From 03f4d9a608b4aa135c4fd7426a78496b6ed81f51 Mon Sep 17 00:00:00 2001
From: Yuta Saito <kateinoigakukun@gmail.com>
Date: Fri, 27 Jun 2025 12:06:08 +0900
Subject: [PATCH] Slice a bytes array when the underlying memory is shared

TextDecoder does not support decoding shared memory slices directly on
browsers, so we need to slice the Uint8Array
---
 .../Sources/BridgeJSLink/BridgeJSLink.swift       | 15 +++++++++++++--
 .../BridgeJSToolTests/BridgeJSLinkTests.swift     |  4 ++--
 Plugins/PackageToJS/Sources/PackageToJS.swift     |  9 +++++++--
 3 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/Plugins/BridgeJS/Sources/BridgeJSLink/BridgeJSLink.swift b/Plugins/BridgeJS/Sources/BridgeJSLink/BridgeJSLink.swift
index f1605670..f9e15984 100644
--- a/Plugins/BridgeJS/Sources/BridgeJSLink/BridgeJSLink.swift
+++ b/Plugins/BridgeJS/Sources/BridgeJSLink/BridgeJSLink.swift
@@ -4,6 +4,17 @@ struct BridgeJSLink {
     /// The exported skeletons
     var exportedSkeletons: [ExportedSkeleton] = []
     var importedSkeletons: [ImportedModuleSkeleton] = []
+    let sharedMemory: Bool
+
+    init(
+        exportedSkeletons: [ExportedSkeleton] = [],
+        importedSkeletons: [ImportedModuleSkeleton] = [],
+        sharedMemory: Bool
+    ) {
+        self.exportedSkeletons = exportedSkeletons
+        self.importedSkeletons = importedSkeletons
+        self.sharedMemory = sharedMemory
+    }
 
     mutating func addExportedSkeletonFile(data: Data) throws {
         let skeleton = try JSONDecoder().decode(ExportedSkeleton.self, from: data)
@@ -118,7 +129,7 @@ struct BridgeJSLink {
                         const bjs = {};
                         importObject["bjs"] = bjs;
                         bjs["return_string"] = function(ptr, len) {
-                            const bytes = new Uint8Array(memory.buffer, ptr, len);
+                            const bytes = new Uint8Array(memory.buffer, ptr, len)\(sharedMemory ? ".slice()" : "");
                             tmpRetString = textDecoder.decode(bytes);
                         }
                         bjs["init_memory"] = function(sourceId, bytesPtr) {
@@ -127,7 +138,7 @@ struct BridgeJSLink {
                             bytes.set(source);
                         }
                         bjs["make_jsstring"] = function(ptr, len) {
-                            const bytes = new Uint8Array(memory.buffer, ptr, len);
+                            const bytes = new Uint8Array(memory.buffer, ptr, len)\(sharedMemory ? ".slice()" : "");
                             return swift.memory.retain(textDecoder.decode(bytes));
                         }
                         bjs["init_memory_with_result"] = function(ptr, len) {
diff --git a/Plugins/BridgeJS/Tests/BridgeJSToolTests/BridgeJSLinkTests.swift b/Plugins/BridgeJS/Tests/BridgeJSToolTests/BridgeJSLinkTests.swift
index e052ed42..3e65ca04 100644
--- a/Plugins/BridgeJS/Tests/BridgeJSToolTests/BridgeJSLinkTests.swift
+++ b/Plugins/BridgeJS/Tests/BridgeJSToolTests/BridgeJSLinkTests.swift
@@ -55,7 +55,7 @@ import Testing
         let encoder = JSONEncoder()
         encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
         let outputSkeletonData = try encoder.encode(outputSkeleton)
-        var bridgeJSLink = BridgeJSLink()
+        var bridgeJSLink = BridgeJSLink(sharedMemory: false)
         try bridgeJSLink.addExportedSkeletonFile(data: outputSkeletonData)
         try snapshot(bridgeJSLink: bridgeJSLink, name: name + ".Export")
     }
@@ -73,7 +73,7 @@ import Testing
         encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
         let outputSkeletonData = try encoder.encode(importTS.skeleton)
 
-        var bridgeJSLink = BridgeJSLink()
+        var bridgeJSLink = BridgeJSLink(sharedMemory: false)
         try bridgeJSLink.addImportedSkeletonFile(data: outputSkeletonData)
         try snapshot(bridgeJSLink: bridgeJSLink, name: name + ".Import")
     }
diff --git a/Plugins/PackageToJS/Sources/PackageToJS.swift b/Plugins/PackageToJS/Sources/PackageToJS.swift
index 43e2c244..48f84e54 100644
--- a/Plugins/PackageToJS/Sources/PackageToJS.swift
+++ b/Plugins/PackageToJS/Sources/PackageToJS.swift
@@ -583,7 +583,8 @@ struct PackagingPlanner {
                             let decoder = JSONDecoder()
                             let data = try Data(contentsOf: URL(fileURLWithPath: scope.resolve(path: $0).path))
                             return try decoder.decode(ImportedModuleSkeleton.self, from: data)
-                        }
+                        },
+                        sharedMemory: Self.isSharedMemoryEnabled(triple: triple)
                     )
                     let (outputJs, outputDts) = try link.link()
                     try system.writeFile(atPath: scope.resolve(path: bridgeJs).path, content: Data(outputJs.utf8))
@@ -699,7 +700,7 @@ struct PackagingPlanner {
 
         let inputPath = selfPackageDir.appending(path: file)
         let conditions: [String: Bool] = [
-            "USE_SHARED_MEMORY": triple == "wasm32-unknown-wasip1-threads",
+            "USE_SHARED_MEMORY": Self.isSharedMemoryEnabled(triple: triple),
             "IS_WASI": triple.hasPrefix("wasm32-unknown-wasi"),
             "USE_WASI_CDN": options.useCDN,
             "HAS_BRIDGE": exportedSkeletons.count > 0 || importedSkeletons.count > 0,
@@ -742,6 +743,10 @@ struct PackagingPlanner {
             try system.writeFile(atPath: $1.resolve(path: $0.output).path, content: Data(content.utf8))
         }
     }
+
+    private static func isSharedMemoryEnabled(triple: String) -> Bool {
+        return triple == "wasm32-unknown-wasip1-threads"
+    }
 }
 
 // MARK: - Utilities