PIL.ContainerIO 源代码

#
# 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.
#

##
# A file object that provides read access to a part of an existing
# file (for example a TAR file).


[文档]class ContainerIO(object): ## # Create file object. # # @param file Existing file. # @param offset Start of region, in bytes. # @param length Size of region, in bytes. def __init__(self, file, offset, length): self.fh = file self.pos = 0 self.offset = offset self.length = length self.fh.seek(offset) ## # Always false.
[文档] def isatty(self): return 0
## # 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.
[文档] def seek(self, offset, mode=0): 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)
## # Get current file pointer. # # @return Offset from start of region, in bytes.
[文档] def tell(self): return self.pos
## # Read data. # # @def read(bytes=0) # @param bytes Number of bytes to read. If omitted or zero, # read until end of region. # @return An 8-bit string.
[文档] def read(self, n=0): if n: n = min(n, self.length - self.pos) else: n = self.length - self.pos if not n: # EOF return "" self.pos = self.pos + n return self.fh.read(n)
## # Read a line of text. # # @return An 8-bit string.
[文档] def readline(self): s = "" while True: c = self.read(1) if not c: break s = s + c if c == "\n": break return s
## # Read multiple lines of text. # # @return A list of 8-bit strings.
[文档] def readlines(self): l = [] while True: s = self.readline() if not s: break l.append(s) return l