From 5affb039ee4515047e85dc72a00c89624c61a4f9 Mon Sep 17 00:00:00 2001
From: Guy Bedford <gbedford@fastly.com>
Date: Tue, 8 Aug 2023 15:16:35 -0700
Subject: [PATCH] fixup

---
 .../src/transpile_bindgen.rs                  | 46 +++++++++++++++----
 1 file changed, 38 insertions(+), 8 deletions(-)

diff --git a/crates/js-component-bindgen/src/transpile_bindgen.rs b/crates/js-component-bindgen/src/transpile_bindgen.rs
index 787b063bd..ba7e63844 100644
--- a/crates/js-component-bindgen/src/transpile_bindgen.rs
+++ b/crates/js-component-bindgen/src/transpile_bindgen.rs
@@ -19,8 +19,9 @@ use wasmtime_environ::{
         GlobalInitializer, InstantiateModule, LoweredIndex, RuntimeImportIndex,
         RuntimeInstanceIndex, StaticModuleIndex, Trampoline, TrampolineIndex,
     },
+    fact::{FixedEncoding, Transcode},
+    EntityIndex, PrimaryMap,
 };
-use wasmtime_environ::{EntityIndex, PrimaryMap};
 use wit_component::StringEncoding;
 use wit_parser::abi::{AbiVariant, LiftLower};
 use wit_parser::*;
@@ -355,12 +356,41 @@ impl<'a> Instantiator<'a, '_> {
             // for now since it can't be tested and additionally JS doesn't
             // support multi-memory which transcoders rely on anyway.
             Trampoline::Transcoder {
-                op: _,
-                from: _,
-                from64: _,
-                to: _,
-                to64: _,
-            } => unimplemented!(),
+                op,
+                from,
+                from64,
+                to,
+                to64,
+            } => {
+                if *from64 || *to64 {
+                    unimplemented!();
+                }
+                let create_transcoder = match op {
+                    Transcode::Copy(FixedEncoding::Utf8) => {
+                        self.gen.intrinsic(Intrinsic::CreateUtf8Copier)
+                    }
+                    Transcode::Copy(FixedEncoding::Utf16) => unimplemented!(),
+                    Transcode::Copy(FixedEncoding::Latin1) => unimplemented!(),
+                    Transcode::Latin1ToUtf16 => unimplemented!(),
+                    Transcode::Latin1ToUtf8 => unimplemented!(),
+                    Transcode::Utf16ToCompactProbablyUtf16 => unimplemented!(),
+                    Transcode::Utf16ToCompactUtf16 => unimplemented!(),
+                    Transcode::Utf16ToLatin1 => unimplemented!(),
+                    Transcode::Utf16ToUtf8 => unimplemented!(),
+                    Transcode::Utf8ToCompactUtf16 => unimplemented!(),
+                    Transcode::Utf8ToLatin1 => unimplemented!(),
+                    Transcode::Utf8ToUtf16 => unimplemented!(),
+                };
+
+                // println!("{:?}", signature);
+                uwriteln!(
+                    self.src.js_init,
+                    "const transcoder{} = {create_transcoder}(memory{}, memory{});",
+                    i.as_u32(),
+                    from.as_u32(),
+                    to.as_u32()
+                );
+            }
 
             Trampoline::LowerImport {
                 index,
@@ -722,7 +752,7 @@ impl<'a> Instantiator<'a, '_> {
             CoreDef::Trampoline(i) => format!("trampoline{}", i.as_u32()),
             CoreDef::InstanceFlags(i) => {
                 format!("instanceFlags{}", i.as_u32())
-            },
+            }
         }
     }