diff --git a/lang/src/tokeniser.asm b/lang/src/tokeniser.asm
index 6b050a7..9a84f37 100644
--- a/lang/src/tokeniser.asm
+++ b/lang/src/tokeniser.asm
@@ -19,6 +19,7 @@ extern is_id_start
 extern is_whitespace
 
 global tokeniser_init
+global tokeniser_init_buf
 global tokeniser_print
 global find_lexeme
 global expect_token
@@ -54,6 +55,22 @@ section .bss
 statbuf: resb 144
 
 section .text
+
+;; rdi: pointer to buffer
+;; rsi: length of buffer
+tokeniser_init_buf:
+    push rbp
+    mov rbp, rsp
+
+    mov dword [rel input_file], 0
+    mov qword [rel buffer], rdi
+    mov qword [rel buffer_len], rsi
+    mov qword [rel cursor], 0
+
+    pop rbp
+    ret
+
+
 ;; Initialises the tokeniser
 ;; rdx: pointer to filename (null-terminated)
 tokeniser_init:
diff --git a/lang/tests/shared/shared.rs b/lang/tests/shared/shared.rs
index 091e770..7eed257 100644
--- a/lang/tests/shared/shared.rs
+++ b/lang/tests/shared/shared.rs
@@ -1,8 +1,13 @@
 #![allow(dead_code)]
 
+#[inline(never)]
+fn __do_panic() -> ! {
+    panic!("Called panic from external code.");
+}
+
 #[unsafe(no_mangle)]
 extern "C" fn panic() -> ! {
-    panic!("Called panic from external code.");
+    __do_panic()
 }
 
 #[repr(C)]
diff --git a/lang/tests/tokens.rs b/lang/tests/tokens.rs
index c96102b..24c80fe 100644
--- a/lang/tests/tokens.rs
+++ b/lang/tests/tokens.rs
@@ -43,6 +43,7 @@ impl AsLexeme for LexemeRaw {
 #[allow(dead_code)]
 unsafe extern "C" {
     unsafe fn tokeniser_init(path: *const i8) -> ();
+    unsafe fn tokeniser_init_buf(bytes: *const u8, len: usize) -> ();
     unsafe fn tokeniser_print() -> ();
     unsafe fn is_ident(len: usize) -> bool;
     unsafe fn is_number(len: usize) -> bool;
@@ -133,16 +134,16 @@ fn main() {
         assert_eq!(
             &collect_tokens()[..],
             &[
-                Lexeme(30, "this-is-an-ident"),
-                Lexeme(30, "another_ident123"),
-                Lexeme(30, "_underscore_test"),
-                Lexeme(30, "mixedCASEIdent"),
-                Lexeme(30, "number12345"),
-                Lexeme(30, "____"),
-                Lexeme(30, "_"),
+                Lexeme(31, "this-is-an-ident"),
+                Lexeme(31, "another_ident123"),
+                Lexeme(31, "_underscore_test"),
+                Lexeme(31, "mixedCASEIdent"),
+                Lexeme(31, "number12345"),
+                Lexeme(31, "____"),
+                Lexeme(31, "_"),
                 Lexeme(17, ""),
-                Lexeme(30, "leading-minus"),
-                Lexeme(30, "trailing-minus-"),
+                Lexeme(31, "leading-minus"),
+                Lexeme(31, "trailing-minus-"),
             ]
         );
 
@@ -154,7 +155,7 @@ fn main() {
             &collect_tokens()[..],
             &[
                 Lexeme(4, ""),
-                Lexeme(30, "my-function"),
+                Lexeme(31, "my-function"),
                 Lexeme(19, ""),
                 Lexeme(18, ""),
                 Lexeme(12, ""),
@@ -173,7 +174,7 @@ fn main() {
 
         assert_eq!(expect_token(2).into_option(), None);
         assert_eq!(expect_token(4).into_option().unwrap().as_str(), "fn");
-        assert_eq!(unwrap_token(30).as_str(), "my-function");
+        assert_eq!(unwrap_token(31).as_str(), "my-function");
 
         eprint!("Initializing tokeniser.. ");
         tokeniser_init(c"tests/tokens/comment.l".as_ptr());
@@ -182,15 +183,15 @@ fn main() {
         assert_eq!(
             &collect_tokens()[..],
             &[
-                Lexeme(33, ""),
+                Lexeme(34, ""),
                 Lexeme(4, ""),
-                Lexeme(30, "my-function"),
+                Lexeme(31, "my-function"),
                 Lexeme(19, ""),
                 Lexeme(18, ""),
                 Lexeme(12, ""),
                 Lexeme(11, ""),
                 Lexeme(21, ""),
-                Lexeme(33, ""),
+                Lexeme(34, ""),
                 Lexeme(5, ""),
                 Lexeme(10, ""),
                 Lexeme(23, ""),
@@ -205,11 +206,11 @@ fn main() {
         assert_eq!(
             &collect_tokens()[..],
             &[
-                Lexeme(31, "1234"),
-                Lexeme(31, "123_345_"),
-                Lexeme(31, "1234____56"),
-                Lexeme(31, "1"),
-                Lexeme(31, "0"),
+                Lexeme(32, "1234"),
+                Lexeme(32, "123_345_"),
+                Lexeme(32, "1234____56"),
+                Lexeme(32, "1"),
+                Lexeme(32, "0"),
             ]
         );
 
@@ -220,14 +221,24 @@ fn main() {
         assert_eq!(
             &collect_tokens()[..],
             &[
-                Lexeme(32, "\"this is a string\""),
-                Lexeme(32, "\"another\nstring\nspanning multiple\n   lines\""),
-                Lexeme(32, "\"string with a \\\"quoted\\\" word\""),
-                Lexeme(32, "\"a\""),
-                Lexeme(32, "\"\"")
+                Lexeme(33, "\"this is a string\""),
+                Lexeme(33, "\"another\nstring\nspanning multiple\n   lines\""),
+                Lexeme(33, "\"string with a \\\"quoted\\\" word\""),
+                Lexeme(33, "\"a\""),
+                Lexeme(33, "\"\"")
             ],
         );
 
+        eprint!("Initializing tokeniser.. ");
+        let src = b"3 + 4";
+        tokeniser_init_buf(src.as_ptr(), src.len());
+        eprintln!("ok.");
+
+        assert_eq!(
+            &collect_tokens()[..],
+            &[Lexeme(32, "3"), Lexeme(16, "+"), Lexeme(32, "4")],
+        );
+
         eprintln!("Finished tokenising.");
     }
 }