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module WaveFile
module ChunkReaders
# Internal: Used to read the RIFF chunks in a wave file up until the data chunk. Thus it
# can be used to open a wave file and "queue it up" to the start of the actual sample data,
# as well as extract information out of pre-data chunks, such as the format chunk.
class RiffReader # :nodoc:
def initialize(io, format=nil)
@io = io
read_until_data_chunk(format)
end
attr_reader :native_format, :data_chunk_reader, :sample_chunk
private
def read_riff_format_code
riff_format = @io.read(4)
unless riff_format == WAVEFILE_FORMAT_CODE
raise_error InvalidFormatError, "Expected RIFF format of '#{WAVEFILE_FORMAT_CODE}', but was '#{riff_format}'"
end
end
def read_until_data_chunk(format)
chunk_id, riff_chunk_size = read_chunk_header
unless chunk_id == CHUNK_IDS[:riff]
raise_error InvalidFormatError, "Expected chunk ID '#{CHUNK_IDS[:riff]}', but was '#{chunk_id}'"
end
end_of_file_pos = @io.pos + riff_chunk_size
read_riff_format_code()
data_chunk_seek_pos = nil
data_chunk_size = nil
data_chunk_is_final_chunk = nil
loop do
chunk_id, chunk_size = read_chunk_header
case chunk_id
when CHUNK_IDS[:format]
if data_chunk_seek_pos != nil
raise_error InvalidFormatError, "The format chunk is after the data chunk; it must come before."
end
@native_format = FormatChunkReader.new(@io, chunk_size).read
when CHUNK_IDS[:sample]
@sample_chunk = SampleChunkReader.new(@io, chunk_size).read
when CHUNK_IDS[:data]
data_chunk_seek_pos = @io.pos
data_chunk_size = chunk_size
# Only look for chunks after the data chunk if there are enough bytes
# left in the file for that to be possible.
start_of_next_chunk_pos = (@io.pos + data_chunk_size)
start_of_next_chunk_pos += 1 if chunk_size.odd?
if start_of_next_chunk_pos < end_of_file_pos
@io.seek(data_chunk_seek_pos + chunk_size, IO::SEEK_SET)
else
data_chunk_is_final_chunk = true
end
else
# Unsupported chunk types are ignored
@io.read(chunk_size)
end
# The RIFF specification requires that each chunk be aligned to an even number of bytes,
# even if the byte count is an odd number.
#
# See http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/Docs/riffmci.pdf, page 11.
if chunk_size.odd?
@io.read(1)
end
break if @io.pos >= end_of_file_pos || data_chunk_is_final_chunk
end
if @native_format == nil
raise_error InvalidFormatError, "Format chunk couldn't be found."
end
if data_chunk_seek_pos.nil?
raise_error InvalidFormatError, "Data chunk couldn't be found."
end
if @io.pos != data_chunk_seek_pos
@io.seek(data_chunk_seek_pos, IO::SEEK_SET)
end
@data_chunk_reader = DataChunkReader.new(@io, data_chunk_size, @native_format, format)
end
def read_chunk_header
chunk_id = @io.read(4)
chunk_size = @io.read(4)
unless chunk_size.nil?
chunk_size = chunk_size.unpack(UNSIGNED_INT_32).first
end
if chunk_size.nil?
raise_error InvalidFormatError, "Unexpected end of file."
end
return chunk_id, chunk_size
end
def raise_error(exception_class, message)
raise exception_class, "Not a supported wave file. #{message}"
end
end
end
end
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