Initial Commit

lib/mutagen/oggflac.py

@@ -0,0 +1,147 @@
+# -*- coding: utf-8 -*-
+
+# Copyright (C) 2006  Joe Wreschnig
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+
+"""Read and write Ogg FLAC comments.
+
+This module handles FLAC files wrapped in an Ogg bitstream. The first
+FLAC stream found is used. For 'naked' FLACs, see mutagen.flac.
+
+This module is based off the specification at
+http://flac.sourceforge.net/ogg_mapping.html.
+"""
+
+__all__ = ["OggFLAC", "Open", "delete"]
+
+import struct
+
+from ._compat import cBytesIO
+
+from mutagen.flac import StreamInfo, VCFLACDict, StrictFileObject
+from mutagen.ogg import OggPage, OggFileType, error as OggError
+
+
+class error(OggError):
+    pass
+
+
+class OggFLACHeaderError(error):
+    pass
+
+
+class OggFLACStreamInfo(StreamInfo):
+    """Ogg FLAC general header and stream info.
+
+    This encompasses the Ogg wrapper for the FLAC STREAMINFO metadata
+    block, as well as the Ogg codec setup that precedes it.
+
+    Attributes (in addition to StreamInfo's):
+
+    * packets -- number of metadata packets
+    * serial -- Ogg logical stream serial number
+    """
+
+    packets = 0
+    serial = 0
+
+    def load(self, data):
+        # Ogg expects file objects that don't raise on read
+        if isinstance(data, StrictFileObject):
+            data = data._fileobj
+
+        page = OggPage(data)
+        while not page.packets[0].startswith(b"\x7FFLAC"):
+            page = OggPage(data)
+        major, minor, self.packets, flac = struct.unpack(
+            ">BBH4s", page.packets[0][5:13])
+        if flac != b"fLaC":
+            raise OggFLACHeaderError("invalid FLAC marker (%r)" % flac)
+        elif (major, minor) != (1, 0):
+            raise OggFLACHeaderError(
+                "unknown mapping version: %d.%d" % (major, minor))
+        self.serial = page.serial
+
+        # Skip over the block header.
+        stringobj = StrictFileObject(cBytesIO(page.packets[0][17:]))
+        super(OggFLACStreamInfo, self).load(stringobj)
+
+    def _post_tags(self, fileobj):
+        if self.length:
+            return
+        page = OggPage.find_last(fileobj, self.serial)
+        self.length = page.position / float(self.sample_rate)
+
+    def pprint(self):
+        return u"Ogg " + super(OggFLACStreamInfo, self).pprint()
+
+
+class OggFLACVComment(VCFLACDict):
+    def load(self, data, info, errors='replace'):
+        # data should be pointing at the start of an Ogg page, after
+        # the first FLAC page.
+        pages = []
+        complete = False
+        while not complete:
+            page = OggPage(data)
+            if page.serial == info.serial:
+                pages.append(page)
+                complete = page.complete or (len(page.packets) > 1)
+        comment = cBytesIO(OggPage.to_packets(pages)[0][4:])
+        super(OggFLACVComment, self).load(comment, errors=errors)
+
+    def _inject(self, fileobj):
+        """Write tag data into the FLAC Vorbis comment packet/page."""
+
+        # Ogg FLAC has no convenient data marker like Vorbis, but the
+        # second packet - and second page - must be the comment data.
+        fileobj.seek(0)
+        page = OggPage(fileobj)
+        while not page.packets[0].startswith(b"\x7FFLAC"):
+            page = OggPage(fileobj)
+
+        first_page = page
+        while not (page.sequence == 1 and page.serial == first_page.serial):
+            page = OggPage(fileobj)
+
+        old_pages = [page]
+        while not (old_pages[-1].complete or len(old_pages[-1].packets) > 1):
+            page = OggPage(fileobj)
+            if page.serial == first_page.serial:
+                old_pages.append(page)
+
+        packets = OggPage.to_packets(old_pages, strict=False)
+
+        # Set the new comment block.
+        data = self.write()
+        data = packets[0][:1] + struct.pack(">I", len(data))[-3:] + data
+        packets[0] = data
+
+        new_pages = OggPage.from_packets(packets, old_pages[0].sequence)
+        OggPage.replace(fileobj, old_pages, new_pages)
+
+
+class OggFLAC(OggFileType):
+    """An Ogg FLAC file."""
+
+    _Info = OggFLACStreamInfo
+    _Tags = OggFLACVComment
+    _Error = OggFLACHeaderError
+    _mimes = ["audio/x-oggflac"]
+
+    @staticmethod
+    def score(filename, fileobj, header):
+        return (header.startswith(b"OggS") * (
+            (b"FLAC" in header) + (b"fLaC" in header)))
+
+
+Open = OggFLAC
+
+
+def delete(filename):
+    """Remove tags from a file."""
+
+    OggFLAC(filename).delete()