emcripten skeleton for address derivation

See [https://kripken.github.io/emscripten-site/index.html] for a guide.

emscripten/Makefile

@@ -0,0 +1,17 @@
+EMFLAGS = \
+	-O2 --closure 1 \
+	--memory-init-file 0 \
+	--pre-js pre.js --post-js post.js \
+	-s EXPORTED_FUNCTIONS='["_hdnode_public_ckd", "_ecdsa_get_address"]' \
+
+SRC = ../bignum.c ../ecdsa.c ../secp256k1.c ../hmac.c ../bip32.c \
+	../base58.c ../ripemd160.c ../sha2.c ../rand.c
+
+test: trezor-crypto.js
+	node test.js
+
+trezor-crypto.js: $(SRC)
+	emcc $(EMFLAGS) -o $@ $^
+
+clean:
+	rm -f trezor-crypto.js

emscripten/post.js

@@ -0,0 +1 @@
+module.exports = Module;

emscripten/test.js

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+var crypto = require('./trezor-crypto');
+
+/* typedef struct {
+   uint32_t depth;
+   uint32_t fingerprint;
+   uint32_t child_num;
+   uint8_t chain_code[32];
+   uint8_t private_key[32];
+   uint8_t public_key[33];
+   } HDNode;
+*/
+
+var HDNODE_SIZE = 4 + 4 + 4 + 32 + 32 + 33;
+var hdnode = crypto._malloc(HDNODE_SIZE);
+
+var ADDRESS_SIZE = 40; // maximum size
+var address = crypto._malloc(ADDRESS_SIZE);
+
+function prepareNode(n) {
+    var b = new ArrayBuffer(HDNODE_SIZE);
+    var u8 = new Uint8Array(b, 0, HDNODE_SIZE);
+    var u32 = new Uint32Array(b, 0, 12);
+
+    u32[0] = n.depth;
+    u32[1] = n.parentFingerprint;
+    u32[2] = n.index;
+    u8.set(n.chainCode, 12);
+    u8.set(n.pubKey.toBuffer(), 12 + 32 + 32);
+
+    return u8;
+}
+
+function deriveAddress(pn, i, version) {
+    crypto.HEAPU8.set(pn, hdnode);
+    crypto._hdnode_public_ckd(hdnode, i);
+    crypto._ecdsa_get_address(hdnode + 12 + 32 + 32, version, address, ADDRESS_SIZE);
+    return crypto.Pointer_stringify(address);
+}
+
+// benching code
+
+var bitcoin = require('bitcoinjs-lib');
+
+var node = bitcoin.HDNode.fromBase58(
+    'xpub6AHA9hZDN11k2ijHMeS5QqHx2KP9aMBRhTDqANMnwVtdyw2TDYRm' +
+        'F8PjpvwUFcL1Et8Hj59S3gTSMcUQ5gAqTz3Wd8EsMTmF3DChhqPQBnU'
+).derive(0);
+
+timeBitcoinjs(node);
+timeTrezorCrypto(node);
+
+function timeBitcoinjs(n) {
+    console.time('bitcoinjs')
+    for (var i = 0; i < 1000; i++) {
+        n.derive(i).getAddress()
+    }
+    console.timeEnd('bitcoinjs')
+}
+
+function timeTrezorCrypto(n) {
+    var nP = prepareNode(n);
+    console.time('trezor-crypto')
+    for (var i = 0; i < 1000; i++) {
+        deriveAddress(nP, i, 0);
+    }
+    console.timeEnd('trezor-crypto')
+}