1 files changed, 51 insertions, 0 deletions
diff --git a/src/user/lib/string.c b/src/user/lib/string.c
new file mode 100644
index 0000000..77b996c
--- /dev/null
+++ b/src/user/lib/string.c
@@ -0,0 +1,51 @@
+#include <errno.h>
+#include <string.h>
+
+int isspace(char c) {
+	return c == ' ' || c == '\t' || c == '\n';
+}
+
+long strtol(const char *restrict s, char **restrict end, int base) {
+	long res = 0;
+	int sign = 1;
+
+	while (isspace(*s)) s++;
+
+	if (*s == '+') {
+		s++;
+	} else if (*s == '-') {
+		s++;
+		sign = -1;
+	}
+
+	if (base == 0) {
+		if (*s == '0') {
+			s++;
+			if (*s == 'x' || *s == 'X') {
+				s++;
+				base = 16;
+			} else {
+				base = 8;
+			}
+		} else {
+			base = 10;
+		}
+	}
+
+	for (;;) {
+		unsigned char digit = *s;
+		if      ('0' <= digit && digit <= '9') digit -= '0';
+		else if ('a' <= digit && digit <= 'z') digit -= 'a' - 10;
+		else if ('A' <= digit && digit <= 'Z') digit -= 'A' - 10;
+		else break;
+
+		if (digit >= base) break;
+		// TODO overflow check
+		res *= base;
+		res += digit;
+
+		s++;
+	}
+	if (end) *end = (void*)s;
+	return res * sign;
+}