hashed-fs

Gracefully and safely manipulate file with cached content hash.

hashed-fs will create hash string from the file content, cache it, and pass it to the callback of each instance method.

All hashed-fs instances in one node session will share the same cache.

Install

$ npm install hashed-fs --save

Usage

var hfs = require('hashed-fs')(options);
hfs.stat('/path/to/a.js', function(err, stat, hash){
  stat; // is the nodejs `fs.Stat` object
  hash; // the result hash
});

• options Object
  • crypto: function() method to crypto a file into a hash
  • decorate: function() method to decorate the destination filename by flavoring with file hash.
  • cache_file path= if specified, hashd-fs will load the cache file at the beginning
  • only_hashed Boolean=false if true, it will only write to the hashed filename. By default, it will write two files.

In comparison with the corresponding vanilla fs method, each hashed-fs method has an additional parameter hash of the callback function, which is the encrypted hash of the file content.

options.crypto function(data)

This method is an iterator handler generater which should returns a function. The chunks of the file content, i.e, data, will be passed into options.crypto() one by one. data has the structure below:

{
  value: <Buffer|String>, // the chunk of data
  done: <true|false>      // whether is the last chunk of data
}

If data.done is true, it means the last chunk of data received, and the options.crypto should return the encrypted result.

By default, it encrypts the file content using md5 algorithm, but you could specify it by yourself.

For example,

var crypto = require('crypto');
 
function sha256 () {
  var shasum = crypto.createHash('sha256');
  return function(data){
    if (data.value) {
      shasum.update(data.value);
    }
 
    if (data.done) {
      return shasum.digest('hex');
    }
  }
}
 
var hfs = require('hashed-fs')({
  crypto: sha256
});

options.decorate function(filename, hash)

Defines how hashed-fs should add hash string to the filename.

It can be synchronous methods or asynchronous ones by using the common this.async() style.

hfs.readFile(filename, callback)

hfs.readFile('/path/to/a.js', function(err, content, hash){
  content;  // '// a'
  hash;     // 'ce2e532998ddb06b4334620d74e0d938'
});

• callback function(err, content, hash)
  • content ``
  • hash the options.crypo()d hash according to the file content.

Reads the file content, and get the stat.

hfs.copy(filename, dest, callback [, force=false])

• callback function(err, hash)

Copies the file of filename to dest along with the hash-decorated dest.

If the file is already in the cache, it will skip copying, except that force is true.

hfs.copy('/path/to/a.js', '/dest/to', function(err, hash){
  hash; // 'ce2e532998ddb06b4334620d74e0d938'
});

Then the /dest/to folder will have TWO files:

/dest/to
       | -- a.js          # if options.only_hashed is not true 
       | -- a-ce2e532.js

ce2e532 is the first seven charactors of the hash. By changing the default options.decorate method, you could define your custom pathname to the destination.

hfs.stat(filename, callback)

• callback function(err, stat, hash, cached)
  • stat fs.Stats is the file status of the file
  • cached Boolean whether has read from cache.

Gets the file stat, and the hashed result.

hfs.writeFile(filename, content, callback)

Similar to hfs.copy(), this method will write TWO files

hfs.cache.save(callback)

if options.cache_file is specified, it will save the cache to the file.

hfs.cache.map()

Returns the {filename: hash} object.

License

MIT