Popularity is the hallmark of mediocrity

Sun, 26 Aug 12 10:31:09 +0000

So said Dr. Niles Crane, quoting an unspecified "great man".

I've sunk a lot of hours into building various different programs. Partly because I enjoy it, partly due to necessity and partly because sometimes I genuinely believe I'm creating something useful. The latter encompasses a bunch of my projects and with these I aim for painstakingly high quality because I want people to use them. I spend hours making sure code is written and formatted well, making sure unit test coverage is good, and ensuring that APIs are well documented, etc.

And then we have loljs. loljs is my LOLCODE to JavaScript translator/interpreter. It's a proper translator with a recursive descent parse, not just a hideous regular expression thing, but it's still pretty rubbish. Probably its one saving grace in my eyes is that it correctly converts LOLCODE's prefix notation to JavaScript's infix notation for operators with arbitrary arity. I wrote it as a "let's learn JavaScript project" in about two days. It's very rough, the internals are awful (it's pretty obvious I didn't know JavaScript) and it's not exactly easy to use.

And yet it's had literally thousands and thousands of visits. It's far and away the most successful project I've done. Even taking into account professional projects, and I've worked on some for a few big names, I think loljs is a pretty strong contendor in the popularity stakes.

It's recently been the subject of a "learn to program" video on a popular channel on YouTube and according to my primitive stats, it's had six thousand views in the last 36 hours (not *all* from YouTube). Which is great. My web host is earning their monthly fee. I'm very happy. I just wish you'd all be so interested in the stuff I spent more time doing.

HTTP 206 (Partial Content) For Flask/Python

Fri, 03 Aug 12 11:32:53 +0000

Serving media files with HTTP 200 seems to make browsers act a bit strangely. Chrome refuses to fire onended events, and neither Chrome nor Firefox seems happy seeking through them. I am Not entirely sure for the reasons for this; I guess that they try to play the media before receiving all of it and can't guarantee they'll have downloaded the right chunk for seeking, while having no way of requesting it specifically. Who knows.

Here's a simple replacement to Flask's send_file that supports 206 partial content via byte ranges (and a function that adds the appropriate headers to all responses). It doesn't fully wrap send_file, if you care about all the other arguments and mirroring the exact behaviour, it needs a bit more work, but should suffice for 99% of uses.

[update 31/8: sorry there was a bug in this which caused strange things with certain Chrome versions, it's now been fixed]

import mimetypes
import os
import re

from flask import request, send_file, Response

@app.after_request
def after_request(response):
    response.headers.add('Accept-Ranges', 'bytes')
    return response


def send_file_partial(path):
    """ 
        Simple wrapper around send_file which handles HTTP 206 Partial Content
        (byte ranges)
        TODO: handle all send_file args, mirror send_file's error handling
        (if it has any)
    """
    range_header = request.headers.get('Range', None)
    if not range_header: return send_file(path)
    
    size = os.path.getsize(path)    
    byte1, byte2 = 0, None
    
    m = re.search('(\d+)-(\d*)', range_header)
    g = m.groups()
    
    if g[0]: byte1 = int(g[0])
    if g[1]: byte2 = int(g[1])

    length = size - byte1
    if byte2 is not None:
        length = byte2 - byte1
    
    data = None
    with open(path, 'rb') as f:
        f.seek(byte1)
        data = f.read(length)

    rv = Response(data, 
        206,
        mimetype=mimetypes.guess_type(path)[0], 
        direct_passthrough=True)
    rv.headers.add('Content-Range', 'bytes {0}-{1}/{2}'.format(byte1, byte1 + length - 1, size))

    return rv

asgaard

Popularity is the hallmark of mediocrity

HTTP 206 (Partial Content) For Flask/Python