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#
# The Python Imaging Library.
# $Id$
#
# a class to read from a container file
#
# History:
# 1995-06-18 fl Created
# 1995-09-07 fl Added readline(), readlines()
#
# Copyright (c) 1997-2001 by Secret Labs AB
# Copyright (c) 1995 by Fredrik Lundh
#
# See the README file for information on usage and redistribution.
#
from __future__ import annotations
import io
from collections.abc import Iterable
from typing import IO, AnyStr, NoReturn
class ContainerIO(IO[AnyStr]):
"""
A file object that provides read access to a part of an existing
file (for example a TAR file).
"""
def __init__(self, file: IO[AnyStr], offset: int, length: int) -> None:
"""
Create file object.
:param file: Existing file.
:param offset: Start of region, in bytes.
:param length: Size of region, in bytes.
"""
self.fh: IO[AnyStr] = file
self.pos = 0
self.offset = offset
self.length = length
self.fh.seek(offset)
##
# Always false.
def isatty(self) -> bool:
return False
def seekable(self) -> bool:
return True
def seek(self, offset: int, mode: int = io.SEEK_SET) -> int:
"""
Move file pointer.
:param offset: Offset in bytes.
:param mode: Starting position. Use 0 for beginning of region, 1
for current offset, and 2 for end of region. You cannot move
the pointer outside the defined region.
:returns: Offset from start of region, in bytes.
"""
if mode == 1:
self.pos = self.pos + offset
elif mode == 2:
self.pos = self.length + offset
else:
self.pos = offset
# clamp
self.pos = max(0, min(self.pos, self.length))
self.fh.seek(self.offset + self.pos)
return self.pos
def tell(self) -> int:
"""
Get current file pointer.
:returns: Offset from start of region, in bytes.
"""
return self.pos
def readable(self) -> bool:
return True
def read(self, n: int = -1) -> AnyStr:
"""
Read data.
:param n: Number of bytes to read. If omitted, zero or negative,
read until end of region.
:returns: An 8-bit string.
"""
if n > 0:
n = min(n, self.length - self.pos)
else:
n = self.length - self.pos
if n <= 0: # EOF
return b"" if "b" in self.fh.mode else "" # type: ignore[return-value]
self.pos = self.pos + n
return self.fh.read(n)
def readline(self, n: int = -1) -> AnyStr:
"""
Read a line of text.
:param n: Number of bytes to read. If omitted, zero or negative,
read until end of line.
:returns: An 8-bit string.
"""
s: AnyStr = b"" if "b" in self.fh.mode else "" # type: ignore[assignment]
newline_character = b"\n" if "b" in self.fh.mode else "\n"
while True:
c = self.read(1)
if not c:
break
s = s + c
if c == newline_character or len(s) == n:
break
return s
def readlines(self, n: int | None = -1) -> list[AnyStr]:
"""
Read multiple lines of text.
:param n: Number of lines to read. If omitted, zero, negative or None,
read until end of region.
:returns: A list of 8-bit strings.
"""
lines = []
while True:
s = self.readline()
if not s:
break
lines.append(s)
if len(lines) == n:
break
return lines
def writable(self) -> bool:
return False
def write(self, b: AnyStr) -> NoReturn:
raise NotImplementedError()
def writelines(self, lines: Iterable[AnyStr]) -> NoReturn:
raise NotImplementedError()
def truncate(self, size: int | None = None) -> int:
raise NotImplementedError()
def __enter__(self) -> ContainerIO[AnyStr]:
return self
def __exit__(self, *args: object) -> None:
self.close()
def __iter__(self) -> ContainerIO[AnyStr]:
return self
def __next__(self) -> AnyStr:
line = self.readline()
if not line:
msg = "end of region"
raise StopIteration(msg)
return line
def fileno(self) -> int:
return self.fh.fileno()
def flush(self) -> None:
self.fh.flush()
def close(self) -> None:
self.fh.close()
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