1 files changed, 83 insertions, 0 deletions
diff --git a/kernel/libc/stdlib/parsenum.c b/kernel/libc/stdlib/parsenum.c
new file mode 100644
index 0000000..3990c7b
--- /dev/null
+++ b/kernel/libc/stdlib/parsenum.c
@@ -0,0 +1,83 @@
+#include <assert.h>
+#include <ctype.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+
+#define MAX_64 0xFFFFFFFFFFFFFFFF
+
+extern int errno;
+int get_value(char c, long base) {
+  int r;
+  int l = tolower(c);
+  if (l >= '0' && l <= '9') {
+    r = l - '0';
+  } else if (l >= 'a' && l <= 'z') {
+    r = (l - 'a') + 10;
+  } else {
+    return -1;
+  }
+  if (r >= base) {
+    return -1;
+  }
+  return r;
+}
+
+u64 parse_u64(const char *restrict str, char **restrict endptr, int base,
+              int *err) {
+  if (err) {
+    *err = 0;
+  }
+  u64 ret_value = 0;
+  if (endptr) {
+    *endptr = (char *)str;
+  }
+  if (!*str) {
+    return ret_value;
+  }
+
+  if (0 == base) {
+    char prefix = *str;
+    if ('0' == prefix) {
+      str++;
+      if ('x' == tolower(*str)) {
+        str++;
+        base = 16;
+      } else {
+        base = 8;
+      }
+    } else {
+      base = 10;
+    }
+  }
+
+  if (2 <= base && 36 >= base) {
+    for (; *str; str++) {
+      int val = get_value(*str, base);
+      if (-1 == val) {
+        break;
+      }
+      if (-1 == val) {
+        break;
+      }
+      ret_value *= base;
+      if (ret_value > MAX_64 - val) {
+        if (err) {
+          *err = 1;
+        }
+        return 0;
+      }
+
+      ret_value += val;
+    }
+  } else {
+    if (err) {
+      *err = 1;
+    }
+    return 0;
+  }
+  if (endptr) {
+    *endptr = (char *)str;
+  }
+  return ret_value;
+}