added: copying data directy from Onyx to JS through Uint8Array

core/js/foreign.onyx

@@ -31,6 +31,9 @@ use core.alloc
 
         __new_object :: () -> Value ---
         __new_array  :: () -> Value ---
+
+        __copy_to_js   :: (arraybuf: Value, buf: [] u8) -> i32 ---
+        __copy_to_onyx :: (buf: [] u8, arraybuf: Value) -> i32 ---
     }
 
     // Func

core/js/onyx.js

@@ -297,6 +297,32 @@ Onyx.register_module("__syscall", instance => ({
         const onyxmem = new Uint8Array(instance.memory.buffer)
         onyxmem.set(encoded, outptr)
         return encoded.length
+    },
+    __copy_to_js(a_ref, bufptr, buflen) {
+        const a = instance.load_value(a_ref)
+        if (!(a instanceof Uint8Array || a instanceof Uint8ClampedArray)) {
+            return -1
+        }
+
+        const onyxmem = new Uint8Array(instance.memory.buffer)
+        const copylen = Math.min(buflen, a.length)
+        const to_copy = onyxmem.subarray(bufptr, bufptr+copylen)
+        a.set(to_copy)
+
+        return copylen
+    },
+    __copy_to_onyx(bufptr, buflen, a_ref) {
+        const a = instance.load_value(a_ref)
+        if (!(a instanceof Uint8Array || a instanceof Uint8ClampedArray)) {
+            return -1
+        }
+
+        const onyxmem = new Uint8Array(instance.memory.buffer, bufptr)
+        const copylen = Math.min(buflen, a.length)
+        const to_copy = a.subarray(0, copylen)
+        onyxmem.set(to_copy)
+
+        return copylen
     }
 }))
 

core/js/value.onyx

@@ -324,6 +324,23 @@ Value.truthy :: (v: Value) -> bool {
     }
 }
 
+#doc """
+    Copies data from a Uint8Array in JS to a buffer in Onyx.
+    Returns the number of bytes copied, or -1 if the value was not a Uint8Array.
+"""
+Value.copy_to_onyx :: (v: Value, buf: [] u8) -> i32 {
+    return __copy_to_onyx(buf, v);
+}
+
+
+#doc """
+    Copies data into a Uint8Array in JS from a buffer in Onyx.
+    Returns the number of bytes copied, or -1 if the value was not a Uint8Array.
+"""
+Value.copy_to_js :: (v: Value, buf: [] u8) -> i32 {
+    return __copy_to_js(v, buf);
+}
+
 
 #local
 transform_args :: macro (args: [] any, $body: Code) {