ó
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L\¬Qc @ s d Z d d d YZ d S( s Simple class to read IFF chunks.
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An IFF chunk (used in formats such as AIFF, TIFF, RMFF (RealMedia File
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Format)) has the following structure:
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+----------------+
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| ID (4 bytes) |
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+----------------+
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| size (4 bytes) |
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+----------------+
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| data |
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| ... |
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+----------------+
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The ID is a 4-byte string which identifies the type of chunk.
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The size field (a 32-bit value, encoded using big-endian byte order)
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gives the size of the whole chunk, including the 8-byte header.
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Usually an IFF-type file consists of one or more chunks. The proposed
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usage of the Chunk class defined here is to instantiate an instance at
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the start of each chunk and read from the instance until it reaches
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the end, after which a new instance can be instantiated. At the end
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of the file, creating a new instance will fail with a EOFError
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exception.
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Usage:
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while True:
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try:
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chunk = Chunk(file)
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except EOFError:
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break
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chunktype = chunk.getname()
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while True:
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data = chunk.read(nbytes)
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if not data:
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pass
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# do something with data
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The interface is file-like. The implemented methods are:
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read, close, seek, tell, isatty.
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Extra methods are: skip() (called by close, skips to the end of the chunk),
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getname() (returns the name (ID) of the chunk)
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The __init__ method has one required argument, a file-like object
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(including a chunk instance), and one optional argument, a flag which
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specifies whether or not chunks are aligned on 2-byte boundaries. The
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default is 1, i.e. aligned.
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c C s | j S( s* Return the name (ID) of the current chunk.( R
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( R ( ( sM /tmp/ndk-User/buildhost/install/prebuilt/darwin-x86_64/lib/python2.7/chunk.pyt getnameN s c C s | j S( s% Return the size of the current chunk.( R ( R ( ( sM /tmp/ndk-User/buildhost/install/prebuilt/darwin-x86_64/lib/python2.7/chunk.pyt getsizeR s c C s# | j s | j t | _ n d S( N( R t skipR ( R ( ( sM /tmp/ndk-User/buildhost/install/prebuilt/darwin-x86_64/lib/python2.7/chunk.pyt closeV s
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c C s | j r t d n t S( Ns I/O operation on closed file( R t
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ValueErrorR ( R ( ( sM /tmp/ndk-User/buildhost/install/prebuilt/darwin-x86_64/lib/python2.7/chunk.pyt isatty[ s i c C s | j r t d n | j s* t d n | d k rF | | j } n | d k rb | | j } n | d k s} | | j k r t n | j j | j | d | | _ d S( s¦ Seek to specified position into the chunk.
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Default position is 0 (start of chunk).
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If the file is not seekable, this will result in an error.
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s I/O operation on closed files cannot seeki i i N(
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R R R R R R t RuntimeErrorR t seekR ( R t post whence( ( sM /tmp/ndk-User/buildhost/install/prebuilt/darwin-x86_64/lib/python2.7/chunk.pyR# ` s c C s | j r t d n | j S( Ns I/O operation on closed file( R R R ( R ( ( sM /tmp/ndk-User/buildhost/install/prebuilt/darwin-x86_64/lib/python2.7/chunk.pyR s s iÿÿÿÿc C sò | j r t d n | j | j k r+ d S| d k rJ | j | j } n | | j | j k rs | j | j } n | j j | } | j t | | _ | j | j k rî | j rî | j d @rî | j j d } | j t | | _ n | S( s Read at most size bytes from the chunk.
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If size is omitted or negative, read until the end
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of the chunk.
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r q Xn xM | j | j k râ t d | j | j } | j
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| } | s t q q Wd S( sÉ Skip the rest of the chunk.
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If you are not interested in the contents of the chunk,
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this method should be called so that the file points to
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the start of the next chunk.
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