diff --git a/reactos/lib/sdk/libcntpr/string/strtoull.c b/reactos/lib/sdk/libcntpr/string/strtoull.c
new file mode 100644
index 00000000000..893e4a64bcf
--- /dev/null
+++ b/reactos/lib/sdk/libcntpr/string/strtoull.c
@@ -0,0 +1,71 @@
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <ctype.h>
+
+
+unsigned long long
+strtoull(const char *nptr, char **endptr, int base)
+{
+  const char *s = nptr;
+  unsigned long long acc;
+  int c;
+  unsigned long long cutoff;
+  int neg = 0, any, cutlim;
+
+  /*
+   * See strtol for comments as to the logic used.
+   */
+  do {
+    c = *s++;
+  } while (isspace(c));
+  if (c == '-')
+  {
+    neg = 1;
+    c = *s++;
+  }
+  else if (c == '+')
+    c = *s++;
+  if ((base == 0 || base == 16) &&
+      c == '0' && (*s == 'x' || *s == 'X'))
+  {
+    c = s[1];
+    s += 2;
+    base = 16;
+  }
+  if (base == 0)
+    base = c == '0' ? 8 : 10;
+  cutoff = (unsigned long long)ULLONG_MAX / (unsigned long long)base;
+  cutlim = (unsigned long long)ULLONG_MAX % (unsigned long long)base;
+  for (acc = 0, any = 0;; c = *s++)
+  {
+    if (isdigit(c))
+      c -= '0';
+    else if (isalpha(c))
+      c -= isupper(c) ? 'A' - 10 : 'a' - 10;
+    else
+      break;
+    if (c >= base)
+      break;
+    if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
+      any = -1;
+    else {
+      any = 1;
+      acc *= base;
+      acc += c;
+    }
+  }
+  if (any < 0)
+  {
+    acc = ULLONG_MAX;
+
+  }
+  else if (neg)
+    acc = -acc;
+  if (endptr != 0)
+    *endptr = any ? (char *)((size_t)(s - 1)) : (char *)((size_t)nptr);
+  return acc;
+}
+
+