Patch/new code by Sjoerd Mullender:
Separate the Chunk class out of the aifc module into a new "chunk" module.
diff --git a/Lib/aifc.py b/Lib/aifc.py
index c317c5f..c50bd79 100644
--- a/Lib/aifc.py
+++ b/Lib/aifc.py
@@ -236,45 +236,7 @@
_write_long(f, himant)
_write_long(f, lomant)
-class Chunk:
- def __init__(self, file):
- self.file = file
- self.chunkname = self.file.read(4)
- if len(self.chunkname) < 4:
- raise EOFError
- self.chunksize = _read_long(self.file)
- self.size_read = 0
- self.offset = self.file.tell()
-
- def rewind(self):
- self.file.seek(self.offset, 0)
- self.size_read = 0
-
- def setpos(self, pos):
- if pos < 0 or pos > self.chunksize:
- raise RuntimeError
- self.file.seek(self.offset + pos, 0)
- self.size_read = pos
-
- def read(self, length):
- if self.size_read >= self.chunksize:
- return ''
- if length > self.chunksize - self.size_read:
- length = self.chunksize - self.size_read
- data = self.file.read(length)
- self.size_read = self.size_read + len(data)
- return data
-
- def skip(self):
- try:
- self.file.seek(self.chunksize - self.size_read, 1)
- except RuntimeError:
- while self.size_read < self.chunksize:
- dummy = self.read(8192)
- if not dummy:
- raise EOFError
- if self.chunksize & 1:
- dummy = self.read(1)
+from chunk import Chunk
class Aifc_read:
# Variables used in this class:
@@ -312,26 +274,16 @@
# _ssnd_chunk -- instantiation of a chunk class for the SSND chunk
# _framesize -- size of one frame in the file
-## if 0: access _file, _nchannels, _nframes, _sampwidth, _framerate, \
-## _comptype, _compname, _markers, _soundpos, _version, \
-## _decomp, _comm_chunk_read, __aifc, _ssnd_seek_needed, \
-## _ssnd_chunk, _framesize: private
-
def initfp(self, file):
- self._file = file
self._version = 0
self._decomp = None
self._convert = None
self._markers = []
self._soundpos = 0
- form = self._file.read(4)
- if form != 'FORM':
+ self._file = Chunk(file)
+ if self._file.getname() != 'FORM':
raise Error, 'file does not start with FORM id'
- formlength = _read_long(self._file)
- if formlength <= 0:
- raise Error, 'invalid FORM chunk data size'
formdata = self._file.read(4)
- formlength = formlength - 4
if formdata == 'AIFF':
self._aifc = 0
elif formdata == 'AIFC':
@@ -339,38 +291,31 @@
else:
raise Error, 'not an AIFF or AIFF-C file'
self._comm_chunk_read = 0
- while formlength > 0:
+ while 1:
self._ssnd_seek_needed = 1
#DEBUG: SGI's soundfiler has a bug. There should
# be no need to check for EOF here.
try:
chunk = Chunk(self._file)
except EOFError:
- if formlength == 8:
- print 'Warning: FORM chunk size too large'
- formlength = 0
- break
- raise EOFError # different error, raise exception
- if chunk.chunkname == 'COMM':
+ break
+ chunkname = chunk.getname()
+ if chunkname == 'COMM':
self._read_comm_chunk(chunk)
self._comm_chunk_read = 1
- elif chunk.chunkname == 'SSND':
+ elif chunkname == 'SSND':
self._ssnd_chunk = chunk
dummy = chunk.read(8)
self._ssnd_seek_needed = 0
- elif chunk.chunkname == 'FVER':
+ elif chunkname == 'FVER':
self._version = _read_long(chunk)
- elif chunk.chunkname == 'MARK':
+ elif chunkname == 'MARK':
self._readmark(chunk)
- elif chunk.chunkname in _skiplist:
+ elif chunkname in _skiplist:
pass
else:
raise Error, 'unrecognized chunk type '+chunk.chunkname
- formlength = formlength - 8 - chunk.chunksize
- if chunk.chunksize & 1:
- formlength = formlength - 1
- if formlength > 0:
- chunk.skip()
+ chunk.skip()
if not self._comm_chunk_read or not self._ssnd_chunk:
raise Error, 'COMM chunk and/or SSND chunk missing'
if self._aifc and self._decomp:
@@ -460,7 +405,7 @@
def readframes(self, nframes):
if self._ssnd_seek_needed:
- self._ssnd_chunk.rewind()
+ self._ssnd_chunk.seek(0)
dummy = self._ssnd_chunk.read(8)
pos = self._soundpos * self._framesize
if pos:
@@ -477,7 +422,6 @@
#
# Internal methods.
#
-## if 0: access *: private
def _decomp_data(self, data):
import cl
@@ -611,10 +555,6 @@
# _datalength -- the size of the audio samples written to the header
# _datawritten -- the size of the audio samples actually written
-## if 0: access _file, _comptype, _compname, _nchannels, _sampwidth, \
-## _framerate, _nframes, _aifc, _version, _comp, \
-## _nframeswritten, _datalength, _datawritten: private
-
def __init__(self, f):
if type(f) == type(''):
filename = f
@@ -805,7 +745,6 @@
#
# Internal methods.
#
-## if 0: access *: private
def _comp_data(self, data):
import cl
diff --git a/Lib/chunk.py b/Lib/chunk.py
new file mode 100644
index 0000000..0a9abd2
--- /dev/null
+++ b/Lib/chunk.py
@@ -0,0 +1,142 @@
+"""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 a 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 1:
+ try:
+ chunk = Chunk(file)
+ except EOFError:
+ break
+ chunktype = chunk.getname()
+ while 1:
+ 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 = 1):
+ import struct
+ self.closed = 0
+ self.align = align # whether to align to word (2-byte) boundaries
+ self.file = file
+ self.chunkname = file.read(4)
+ if len(self.chunkname) < 4:
+ raise EOFError
+ try:
+ self.chunksize = struct.unpack('>l', file.read(4))[0]
+ except struct.error:
+ raise EOFError
+ self.size_read = 0
+ self.offset = self.file.tell()
+
+ def getname(self):
+ """Return the name (ID) of the current chunk."""
+ return self.chunkname
+
+ def close(self):
+ if not self.closed:
+ self.skip()
+ self.closed = 1
+
+ def isatty(self):
+ if self.closed:
+ raise ValueError, "I/O operation on closed file"
+ return 0
+
+ def seek(self, pos, mode = 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 mode == 1:
+ pos = pos + self.size_read
+ elif mode == 2:
+ pos = pos + self.chunk_size
+ 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, n = -1):
+ """Read at most n bytes from the chunk.
+ If n 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 n < 0:
+ n = self.chunksize - self.size_read
+ if n > self.chunksize - self.size_read:
+ n = self.chunksize - self.size_read
+ data = self.file.read(n)
+ 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"
+ try:
+ self.file.seek(self.chunksize - self.size_read, 1)
+ except RuntimeError:
+ while self.size_read < self.chunksize:
+ dummy = self.read(8192)
+ if not dummy:
+ raise EOFError
+