RaiBlocksWebAssemblyPoW

Overview

This repo contains a simple RaiBlocks PoW implementation compiled to WebAssembly to boost its performance on browsers. That's been done using emscripten. Compiling to WebAssembly, the result is around 10 times faster than a pure JS PoW implementation (e.g.: RaiBlocksJS).
This basically makes possible to generate proofs of work on modern browsers in a reasonable time. So yep, lets see...

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Installation and usage

All the PoW thing takes place at functions.cpp. There is the main loop which calculates stuff and a function which can be called from JS and runs the loop (the iterations function).

To compile it to webassembly you need to install emscripten:

git clone https://github.com/juj/emsdk.git
cd emsdk

# on Linux or Mac OS X
./emsdk install --build=Release sdk-incoming-64bit binaryen-master-64bit
./emsdk activate --global --build=Release sdk-incoming-64bit binaryen-master-64bit

# on Windows
emsdk install --build=Release sdk-incoming-64bit binaryen-master-64bit
emsdk activate --global --build=Release sdk-incoming-64bit binaryen-master-64bit

Then:

# on Linux or Mac OS X
source ./emsdk_env.sh

# on Windows
emsdk_env.bat

(From here)

With that done, at the repo folder run this:

emcc functions.cpp blake2/blake2b-ref.cpp  -o pow.js -s WASM=1 -std=gnu++11 -O3 -s EXPORTED_FUNCTIONS="['_launchPoW']"

It will output 2 files: pow.js and pow.wasm, place those files together somewhere and include pow.js in your html as usual.

To call the "launchPoW" function you can do 2 things:

var hash = "SOME_RAIBLOCKS_HASH_HERE_AND_STUFF_HEX_ENCODED_32_BYTES";
var pow = Module.ccall("launchPoW", "string", ["string"], hash);
console.log(pow);

OR

var hash = "SOME_RAIBLOCKS_HASH_HERE_AND_STUFF_HEX_ENCODED_32_BYTES";
var calculatePoW = Module.cwrap("launchPoW", "string", ["string"]);
var pow = calculatePoW(hash);
console.log(pow);

I prefer the second option :D

What that function does is to try to find a valid PoW in 10,000,000 iterations. If it finds it it will return the result as a hex string. If it does not find it, will return a 64bit hex 0 (0000000000000000). Keep that in mind :P

BUT ... but. You cannot call the function before WebAssembly is loaded and compiled. How do we know when that happens? Well, we have:

Module['onRuntimeInitialized'] = function() {
    // Its all fine here
    // do stuff
    // ...
}

If Module['onRuntimeInitialized'] is a function it will be called once its all ready to run. So yeah, be aware of that :)
There are more docs about the Module API and emscripten itself here http://kripken.github.io/emscripten-site/docs/porting/connecting_cpp_and_javascript/index.html.

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Compatibility

This implementation has just been tested in Chrome (Windows 64bit), Firefox (Windows 64bit) and Chrome (Android) but should also work in all the devices supporting WASM.

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Examples

I've made two examples for you to see/use/improve/whatever. They are at the /examples folder. One of them uses webworkers to multithread this stuff. The other one is single threaded.
Yeah, take a look there :P