Added support for seek() and truncate()

[piranna]

Added support for seek() and truncate() methods on FileWriter and also improved write() support according to the File API specification based on code from FileWriter polyfill (https://github.com/piranna/ShareIt/blob/master/js/webp2p/polyfills/FileWriter.js) at ShareIt! project (also developed by myself). Since I started the polyfill using your implementation as basis, I think it's fair to return my improved and fixed version... :-)

[ebidel]

Haven't looked closely at the code yet, but can you use Google's JS style guide for spacing, brackets, etc. http://google-styleguide.googlecode.com/svn/trunk/javascriptguide.xml.

[piranna]

Fixed :-) I'm too much used to the BSD and Pep-8 styles... :-P

[shacharz]

I'd like to see this pull request accepted, is it inefficient or anything?

[ebidel]

Thanks for this. Sorry about taking to long to review. LGTM

[ebidel]

This isn't passing the tests. Can you fire them up in FF (start a web serve in the root dir and hit http://localhost/tests/)?

[piranna]

Don't worry, to be honest I forgot about it X-D I'll check it now.

[piranna]

I've started it and got the next error:

Uncaught ReferenceError: module is not defined tests.js:6
(anonymous function) tests.js:6

The line is:

module('window methods', {

Seems qUnit is not available, I've added it by hand and now it's working. I'm going to look on the bug.

[piranna]

I can't be able to fix it, the bug is happening when you create an empty FileEntry, so it don't have a blob object. I've tried to fix it using a mock file:

var blob_ = fileEntry.file_ ? fileEntry.file_.blob_ : {size: 0};

but now test doesn't work, it only show the first one as running. Any idea?

[ebidel]

That's one change I've made ad well. Currently having other issues with this business:

// Calc the head and tail fragments
var head = blob_.slice(0, position_);
var tail = blob_.slice(position_ + data.length);

I'm looking into it, don't sweat it.

[piranna]

Yeah, I did it to be able to do a 'data' write in the middle of a file at current 'position_' just like the specification (and POSIX, by the way) say.

Ok, I'll keep me code here if you need that I review something :-)

[ebidel]

Got the tests working. You had a data.length instead of data.size that tripped me up for far too long :(

Here's what write() looks like now:

this.write = function(data) { if (!data) { throw Error('Expected blob argument to write.'); }

// Call onwritestart if it was defined.
if (this.onwritestart) {
  this.onwritestart();
}

// TODO: not handling onprogress, onwrite, onabort. Throw an error if
// they're defined.

if (!blob_) {
  blob_ = new Blob([data], {type: data.type});
} else {
  // Calc the head and tail fragments
  var head = blob_.slice(0, position_);
  var tail = blob_.slice(position_ + data.size);

  // Calc the padding
  var padding = position_ - head.size;
  if (padding < 0) {
    padding = 0;
  }
  // Do the "write". In fact, a full overwrite of the Blob.
  // TODO: figure out if data.type should overwrite the exist blob's type.
  blob_ = new Blob([head, new Uint8Array(padding), data, tail],
                   {type: blob_.type});
}

// Set the blob we're writing on this file entry so we can recall it later.
fileEntry.file_.blob_ = blob_;

idb_.put(fileEntry, function(entry) {
  // Add size of data written to writer.position.
  position_ += data.size;

  if (this.onwriteend) {
    this.onwriteend();
  }
}.bind(this), this.onerror);

};

I'm going to add tests for seek() and truncate().

[piranna]

Don't know why I was using .length instead of .size, maybe they are equivalent for other objects? Code looks good anyway, thank you for your time looking it :-)

[ebidel]

Blob doesn't have a .length but ArrayBuffer's do and the FileWriter interface does. It's easy to get things mixed up!!

[piranna]

Maybe that's the reason, in my original code (ShareIt!) I was using ArrayBuffers...

[ebidel]

Everything should be right as mud now. Give v0.0.3 a test and see if it breaks anything. Thanks again!

https://github.com/ebidel/idb.filesystem.js/commit/e92d5959ba109ee7cd076f7f20ad63b229f67f3f

[piranna]

Tests are being passed on the latest version, good job! :-)