feat: add Host.arrayBufferToBase64 and Host.base64ToArrayBuffer

Author: Chris Dickinson

crates/core/Cargo.toml

@@ -12,7 +12,8 @@ extism-pdk = "1"
 once_cell = "1.16"
 anyhow = { workspace = true }
 quickjs-wasm-rs = "3"
-chrono = { version = "0.4", default_features = false, features = ["clock"]}
+chrono = { version = "0.4", default_features = false, features = ["clock"] }
+base64 = "0.22.1"
 
 [lib]
 crate_type = ["cdylib"]

crates/core/src/globals.rs

@@ -155,11 +155,44 @@ fn build_host_object(context: &JSContextRef) -> anyhow::Result<JSValueRef> {
             Ok(JSValue::Bool(true))
         },
     )?;
+
+    let to_base64 = context.wrap_callback(
+        |_ctx: &JSContextRef, _this: JSValueRef, args: &[JSValueRef]| {
+            let data = args.first().unwrap();
+            if !data.is_array_buffer() {
+                return Err(anyhow!("expected array buffer"));
+            }
+
+            use base64::prelude::*;
+            let bytes = data.as_bytes()?;
+            let as_string = BASE64_STANDARD.encode(bytes);
+
+            Ok(JSValue::String(as_string))
+        },
+    )?;
+
+    let from_base64 = context.wrap_callback(
+        |_ctx: &JSContextRef, _this: JSValueRef, args: &[JSValueRef]| {
+            let data = args.first().unwrap();
+            if !data.is_str() {
+                return Err(anyhow!("expected string"));
+            }
+
+            use base64::prelude::*;
+            let string = data.as_str()?;
+            let bytes = BASE64_STANDARD.decode(string)?;
+
+            Ok(JSValue::ArrayBuffer(bytes))
+        },
+    )?;
+
     let host_object = context.object_value()?;
     host_object.set_property("inputBytes", host_input_bytes)?;
     host_object.set_property("inputString", host_input_string)?;
     host_object.set_property("outputBytes", host_output_bytes)?;
     host_object.set_property("outputString", host_output_string)?;
+    host_object.set_property("arrayBufferToBase64", to_base64)?;
+    host_object.set_property("base64ToArrayBuffer", from_base64)?;
     Ok(host_object)
 }
 

crates/core/src/prelude/src/host.ts

@@ -12,12 +12,14 @@ declare global {
     outputBytes(output: ArrayBufferLike): boolean;
     outputString(output: string): boolean;
     getFunctions(): import("extism:host").user;
+    arrayBufferToBase64(input: ArrayBuffer): string;
+    base64ToArrayBuffer(input: string): ArrayBuffer;
   }
 
   var Host: Host;
 }
 
-Host.getFunctions = function () {
+Host.getFunctions = function() {
   function createInvoke(id: number, results: number) {
     if (results === 0) {
       return Host.invokeFunc0.bind(null, id);
@@ -32,4 +34,4 @@ Host.getFunctions = function () {
   }, {});
 };
 
-export {};
+export { };