Synnefo » Pithos

# Copyright 2011 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

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# The views and conclusions contained in the software and

# documentation are those of the authors and should not be

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from functools import wraps

from time import time

from traceback import format_exc

from wsgiref.handlers import format_date_time

from binascii import hexlify, unhexlify

from datetime import datetime, tzinfo, timedelta

from django.conf import settings

from django.http import HttpResponse

from django.utils import simplejson as json

from django.utils.http import http_date, parse_etags

from django.utils.encoding import smart_str

from pithos.api.compat import parse_http_date_safe, parse_http_date

from pithos.api.faults import (Fault, NotModified, BadRequest, Unauthorized, Forbidden, ItemNotFound,

                                Conflict, LengthRequired, PreconditionFailed, RequestEntityTooLarge,

                                RangeNotSatisfiable, ServiceUnavailable)

from pithos.backends import connect_backend

from pithos.backends.base import NotAllowedError, QuotaError

import logging

import re

import hashlib

import uuid

import decimal

logger = logging.getLogger(__name__)

class UTC(tzinfo):

   def utcoffset(self, dt):

       return timedelta(0)

   def tzname(self, dt):

       return 'UTC'

   def dst(self, dt):

       return timedelta(0)

def json_encode_decimal(obj):

    if isinstance(obj, decimal.Decimal):

        return str(obj)

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

def isoformat(d):

   """Return an ISO8601 date string that includes a timezone."""

   return d.replace(tzinfo=UTC()).isoformat()

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.

    """

    d['last_modified'] = isoformat(datetime.fromtimestamp(d['last_modified']))

    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 get_account_headers(request):

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

    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):

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

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

        meta['Content-Type'] = request.META['CONTENT_TYPE']

    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 meta, get_sharing(request), get_public(request)

def put_object_headers(response, meta, restricted=False):

    response['ETag'] = meta['ETag']

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

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

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

    if not restricted:

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

        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] = meta[k]

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], x[1])

                etag += src_meta['ETag']

                bytes += src_meta['bytes']

        except:

            # Ignore errors.

            return

        meta['bytes'] = bytes

        md5 = hashlib.md5()

        md5.update(etag)

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

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

    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'] = public

def validate_modification_preconditions(request, meta):

    """Check that 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 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 PreconditionFailed('Resource has been modified')

def validate_matching_preconditions(request, meta):

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

    etag = meta.get('ETag', None)

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

    if if_match is not None:

        if etag is None:

            raise PreconditionFailed('Resource does not exist')

        if if_match != '*' and etag not in [x.lower() for x in parse_etags(if_match)]:

            raise 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 NotModified('Resource ETag matches')

                raise 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:

        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):

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

    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,

                                                        meta, False, permissions)

        else:

            version_id = request.backend.copy_object(request.user_uniq, src_account, src_container, src_name,

                                                        dest_account, dest_container, dest_name,

                                                        meta, False, permissions, src_version)

    except NotAllowedError:

        raise Forbidden('Not allowed')

    except (NameError, IndexError):

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

    except ValueError:

        raise BadRequest('Invalid sharing header')

    except AttributeError, e:

        raise Conflict('\n'.join(e.data) + '\n')

    except QuotaError:

        raise RequestEntityTooLarge('Quota exceeded')

    if public is not None:

        try:

            request.backend.update_object_public(request.user_uniq, dest_account, dest_container, dest_name, public)

        except NotAllowedError:

            raise Forbidden('Not allowed')

        except NameError:

            raise 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 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 BadRequest('Bad X-Object-Sharing header value')

        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 BadRequest('Bad X-Object-Sharing header value')

        else:

            raise BadRequest('Bad X-Object-Sharing header value')

    # 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 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 ServiceUnavailable('Unknown server software')

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

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

    """Return a 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 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, e:

                raise 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 BadRequest('Maximum size is reached')

    else:

        if length > MAX_UPLOAD_SIZE:

            raise BadRequest('Maximum size is reached')

        while length > 0:

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

            if not data:

                raise BadRequest()

            length -= len(data)

            yield data

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 NameError:

                    raise ItemNotFound('Block does not exist')

            # Get the data from the block.

            bo = self.offset % self.backend.block_size

            bl = min(self.length, len(self.block) - 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 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['ETag']:

                    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, public)

    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):

        hashmap[bi] = request.backend.update_block(hashmap[bi], data[:bl], bo)

    else:

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

    return bl # Return ammount of data written.

def hashmap_hash(request, hashmap):

    """Produce the root hash, treating the hashmap as a Merkle-like tree."""

    def subhash(d):

        h = hashlib.new(request.backend.hash_algorithm)

        h.update(d)

        return h.digest()

    if len(hashmap) == 0:

        return hexlify(subhash(''))

    if len(hashmap) == 1:

        return hashmap[0]

    s = 2

    while s < len(hashmap):

        s = s * 2

    h = [unhexlify(x) for x in hashmap]

    h += [('\x00' * len(h[0]))] * (s - len(hashmap))

    while len(h) > 1:

        h = [subhash(h[x] + h[x + 1]) for x in range(0, len(h), 2)]

    return hexlify(h[0])

def update_response_headers(request, response):

    if request.serialization == 'xml':

        response['Content-Type'] = 'application/xml; charset=UTF-8'

    elif request.serialization == 'json':

        response['Content-Type'] = 'application/json; charset=UTF-8'

    elif not response['Content-Type']:

        response['Content-Type'] = 'text/plain; charset=UTF-8'

    if not response.has_header('Content-Length') and not (response.has_header('Content-Type') and response['Content-Type'].startswith('multipart/byteranges')):

        response['Content-Length'] = len(response.content)

    if settings.TEST:

        response['Date'] = format_date_time(time())

def render_fault(request, fault):

    if settings.DEBUG or settings.TEST:

        fault.details = format_exc(fault)

    request.serialization = 'text'

    data = '\n'.join((fault.message, fault.details)) + '\n'

    response = HttpResponse(data, status=fault.code)

    update_response_headers(request, response)

    return response

def request_serialization(request, format_allowed=False):

    """Return the serialization format requested.

    Valid formats are 'text' and 'json', 'xml' if 'format_allowed' is True.

    """

    if not format_allowed:

        return 'text'

    format = request.GET.get('format')

    if format == 'json':

        return 'json'

    elif format == 'xml':

        return 'xml'

    for item in request.META.get('HTTP_ACCEPT', '').split(','):

        accept, sep, rest = item.strip().partition(';')

        if accept == 'application/json':

            return 'json'

        elif accept == 'application/xml' or accept == 'text/xml':

            return 'xml'

    return 'text'

def api_method(http_method=None, format_allowed=False, user_required=True):

    """Decorator function for views that implement an API method."""

    def decorator(func):

        @wraps(func)

        def wrapper(request, *args, **kwargs):

            try:

                if http_method and request.method != http_method:

                    raise BadRequest('Method not allowed.')

                if user_required and getattr(request, 'user', None) is None:

                    raise Unauthorized('Access denied')

                # The args variable may contain up to (account, container, object).

                if len(args) > 1 and len(args[1]) > 256:

                    raise BadRequest('Container name too large.')

                if len(args) > 2 and len(args[2]) > 1024:

                    raise BadRequest('Object name too large.')

                # Fill in custom request variables.

                request.serialization = request_serialization(request, format_allowed)

                request.backend = connect_backend()

                response = func(request, *args, **kwargs)

                update_response_headers(request, response)

                return response

            except Fault, fault:

                return render_fault(request, fault)

            except BaseException, e:

                logger.exception('Unexpected error: %s' % e)

                fault = ServiceUnavailable('Unexpected error')

                return render_fault(request, fault)

            finally:

                if getattr(request, 'backend', None) is not None:

                    request.backend.close()

        return wrapper

    return decorator