add build-rust and readme for rust repos

Author: PeterAlfredLee

rust/README.md

@@ -0,0 +1,19 @@
+# Prepare for compiling
+
+The rust repos require rust toolchains(cargo, rustup, rustc, etc.). You can find the latest rust toolchains [here](https://www.rust-lang.org/tools/install).
+Besides the rust toolchains, we also need the [wasm-pack](https://github.com/rustwasm/wasm-pack) to compile our rust code into wasm.
+
+# How to compile
+
+With all gear up, you can compile the rust repos like this(take md5 as an example):
+```shell
+cd md5
+wasm-pack build --release
+```
+The compiled wasm binary(_bg.wasm) and javascript glue code(_bg.js) will be generated in the `pkg` directory if nothing goes wrong.
+
+# Some extra work
+
+In `crypto-js-wasm`, we use base64-encoded wasm binary(_bg.wasm).
+To get a smaller size, we use `pako` to compress the base64-encoded binary.
+You can check the `build_rust.js` for more details.

rust/build-rust.js

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+// the file is supposed to be run in node.js
+const fs = require('fs');
+const pako = require('pako');
+
+const contents = fs.readFileSync('./md5/pkg/md5Rust_bg.wasm', null);
+const compressedBytes = pako.deflate(contents);
+const base64Encoded = Buffer.from((compressedBytes)).toString('base64');
+console.log(base64Encoded);

rust/package.json

@@ -0,0 +1,13 @@
+{
+  "name": "crypto-js-wasm-rust",
+  "version": "1.0.0",
+  "description": "The rust repos require rust toolchains(cargo, rustup, rustc, etc.). You can find the latest rust toolchains [here](https://www.rust-lang.org/tools/install). Besides the rust toolchains, we also need the [wasm-pack](https://github.com/rustwasm/wasm-pack) to compile our rust code into wasm.",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "",
+  "dependencies": {
+    "pako": "^2.0.4"
+  }
+}