expanding url(./img/hoge.png) => url(data:image/png;....) with filesystem-based caching

cssdatauriexpander.py

import re
import base64
import hashlib
import os.path
import gevent.fileobject as gfo

def _read_file(filepath):
    fh = open(filepath, 'rb')
    gfh = gfo.FileObject(fh, 'rb')
    ret = gfh.read()
    gfh.close()
    return ret


def _write_file(filepath, content):
    fh = open(filepath, 'wb')
    gfh = gfo.FileObject(fh, 'wb')
    gfh.write(content)
    gfh.close()


class CSSDataUriExpander(object):
    def __init__(self, cache_dir):
        self.cache_dir = cache_dir
        self.urlpat = re.compile(r'url\("([^"]*)"\)')

    def expand_file(self, css_file, base_dir=None):
        base_dir = base_dir or os.path.dirname(css_file)
        css_content = _read_file(css_file)
        return self.expand_file(css_content, base_dir);

    def expand(self, css_content, base_dir):
        ret = css_content
        for match in self.urlpat.finditer(css_content):
            rel_path = match.groups()[0]
            path = os.path.normpath(os.path.join(base_dir, rel_path))
            data_uri = self.get_data_uri(path)
            ret = ret.replace('url("%s")' % rel_path, 'url("%s")' % data_uri)
        return ret

    def get_data_uri(self, full_path):
        cache_path = self.get_cache_path(full_path)
        if os.path.exists(cache_path):
            return _read_file(cache_path)
        else:
            data_uri = self.gen_data_uri(full_path)
            _write_file(cache_path, data_uri)
            return data_uri

    def get_cache_path(self, path):
        pathhash = hashlib.md5(path).hexdigest()
        return os.path.normpath(os.path.join(self.cache_dir, pathhash))

    def gen_data_uri(self, path):
        mime = self.get_mime(path)
        content = _read_file(path)
        b64data = base64.b64encode(content)
        return 'data:%s;base64,%s' % (mime, b64data)

    def get_mime(self, path):
        lp = path.lower()
        mime = {
            '.png': 'image/png',
            '.jpe': 'image/jpeg',
            '.jpg': 'image/jpeg',
            '.jpeg': 'image/jpeg',
            '.gif': 'image/gif',
            '.ico': 'image/x-icon',
            '.bmp': 'image/bmp',
            '.svg': 'image/svg+xml',
            '.tif': 'image/tiff',
            '.tiff': 'image/tiff'
        }
        for ext in mime:
            if lp.endswith(ext):
                return mime[ext]
        return 'image/jpeg'