1 files changed, 34 insertions, 0 deletions
diff --git a/third_party/rust/jsparagus-emitter/src/dis.rs b/third_party/rust/jsparagus-emitter/src/dis.rs
new file mode 100644
index 0000000000..f9978b8d9c
--- /dev/null
+++ b/third_party/rust/jsparagus-emitter/src/dis.rs
@@ -0,0 +1,34 @@
+use std::convert::TryFrom;
+use std::fmt::Write;
+use stencil::opcode::Opcode;
+
+/// Return a string form of the given bytecode.
+pub fn dis(bc: &[u8]) -> String {
+    let mut result = String::new();
+    let mut iter = bc.iter();
+    let mut offset = 0;
+    loop {
+        let len = match iter.next() {
+            Some(byte) => match Opcode::try_from(*byte) {
+                Ok(op) => {
+                    write!(&mut result, "{}", format!("{:05}: {:?}", offset, op)).unwrap();
+                    offset = offset + op.instruction_length();
+                    op.instruction_length()
+                }
+                Err(()) => {
+                    write!(&mut result, "{}", byte).unwrap();
+                    1
+                }
+            },
+            None => break,
+        };
+
+        for _ in 1..len {
+            write!(&mut result, " {}", iter.next().unwrap()).unwrap();
+        }
+
+        writeln!(&mut result).unwrap();
+    }
+
+    result
+}