/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-â
'-'âvi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :viâ
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â Copyright 2020 Justine Alexandra Roberts Tunney                              â
â                                                                              â
â Permission to use, copy, modify, and/or distribute this software for         â
â any purpose with or without fee is hereby granted, provided that the         â
â above copyright notice and this permission notice appear in all copies.      â
â                                                                              â
â THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                â
â WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                â
â WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             â
â AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         â
â DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        â
â PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               â
â TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             â
â PERFORMANCE OF THIS SOFTWARE.                                                â
ââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ*/
#include "libc/errno.h"
#include "libc/fmt/conv.h"
#include "libc/limits.h"
#include "libc/str/str.h"

/**
 * Decodes decimal integer from ASCII string.
 *
 *     atoi 10â¸              22ð         7ðð 
 *     strtol 10â¸            37ð        12ðð 
 *     strtoul 10â¸           35ð        11ðð 
 *     wcstol 10â¸            30ð        10ðð 
 *     wcstoul 10â¸           30ð        10ðð 
 *     strtoimax 10â¸         80ð        26ðð 
 *     strtoumax 10â¸         78ð        25ðð 
 *     wcstoimax 10â¸         77ð        25ðð 
 *     wcstoumax 10â¸         76ð        25ðð 
 *
 * @param s is a non-null nul-terminated string
 * @return the decoded signed saturated integer
 * @raise ERANGE on overflow
 */
int atoi(const char *s) {
  int x, c, d;
  do {
    c = *s++;
  } while (c == ' ' || c == '\t');
  d = c == '-' ? -1 : 1;
  if (c == '-' || c == '+') c = *s++;
  for (x = 0; isdigit(c); c = *s++) {
    if (__builtin_mul_overflow(x, 10, &x) ||
        __builtin_add_overflow(x, (c - '0') * d, &x)) {
      errno = ERANGE;
      if (d > 0) {
        return INT_MAX;
      } else {
        return INT_MIN;
      }
    }
  }
  return x;
}
