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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. | |
| # | |
| import io | |
| class ContainerIO: | |
| """ | |
| A file object that provides read access to a part of an existing | |
| file (for example a TAR file). | |
| """ | |
| def __init__(self, file, offset, length): | |
| """ | |
| Create file object. | |
| :param file: Existing file. | |
| :param offset: Start of region, in bytes. | |
| :param length: Size of region, in bytes. | |
| """ | |
| self.fh = file | |
| self.pos = 0 | |
| self.offset = offset | |
| self.length = length | |
| self.fh.seek(offset) | |
| ## | |
| # Always false. | |
| def isatty(self): | |
| return False | |
| def seek(self, offset, mode=io.SEEK_SET): | |
| """ | |
| 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. | |
| """ | |
| 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) | |
| def tell(self): | |
| """ | |
| Get current file pointer. | |
| :returns: Offset from start of region, in bytes. | |
| """ | |
| return self.pos | |
| def read(self, n=0): | |
| """ | |
| Read data. | |
| :param n: Number of bytes to read. If omitted or zero, | |
| read until end of region. | |
| :returns: An 8-bit string. | |
| """ | |
| if n: | |
| n = min(n, self.length - self.pos) | |
| else: | |
| n = self.length - self.pos | |
| if not n: # EOF | |
| return b"" if "b" in self.fh.mode else "" | |
| self.pos = self.pos + n | |
| return self.fh.read(n) | |
| def readline(self): | |
| """ | |
| Read a line of text. | |
| :returns: An 8-bit string. | |
| """ | |
| s = b"" if "b" in self.fh.mode else "" | |
| 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: | |
| break | |
| return s | |
| def readlines(self): | |
| """ | |
| Read multiple lines of text. | |
| :returns: A list of 8-bit strings. | |
| """ | |
| lines = [] | |
| while True: | |
| s = self.readline() | |
| if not s: | |
| break | |
| lines.append(s) | |
| return lines | |