Support compiling to wasm

Author: axic

Makefile

@@ -13,7 +13,5 @@ all:
 	sed -ibak 's/run();$$/Module\["arguments"\]=\[\];run();module\.exports=Module;/' lib/index.asm.js
 
 wasm:
-	cargo build --target=wasm32-unknown-emscripten --release
-	mkdir -p exp
-	find target/wasm32-unknown-emscripten/release/deps -type f -name "*.wasm" | xargs -I {} cp {} exp/rustbn.wasm
-	find target/wasm32-unknown-emscripten/release/deps -type f ! -name "*.asm.js" -name "*.js" | xargs -I {} cp {} exp/index.wasm.js
+	cargo build --target=wasm32-unknown-unknown --release
+	cp target/wasm32-unknown-unknown/release/rustbn-js.wasm lib/rustbn.wasm

index.js

@@ -1,8 +1,48 @@
-const bn128 = require('./lib/index.asm.js')
+if (global.WebAssembly !== undefined) {
+  const wasmModule = require('fs').readFileSync('./lib/rustbn.wasm')
+  const bn128 = WebAssembly.instantiate(wasmModule, { env: {} }).then(function (bn128) {
+    const ec_add = bn128.instance.exports.ec_add
+    const ec_mul = bn128.instance.exports.ec_mul
+    const ec_pairing = bn128.instance.exports.ec_pairing
+    let memory = bn128.instance.exports.memory
 
-const ec_add = bn128.cwrap('ec_add', 'string', ['string'])
-const ec_mul = bn128.cwrap('ec_mul', 'string', ['string'])
-const ec_pairing = bn128.cwrap('ec_pairing', 'string', ['string'])
+    function findFreeMemoryPtr () {
+       // FIXME: implement
+       return 42
+    }
+
+    function writeHexString (buffer, startOffset, data) {
+      // FIXME: implement
+      console.log('writing to', startOffset)
+
+      let bufferView = new Uint8Array(buffer)
+      data.copy(bufferView, startOffset)
+    }
+
+    function extractHexString (buffer, startOffset) {
+      console.log('reading from', startOffset)
+
+      const bufferView = new Uint8Array(buffer)
+
+      let endOffset = startOffset
+      for (; bufferView[endOffset] !== 0; endOffset++) { }
+
+      return Buffer.from(bufferView.slice(startOffset, endOffset), 'hex')
+    }
+
+    let ptr = findFreeMemoryPtr()
+    writeHexString(memory.buffer, ptr, Buffer.from('00112200', 'hex'))
+    let retPtr = ec_add(ptr)
+    let ret = extractHexString(memory.buffer, retPtr)
+
+    console.log('returned', ret.toString('hex'))
+  })
+} else {
+  const bn128 = require('./lib/index.asm.js')
+  const ec_add = bn128.cwrap('ec_add', 'string', ['string'])
+  const ec_mul = bn128.cwrap('ec_mul', 'string', ['string'])
+  const ec_pairing = bn128.cwrap('ec_pairing', 'string', ['string'])
+}
 
 function bn128add (input) {
   return Buffer.from(ec_add(input.toString('hex')), 'hex')

lib/rustbn.wasm

@@ -63,6 +63,7 @@ extern "C" {
 }
 
 fn main() {
+    #[cfg(not(target_arch = "wasm32"))]
     unsafe {
         emscripten_exit_with_live_runtime();
     }