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