Add noniso.c implementation from ESP8266

cores/esp32/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;
+}