--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/symbian-qemu-0.9.1-12/python-2.6.1/Lib/chunk.py Fri Jul 31 15:01:17 2009 +0100
@@ -0,0 +1,167 @@
+"""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(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