Download any Chromium build

Is it hard to download any Chromium build?

Taking in account that:

• Google stores old versions of Chromium browser in several repositories.
• These pages are built by AJAX scripts which load contents progressively.
• Builds are saved in folders using revision numbers from Chrome CVS, but luckily omahaproxy has an JSON service to get revision number from a version number.
• However, not all versions exist in these repos. So we'll check nearest versions (plus-minus 1, 2, etc)

We can make a function like this:

import json
import re
import string
import sys
import urllib2

def get_best_URL_for_version(version):
    platforms = {'win32':0, 'cygwin':0, 'darwin':1}
    version_to_revision_url = 'http://omahaproxy.appspot.com/revision.json?version=%s'
    storages = [
            {
                'url': 'http://commondatastorage.googleapis.com/chromium-browser-continuous/',
                'filters': [
                    ['?delimiter=/&prefix=Win/','?delimiter=/&prefix=Win_x64/'],
                    ['?delimiter=/&prefix=Mac/'],
                ],
            },
            {
                'url': 'https://storage.googleapis.com/chromium-browser-snapshots/',
                'filters': [
                    ['?delimiter=/&prefix=Win/','?delimiter=/&prefix=WinGit/'],
                    [], # these use SHAs as folder names :(
                ],
            },
        ]
    chromium_install_filename = [
            'chrome-win32.zip',
            'chrome-mac.zip',
        ]
    platform_id = 0
    if not sys.platform in platforms:
        print 'Sorry, platform [%s] is not supported by this script' % sys.platform
        return None
    else:
        platform_id = platforms[sys.platform]
    print 'Loading all repos...'
    global revisions
    revisions = {}
    def parse_url(url, filter, marker=''):
        global revisions
        if marker:
            marker = '&marker=' + marker
        print 'Reading [%s]' % (url+filter+marker)
        data = urllib2.urlopen(url+filter+marker).read()
        for match in re.finditer('\<Prefix\>([a-zA-Z]+/(\\d+)/)\</Prefix\>', data):
            revisions[int(match.group(2))] = (
                url + match.group(1) + chromium_install_filename[platform_id])
        if string.find(data, '<IsTruncated>true</IsTruncated>')>-1:
            match = re.search('\<NextMarker\>([^<]*)\</NextMarker\>', data)
            if match:
                parse_url(url, filter, match.group(1))
            else:
                print 'BUG! IsTruncated, but no NextMarker'
    for storage in storages:
        url = storage['url']
        for filter in storage['filters'][platform_id]:
            parse_url(url,filter)
    print 'Finding closest version...'
    def change_version(version, adjust):
        def version_string_to_array(version):
            return map(int,version.split('.'))
        def array_to_version_string(version):
            return '.'.join(map(str,version))
        version = version_string_to_array(version)
        version.reverse()
        for i, a in enumerate(version):
            if a != 0:
                a += adjust
                if a>0:
                    version[i] = a
                    break
                else:
                    # when asked to adjust 1234.5 by -6 then instead of 1234.(-1)
                    version[i] = 0 # 1234.0
                    adjust = a     # (1234-1).0
        version.reverse()
        return array_to_version_string(version)
    adjust = 0
    while True:
        for sign in [1, -1]:
            url = version_to_revision_url % change_version(version, sign*adjust)
            print "checking %s" % url
            revision = None
            try:
                revision = json.load(urllib2.urlopen(url))['chromium_revision']
            except urllib2.HTTPError:
                pass
            if revision in revisions:
                return revisions[revision]
        adjust += 1

It first loads all the repos and builds a list of revisions and matching URLs, and then scans all versions, starting with given one, trying to find a closest version which exists in this list. You can use it like this:

    if __name__ == "__main__":
        print get_best_URL_for_version(raw_input('Enter Chromium version to find (f.ex 34.0.1788.0): '))