diff --git a/benchs/stubs.c b/benchs/stubs.c
new file mode 100644
index 00000000..ce2398ac
--- /dev/null
+++ b/benchs/stubs.c
@@ -0,0 +1,80 @@
+
+#include <caml/alloc.h>
+#include <caml/memory.h>
+#include <caml/mlvalues.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+inline int pbrt_varint_size(int64_t i) {
+  int n = 0;
+  while (1) {
+    n++;
+    int64_t cur = i & 0x7f;
+    if (cur == i)
+      break;
+    i = i >> 7;
+  }
+  return n;
+}
+
+// number of bytes for i
+CAMLprim value caml_pbrt_varint_size(int64_t i) {
+  int res = pbrt_varint_size(i);
+  return Val_int(res);
+}
+
+CAMLprim value caml_pbrt_varint_size_byte(value v_i) {
+  CAMLparam1(v_i);
+
+  int64_t i = Int64_val(v_i);
+  int res = pbrt_varint_size(i);
+  CAMLreturn(Val_int(res));
+}
+
+// write i at str[idx…]
+inline void pbrt_varint(unsigned char *str, int64_t i) {
+  while (true) {
+    int64_t cur = i & 0x7f;
+    if (cur == i) {
+      *str = (unsigned char)cur;
+      break;
+    } else {
+      *str = (unsigned char)(cur | 0x80);
+      i = i >> 7;
+      ++str;
+    }
+  }
+}
+
+//    let[@inline] varint (i : int64) (e : t) : unit =
+//      let n_bytes = varint_size i in
+//      let start = reserve_n e n_bytes in
+//
+//      let i = ref i in
+//      for j = 0 to n_bytes - 1 do
+//        let cur = Int64.(logand !i 0x7fL) in
+//        if j = n_bytes - 1 then
+//          Bytes.set e.b (start + j) (Char.unsafe_chr Int64.(to_int cur))
+//        else (
+//          Bytes.set e.b (start + j)
+//            (Char.unsafe_chr Int64.(to_int (logor 0x80L cur)));
+//          i := Int64.shift_right_logical !i 7
+//        )
+//      done
+
+// write `i` starting at `idx`
+CAMLprim value caml_pbrt_varint(value _str, intnat idx, int64_t i) {
+  CAMLparam1(_str);
+  char *str = Bytes_val(_str);
+  pbrt_varint(str + idx, i);
+  CAMLreturn(Val_unit);
+}
+
+CAMLprim value caml_pbrt_varint_bytes(value _str, value _idx, value _i) {
+  CAMLparam3(_str, _idx, _i);
+  char *str = Bytes_val(_str);
+  int idx = Int_val(_idx);
+  int64_t i = Int64_val(_idx);
+  pbrt_varint(str + idx, i);
+  CAMLreturn(Val_unit);
+}