Move leb128 stuff to Rust

rts/motoko-rts/src/leb128.rs

@@ -0,0 +1,32 @@
+//! LEB1128 encoding. Reference: https://en.wikipedia.org/wiki/LEB128
+
+#[no_mangle]
+unsafe extern "C" fn leb128_encode(mut val: u32, mut buf: *mut u8) {
+    loop {
+        let byte = (val & 0b0111_1111) as u8;
+        val >>= 7;
+        if val == 0 {
+            *buf = byte;
+            break;
+        } else {
+            *buf = byte | 0b1000_0000;
+            buf = buf.add(1);
+        }
+    }
+}
+
+#[no_mangle]
+unsafe extern "C" fn sleb128_encode(mut val: i32, mut buf: *mut u8) {
+    loop {
+        let byte = (val & 0b0111_1111) as u8;
+        val >>= 7;
+        if (val == 0 && byte & 0b0100_0000 == 0) || (val == -1 && byte & 0b0100_0000 == 0b0100_0000)
+        {
+            *buf = byte;
+            break;
+        } else {
+            *buf = byte | 0b1000_0000;
+            buf = buf.add(1);
+        }
+    }
+}

rts/motoko-rts/src/lib.rs

@@ -16,6 +16,7 @@ mod buf;
 mod char;
 pub mod closure_table;
 mod debug;
+mod leb128;
 mod mem;
 mod text;
 mod text_iter;

rts/rts.c

@@ -30,33 +30,3 @@ as_ptr get_version() { return text_of_cstr(RTS_VERSION); }
 as_ptr (*version_getter)() = &get_version;
 
 export as_ptr version() { return (*version_getter)(); }
-
-/* (S)LEB128 Encoding of words */
-
-export void leb128_encode(uint32_t n, unsigned char *buf) {
-  while (true) {
-    buf[0] = (unsigned char)n; // get low bits
-    if (n >>= 7) {
-      // more bytes to come, set high bit and continue
-      buf[0] |= 1<<7;
-      buf++;
-    } else {
-      // we are done. high bit should be cleared anyway
-      return;
-    }
-  }
-}
-
-export void sleb128_encode(int32_t n, unsigned char *buf) {
-  while (true) {
-    *buf = n & 0x7F; // get low bits
-    if (n >= -64 && n < 64) {
-      // last byte written, high bit is clear
-      return;
-    } else {
-      // more bytes to come, set high bit and continue
-      *buf++ |= 0x80;
-      n >>= 7;
-    }
-  }
-}