Add wasmer web assembly submodule and a POC engine

The `wasmer-d` submodule supports running web assembly outside of the web
browser. The class `node/WasmEngine.d` provides a POC engine to run web
assembly programs within agora.
This is still very much a work in progress. There are some unit tests
that can be used to experiment.

.gitmodules

@@ -58,3 +58,6 @@
 [submodule "serialization"]
 	path = submodules/serialization
 	url = https://github.com/bosagora/serialization.git
+[submodule "wasmer-d"]
+	path = submodules/wasmer-d
+	url = https://github.com/chances/wasmer-d.git

README.md

@@ -39,6 +39,7 @@ Additionally, the following are dependencies:
 - `openssl`:    Binary (to detect the version) and development library
 - `sqlite3`:    Development library
 - `zlib`:       Development library
+- `wasmer`:     Web Assembly Engine - [Install](https://github.com/wasmerio/wasmer-install#readme)
 
 Additionally, on OSX, `PKG_CONFIG_PATH` needs to be properly set to pick up `sqlite3` and `openssl`.
 Provided you installed those packages via `brew`, you can run the following command prior to building:

dub.json

@@ -219,6 +219,7 @@
         "localrest":        { "version": "*", "dflags" : ["-preview=in"] },
         "ocean":            { "version": "*", "dflags" : ["-preview=in"] },
         "serialization":    { "version": "*", "dflags" : ["-preview=in"] },
-        "vibe-d":           { "version": "*", "dflags" : ["-preview=in"] }
+        "vibe-d":           { "version": "*", "dflags" : ["-preview=in"] },
+        "wasmer":           { "version": "*", "dflags" : ["-preview=in"] }
     }
 }

dub.selections.json

@@ -22,6 +22,7 @@
 		"taggedalgebraic": {"path":"submodules/taggedalgebraic/"},
 		"tinyendian": {"path":"submodules/tinyendian/"},
 		"vibe-core": {"path":"submodules/vibe-core/"},
-		"vibe-d": {"path":"submodules/vibe.d/"}
+		"vibe-d": {"path":"submodules/vibe.d/"},
+		"wasmer": {"path":"submodules/wasmer-d/"}
 	}
 }

source/agora/node/WasmEngine.d

@@ -0,0 +1,149 @@
+/*******************************************************************************
+
+    Contains the wasmer WebAssembly engine to be used for Trust Contracts
+
+    Copyright:
+        Copyright (c) 2021 BOS Platform Foundation Korea
+        All rights reserved.
+
+    License:
+        MIT License. See LICENSE for details.
+
+*******************************************************************************/
+
+module agora.node.WasmEngine;
+
+import agora.utils.Log;
+
+mixin AddLogger!();
+
+/// Ditto
+public class WasmEngine
+{
+    import wasmer;
+
+    Engine engine;
+    Store store;
+
+    public void start ()
+    {
+        log.info("Starting WasmEngine");
+        engine = new Engine();
+        store = new Store(engine);
+        log.info("Started WasmEngine");
+    }
+
+    public void stop ()
+    {
+        log.info("Stopping WasmEngine");
+        destroy(store);
+        destroy(engine);
+        log.info("Stopped WasmEngine");
+    }
+
+    public void exampleTime ()
+    {
+        log.info("Running {} using WasmEngine", __FUNCTION__);
+        const wat_callback_module_time = "(module
+            (type $FUNCSIG$ii (func (param i32) (result i32)))
+            (import \"env\" \"time\" (func $time (param i32) (result i32)))
+            (table 0 anyfunc)
+            (memory $0 1)
+            (export \"memory\" (memory $0))
+            (export \"main\" (func $main))
+            (func $main (; 1 ;) (result i32)
+            (call $time
+            (i32.const 0)
+            )
+            )
+        )";
+        log.trace("wat (text representation of wasm)");
+        log.trace("==============================");
+        log.trace("{}", wat_callback_module_time);
+        log.trace("==============================");
+        auto module_ = Module.from(store, wat_callback_module_time);
+        assert(module_.valid, "Error compiling module!");
+
+        auto print = (Module module_, int value) =>
+        {
+            return value;
+        }();
+        auto imports = [new Function(store, module_, print.toDelegate).asExtern];
+        auto instance = module_.instantiate(imports);
+        assert(instance.valid, "Could not instantiate module!");
+        auto runFunc = Function.from(instance.exports[1]);
+        assert(instance.exports[1].name == "main", "Failed to get the `main` function!");
+        assert(runFunc.valid, "`main` function invalid!");
+        Value[] results;
+        assert(runFunc.call(results), "Error calling the `main` function!");
+        assert(results.length == 1, "length of results should be 1!");
+        // assert(results[0].value.of.i32 > 0, "time should be greater than 0");
+        log.info("Used web assembly engine to get time. Result = {}", results[0].value.of.i32);
+        destroy(instance);
+        destroy(module_);
+    }
+
+
+    public void exampleAdd ()
+    {
+        const wat_callback_module_add = "(module" ~
+                "  (func $print (import \"\" \"print\") (param i32) (result i32))" ~
+                "  (func (export \"run\") (param $x i32) (param $y i32) (result i32)" ~
+                "    (call $print (i32.add (local.get $x) (local.get $y)))" ~
+                "  )" ~
+                ")";
+        log.info("Running {} using WasmEngine", __FUNCTION__);
+        log.trace("wat (text representation of wasm)");
+        log.trace("==============================");
+        log.trace("{}", wat_callback_module_add);
+        log.trace("==============================");
+
+        auto module_ = Module.from(store, wat_callback_module_add);
+        assert(module_.valid, "Error compiling module!");
+
+        auto print = (Module module_, int value) =>
+        {
+            return value;
+        }();
+        auto imports = [new Function(store, module_, print.toDelegate).asExtern];
+        auto instance = module_.instantiate(imports);
+        assert(instance.valid, "Could not instantiate module!");
+        auto runFunc = Function.from(instance.exports[0]);
+        assert(instance.exports[0].name == "run" && runFunc.valid, "Failed to get the `run` function!");
+
+        auto three = new Value(3);
+        auto four = new Value(4);
+        Value[] results;
+        assert(runFunc.call([three, four], results), "Error calling the `run` function!");
+        assert(results.length == 1 && results[0].value.of.i32 == 7);
+        log.info("Used web assembly engine to add 3 and 4. Result = {}", results[0].value.of.i32);
+
+        destroy(three);
+        destroy(four);
+        destroy(instance);
+        destroy(module_);
+    }
+}
+
+unittest
+{
+    import std.stdio;
+    import std.format;
+
+    Log.root.level(LogLevel.Trace, true);
+    auto output = stdout.lockingTextWriter();
+    try
+    {
+        auto wasmEngine = new WasmEngine();
+        wasmEngine.start();
+        wasmEngine.exampleAdd();
+        wasmEngine.exampleTime();
+        wasmEngine.stop();
+    }
+    catch (Exception e)
+    {
+        output.formattedWrite("%s", e);
+    }
+    // print logs of the work thread
+    CircularAppender!()().print(output);
+}