Reimplement strtol/strtoul/atoi (#5400)

newlibc version is pulling in (part of) locale support

Adapted from uClibc source code
Addded support for 0b.... prefix for binary numbers

make/source.mk

@@ -15,6 +15,7 @@ COMMON_SRC = \
             common/printf.c \
             common/streambuf.c \
             common/string_light.c \
+            common/strtol.c \
             common/time.c \
             common/typeconversion.c \
             config/config_eeprom.c \

src/main/common/strtol.c

@@ -0,0 +1,131 @@
+/*  Copyright (C) 2002     Manuel Novoa III
+ *  From my (incomplete) stdlib library for linux and (soon) elks.
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Library General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2 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
+ *  Library General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Library General Public
+ *  License along with this library; if not, see
+ *  <http://www.gnu.org/licenses/>.
+
+ * Adapted for Betaflight by Petr Ledvina, 2018
+
+ */
+
+
+#include <ctype.h>
+#include <limits.h>
+
+#include "common/utils.h"
+
+#define _STRTO_ENDPTR 1
+
+unsigned long _strto_l(const char * str, char ** endptr, int base, int sflag)
+{
+    unsigned long number, cutoff;
+#if _STRTO_ENDPTR
+    const char *fail_char;
+#define SET_FAIL(X) fail_char = (X)
+#else
+#define SET_FAIL(X) ((void)(X)) /* Keep side effects. */
+#endif
+    unsigned char negative, digit, cutoff_digit;
+
+    SET_FAIL(str);
+
+    while (isspace(*str)) { /* Skip leading whitespace. */
+        ++str;
+    }
+
+    /* Handle optional sign. */
+    negative = 0;
+    switch (*str) {
+        case '-':
+            negative = 1;	/* Fall through to increment str. */
+            FALLTHROUGH;
+        case '+':
+            ++str;
+    }
+
+    if (!base || base == 16 || base == 2) {		/* Either dynamic (base = 0) or base with 0[xb] prefix. */
+        if (*str == '0') {
+            SET_FAIL(++str);
+            if ((!base || base == 16) && tolower(*str) == 'x') {
+                ++str;
+                base = 16;
+            } else if ((!base || base == 2) && tolower(*str) == 'b') {
+                ++str;
+                base = 2;
+            } else if(!base) {
+                base = 8;
+            }
+        }
+    }
+
+    number = 0;
+
+    if (((unsigned)(base - 2)) < 35) { /* Legal base. */
+        cutoff_digit = ULONG_MAX % base;
+        cutoff = ULONG_MAX / base;
+        do {
+            digit = (        (*str - '0') <= 9)
+                ? /* 0..9 */ (*str - '0')
+                : /* else */ (((0x20 | *str) >= 'a') /* WARNING: assumes ascii. */
+                              ? /* >= A/a */ ((0x20 | *str) - ('a' - 10))
+                              : /* else   */ 40 /* bad value */);
+
+            if (digit >= base) {
+                break;
+            }
+
+            SET_FAIL(++str);
+
+            if ((number > cutoff)
+                || ((number == cutoff) && (digit > cutoff_digit))) {
+                number = ULONG_MAX;
+                negative &= sflag;
+            } else {
+                number = number * base + digit;
+            }
+        } while (1);
+    }
+
+#if _STRTO_ENDPTR
+    if (endptr) {
+        *endptr = (char *) fail_char;
+    }
+#endif
+
+    {
+        unsigned long tmp = (negative
+                             ? ((unsigned long)(-(1+LONG_MIN)))+1
+                             : LONG_MAX);
+        if (sflag && (number > tmp)) {
+            number = tmp;
+        }
+    }
+
+    return negative ? (unsigned long)(-((long)number)) : number;
+}
+
+long strtol(const char * str, char ** endptr, int base)
+{
+    return _strto_l(str, endptr, base, 1);
+}
+
+unsigned long strtoul(const char * str, char ** endptr, int base)
+{
+    return _strto_l(str, endptr, base, 0);
+}
+
+int atoi(const char *str)
+{
+    return strtol(str, NULL, 10);
+}