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author | Guido van Rossum <guido@python.org> | 1999-08-26 15:57:44 (GMT) |
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committer | Guido van Rossum <guido@python.org> | 1999-08-26 15:57:44 (GMT) |
commit | e7f19200e8202275ea5677f61853da448b0ca7cd (patch) | |
tree | 8001035ad6a456db3164137a83eff7541f43dce2 /Doc/lib/libchunk.tex | |
parent | b35d6846d9ae6b1d23234b15cb5d8240eeb6c7d9 (diff) | |
download | cpython-e7f19200e8202275ea5677f61853da448b0ca7cd.zip cpython-e7f19200e8202275ea5677f61853da448b0ca7cd.tar.gz cpython-e7f19200e8202275ea5677f61853da448b0ca7cd.tar.bz2 |
Doco update from Sjoerd Mullender.
Diffstat (limited to 'Doc/lib/libchunk.tex')
-rw-r--r-- | Doc/lib/libchunk.tex | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/Doc/lib/libchunk.tex b/Doc/lib/libchunk.tex index 770b525..0825a25 100644 --- a/Doc/lib/libchunk.tex +++ b/Doc/lib/libchunk.tex @@ -13,16 +13,15 @@ chunks.\footnote{``EA IFF 85'' Standard for Interchange Format Files, Jerry Morrison, Electronic Arts, January 1985.} This format is used in at least the Audio\index{Audio Interchange File Format}\index{AIFF}\index{AIFF-C} Interchange File Format -(AIFF/AIFF-C), the Real\index{Real Media File Format} Media File -Format\index{RMFF} (RMFF), and the -Tagged\index{Tagged Image File Format} Image File Format\index{TIFF} -(TIFF). +(AIFF/AIFF-C) and the Real\index{Real Media File Format} Media File +Format\index{RMFF} (RMFF). The WAVE audio file format is closely +related and can also be read using this module. A chunk has the following structure: \begin{tableiii}{c|c|l}{textrm}{Offset}{Length}{Contents} \lineiii{0}{4}{Chunk ID} - \lineiii{4}{4}{Size of chunk in big-endian byte order, including the + \lineiii{4}{4}{Size of chunk in big-endian byte order, not including the header} \lineiii{8}{\var{n}}{Data bytes, where \var{n} is the size given in the preceeding field} @@ -33,7 +32,7 @@ A chunk has the following structure: 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. +gives the size of the chunk data, not including the 8-byte header. Usually an IFF-type file consists of one or more chunks. The proposed usage of the \class{Chunk} class defined here is to instantiate an @@ -42,7 +41,7 @@ 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 \exception{EOFError} exception. -\begin{classdesc}{Chunk}{file\optional{, align}} +\begin{classdesc}{Chunk}{file\optional{, align, bigendian, inclheader}} Class which represents a chunk. The \var{file} argument is expected to be a file-like object. An instance of this class is specifically allowed. The only method that is needed is \method{read()}. If the @@ -51,7 +50,12 @@ raise an exception, they are also used. If these methods are present and raise an exception, they are expected to not have altered the object. If the optional argument \var{align} is true, chunks are assumed to be aligned on 2-byte boundaries. If \var{align} is -false, no alignment is assumed. The default value is true. +false, no alignment is assumed. The default value is true. If the +optional argument \var{bigendian} is false, the chunk size is assumed +to be in little-endian order. This is needed for WAVE audio files. +The default value is true. If the optional argument \var{inclheader} +is true, the size given in the chunk header includes the size of the +header. The default value is false. \end{classdesc} A \class{Chunk} object supports the following methods: @@ -61,6 +65,10 @@ Returns the name (ID) of the chunk. This is the first 4 bytes of the chunk. \end{methoddesc} +\begin{methoddesc}{getsize}{} +Returns the size of the chunk. +\end{methoddesc} + \begin{methoddesc}{close}{} Close and skip to the end of the chunk. This does not close the underlying file. |