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Contents
module FormatParser::MP3Parser::ID3V1
PACKSPEC = [
:tag, :a3,
:song_name, :a30,
:artist, :a30,
:album, :a30,
:year, :N1,
:comment, :a30,
:genre, :C,
]
packspec_keys = PACKSPEC.select.with_index { |_, i| i.even? }
TAG_SIZE_BYTES = 128
class TagInformation < Struct.new(*packspec_keys)
end
def attempt_id3_v1_extraction(io)
return if io.size < TAG_SIZE_BYTES # Won't fit the ID3v1 regardless
io.seek(io.size - 128)
trailer_bytes = io.read(128)
return unless trailer_bytes && trailer_bytes.byteslice(0, 3) == 'TAG'
id3_v1 = parse_id3_v1(trailer_bytes)
# If all of the resulting strings are empty this ID3v1 tag is invalid and
# we should ignore it.
strings_from_id3v1 = id3_v1.values.select { |e| e.is_a?(String) && e != 'TAG' }
return if strings_from_id3v1.all?(&:empty?)
id3_v1
end
def parse_id3_v1(byte_str)
_keys, values = PACKSPEC.partition.with_index { |_, i| i.even? }
unpacked_values = byte_str.unpack(values.join)
unpacked_values.map! { |e| e.is_a?(String) ? trim_id3v1_string(e) : e }
TagInformation.new(unpacked_values)
end
# Remove trailing whitespace and trailing nullbytes
def trim_id3v1_string(str)
str.tr("\x00".b, '').strip
end
extend self
end
Version data entries
22 entries across 22 versions & 1 rubygems