add atoi that convert string to integer

conversions/c_atoi_str_to_integer.c

@@ -0,0 +1,40 @@
+#include <stdio.h>
+
+// recoding the original atoi function in stdlib.h
+int	c_atoi(char *str)
+{
+	int				i;
+	int				sign;
+	long			value;
+	long			prev;
+
+	i = 0;
+	sign = 1;
+	value = 0;
+	// skip wait spaces
+	while (((str[i] <= 13 && str[i] >= 9) || str[i] == 32) && str[i] != '\0')
+		i++;
+	// store the sign
+	if (str[i] == '-' || str[i] == '+')
+		(str[i++] == '-') ? sign = -1 : 1;
+	// convert char by char to an int value
+	while (str[i] >= 48 && str[i] <= 57 && str[i] != '\0')
+	{
+		prev = value;
+		value = value * 10 + sign * (str[i] - '0');
+		// manage the overflow
+		if (sign == 1 && prev > value)
+			return (-1);
+		else if (sign == -1 && prev < value)
+			return (0);
+		i++;
+	}
+	return (value);	
+}
+
+
+int	main()
+{
+	// Test
+	printf("%d\n", c_atoi("-234"));
+}