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-rw-r--r--tests/bytecode/pylib-tests/chunk.py167
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diff --git a/tests/bytecode/pylib-tests/chunk.py b/tests/bytecode/pylib-tests/chunk.py
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-"""Simple class to read IFF chunks.
-
-An IFF chunk (used in formats such as AIFF, TIFF, RMFF (RealMedia File
-Format)) has the following structure:
-
-+----------------+
-| ID (4 bytes) |
-+----------------+
-| size (4 bytes) |
-+----------------+
-| data |
-| ... |
-+----------------+
-
-The ID is a 4-byte string which identifies the type of chunk.
-
-The size field (a 32-bit value, encoded using big-endian byte order)
-gives the size of the whole chunk, including the 8-byte header.
-
-Usually an IFF-type file consists of one or more chunks. The proposed
-usage of the Chunk class defined here is to instantiate an instance at
-the start of each chunk and read from the instance until it reaches
-the end, after which a new instance can be instantiated. At the end
-of the file, creating a new instance will fail with a EOFError
-exception.
-
-Usage:
-while True:
- try:
- chunk = Chunk(file)
- except EOFError:
- break
- chunktype = chunk.getname()
- while True:
- data = chunk.read(nbytes)
- if not data:
- pass
- # do something with data
-
-The interface is file-like. The implemented methods are:
-read, close, seek, tell, isatty.
-Extra methods are: skip() (called by close, skips to the end of the chunk),
-getname() (returns the name (ID) of the chunk)
-
-The __init__ method has one required argument, a file-like object
-(including a chunk instance), and one optional argument, a flag which
-specifies whether or not chunks are aligned on 2-byte boundaries. The
-default is 1, i.e. aligned.
-"""
-
-class Chunk:
- def __init__(self, file, align=True, bigendian=True, inclheader=False):
- import struct
- self.closed = False
- self.align = align # whether to align to word (2-byte) boundaries
- if bigendian:
- strflag = '>'
- else:
- strflag = '<'
- self.file = file
- self.chunkname = file.read(4)
- if len(self.chunkname) < 4:
- raise EOFError
- try:
- self.chunksize = struct.unpack_from(strflag+'L', file.read(4))[0]
- except struct.error:
- raise EOFError
- if inclheader:
- self.chunksize = self.chunksize - 8 # subtract header
- self.size_read = 0
- try:
- self.offset = self.file.tell()
- except (AttributeError, IOError):
- self.seekable = False
- else:
- self.seekable = True
-
- def getname(self):
- """Return the name (ID) of the current chunk."""
- return self.chunkname
-
- def getsize(self):
- """Return the size of the current chunk."""
- return self.chunksize
-
- def close(self):
- if not self.closed:
- self.skip()
- self.closed = True
-
- def isatty(self):
- if self.closed:
- raise ValueError("I/O operation on closed file")
- return False
-
- def seek(self, pos, whence=0):
- """Seek to specified position into the chunk.
- Default position is 0 (start of chunk).
- If the file is not seekable, this will result in an error.
- """
-
- if self.closed:
- raise ValueError("I/O operation on closed file")
- if not self.seekable:
- raise IOError("cannot seek")
- if whence == 1:
- pos = pos + self.size_read
- elif whence == 2:
- pos = pos + self.chunksize
- if pos < 0 or pos > self.chunksize:
- raise RuntimeError
- self.file.seek(self.offset + pos, 0)
- self.size_read = pos
-
- def tell(self):
- if self.closed:
- raise ValueError("I/O operation on closed file")
- return self.size_read
-
- def read(self, size=-1):
- """Read at most size bytes from the chunk.
- If size is omitted or negative, read until the end
- of the chunk.
- """
-
- if self.closed:
- raise ValueError("I/O operation on closed file")
- if self.size_read >= self.chunksize:
- return ''
- if size < 0:
- size = self.chunksize - self.size_read
- if size > self.chunksize - self.size_read:
- size = self.chunksize - self.size_read
- data = self.file.read(size)
- self.size_read = self.size_read + len(data)
- if self.size_read == self.chunksize and \
- self.align and \
- (self.chunksize & 1):
- dummy = self.file.read(1)
- self.size_read = self.size_read + len(dummy)
- return data
-
- def skip(self):
- """Skip the rest of the chunk.
- If you are not interested in the contents of the chunk,
- this method should be called so that the file points to
- the start of the next chunk.
- """
-
- if self.closed:
- raise ValueError("I/O operation on closed file")
- if self.seekable:
- try:
- n = self.chunksize - self.size_read
- # maybe fix alignment
- if self.align and (self.chunksize & 1):
- n = n + 1
- self.file.seek(n, 1)
- self.size_read = self.size_read + n
- return
- except IOError:
- pass
- while self.size_read < self.chunksize:
- n = min(8192, self.chunksize - self.size_read)
- dummy = self.read(n)
- if not dummy:
- raise EOFError