214 lines
6.9 KiB
Python
214 lines
6.9 KiB
Python
from contextlib import contextmanager
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from ctypes import (
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CFUNCTYPE,
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POINTER,
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c_int,
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c_longlong,
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c_void_p,
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cast,
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create_string_buffer,
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)
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import libarchive
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import libarchive.ffi as ffi
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from fsspec import open_files
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from fsspec.archive import AbstractArchiveFileSystem
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from fsspec.implementations.memory import MemoryFile
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from fsspec.utils import DEFAULT_BLOCK_SIZE
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# Libarchive requires seekable files or memory only for certain archive
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# types. However, since we read the directory first to cache the contents
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# and also allow random access to any file, the file-like object needs
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# to be seekable no matter what.
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# Seek call-backs (not provided in the libarchive python wrapper)
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SEEK_CALLBACK = CFUNCTYPE(c_longlong, c_int, c_void_p, c_longlong, c_int)
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read_set_seek_callback = ffi.ffi(
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"read_set_seek_callback", [ffi.c_archive_p, SEEK_CALLBACK], c_int, ffi.check_int
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)
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new_api = hasattr(ffi, "NO_OPEN_CB")
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@contextmanager
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def custom_reader(file, format_name="all", filter_name="all", block_size=ffi.page_size):
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"""Read an archive from a seekable file-like object.
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The `file` object must support the standard `readinto` and 'seek' methods.
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"""
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buf = create_string_buffer(block_size)
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buf_p = cast(buf, c_void_p)
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def read_func(archive_p, context, ptrptr):
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# readinto the buffer, returns number of bytes read
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length = file.readinto(buf)
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# write the address of the buffer into the pointer
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ptrptr = cast(ptrptr, POINTER(c_void_p))
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ptrptr[0] = buf_p
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# tell libarchive how much data was written into the buffer
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return length
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def seek_func(archive_p, context, offset, whence):
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file.seek(offset, whence)
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# tell libarchvie the current position
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return file.tell()
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read_cb = ffi.READ_CALLBACK(read_func)
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seek_cb = SEEK_CALLBACK(seek_func)
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if new_api:
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open_cb = ffi.NO_OPEN_CB
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close_cb = ffi.NO_CLOSE_CB
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else:
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open_cb = libarchive.read.OPEN_CALLBACK(ffi.VOID_CB)
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close_cb = libarchive.read.CLOSE_CALLBACK(ffi.VOID_CB)
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with libarchive.read.new_archive_read(format_name, filter_name) as archive_p:
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read_set_seek_callback(archive_p, seek_cb)
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ffi.read_open(archive_p, None, open_cb, read_cb, close_cb)
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yield libarchive.read.ArchiveRead(archive_p)
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class LibArchiveFileSystem(AbstractArchiveFileSystem):
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"""Compressed archives as a file-system (read-only)
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Supports the following formats:
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tar, pax , cpio, ISO9660, zip, mtree, shar, ar, raw, xar, lha/lzh, rar
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Microsoft CAB, 7-Zip, WARC
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See the libarchive documentation for further restrictions.
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https://www.libarchive.org/
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Keeps file object open while instance lives. It only works in seekable
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file-like objects. In case the filesystem does not support this kind of
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file object, it is recommended to cache locally.
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This class is pickleable, but not necessarily thread-safe (depends on the
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platform). See libarchive documentation for details.
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"""
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root_marker = ""
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protocol = "libarchive"
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cachable = False
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def __init__(
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self,
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fo="",
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mode="r",
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target_protocol=None,
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target_options=None,
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block_size=DEFAULT_BLOCK_SIZE,
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**kwargs,
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):
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"""
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Parameters
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----------
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fo: str or file-like
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Contains ZIP, and must exist. If a str, will fetch file using
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:meth:`~fsspec.open_files`, which must return one file exactly.
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mode: str
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Currently, only 'r' accepted
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target_protocol: str (optional)
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If ``fo`` is a string, this value can be used to override the
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FS protocol inferred from a URL
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target_options: dict (optional)
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Kwargs passed when instantiating the target FS, if ``fo`` is
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a string.
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"""
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super().__init__(self, **kwargs)
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if mode != "r":
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raise ValueError("Only read from archive files accepted")
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if isinstance(fo, str):
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files = open_files(fo, protocol=target_protocol, **(target_options or {}))
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if len(files) != 1:
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raise ValueError(
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f'Path "{fo}" did not resolve to exactly one file: "{files}"'
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)
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fo = files[0]
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self.of = fo
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self.fo = fo.__enter__() # the whole instance is a context
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self.block_size = block_size
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self.dir_cache = None
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@contextmanager
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def _open_archive(self):
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self.fo.seek(0)
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with custom_reader(self.fo, block_size=self.block_size) as arc:
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yield arc
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@classmethod
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def _strip_protocol(cls, path):
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# file paths are always relative to the archive root
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return super()._strip_protocol(path).lstrip("/")
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def _get_dirs(self):
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fields = {
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"name": "pathname",
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"size": "size",
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"created": "ctime",
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"mode": "mode",
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"uid": "uid",
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"gid": "gid",
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"mtime": "mtime",
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}
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if self.dir_cache is not None:
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return
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self.dir_cache = {}
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list_names = []
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with self._open_archive() as arc:
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for entry in arc:
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if not entry.isdir and not entry.isfile:
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# Skip symbolic links, fifo entries, etc.
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continue
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self.dir_cache.update(
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{
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dirname: {"name": dirname, "size": 0, "type": "directory"}
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for dirname in self._all_dirnames(set(entry.name))
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}
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)
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f = {key: getattr(entry, fields[key]) for key in fields}
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f["type"] = "directory" if entry.isdir else "file"
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list_names.append(entry.name)
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self.dir_cache[f["name"]] = f
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# libarchive does not seem to return an entry for the directories (at least
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# not in all formats), so get the directories names from the files names
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self.dir_cache.update(
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{
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dirname: {"name": dirname, "size": 0, "type": "directory"}
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for dirname in self._all_dirnames(list_names)
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}
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)
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def _open(
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self,
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path,
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mode="rb",
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block_size=None,
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autocommit=True,
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cache_options=None,
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**kwargs,
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):
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path = self._strip_protocol(path)
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if mode != "rb":
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raise NotImplementedError
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data = bytes()
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with self._open_archive() as arc:
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for entry in arc:
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if entry.pathname != path:
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continue
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if entry.size == 0:
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# empty file, so there are no blocks
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break
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for block in entry.get_blocks(entry.size):
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data = block
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break
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else:
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raise ValueError
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return MemoryFile(fs=self, path=path, data=data)
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