Pillow/src/PIL/ContainerIO.py

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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.
#
##
# A file object that provides read access to a part of an existing
# file (for example a TAR file).
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class ContainerIO(object):
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def __init__(self, file, offset, length):
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"""
Create file object.
:param file: Existing file.
:param offset: Start of region, in bytes.
:param length: Size of region, in bytes.
"""
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self.fh = file
self.pos = 0
self.offset = offset
self.length = length
self.fh.seek(offset)
##
# Always false.
def isatty(self):
return 0
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def seek(self, offset, mode=0):
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"""
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.
"""
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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):
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"""
Get current file pointer.
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:returns: Offset from start of region, in bytes.
"""
return self.pos
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def read(self, n=0):
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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.
:returns: An 8-bit string.
"""
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if n:
n = min(n, self.length - self.pos)
else:
n = self.length - self.pos
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if not n: # EOF
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return ""
self.pos = self.pos + n
return self.fh.read(n)
def readline(self):
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"""
Read a line of text.
:returns: An 8-bit string.
"""
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s = ""
while True:
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c = self.read(1)
if not c:
break
s = s + c
if c == "\n":
break
return s
def readlines(self):
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"""
Read multiple lines of text.
:returns: A list of 8-bit strings.
"""
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l = []
while True:
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s = self.readline()
if not s:
break
l.append(s)
return l