diff options
Diffstat (limited to 'tests/bytecode/pylib-tests/chunk.py')
-rw-r--r-- | tests/bytecode/pylib-tests/chunk.py | 167 |
1 files changed, 0 insertions, 167 deletions
diff --git a/tests/bytecode/pylib-tests/chunk.py b/tests/bytecode/pylib-tests/chunk.py deleted file mode 100644 index 5863ed0846..0000000000 --- a/tests/bytecode/pylib-tests/chunk.py +++ /dev/null @@ -1,167 +0,0 @@ -"""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 |