WasmPatch

Yet Another Patch Module for iOS/macOS via WebAssembly

WasmPatch bridges Objective-C and WebAssembly. We build C code into WebAssembly, and have the ability to call any Objective-C class and method dynamically. This makes the App obtaining the power of WebAssembly: add features or replacing Objective-C code to fix bugs dynamically.

WasmPatch is a DEMO now, and is still in development, welcome to improve the project together.

How it work

• 中文介绍: 请关注微信订阅号「首先很有趣」，点击菜单「专辑」查看「WasmPatch探索之路」专辑。

Example

View Source Directly

Call Method

// method call - class method
call_class_method_0("CallMe", "sayHi");
    
WAPObject word = new_objc_nsstring("I am from c program");
call_class_method_1("CallMe", "sayWord:", word);
dealloc_object(word);

// method call - instance method
WAPObject call = alloc_objc_class("CallMe");
call_instance_method_0(call,"sayHi");
dealloc_object(call);

WAPObject call1 = alloc_objc_class("CallMe");
word = new_objc_nsstring("I am from c program");
call_instance_method_1(call1,"sayWord:", word);
dealloc_object(word);
dealloc_object(call1);

Replace Method

int my_class_ReplaceMe_request(WAPObject self, const char * cmd) {
    print_string("replaced + ReplaceMe request");
    return 0;
}

int my_class_ReplaceMe_requestfromto(WAPObject self, const char * cmd, WAPArray parameters) {
    print_string("replaced + ReplaceMe requestFrom:Two to:One");
    return 0;
}
int my_instance_ReplaceMe_request(WAPObject self, const char * cmd) {
    print_string("replaced - ReplaceMe request");
    return 0;
}

int my_instance_ReplaceMe_requestfromto(WAPObject self, const char * cmd, WAPArray parameters) {
    print_string("replaced - ReplaceMe requestFrom:Two to:One");
    return 0;
}

int entry() {
    // method replace
    replace_class_method("ReplaceMe", "request", "my_class_ReplaceMe_request");
    replace_class_method("ReplaceMe", "requestFrom:to:", "my_class_ReplaceMe_requestfromto");

    replace_instance_method("ReplaceMe", "request", "my_instance_ReplaceMe_request");
    replace_instance_method("ReplaceMe", "requestFrom:to:", "my_instance_ReplaceMe_requestfromto");
}

Call with many arguments

// many arguments
WAPArray params = alloc_array();
append_array(params, alloc_int32(10));
append_array(params, alloc_int64(666));
append_array(params, alloc_float(7.77));
append_array(params, alloc_double(200.2222));
append_array(params, new_objc_nsstring("excellent"));
append_array(params, alloc_string("WebAssembly"));
call_class_method_param("CallMe", "callWithManyArguments:p1:p2:p3:p4:p5:", params);
dealloc_array(params);

Environment

• iOS/macOS.
• Tested: arm64/arm64e/x86_64 , Should work: armv7/armv7s/i386.
• C++17 standard.

Quick playing with Demo

cd Demo && sh podinstall_all.sh

• iOS demo: open Demo/WasmPatch-iOS/WasmPatch-iOS.xcworkspace
• macOS demo: open Demo/WasmPatch-macOS/WasmPatch-macOS.xcworkspace

Usage

Build C into WebAssembly

To build c code into WebAssembly, we need to install llvm.

brew update
brew install llvm

Playing with Demo

Demo c code for patch building:

TestCase/WasmPatch-TestCase/Assets/script.bundle/objc.c

Run compile-testcase.sh to build it.

cd TestCase && sh compile-testcase.sh

It will call Tool/c2wasm.sh internal.

Then, Pod install iOS and macOS demo.

cd Demo && sh podinstall_all.sh

Open Demo/WasmPatch-iOS/WasmPatch-iOS.xcworkspace for iOS demo, or open Demo/WasmPatch-macOS/WasmPatch-macOS.xcworkspace for macOS demo.

Build Patch

./Tool/c2wasm.sh input.c output.wasm

Load Patch

// header file
#import <WasmPatch/WasmPatch.h>

// ...

// call wap_load_file to load wasm file
NSString *scriptPath = [scriptBundlePath stringByAppendingPathComponent:@"objc.wasm"];
bool result = wap_load_file(scriptPath.UTF8String);
if (!result) {
    NSLog(@"failed load file %@", scriptPath);
    return;
}

Installation

CocoaPods

// local pod
pod 'WasmPatch', :path => '../../'

// online pod
pod 'WasmPatch'

Manual

Drag WasmPatch directory into project, and configure Header Search Path to WasmPatch/Classes/wap/depend/libffi/include

Thanks

• wasm3 https://github.com/wasm3/wasm3
• libffi https://github.com/libffi/libffi
• JSPatch https://github.com/bang590/JSPatch

Wish you enjoy :)