syscall/js: replace TypedArrayOf with CopyBytesToGo/CopyBytesToJS

The typed arrays returned by TypedArrayOf were backed by WebAssembly
memory. They became invalid each time we grow the WebAssembly memory.
This made them very error prone and hard to use correctly.

This change removes TypedArrayOf completely and instead introduces
CopyBytesToGo and CopyBytesToJS for copying bytes between a byte
slice and an Uint8Array. This breaking change is still allowed for
the syscall/js package.

Fixes #31980.
Fixes #31812.

Change-Id: I14c76fdd60b48dd517c1593972a56d04965cb272
Reviewed-on: https://go-review.googlesource.com/c/go/+/177537
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 28 insertions, 1 deletions

diff --git a/misc/wasm/wasm_exec.js b/misc/wasm/wasm_exec.js
index a1d88e6eac..a54bb9a95d 100644
--- a/misc/wasm/wasm_exec.js
+++ b/misc/wasm/wasm_exec.js
@@ -387,6 +387,34 @@
 						mem().setUint8(sp + 24, loadValue(sp + 8) instanceof loadValue(sp + 16));
 					},
 
+					// func copyBytesToGo(dst []byte, src ref) (int, bool)
+					"syscall/js.copyBytesToGo": (sp) => {
+						const dst = loadSlice(sp + 8);
+						const src = loadValue(sp + 32);
+						if (!(src instanceof Uint8Array)) {
+							mem().setUint8(sp + 48, 0);
+							return;
+						}
+						const toCopy = src.subarray(0, dst.length);
+						dst.set(toCopy);
+						setInt64(sp + 40, toCopy.length);
+						mem().setUint8(sp + 48, 1);
+					},
+
+					// func copyBytesToJS(dst ref, src []byte) (int, bool)
+					"syscall/js.copyBytesToJS": (sp) => {
+						const dst = loadValue(sp + 8);
+						const src = loadSlice(sp + 16);
+						if (!(dst instanceof Uint8Array)) {
+							mem().setUint8(sp + 48, 0);
+							return;
+						}
+						const toCopy = src.subarray(0, dst.length);
+						dst.set(toCopy);
+						setInt64(sp + 40, toCopy.length);
+						mem().setUint8(sp + 48, 1);
+					},
+
 					"debug": (value) => {
 						console.log(value);
 					},
@@ -403,7 +431,6 @@
 				true,
 				false,
 				global,
-				this._inst.exports.mem,
 				this,
 			];
 			this._refs = new Map();