add platform module providing implementation of random functions

platform/makefile

@@ -1,4 +1,7 @@
-all: loader.wasm
+all: loader.wasm platform.wasm
 
 loader.wasm: loader.cwa
 	curlywas loader.cwa
+
+platform.wasm: platform.cwa
+	curlywas platform.cwa

platform/platform.cwa

@@ -0,0 +1,16 @@
+import "env.memory" memory(4);
+
+global mut randomState: i32 = 37;
+
+export fn random() -> i32 {
+    let state: i32;
+    randomState = (state := (
+                          state := randomState ^ (randomState << 13)
+                      ) ^ (state >> 17)
+                  ) ^ (state << 5);
+    randomState * 625341585
+}
+
+export fn randomSeed(s: i32) {
+    randomState = (((s + !(s >> 31)) as i64 * 8445297036689579347i64) >> 31i64) as i32;
+}

src/main.rs

@@ -61,6 +61,8 @@ fn main() -> Result<()> {
 
     let mut loader = Loader::new(&engine)?;
 
+    let platform_module = wasmtime::Module::new(&engine, include_bytes!("../platform/platform.wasm"))?;
+
     let module = wasmtime::Module::new(&engine, loader.load(&uw8_module)?)?;
 
     let mut store = wasmtime::Store::new(&engine, ());
@@ -93,6 +95,12 @@ fn main() -> Result<()> {
         )?;
     }
 
+    let platform_instance = linker.instantiate(&mut store, &platform_module)?;
+
+    for export in platform_instance.exports(&mut store) {
+        linker.define("env", export.name(), export.into_func().expect("platform surely only exports functions"))?;
+    }
+
     let instance = linker.instantiate(&mut store, &module)?;
     let tic = instance.get_typed_func::<i32, (), _>(&mut store, "tic")?;
 

uw8-tool/src/base_module.rs

@@ -65,6 +65,9 @@ impl BaseModule {
         add_function(&mut functions, &type_map, "pow", &[F32, F32], Some(F32));
         add_function(&mut functions, &type_map, "log", &[F32], Some(F32));
 
+        add_function(&mut functions, &type_map, "random", &[], Some(I32));
+        add_function(&mut functions, &type_map, "randomSeed", &[I32], None);
+
         for i in functions.len()..64 {
             add_function(
                 &mut functions,

web/src/main.js

@@ -1,4 +1,5 @@
 import loaderUrl from "data-url:../../platform/loader.wasm";
+import platformUrl from "data-url:../../platform/platform.wasm";
 import baseUrl from "data-url:../../uw8-tool/base1.wasm";
 
 async function loadWasm(url, imports) {
@@ -96,6 +97,12 @@ async function runModule(data) {
             importObject.env['g_reserved' + i] = 0;
         }
 
+        let platform_instance = await loadWasm(platformUrl, importObject);
+
+        for(let name in platform_instance.exports) {
+            importObject.env[name] = platform_instance.exports[name]
+        }
+
         let instance = new WebAssembly.Instance(await WebAssembly.compile(data), importObject);
 
         let buffer = imageData.data;