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projecten1/lib/python3.6/site-packages/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).
+
+
+class ContainerIO(object):
+
+    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 0
+
+    def seek(self, offset, mode=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.
+        """
+        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 ""
+        self.pos = self.pos + n
+        return self.fh.read(n)
+
+    def readline(self):
+        """
+        Read a line of text.
+
+        :returns: An 8-bit string.
+        """
+        s = ""
+        while True:
+            c = self.read(1)
+            if not c:
+                break
+            s = s + c
+            if c == "\n":
+                break
+        return s
+
+    def readlines(self):
+        """
+        Read multiple lines of text.
+
+        :returns: A list of 8-bit strings.
+        """
+        l = []
+        while True:
+            s = self.readline()
+            if not s:
+                break
+            l.append(s)
+        return l