return result;
    }

    char* out = result;
    unsigned long quotient = value;

    do {
        const unsigned long tmp = quotient / base;
        *out = "0123456789abcdef"[quotient - (tmp * base)];
        ++out;
        quotient = tmp;
    } while(quotient);

    reverse(result, out);
    *out = 0;
    return result;
}

char * dtostrf(double number, signed char width, unsigned char prec, char *s) {
    bool negative = false;

    if (isnan(number)) {
        strcpy(s, "nan");
        return s;
    }
    if (isinf(number)) {
        strcpy(s, "inf");
        return s;
    }

    char* out = s;

    int fillme = width; // how many cells to fill for the integer part
    if (prec > 0) {
        fillme -= (prec+1);
    }

    // Handle negative numbers
    if (number < 0.0) {
        negative = true;
        fillme--;
        number = -number;
    }

    // Round correctly so that print(1.999, 2) prints as "2.00"
    // I optimized out most of the divisions
    double rounding = 2.0;
    for (uint8_t i = 0; i < prec; ++i)
        rounding *= 10.0;
    rounding = 1.0 / rounding;

    number += rounding;

    // Figure out how big our number really is
    double tenpow = 1.0;
    int digitcount = 1;
    while (number >= 10.0 * tenpow) {
        tenpow *= 10.0;
        digitcount++;
    }

    number /= tenpow;
    fillme -= digitcount;

    // Pad unused cells with spaces
    while (fillme-- > 0) {
        *out++ = ' ';
    }

    // Handle negative sign
    if (negative) *out++ = '-';

    // Print the digits, and if necessary, the decimal point
    digitcount += prec;
    int8_t digit = 0;
    while (digitcount-- > 0) {
        digit = (int8_t)number;
        if (digit > 9) digit = 9; // insurance
        *out++ = (char)('0' | digit);
        if ((digitcount == prec) && (prec > 0)) {
            *out++ = '.';
        }
        number -= digit;
        number *= 10.0;
    }

    // make sure the string is terminated
    *out = 0;
    return s;
}