Synnefo

# Copyright 2011-2013 GRNET S.A. All rights reserved.

#

# Redistribution and use in source and binary forms, with or

# without modification, are permitted provided that the following

# conditions are met:

#

#   1. Redistributions of source code must retain the above

#      copyright notice, this list of conditions and the following

#      disclaimer.

#

#   2. Redistributions in binary form must reproduce the above

#      copyright notice, this list of conditions and the following

#      disclaimer in the documentation and/or other materials

#      provided with the distribution.

#

# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS

# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR

# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF

# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED

# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN

# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

# POSSIBILITY OF SUCH DAMAGE.

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# The views and conclusions contained in the software and

# documentation are those of the authors and should not be

# interpreted as representing official policies, either expressed

# or implied, of GRNET S.A.

from functools import wraps

from datetime import datetime

from urllib import quote, unquote, urlencode

from django.http import (HttpResponse, Http404, HttpResponseRedirect,

                         HttpResponseNotAllowed)

from django.template.loader import render_to_string

from django.utils import simplejson as json

from django.utils.http import http_date, parse_etags

from django.utils.encoding import smart_unicode, smart_str

from django.core.files.uploadhandler import FileUploadHandler

from django.core.files.uploadedfile import UploadedFile

from django.core.urlresolvers import reverse

from django.core.exceptions import PermissionDenied

from snf_django.lib.api.parsedate import parse_http_date_safe, parse_http_date

from snf_django.lib import api

from snf_django.lib.api import faults, utils

from pithos.api.settings import (BACKEND_DB_MODULE, BACKEND_DB_CONNECTION,

                                 BACKEND_BLOCK_MODULE, BACKEND_BLOCK_PATH,

                                 BACKEND_BLOCK_UMASK,

                                 BACKEND_QUEUE_MODULE, BACKEND_QUEUE_HOSTS,

                                 BACKEND_QUEUE_EXCHANGE,

                                 ASTAKOSCLIENT_POOLSIZE,

                                 SERVICE_TOKEN,

                                 ASTAKOS_AUTH_URL,

                                 BACKEND_ACCOUNT_QUOTA,

                                 BACKEND_CONTAINER_QUOTA,

                                 BACKEND_VERSIONING, BACKEND_FREE_VERSIONING,

                                 BACKEND_POOL_ENABLED, BACKEND_POOL_SIZE,

                                 BACKEND_BLOCK_SIZE, BACKEND_HASH_ALGORITHM,

                                 BACKEND_ARCHIPELAGO_CONF,

                                 BACKEND_XSEG_POOL_SIZE,

                                 BACKEND_MAP_CHECK_INTERVAL,

                                 RADOS_STORAGE, RADOS_POOL_BLOCKS,

                                 RADOS_POOL_MAPS, TRANSLATE_UUIDS,

                                 PUBLIC_URL_SECURITY, PUBLIC_URL_ALPHABET,

                                 BASE_HOST, UPDATE_MD5, VIEW_PREFIX,

                                 OAUTH2_CLIENT_CREDENTIALS, UNSAFE_DOMAIN)

from pithos.api.resources import resources

from pithos.backends import connect_backend

from pithos.backends.base import (NotAllowedError, QuotaError, ItemNotExists,

                                  VersionNotExists, IllegalOperationError)

from synnefo.lib import join_urls

from synnefo.util import text

from astakosclient import AstakosClient

from astakosclient.errors import NoUserName, NoUUID, AstakosClientException

import logging

import re

import hashlib

import uuid

import decimal

logger = logging.getLogger(__name__)

def json_encode_decimal(obj):

    if isinstance(obj, decimal.Decimal):

        return str(obj)

    raise TypeError(repr(obj) + " is not JSON serializable")

def rename_meta_key(d, old, new):

    if old not in d:

        return

    d[new] = d[old]

    del(d[old])

def printable_header_dict(d):

    """Format a meta dictionary for printing out json/xml.

    Convert all keys to lower case and replace dashes with underscores.

    Format 'last_modified' timestamp.

    """

    timestamps = ('last_modified', 'x_container_until_timestamp',

                  'x_acount_until_timestamp')

    for timestamp in timestamps:

        if timestamp in d and d[timestamp]:

            d[timestamp] = utils.isoformat(

                datetime.fromtimestamp(d[timestamp]))

    return dict([(k.lower().replace('-', '_'), v) for k, v in d.iteritems()])

def format_header_key(k):

    """Convert underscores to dashes and capitalize intra-dash strings."""

    return '-'.join([x.capitalize() for x in k.replace('_', '-').split('-')])

def get_header_prefix(request, prefix):

    """Get all prefix-* request headers in a dict.

       Reformat keys with format_header_key()."""

    prefix = 'HTTP_' + prefix.upper().replace('-', '_')

    # TODO: Document or remove '~' replacing.

    return dict([(format_header_key(k[5:]), v.replace('~', ''))

                for k, v in request.META.iteritems()

                if k.startswith(prefix) and len(k) > len(prefix)])

def check_meta_headers(meta):

    if len(meta) > 90:

        raise faults.BadRequest('Too many headers.')

    for k, v in meta.iteritems():

        if len(k) > 128:

            raise faults.BadRequest('Header name too large.')

        if len(v) > 256:

            raise faults.BadRequest('Header value too large.')

def get_account_headers(request):

    meta = get_header_prefix(request, 'X-Account-Meta-')

    check_meta_headers(meta)

    groups = {}

    for k, v in get_header_prefix(request, 'X-Account-Group-').iteritems():

        n = k[16:].lower()

        if '-' in n or '_' in n:

            raise faults.BadRequest('Bad characters in group name')

        groups[n] = v.replace(' ', '').split(',')

        while '' in groups[n]:

            groups[n].remove('')

    return meta, groups

def put_account_headers(response, meta, groups, policy):

    if 'count' in meta:

        response['X-Account-Container-Count'] = meta['count']

    if 'bytes' in meta:

        response['X-Account-Bytes-Used'] = meta['bytes']

    response['Last-Modified'] = http_date(int(meta['modified']))

    for k in [x for x in meta.keys() if x.startswith('X-Account-Meta-')]:

        response[smart_str(

            k, strings_only=True)] = smart_str(meta[k], strings_only=True)

    if 'until_timestamp' in meta:

        response['X-Account-Until-Timestamp'] = http_date(

            int(meta['until_timestamp']))

    for k, v in groups.iteritems():

        k = smart_str(k, strings_only=True)

        k = format_header_key('X-Account-Group-' + k)

        v = smart_str(','.join(v), strings_only=True)

        response[k] = v

    for k, v in policy.iteritems():

        response[smart_str(format_header_key('X-Account-Policy-' + k),

                 strings_only=True)] = smart_str(v, strings_only=True)

def get_container_headers(request):

    meta = get_header_prefix(request, 'X-Container-Meta-')

    check_meta_headers(meta)

    policy = dict([(k[19:].lower(), v.replace(' ', '')) for k, v in

                  get_header_prefix(request,

                                    'X-Container-Policy-').iteritems()])

    return meta, policy

def put_container_headers(request, response, meta, policy):

    if 'count' in meta:

        response['X-Container-Object-Count'] = meta['count']

    if 'bytes' in meta:

        response['X-Container-Bytes-Used'] = meta['bytes']

    response['Last-Modified'] = http_date(int(meta['modified']))

    for k in [x for x in meta.keys() if x.startswith('X-Container-Meta-')]:

        response[smart_str(

            k, strings_only=True)] = smart_str(meta[k], strings_only=True)

    l = [smart_str(x, strings_only=True) for x in meta['object_meta']

         if x.startswith('X-Object-Meta-')]

    response['X-Container-Object-Meta'] = ','.join([x[14:] for x in l])

    response['X-Container-Block-Size'] = request.backend.block_size

    response['X-Container-Block-Hash'] = request.backend.hash_algorithm

    if 'until_timestamp' in meta:

        response['X-Container-Until-Timestamp'] = http_date(

            int(meta['until_timestamp']))

    for k, v in policy.iteritems():

        response[smart_str(format_header_key('X-Container-Policy-' + k),

                           strings_only=True)] = smart_str(v,

                                                           strings_only=True)

def get_object_headers(request):

    content_type = request.META.get('CONTENT_TYPE', None)

    meta = get_header_prefix(request, 'X-Object-Meta-')

    check_meta_headers(meta)

    if request.META.get('HTTP_CONTENT_ENCODING'):

        meta['Content-Encoding'] = request.META['HTTP_CONTENT_ENCODING']

    if request.META.get('HTTP_CONTENT_DISPOSITION'):

        meta['Content-Disposition'] = request.META['HTTP_CONTENT_DISPOSITION']

    if request.META.get('HTTP_X_OBJECT_MANIFEST'):

        meta['X-Object-Manifest'] = request.META['HTTP_X_OBJECT_MANIFEST']

    return content_type, meta, get_sharing(request), get_public(request)

def put_object_headers(response, meta, restricted=False, token=None):

    response['ETag'] = meta['hash'] if not UPDATE_MD5 else meta['checksum']

    response['Content-Length'] = meta['bytes']

    response.override_serialization = True

    response['Content-Type'] = meta.get('type', 'application/octet-stream')

    response['Last-Modified'] = http_date(int(meta['modified']))

    response['Map-Exists'] = meta['available']

    response['Map-Checked-At'] = (

        http_date(int(meta['map_check_timestamp'])) if

        meta['map_check_timestamp'] is not None else '')

    if not restricted:

        response['X-Object-Hash'] = meta['hash']

        response['X-Object-UUID'] = meta['uuid']

        if TRANSLATE_UUIDS:

            meta['modified_by'] = \

                retrieve_displayname(token, meta['modified_by'])

        response['X-Object-Modified-By'] = smart_str(

            meta['modified_by'], strings_only=True)

        response['X-Object-Version'] = meta['version']

        response['X-Object-Version-Timestamp'] = http_date(

            int(meta['version_timestamp']))

        for k in [x for x in meta.keys() if x.startswith('X-Object-Meta-')]:

            response[smart_str(

                k, strings_only=True)] = smart_str(meta[k], strings_only=True)

        for k in (

            'Content-Encoding', 'Content-Disposition', 'X-Object-Manifest',

            'X-Object-Sharing', 'X-Object-Shared-By', 'X-Object-Allowed-To',

                'X-Object-Public'):

            if k in meta:

                response[k] = smart_str(meta[k], strings_only=True)

    else:

        for k in ('Content-Encoding', 'Content-Disposition'):

            if k in meta:

                response[k] = smart_str(meta[k], strings_only=True)

def update_manifest_meta(request, v_account, meta):

    """Update metadata if the object has an X-Object-Manifest."""

    if 'X-Object-Manifest' in meta:

        etag = ''

        bytes = 0

        try:

            src_container, src_name = split_container_object_string(

                '/' + meta['X-Object-Manifest'])

            objects = request.backend.list_objects(

                request.user_uniq, v_account,

                src_container, prefix=src_name, virtual=False)

            for x in objects:

                src_meta = request.backend.get_object_meta(

                    request.user_uniq, v_account, src_container, x[0],

                    'pithos', x[1])

                etag += (src_meta['hash'] if not UPDATE_MD5 else

                         src_meta['checksum'])

                bytes += src_meta['bytes']

        except:

            # Ignore errors.

            return

        meta['bytes'] = bytes

        md5 = hashlib.md5()

        md5.update(etag)

        meta['checksum'] = md5.hexdigest().lower()

def is_uuid(str):

    if str is None:

        return False

    try:

        uuid.UUID(str)

    except ValueError:

        return False

    else:

        return True

##########################

# USER CATALOG utilities #

##########################

def retrieve_displayname(token, uuid, fail_silently=True):

    astakos = AstakosClient(token, ASTAKOS_AUTH_URL,

                            retry=2, use_pool=True,

                            logger=logger)

    try:

        displayname = astakos.get_username(uuid)

    except NoUserName:

        if not fail_silently:

            raise ItemNotExists(uuid)

        else:

            # just return the uuid

            return uuid

    return displayname

def retrieve_displaynames(token, uuids, return_dict=False, fail_silently=True):

    astakos = AstakosClient(token, ASTAKOS_AUTH_URL,

                            retry=2, use_pool=True,

                            logger=logger)

    catalog = astakos.get_usernames(uuids) or {}

    missing = list(set(uuids) - set(catalog))

    if missing and not fail_silently:

        raise ItemNotExists('Unknown displaynames: %s' % ', '.join(missing))

    return catalog if return_dict else [catalog.get(i) for i in uuids]

def retrieve_uuid(token, displayname):

    if is_uuid(displayname):

        return displayname

    astakos = AstakosClient(token, ASTAKOS_AUTH_URL,

                            retry=2, use_pool=True,

                            logger=logger)

    try:

        uuid = astakos.get_uuid(displayname)

    except NoUUID:

        raise ItemNotExists(displayname)

    return uuid

def retrieve_uuids(token, displaynames, return_dict=False, fail_silently=True):

    astakos = AstakosClient(token, ASTAKOS_AUTH_URL,

                            retry=2, use_pool=True,

                            logger=logger)

    catalog = astakos.get_uuids(displaynames) or {}

    missing = list(set(displaynames) - set(catalog))

    if missing and not fail_silently:

        raise ItemNotExists('Unknown uuids: %s' % ', '.join(missing))

    return catalog if return_dict else [catalog.get(i) for i in displaynames]

def replace_permissions_displayname(token, holder):

    if holder == '*':

        return holder

    try:

        # check first for a group permission

        account, group = holder.split(':', 1)

    except ValueError:

        return retrieve_uuid(token, holder)

    else:

        return ':'.join([retrieve_uuid(token, account), group])

def replace_permissions_uuid(token, holder):

    if holder == '*':

        return holder

    try:

        # check first for a group permission

        account, group = holder.split(':', 1)

    except ValueError:

        return retrieve_displayname(token, holder)

    else:

        return ':'.join([retrieve_displayname(token, account), group])

def update_sharing_meta(request, permissions, v_account,

                        v_container, v_object, meta):

    if permissions is None:

        return

    allowed, perm_path, perms = permissions

    if len(perms) == 0:

        return

    # replace uuid with displayname

    if TRANSLATE_UUIDS:

        perms['read'] = [replace_permissions_uuid(

            getattr(request, 'token', None), x)

            for x in perms.get('read', [])]

        perms['write'] = [replace_permissions_uuid(

            getattr(request, 'token', None), x)

            for x in perms.get('write', [])]

    ret = []

    r = ','.join(perms.get('read', []))

    if r:

        ret.append('read=' + r)

    w = ','.join(perms.get('write', []))

    if w:

        ret.append('write=' + w)

    meta['X-Object-Sharing'] = '; '.join(ret)

    if '/'.join((v_account, v_container, v_object)) != perm_path:

        meta['X-Object-Shared-By'] = perm_path

    if request.user_uniq != v_account:

        meta['X-Object-Allowed-To'] = allowed

def update_public_meta(public, meta):

    if not public:

        return

    meta['X-Object-Public'] = join_urls(

        BASE_HOST, reverse('pithos.api.public.public_demux', args=(public,)))

def validate_modification_preconditions(request, meta):

    """Check the modified timestamp conforms with the preconditions set."""

    if 'modified' not in meta:

        return  # TODO: Always return?

    if_modified_since = request.META.get('HTTP_IF_MODIFIED_SINCE')

    if if_modified_since is not None:

        if_modified_since = parse_http_date_safe(if_modified_since)

    if (if_modified_since is not None

            and int(meta['modified']) <= if_modified_since):

        raise faults.NotModified('Resource has not been modified')

    if_unmodified_since = request.META.get('HTTP_IF_UNMODIFIED_SINCE')

    if if_unmodified_since is not None:

        if_unmodified_since = parse_http_date_safe(if_unmodified_since)

    if (if_unmodified_since is not None

            and int(meta['modified']) > if_unmodified_since):

        raise faults.PreconditionFailed('Resource has been modified')

def validate_matching_preconditions(request, meta):

    """Check that the ETag conforms with the preconditions set."""

    etag = meta['hash'] if not UPDATE_MD5 else meta['checksum']

    if not etag:

        etag = None

    if_match = request.META.get('HTTP_IF_MATCH')

    if if_match is not None:

        if etag is None:

            raise faults.PreconditionFailed('Resource does not exist')

        if (if_match != '*'

                and etag not in [x.lower() for x in parse_etags(if_match)]):

            raise faults.PreconditionFailed('Resource ETag does not match')

    if_none_match = request.META.get('HTTP_IF_NONE_MATCH')

    if if_none_match is not None:

        # TODO: If this passes, must ignore If-Modified-Since header.

        if etag is not None:

            if (if_none_match == '*' or etag in [x.lower() for x in

                                                 parse_etags(if_none_match)]):

                # TODO: Continue if an If-Modified-Since header is present.

                if request.method in ('HEAD', 'GET'):

                    raise faults.NotModified('Resource ETag matches')

                raise faults.PreconditionFailed(

                    'Resource exists or ETag matches')

def split_container_object_string(s):

    if not len(s) > 0 or s[0] != '/':

        raise ValueError

    s = s[1:]

    pos = s.find('/')

    if pos == -1 or pos == len(s) - 1:

        raise ValueError

    return s[:pos], s[(pos + 1):]

def copy_or_move_object(request, src_account, src_container, src_name,

                        dest_account, dest_container, dest_name,

                        move=False, delimiter=None):

    """Copy or move an object."""

    if 'ignore_content_type' in request.GET and 'CONTENT_TYPE' in request.META:

        del(request.META['CONTENT_TYPE'])

    content_type, meta, permissions, public = get_object_headers(request)

    src_version = request.META.get('HTTP_X_SOURCE_VERSION')

    try:

        if move:

            version_id = request.backend.move_object(

                request.user_uniq, src_account, src_container, src_name,

                dest_account, dest_container, dest_name,

                content_type, 'pithos', meta, False, permissions, delimiter)

        else:

            version_id = request.backend.copy_object(

                request.user_uniq, src_account, src_container, src_name,

                dest_account, dest_container, dest_name,

                content_type, 'pithos', meta, False, permissions,

                src_version, delimiter)

    except NotAllowedError:

        raise faults.Forbidden('Not allowed')

    except (ItemNotExists, VersionNotExists):

        raise faults.ItemNotFound('Container or object does not exist')

    except ValueError:

        raise faults.BadRequest('Invalid sharing header')

    except QuotaError, e:

        raise faults.RequestEntityTooLarge('Quota error: %s' % e)

    if public is not None:

        try:

            request.backend.update_object_public(

                request.user_uniq, dest_account,

                dest_container, dest_name, public)

        except NotAllowedError:

            raise faults.Forbidden('Not allowed')

        except ItemNotExists:

            raise faults.ItemNotFound('Object does not exist')

    return version_id

def get_int_parameter(p):

    if p is not None:

        try:

            p = int(p)

        except ValueError:

            return None

        if p < 0:

            return None

    return p

def get_content_length(request):

    content_length = get_int_parameter(request.META.get('CONTENT_LENGTH'))

    if content_length is None:

        raise faults.LengthRequired('Missing or invalid Content-Length header')

    return content_length

def get_range(request, size):

    """Parse a Range header from the request.

    Either returns None, when the header is not existent or should be ignored,

    or a list of (offset, length) tuples - should be further checked.

    """

    ranges = request.META.get('HTTP_RANGE', '').replace(' ', '')

    if not ranges.startswith('bytes='):

        return None

    ret = []

    for r in (x.strip() for x in ranges[6:].split(',')):

        p = re.compile('^(?P<offset>\d*)-(?P<upto>\d*)$')

        m = p.match(r)

        if not m:

            return None

        offset = m.group('offset')

        upto = m.group('upto')

        if offset == '' and upto == '':

            return None

        if offset != '':

            offset = int(offset)

            if upto != '':

                upto = int(upto)

                if offset > upto:

                    return None

                ret.append((offset, upto - offset + 1))

            else:

                ret.append((offset, size - offset))

        else:

            length = int(upto)

            ret.append((size - length, length))

    return ret

def get_content_range(request):

    """Parse a Content-Range header from the request.

    Either returns None, when the header is not existent or should be ignored,

    or an (offset, length, total) tuple - check as length, total may be None.

    Returns (None, None, None) if the provided range is '*/*'.

    """

    ranges = request.META.get('HTTP_CONTENT_RANGE', '')

    if not ranges:

        return None

    p = re.compile('^bytes (?P<offset>\d+)-(?P<upto>\d*)/(?P<total>(\d+|\*))$')

    m = p.match(ranges)

    if not m:

        if ranges == 'bytes */*':

            return (None, None, None)

        return None

    offset = int(m.group('offset'))

    upto = m.group('upto')

    total = m.group('total')

    if upto != '':

        upto = int(upto)

    else:

        upto = None

    if total != '*':

        total = int(total)

    else:

        total = None

    if (upto is not None and offset > upto) or \

        (total is not None and offset >= total) or \

            (total is not None and upto is not None and upto >= total):

        return None

    if upto is None:

        length = None

    else:

        length = upto - offset + 1

    return (offset, length, total)

def get_sharing(request):

    """Parse an X-Object-Sharing header from the request.

    Raises BadRequest on error.

    """

    permissions = request.META.get('HTTP_X_OBJECT_SHARING')

    if permissions is None:

        return None

    # TODO: Document or remove '~' replacing.

    permissions = permissions.replace('~', '')

    ret = {}

    permissions = permissions.replace(' ', '')

    if permissions == '':

        return ret

    for perm in (x for x in permissions.split(';')):

        if perm.startswith('read='):

            ret['read'] = list(set(

                [v.replace(' ', '').lower() for v in perm[5:].split(',')]))

            if '' in ret['read']:

                ret['read'].remove('')

            if '*' in ret['read']:

                ret['read'] = ['*']

            if len(ret['read']) == 0:

                raise faults.BadRequest(

                    'Bad X-Object-Sharing header value: invalid length')

        elif perm.startswith('write='):

            ret['write'] = list(set(

                [v.replace(' ', '').lower() for v in perm[6:].split(',')]))

            if '' in ret['write']:

                ret['write'].remove('')

            if '*' in ret['write']:

                ret['write'] = ['*']

            if len(ret['write']) == 0:

                raise faults.BadRequest(

                    'Bad X-Object-Sharing header value: invalid length')

        else:

            raise faults.BadRequest(

                'Bad X-Object-Sharing header value: missing prefix')

    # replace displayname with uuid

    if TRANSLATE_UUIDS:

        try:

            ret['read'] = [replace_permissions_displayname(

                getattr(request, 'token', None), x)

                for x in ret.get('read', [])]

            ret['write'] = [replace_permissions_displayname(

                getattr(request, 'token', None), x)

                for x in ret.get('write', [])]

        except ItemNotExists, e:

            raise faults.BadRequest(

                'Bad X-Object-Sharing header value: unknown account: %s' % e)

    # Keep duplicates only in write list.

    dups = [x for x in ret.get(

        'read', []) if x in ret.get('write', []) and x != '*']

    if dups:

        for x in dups:

            ret['read'].remove(x)

        if len(ret['read']) == 0:

            del(ret['read'])

    return ret

def get_public(request):

    """Parse an X-Object-Public header from the request.

    Raises BadRequest on error.

    """

    public = request.META.get('HTTP_X_OBJECT_PUBLIC')

    if public is None:

        return None

    public = public.replace(' ', '').lower()

    if public == 'true':

        return True

    elif public == 'false' or public == '':

        return False

    raise faults.BadRequest('Bad X-Object-Public header value')

def raw_input_socket(request):

    """Return the socket for reading the rest of the request."""

    server_software = request.META.get('SERVER_SOFTWARE')

    if server_software and server_software.startswith('mod_python'):

        return request._req

    if 'wsgi.input' in request.environ:

        return request.environ['wsgi.input']

    raise NotImplemented('Unknown server software')

MAX_UPLOAD_SIZE = 5 * (1024 * 1024 * 1024)  # 5GB

def socket_read_iterator(request, length=0, blocksize=4096):

    """Return maximum of blocksize data read from the socket in each iteration

    Read up to 'length'. If 'length' is negative, will attempt a chunked read.

    The maximum ammount of data read is controlled by MAX_UPLOAD_SIZE.

    """

    sock = raw_input_socket(request)

    if length < 0:  # Chunked transfers

        # Small version (server does the dechunking).

        if (request.environ.get('mod_wsgi.input_chunked', None)

                or request.META['SERVER_SOFTWARE'].startswith('gunicorn')):

            while length < MAX_UPLOAD_SIZE:

                data = sock.read(blocksize)

                if data == '':

                    return

                yield data

            raise faults.BadRequest('Maximum size is reached')

        # Long version (do the dechunking).

        data = ''

        while length < MAX_UPLOAD_SIZE:

            # Get chunk size.

            if hasattr(sock, 'readline'):

                chunk_length = sock.readline()

            else:

                chunk_length = ''

                while chunk_length[-1:] != '\n':

                    chunk_length += sock.read(1)

                chunk_length.strip()

            pos = chunk_length.find(';')

            if pos >= 0:

                chunk_length = chunk_length[:pos]

            try:

                chunk_length = int(chunk_length, 16)

            except Exception:

                raise faults.BadRequest('Bad chunk size')

                                 # TODO: Change to something more appropriate.

            # Check if done.

            if chunk_length == 0:

                if len(data) > 0:

                    yield data

                return

            # Get the actual data.

            while chunk_length > 0:

                chunk = sock.read(min(chunk_length, blocksize))

                chunk_length -= len(chunk)

                if length > 0:

                    length += len(chunk)

                data += chunk

                if len(data) >= blocksize:

                    ret = data[:blocksize]

                    data = data[blocksize:]

                    yield ret

            sock.read(2)  # CRLF

        raise faults.BadRequest('Maximum size is reached')

    else:

        if length > MAX_UPLOAD_SIZE:

            raise faults.BadRequest('Maximum size is reached')

        while length > 0:

            data = sock.read(min(length, blocksize))

            if not data:

                raise faults.BadRequest()

            length -= len(data)

            yield data

class SaveToBackendHandler(FileUploadHandler):

    """Handle a file from an HTML form the django way."""

    def __init__(self, request=None):

        super(SaveToBackendHandler, self).__init__(request)

        self.backend = request.backend

    def put_data(self, length):

        if len(self.data) >= length:

            block = self.data[:length]

            self.file.hashmap.append(self.backend.put_block(block))

            self.checksum_compute.update(block)

            self.data = self.data[length:]

    def new_file(self, field_name, file_name, content_type,

                 content_length, charset=None):

        self.checksum_compute = NoChecksum() if not UPDATE_MD5 else Checksum()

        self.data = ''

        self.file = UploadedFile(

            name=file_name, content_type=content_type, charset=charset)

        self.file.size = 0

        self.file.hashmap = []

    def receive_data_chunk(self, raw_data, start):

        self.data += raw_data

        self.file.size += len(raw_data)

        self.put_data(self.request.backend.block_size)

        return None

    def file_complete(self, file_size):

        l = len(self.data)

        if l > 0:

            self.put_data(l)

        self.file.etag = self.checksum_compute.hexdigest()

        return self.file

class ObjectWrapper(object):

    """Return the object's data block-per-block in each iteration.

    Read from the object using the offset and length provided

    in each entry of the range list.

    """

    def __init__(self, backend, ranges, sizes, hashmaps, boundary):

        self.backend = backend

        self.ranges = ranges

        self.sizes = sizes

        self.hashmaps = hashmaps

        self.boundary = boundary

        self.size = sum(self.sizes)

        self.file_index = 0

        self.block_index = 0

        self.block_hash = -1

        self.block = ''

        self.range_index = -1

        self.offset, self.length = self.ranges[0]

    def __iter__(self):

        return self

    def part_iterator(self):

        if self.length > 0:

            # Get the file for the current offset.

            file_size = self.sizes[self.file_index]

            while self.offset >= file_size:

                self.offset -= file_size

                self.file_index += 1

                file_size = self.sizes[self.file_index]

            # Get the block for the current position.

            self.block_index = int(self.offset / self.backend.block_size)

            if self.block_hash != \

                    self.hashmaps[self.file_index][self.block_index]:

                self.block_hash = self.hashmaps[

                    self.file_index][self.block_index]

                try:

                    self.block = self.backend.get_block(self.block_hash)

                except ItemNotExists:

                    raise faults.ItemNotFound('Block does not exist')

            # Get the data from the block.

            bo = self.offset % self.backend.block_size

            bs = self.backend.block_size

            if (self.block_index == len(self.hashmaps[self.file_index]) - 1 and

                    self.sizes[self.file_index] % self.backend.block_size):

                bs = self.sizes[self.file_index] % self.backend.block_size

            bl = min(self.length, bs - bo)

            data = self.block[bo:bo + bl]

            self.offset += bl

            self.length -= bl

            return data

        else:

            raise StopIteration

    def next(self):

        if len(self.ranges) == 1:

            return self.part_iterator()

        if self.range_index == len(self.ranges):

            raise StopIteration

        try:

            if self.range_index == -1:

                raise StopIteration

            return self.part_iterator()

        except StopIteration:

            self.range_index += 1

            out = []

            if self.range_index < len(self.ranges):

                # Part header.

                self.offset, self.length = self.ranges[self.range_index]

                self.file_index = 0

                if self.range_index > 0:

                    out.append('')

                out.append('--' + self.boundary)

                out.append('Content-Range: bytes %d-%d/%d' % (

                    self.offset, self.offset + self.length - 1, self.size))

                out.append('Content-Transfer-Encoding: binary')

                out.append('')

                out.append('')

                return '\r\n'.join(out)

            else:

                # Footer.

                out.append('')

                out.append('--' + self.boundary + '--')

                out.append('')

                return '\r\n'.join(out)

def object_data_response(request, sizes, hashmaps, meta, public=False):

    """Get the HttpResponse object for replying with the object's data."""

    # Range handling.

    size = sum(sizes)

    ranges = get_range(request, size)

    if ranges is None:

        ranges = [(0, size)]

        ret = 200

    else:

        check = [True for offset, length in ranges if

                 length <= 0 or length > size or

                 offset < 0 or offset >= size or

                 offset + length > size]

        if len(check) > 0:

            raise faults.RangeNotSatisfiable(

                'Requested range exceeds object limits')

        ret = 206

        if_range = request.META.get('HTTP_IF_RANGE')

        if if_range:

            try:

                # Modification time has passed instead.

                last_modified = parse_http_date(if_range)

                if last_modified != meta['modified']:

                    ranges = [(0, size)]

                    ret = 200

            except ValueError:

                if if_range != meta['checksum']:

                    ranges = [(0, size)]

                    ret = 200

    if ret == 206 and len(ranges) > 1:

        boundary = uuid.uuid4().hex

    else:

        boundary = ''

    wrapper = ObjectWrapper(request.backend, ranges, sizes, hashmaps, boundary)

    response = HttpResponse(wrapper, status=ret)

    put_object_headers(

        response, meta, restricted=public,

        token=getattr(request, 'token', None))

    if ret == 206:

        if len(ranges) == 1:

            offset, length = ranges[0]

            response[

                'Content-Length'] = length  # Update with the correct length.

            response['Content-Range'] = 'bytes %d-%d/%d' % (

                offset, offset + length - 1, size)

        else:

            del(response['Content-Length'])

            response['Content-Type'] = 'multipart/byteranges; boundary=%s' % (

                boundary,)

    return response

def put_object_block(request, hashmap, data, offset):

    """Put one block of data at the given offset."""

    bi = int(offset / request.backend.block_size)

    bo = offset % request.backend.block_size

    bl = min(len(data), request.backend.block_size - bo)

    if bi < len(hashmap):

        try:

            hashmap[bi] = request.backend.update_block(hashmap[bi],

                                                       data[:bl], bo)

        except IllegalOperationError, e:

            raise faults.Forbidden(e[0])

    else:

        hashmap.append(request.backend.put_block(('\x00' * bo) + data[:bl]))

    return bl  # Return ammount of data written.

def hashmap_md5(backend, hashmap, size):

    """Produce the MD5 sum from the data in the hashmap."""

    # TODO: Search backend for the MD5 of another object

    #       with the same hashmap and size...

    md5 = hashlib.md5()

    bs = backend.block_size

    for bi, hash in enumerate(hashmap):

        data = backend.get_block(hash)  # Blocks come in padded.

        if bi == len(hashmap) - 1:

            data = data[:size % bs]

        md5.update(data)

    return md5.hexdigest().lower()

def simple_list_response(request, l):

    if request.serialization == 'text':

        return '\n'.join(l) + '\n'

    if request.serialization == 'xml':

        return render_to_string('items.xml', {'items': l})

    if request.serialization == 'json':

        return json.dumps(l)