Update dependencies

[ralphtheninja]

Closes #9
Closes #24
Closes #22
Supersedes #7

Squash when merge.

[ralphtheninja]

What's left now are some minor cleanup, docs, changelog, upgrade guide etc.

[ralphtheninja]

And later on refactoring to get rid of down() function.

[ralphtheninja]

This fixes the open, close, open, close test in abstract-leveldown (which @finnp commented out in previous PR)

[ralphtheninja]

Maybe we should tweak it to do if (this.db.isClosed()) { this.db.open() }?

[vweevers]

I think we can simplify the whole thing and take advantage of the fact that levelup#open does process.nextTick(callback) if already open.

[vweevers]

@ralphtheninja would this work?

SubDown.prototype._open = function (opts, cb) {
  var self = this

  this.db.open(function (err) {
    if (err) return cb(err)

    var subdb = down(self.db, 'subleveldown')

    if (subdb && subdb.prefix) {
      self.prefix = subdb.prefix + self.prefix
      self.leveldown = down(subdb.db)
    } else {
      self.leveldown = down(self.db)
    }

    if (self._beforeOpen) self._beforeOpen(cb)
    else cb()
  })
}

[vweevers]

@ralphtheninja ping in case you missed this because GH hides it

[ralphtheninja]

Much cleaner! Let me try it out.

[ralphtheninja]

Updated.

[vweevers]

I'll review tomorrow.

[vweevers]

Can remove the location argument (5x)

[vweevers]

🎉

[vweevers]

Could _serializeKey and _serializeValue be(come) a problem?

[ralphtheninja]

@vweevers You mean the default in abstract-leveldown?

AbstractLevelDOWN.prototype._serializeKey = function (key) {              
  return Buffer.isBuffer(key) ? key : String(key)                         
}                                                                         
                                                                          
AbstractLevelDOWN.prototype._serializeValue = function (value) {          
  if (value == null) return ''                                            
  return Buffer.isBuffer(value) || process.browser ? value : String(value)
}                                                                         

[ralphtheninja]

_serializeKey looks ok for Buffer case but might be a problem with keys that aren't strings, OTOH concat doesn't care about prefix if it's not a string or a Buffer:

var concat = function (prefix, key, force) {                               
  if (typeof key === 'string' && (force || key.length)) return prefix + key
  if (Buffer.isBuffer(key) && (force || key.length)) {                     
    return Buffer.concat([Buffer.from(prefix), key])                       
  }                                                                        
  return key                                                               
}                                                                          

So for sub levels to work at all it seems to me that SubDb requires keys to be string or Buffer

[ralphtheninja]

@vweevers Also, remember that levelup + encoding-down is in front of all these ._put(), ._get() (etc) operations. So as long as the encoding from levelup -> subdown makes keys as strings or buffers, we should be good.