| import collections |
| import io |
| import mmap |
| import struct |
|
|
| TarHeader = collections.namedtuple( |
| "TarHeader", |
| [ |
| "name", |
| "mode", |
| "uid", |
| "gid", |
| "size", |
| "mtime", |
| "chksum", |
| "typeflag", |
| "linkname", |
| "magic", |
| "version", |
| "uname", |
| "gname", |
| "devmajor", |
| "devminor", |
| "prefix", |
| ], |
| ) |
|
|
|
|
| def parse_tar_header(header_bytes): |
| header = struct.unpack("!100s8s8s8s12s12s8s1s100s6s2s32s32s8s8s155s", header_bytes) |
| return TarHeader(*header) |
|
|
|
|
| def next_header(offset, header): |
| block_size = 512 |
| size = header.size.decode("utf-8").strip("\x00") |
| if size == "": |
| return -1 |
| size = int(size, 8) |
| |
| padded_file_size = (size + block_size - 1) // block_size * block_size |
| return offset + block_size + padded_file_size |
|
|
|
|
| class MMIndexedTar: |
| def __init__(self, fname, index_file=None, verbose=True): |
| self.fname = fname |
| with open(fname, "rb") as file: |
| self.mmapped_file = mmap.mmap(file.fileno(), 0, access=mmap.ACCESS_READ) |
| self._build_index() |
|
|
| def _build_index(self): |
| self.by_name = {} |
| self.by_index = [] |
| offset = 0 |
| while offset >= 0 and offset < len(self.mmapped_file): |
| header = parse_tar_header(self.mmapped_file[offset : offset + 500]) |
| name = header.name.decode("utf-8").strip("\x00") |
| typeflag = header.typeflag.decode("utf-8").strip("\x00") |
| if name != "" and name != "././@PaxHeader" and typeflag in ["0", ""]: |
| try: |
| size = int(header.size.decode("utf-8")[:-1], 8) |
| except ValueError as exn: |
| print(header) |
| raise exn |
| self.by_name[name] = offset |
| self.by_index.append((name, offset, size)) |
| offset = next_header(offset, header) |
|
|
| def names(self): |
| return self.by_name.keys() |
|
|
| def get_at_offset(self, offset): |
| header = parse_tar_header(self.mmapped_file[offset : offset + 500]) |
| name = header.name.decode("utf-8").strip("\x00") |
| start = offset + 512 |
| end = start + int(header.size.decode("utf-8")[:-1], 8) |
| return name, self.mmapped_file[start:end] |
|
|
| def get_at_index(self, index): |
| name, offset, size = self.by_index[index] |
| return self.get_at_offset(offset) |
|
|
| def get_by_name(self, name): |
| offset = self.by_name[name] |
| return self.get_at_offset(offset) |
|
|
| def __iter__(self): |
| for name, offset, size in self.by_index: |
| yield name, self.mmapped_file[offset + 512 : offset + 512 + size] |
|
|
| def __getitem__(self, key): |
| if isinstance(key, int): |
| return self.get_at_index(key) |
| else: |
| return self.get_by_name(key) |
|
|
| def __len__(self): |
| return len(self.by_index) |
|
|
| def get_file(self, i): |
| fname, data = self.get_at_index(i) |
| return fname, io.BytesIO(data) |
|
|
| def close(self): |
| self.mmapped_file.close() |
|
|
