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cache.py
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cache.py
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# $Progeny$
#
# Copyright 2005 Progeny Linux Systems, Inc.
#
# This file is part of PDK.
#
# PDK is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# PDK is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
# License for more details.
#
# You should have received a copy of the GNU General Public License
# along with PDK; if not, write to the Free Software Foundation,
# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
"""
cache.py
Manage a cache of packages and other files, all for use
when referenced by component descriptors.
Cache is indexed by 'blob', which is currently an sha1
checksum.
Cache contains .header files.
"""
__revision__ = "$Progeny$"
import os
import os.path
import stat
import re
from stat import ST_INO, ST_SIZE
import sha
import md5
import hashlib
import gzip
import pycurl
from shutil import copy2
from urlparse import urlparse
from tempfile import mkstemp
from pdk.package import get_package_type
from pdk.util import ensure_directory_exists, make_path_to, get_remote_file
from pdk.exceptions import SemanticError, ConfigurationError
# Debugging aids
import pdk.log
log = pdk.log.get_logger()
def calculate_checksums(file_path):
"""Calculate both sha-1 and md5 checksums for a file, returned
as blob_ids
"""
readsize = (1024 * 16)
md5_calc = md5.new()
sha1_calc = sha.new()
sha256_calc = hashlib.sha256()
input_file = open(file_path)
while True:
block = input_file.read(readsize)
if not block:
break
md5_calc.update(block)
sha1_calc.update(block)
sha256_calc.update(block)
input_file.close()
return 'sha-1:' + sha1_calc.hexdigest(), \
'md5:' + md5_calc.hexdigest(), \
'sha256:' + sha256_calc.hexdigest()
class CacheImportError(SemanticError):
"""Generic error for trouble importing to cache"""
pass
########################################################################
class SimpleCache(object):
"""A moderately dumb data structure representing a physical cache
directory on disk.
Special capabilities are:
1) the naming algorithm for file paths
2) Checksumming & linking of contents by md5/sha1
3) Awareness and use of a backing cache
"""
def __init__(self, cache_path):
self.path = os.path.abspath(cache_path)
if os.path.exists(cache_path) and not os.path.isdir(cache_path):
raise ConfigurationError("%s is not a directory path"
% cache_path)
# Check for a backing cache
backing_path = os.path.join(cache_path, '.backing')
if os.path.exists(backing_path):
self.backing = SimpleCache(backing_path)
else:
self.backing = None
def make_relative_filename(self, filename):
"""Calculate where the file should exist within the cache"""
filename = os.path.split(filename)[1] or filename
dirpath = '.'
if ':' in filename:
# md5 or sha-1 sum
scheme, name = filename.split(':')
dirpath = os.path.join(scheme, name[:2])
# Note: else path is just ./filename
return os.path.join(dirpath, filename)
def file_path(self, filename):
"""Calculate the full file path (not absolute) for a file"""
return os.path.join(
self.path
, self.make_relative_filename(filename)
)
def __contains__(self, filepath):
"""Determine if the cache already contains a file"""
result = False
if filepath and not os.path.basename(filepath).startswith('.'):
local_path = self.file_path(filepath)
result = os.path.exists(local_path)
return result
def send_via_framer(self, blob_id, framer, callback_adapter):
'''Send a blob via the given framer.'''
cache_file = self.file_path(blob_id)
mtime = os.stat(cache_file)[stat.ST_MTIME]
handle = open(cache_file)
framer.write_frame(blob_id)
framer.write_handle(handle, callback_adapter)
handle.close()
framer.write_stream([str(mtime)])
def import_from_framer(self, framer, mass_progress):
'''Import a blob via the given framer.'''
while True:
local_filename = None
try:
first = framer.read_frame()
if first == 'done':
framer.assert_end_of_stream();
break
blob_id = first
local_filename = self.make_download_filename()
handle = open(local_filename, 'w')
progress = mass_progress.get_single_progress(blob_id)
total = mass_progress.get_size(blob_id)
current = 0
progress.start()
for frame in framer.iter_stream():
current += len(frame)
handle.write(frame)
progress.write_bar(total, current)
progress.done()
handle.close()
mtime = int(framer.read_frame())
framer.assert_end_of_stream()
if mtime != -1:
os.utime(local_filename, (mtime, mtime))
self.incorporate_file(local_filename, blob_id)
mass_progress.note_finished(blob_id)
mass_progress.write_progress()
finally:
if local_filename and os.path.exists(local_filename):
os.unlink(local_filename)
def import_file(self, locator, mass_progress):
'''Download and incorporate a potentially remote source.
locator - A FileLocator
If the locator has a blob_id, it is used to verify the correctness
of the acquired file. If the blob_id is missing, the file is not
verified.
'''
local_filename = self.make_download_filename()
get_progress = mass_progress.get_single_progress
progress = get_progress(locator.blob_id, locator.get_full_url())
try:
full_url = locator.get_full_url()
parts = urlparse(full_url)
scheme = parts[0]
if scheme in ('file', ''):
source_file = parts[2]
try:
progress.start()
copy2(source_file, local_filename)
progress.done()
self.umask_permissions(local_filename)
except IOError, e:
if e.errno == 2 and os.path.exists(local_filename):
raise CacheImportError('%s not found' % full_url)
else:
raise
else:
try:
get_remote_file(full_url, local_filename,
progress = progress)
except pycurl.error, msg:
raise CacheImportError('%s, %s' % (msg, full_url))
self.incorporate_file(local_filename, locator.blob_id)
mass_progress.note_finished(locator.blob_id)
mass_progress.write_progress()
finally:
if os.path.exists(local_filename):
os.unlink(local_filename)
def _add_links(self, source, blob_ids):
'''Create visible links to the blob contained in source.
Assume the blob_ids are correct.
'''
seed = self.make_download_filename()
try:
# optimization opportunity
# we could attempt linking directly from source
# to visible link to save on a copy here.
copy2(source, seed)
for blob_id in blob_ids:
filename = self.file_path(blob_id)
if os.path.exists(filename):
continue
make_path_to(filename)
os.link(seed, filename)
finally:
os.unlink(seed)
def umask_permissions(self, filename):
'''Set the filename permissions according to umask.'''
current_umask = os.umask(0)
os.umask(current_umask)
new_mode = 0666 & ~current_umask
os.chmod(filename, new_mode)
def make_download_filename(self):
"""Create a pathname convenient for creating files for
later linkage into the cache.
"""
# mkstemp actually creates the file, so we must enusre this can
# succeed.
ensure_directory_exists(self.path)
temp_fd, temp_fname = mkstemp('.partial', '.', self.path)
os.close(temp_fd)
self.umask_permissions(temp_fname)
return temp_fname
def incorporate_file(self, filepath, blob_id):
"""Places a temp file in its final cache location,
by md5 and sha1, and unlinks the original filepath.
"""
# Link it according to the given blob ids - note: does
# not affect backing cache
if self.backing:
blob_ids = self.backing.incorporate_file(filepath, blob_id)
else:
blob_ids = calculate_checksums(filepath)
if blob_id:
if not blob_id in blob_ids:
message = 'Checksum mismatch: %s vs. %s.' \
% (blob_id, str(blob_ids))
raise CacheImportError(message)
self._add_links(filepath, blob_ids)
return blob_ids
def __iter__(self):
for record in os.walk(self.path):
filenames = record[2] # (dir, subdirs, filename)
for filename in filenames:
yield filename
def get_inode(self, blob_id):
"""Return the inode of a file given blob_id"""
filepath = self.file_path(blob_id)
return os.stat(filepath)[ST_INO]
def get_size(self, blob_id):
"""Return the inode of a file given blob_id"""
filepath = self.file_path(blob_id)
return os.stat(filepath)[ST_SIZE]
def iter_sha1_ids(self):
"""Iterate over the list of all the sha-1 ids in this cache."""
rexp = re.compile('sha-1:[a-fA-F0-9]+$')
for filename in self:
if rexp.match(filename):
yield filename
def get_index_file(self):
'''Return the path to the blob index file.'''
index_file = os.path.join(self.path, 'blob_list.gz')
return index_file
def write_index(self):
"""Write an index file describing the contents of the cache."""
index_file = self.get_index_file()
handle = gzip.open(index_file, 'w')
regex = re.compile('(sha-1:|md5:|sha256:)[a-fA-F0-9]+$')
for filename in self:
if regex.match(filename):
path = self.make_relative_filename(filename)
size = self.get_size(filename)
handle.write('%s %s %d\n' % (filename, path, size))
handle.flush()
handle.close()
class Cache(SimpleCache):
"""Manage and report on the contents of the cache
Adds higher-level functions
"""
def __init__(self, cache_path):
SimpleCache.__init__(self, cache_path)
ensure_directory_exists(self.path)
def get_header_filename(self, blob_id):
"Return the filename of a blob's header file"
fname = self.file_path(blob_id) + '.header'
return fname
def add_header(self, header, blob_id):
""" write a header to a file, identified by blob_id"""
# Always start with a temp file
temp_path = self.make_download_filename()
try:
# Fill it.
open(temp_path, 'w').write(header)
# Link it to the appropriate blob_id.header file
filename = self.get_header_filename(blob_id)
try:
os.link(temp_path, filename)
except OSError, msg:
# file exists
if msg.errno == 17:
pass
else:
raise
finally:
# Get rid of the temp file
os.unlink(temp_path)
def load_package(self, blob_id, package_format):
"""Load the raw header data into memory from a package
"""
package_type = get_package_type(format = package_format)
header_file = self.get_header_filename(blob_id)
# check if the header file is already present
# don't bother with synchronization issues.
if os.path.basename(header_file) not in self:
# Suck the header out and install it
blob_filename = self.file_path(blob_id)
try:
header = package_type.extract_header(blob_filename)
except IOError, error:
if error.errno == 2:
message = "Missing package file in file cache\n"
message += "ref = '%s'\n" % blob_id
message += "Consider running pdk download on any new "
message += "or recently modified components."
raise SemanticError, message
self.add_header(header, blob_id)
header = open(header_file).read()
return package_type.parse(header, blob_id)
# vim:set ai et sw=4 ts=4 tw=75: