erlccache/erlccache

#!/usr/bin/env node
/*
  erlccache — (c) 2010 Jan Lehnardt <jan@apache.org>
  use instead of erlc and your builds will magically speed up
  somebody needs to turn this into proper node code, or sh or whatever
  MIT License
*/

// CUSTOMIZE HERE
var erlc = "/Users/jan/.local/bin/erlc";
var dir = "/Users/jan/.erlccache/";
// STOP CUSTOMIZING


var sys = require("sys");
var child_process = require("child_process");
var crypto = require("crypto");
var fs = require("fs");


var args = process.argv.slice(2).toString();
var cmd = erlc + " " + args;

// execute a shell command
function exec(cmd, fun) {
  fun = fun || function (error, stdout, stderr) {
    sys.print("stdout: " + stdout);
    sys.print("stderr: " + stderr);
    if (error !== null) {
      sys.puts("exec error: " + error);
    }
  };
  child_process.exec(cmd, fun);
}

// get the .erl file out of cmd
function erl_parse_file(cmd) {
  var file = cmd.match(/[\w]+\.erl\s*/).toString();
  return file;
}

// find location of .beam file given the cmd
function erl_beamfile(cmd) {
  return process.cwd() + "/" + erl_parse_file(cmd).replace(/.erl/, ".beam");
}

// create a sha1 hex digest from the cmd .erl file
function cache_hash(cmd) {
  var hash = crypto.createHash("sha1");
  var file = erl_parse_file(cmd);
  hash.update(fs.readFileSync(file, "binary"));
  return hash.digest("hex");
}

// copy(from, to); -- synchronous
function cache_file_copy(from, to) {
  fs.writeFileSync(to, fs.readFileSync(from, "binary"), "binary");
  
}

// see if the filename in cmd is cached, if not compile and cache
function cache_hit(cmd) {
  // make cache dir if it doesn't exist
  try {
    fs.statSync(dir);
  } catch(e) {
    fs.mkdirSync(dir, 0700);
  }

  // hash cmd
  var hash = cache_hash(cmd);
  try {
    fs.statSync(dir + hash);
  } catch(e) {
    // compile
    exec(cmd, function(error, stdout, stderr) {
      if(!error) {
        var beamfile = erl_beamfile(cmd);
        // add beam file to dir + hash(cmd)
        cache_file_copy(beamfile, dir + hash);
      }
    });
    return false;
  }
  return true
}

// copy the cached beamfile to the final destination as if erlc did it
function cache_copy(cmd) {
  var beamfile = erl_beamfile(cmd);
  var cachefile = dir + cache_hash(cmd);
  cache_file_copy(cachefile, beamfile);
}

if(cache_hit(cmd)) {
  cache_copy(cmd);
}

//done