~launchpad-pqm/launchpad/devel

# Copyright 2009 Canonical Ltd.  This software is licensed under the

# GNU Affero General Public License version 3 (see the file LICENSE).

__metaclass__ = type

__all__ = [

    'copy_and_close',

    'filechunks',

    'guess_librarian_encoding',

    'sha1_from_path',

    ]

import hashlib

MEGABYTE = 1024*1024

def filechunks(file, chunk_size=4*MEGABYTE):

    """Return an iterator which reads chunks of the given file."""

    return iter(lambda: file.read(chunk_size), '')

def copy_and_close(from_file, to_file):

    """Copy from_file to to_file and close both.

    It requires both arguments to be opened file-like objects.

    'filechunks' trick is used reduce the buffers memory demanded

    when handling large files.

    It's suitable to copy contents from ILibraryFileAlias instances to the

    local filesystem.

    Both file_descriptors are closed before return.

    """

    for chunk in filechunks(from_file):

        to_file.write(chunk)

    from_file.close()

    to_file.close()

def sha1_from_path(path):

    """Return the hexdigest SHA1 for the contents of the path."""

    the_file = open(path)

    the_hash = hashlib.sha1()

    for chunk in filechunks(the_file):

        the_hash.update(chunk)

    the_file.close()

    return the_hash.hexdigest()

def guess_librarian_encoding(filename, mimetype):

    """Return the appropriate encoding for the given filename and mimetype.

    Files with the following extensions will be served as

    'Content-Encoding: gzip' and 'Content-Type: text/plain',

    which indicates to browsers that, after being unzipped,

    their contents can be rendered inline.

    * 'txt.gz': gzipped sources buildlogs;

    * 'diff.gz': gzipped sources diffs;

    :param filename: string containing the filename to be guessed;

    :param mimetype: string containing the stored mimetype;

    :return: a tuple containing the appropriate 'encoding' and 'mimetype'

        that should be used to serve the file.

    """

    if filename.endswith('txt.gz'):

        encoding = 'gzip'

        mimetype = 'text/plain'

    elif filename.endswith('diff.gz'):

        encoding = 'gzip'

        mimetype = 'text/plain'

    else:

        encoding = None

        mimetype = mimetype.encode('ascii')

    return encoding, mimetype