std library function almost done, tested with libft-unit-tests

1 files changed, 33 insertions, 0 deletions

diff --git a/ft_atoi.c b/ft_atoi.c
new file mode 100644
index 0000000..94c42cc
--- /dev/null
+++ b/ft_atoi.c
@@ -0,0 +1,33 @@
+#define MIN_INT (1 << 31)
+#define MAX_INT (~(1 << 31))
+
+int ft_atoi(const char *nptr)
+{
+	unsigned int	nb;
+	int	i;
+	int	is_negative;
+
+	while (*nptr == ' ' || *nptr == '\t'|| *nptr == '\n'
+		   || *nptr == '\v'|| *nptr == '\f'|| *nptr == '\r')
+		nptr++;
+    is_negative = 0;
+	if (*nptr == '-' || *nptr == '+')
+	{
+        if (*nptr == '-')
+            is_negative = 1;
+		nptr++;
+	}
+    i = 0;
+    nb = 0;
+	while (nptr[i] >= '0' && nptr[i] <= '9')
+	{
+        if (!is_negative && nb > (unsigned int)MAX_INT)
+            return (-1);
+        else if (nb > (unsigned int)MIN_INT)
+            return (0);
+        nb *= 10;
+        nb += nptr[i] - '0';
+        i++;
+	}
+	return ((int)(is_negative ? -nb : nb));
+}