forked from openlp/openlp
Implemented BinaryReader.Read7BitEncodedInt from .NET. Tidy code.
This commit is contained in:
Samuel Findlay
parent
76de0f0c60
commit
45c180308a
@ -42,31 +42,30 @@ class PowerSongImport(SongImport):
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**PowerSong Song File Format:**
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The file has a number of label-field pairs of variable length.
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The file has a number of label-field pairs.
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Labels and Fields:
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* Every label and field is preceded by an integer which specifies its
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byte-length.
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* If the length < 128 bytes, only one byte is used to encode
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the length integer.
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* But if it's greater, as many bytes are used as necessary:
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* the first byte = (length % 128) + 128
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* the next byte = length / 128
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* another byte is only used if (length / 128) >= 128
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* and so on (3 bytes needed iff length > 16383)
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Label and Field strings:
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* Every label and field is a variable length string preceded by an
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integer specifying it's byte length.
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* Integer is 32-bit but is encoded in 7-bit format to save space. Thus
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if length will fit in 7 bits (ie <= 127) it takes up only one byte.
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Metadata fields:
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* Every PowerSong file begins with a TITLE field.
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* This is followed by zero or more AUTHOR fields.
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* The next label is always COPYRIGHTLINE, but its field may be empty.
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* Every PowerSong file has a TITLE field.
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* There is zero or more AUTHOR fields.
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* There is always a COPYRIGHTLINE label, but its field may be empty.
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This field may also contain a CCLI number: e.g. "CCLI 176263".
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Lyrics fields:
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* Each verse is contained in a PART field.
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* Lines have Windows line endings ``CRLF`` (0x0d, 0x0a).
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* There is no concept of verse types.
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Valid extensions for a PowerSong song file are:
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* .song
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"""
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@ -75,6 +74,8 @@ class PowerSongImport(SongImport):
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Receive a list of files to import.
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"""
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if not isinstance(self.importSource, list):
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self.logError(unicode(translate('SongsPlugin.PowerSongImport',
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'No files to import.')))
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return
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self.importWizard.progressBar.setMaximum(len(self.importSource))
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for file in self.importSource:
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@ -82,83 +83,103 @@ class PowerSongImport(SongImport):
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return
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self.setDefaults()
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parse_error = False
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with open(file, 'rb') as self.song_file:
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# Get title to check file is valid PowerSong song format
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label, field = self.readLabelField()
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if label == u'TITLE':
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self.title = field.replace(u'\n', u' ')
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else:
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self.logError(file, unicode(
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translate('SongsPlugin.PowerSongSongImport', \
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'Invalid PowerSong file. Missing "TITLE" header.')))
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continue
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# Get rest of fields from file
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with open(file, 'rb') as song_data:
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while True:
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label, field = self.readLabelField()
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if not label:
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break
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if label == u'AUTHOR':
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self.parseAuthor(field)
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elif label == u'COPYRIGHTLINE':
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found_copyright = True
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self.parseCopyrightCCLI(field)
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elif label == u'PART':
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self.addVerse(field)
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else:
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try:
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label = self._readString(song_data)
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if not label:
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break
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field = self._readString(song_data)
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except ValueError:
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parse_error = True
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self.logError(file, unicode(
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translate('SongsPlugin.PowerSongSongImport', \
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'"%s" Invalid PowerSong file. Unknown header: "%s".'
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% (self.title, label))))
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translate('SongsPlugin.PowerSongImport',
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'Invalid PowerSong file. Unexpected byte value.')))
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break
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if parse_error:
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continue
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# Check that file had COPYRIGHTLINE label
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if not found_copyright:
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self.logError(file, unicode(
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translate('SongsPlugin.PowerSongSongImport', \
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'"%s" Invalid PowerSong file. Missing "COPYRIGHTLINE" \
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header.' % self.title)))
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continue
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# Check that file had at least one verse
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if not self.verses:
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self.logError(file, unicode(
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translate('SongsPlugin.PowerSongSongImport', \
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'"%s" Verses not found. Missing "PART" header.'
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% self.title)))
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continue
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else:
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if label == u'TITLE':
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self.title = field.replace(u'\n', u' ')
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elif label == u'AUTHOR':
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self.parseAuthor(field)
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elif label == u'COPYRIGHTLINE':
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found_copyright = True
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self._parseCopyrightCCLI(field)
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elif label == u'PART':
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self.addVerse(field)
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if parse_error:
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continue
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# Check that file had TITLE field
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if not self.title:
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self.logError(file, unicode(
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translate('SongsPlugin.PowerSongImport',
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'Invalid PowerSong file. Missing "TITLE" header.')))
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continue
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# Check that file had COPYRIGHTLINE label
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if not found_copyright:
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self.logError(file, unicode(
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translate('SongsPlugin.PowerSongImport',
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'"%s" Invalid PowerSong file. Missing "COPYRIGHTLINE" '
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'header.' % self.title)))
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continue
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# Check that file had at least one verse
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if not self.verses:
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self.logError(file, unicode(
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translate('SongsPlugin.PowerSongImport',
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'"%s" Verses not found. Missing "PART" header.'
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% self.title)))
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continue
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if not self.finish():
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self.logError(file)
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def readLabelField(self):
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def _readString(self, file_object):
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"""
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Read (as a 2-tuple) the next two variable-length strings
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Reads in next variable-length string.
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"""
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label = unicode(self.song_file.read(
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self.readLength()), u'utf-8', u'ignore')
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if label:
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field = unicode(self.song_file.read(
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self.readLength()), u'utf-8', u'ignore')
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else:
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field = u''
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return label, field
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string_len = self._read7BitEncodedInteger(file_object)
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return unicode(file_object.read(string_len), u'utf-8', u'ignore')
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def readLength(self):
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def _read7BitEncodedInteger(self, file_object):
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"""
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Read the byte-length of the next variable-length string
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Reads in a 32-bit integer in compressed 7-bit format.
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If at the end of the file, returns 0.
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Accomplished by reading the integer 7 bits at a time. The high bit
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of the byte when set means to continue reading more bytes.
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If the integer will fit in 7 bits (ie <= 127), it only takes up one
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byte. Otherwise, it may take up to 5 bytes.
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Reference: .NET method System.IO.BinaryReader.Read7BitEncodedInt
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"""
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this_byte = self.song_file.read(1)
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if not this_byte:
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val = 0
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shift = 0
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i = 0
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while True:
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# Check for corrupted stream (since max 5 bytes per 32-bit integer)
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if i == 5:
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raise ValueError
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byte = self._readByte(file_object)
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# Strip high bit and shift left
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val += (byte & 0x7f) << shift
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shift += 7
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high_bit_set = byte & 0x80
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if not high_bit_set:
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break
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i += 1
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return val
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def _readByte(self, file_object):
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"""
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Reads in next byte as an unsigned integer
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Note: returns 0 at end of file.
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"""
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byte_str = file_object.read(1)
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# If read result is empty, then reached end of file
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if not byte_str:
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return 0
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this_byte_val = ord(this_byte)
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if this_byte_val < 128:
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return this_byte_val
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else:
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return (self.readLength() * 128) + (this_byte_val - 128)
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return ord(byte_str)
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def parseCopyrightCCLI(self, field):
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def _parseCopyrightCCLI(self, field):
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"""
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Look for CCLI song number, and get copyright
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"""
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