How to use the hachoir.field.Bits function in hachoir

extrafield._description = "Length Extra Bits (%i), total length %i" % (
                        extrafield.value, length)
                    yield extrafield
                field = HuffmanCode(self, "distance_code[]", distance_tree)
                value = field.realvalue
                info = self.DISTANCE_SYMBOLS[value]
                if info[2] == 0:
                    field._description = "Distance Code %i, Value %i (Huffman Code %i)" % (
                        value, info[0], field.value)
                    distance = info[0]
                    yield field
                else:
                    field._description = "Distance Code %i, Values %i to %i (Huffman Code %i)" % (
                        value, info[0], info[1], field.value)
                    yield field
                    extrafield = Bits(
                        self, "distance_extra[%s" % field.name.split('[')[1], info[2])
                    distance = extrafield.value + info[0]
                    extrafield._description = "Distance Extra Bits (%i), total length %i" % (
                        extrafield.value, distance)
                    yield extrafield
                self.uncomp_data = extend_data(
                    self.uncomp_data, length, distance)

if ext_type == 1:
            # Sequence extension
            yield Bits(self, 'profile_and_level', 8)
            yield Bit(self, 'progressive_sequence')
            yield Bits(self, 'chroma_format', 2)
            yield Bits(self, 'horiz_size_ext', 2)
            yield Bits(self, 'vert_size_ext', 2)
            yield Bits(self, 'bit_rate_ext', 12)
            yield Bits(self, 'pad[]', 1)
            yield Bits(self, 'vbv_buffer_size_ext', 8)
            yield Bit(self, 'low_delay')
            yield Bits(self, 'frame_rate_ext_n', 2)
            yield Bits(self, 'frame_rate_ext_d', 5)
        elif ext_type == 2:
            # Sequence Display extension
            yield Bits(self, 'video_format', 3)
            yield Bit(self, 'color_desc_present')
            if self['color_desc_present'].value:
                yield UInt8(self, 'color_primaries')
                yield UInt8(self, 'transfer_characteristics')
                yield UInt8(self, 'matrix_coeffs')
            yield Bits(self, 'display_horiz_size', 14)
            yield Bits(self, 'pad[]', 1)
            yield Bits(self, 'display_vert_size', 14)
            yield NullBits(self, 'pad[]', 3)
        elif ext_type == 8:
            yield Bits(self, 'f_code[0][0]', 4, description="forward horizontal")
            yield Bits(self, 'f_code[0][1]', 4, description="forward vertical")
            yield Bits(self, 'f_code[1][0]', 4, description="backward horizontal")
            yield Bits(self, 'f_code[1][1]', 4, description="backward vertical")
            yield Bits(self, 'intra_dc_precision', 2)
            yield Bits(self, 'picture_structure', 2)

def createFields(self):
        yield Bits(self, "unused", 2)
        yield Bit(self, "is_tonable")
        yield Bit(self, "16bits")
        yield Bit(self, "loop_bidir")
        yield Bit(self, "loop")
        yield Enum(Bits(self, "origin", 2), self.TYPES)

def createFields(self):
        yield textHandler(Bits(self, "blockheader", 48, "Block header"), hexadecimal)
        if self["blockheader"].value != 0x314159265359:  # pi
            raise ParserError("Invalid block header!")
        yield textHandler(UInt32(self, "crc32", "CRC32 for this block"), hexadecimal)
        yield Bit(self, "randomized", "Is this block randomized?")
        yield Bits(self, "orig_bwt_pointer", 24, "Starting pointer into BWT after untransform")
        yield GenericVector(self, "huffman_used_map", 16, Bit, 'block_used', "Bitmap showing which blocks (representing 16 literals each) are in use")
        symbols_used = []
        for index, block_used in enumerate(self["huffman_used_map"].array('block_used')):
            if block_used.value:
                start_index = index * 16
                field = Bzip2Bitmap(self, "huffman_used_bitmap[%i]" % index, 16, start_index, "Bitmap for block %i (literals %i to %i) showing which symbols are in use" % (
                    index, start_index, start_index + 15))
                yield field
                for i, used in enumerate(field):
                    if used.value:
                        symbols_used.append(start_index + i)
        yield Bits(self, "huffman_groups", 3, "Number of different Huffman tables in use")
        yield Bits(self, "selectors_used", 15, "Number of times the Huffman tables are switched")
        yield Bzip2Selectors(self, "selectors_list", self["huffman_groups"].value)
        trees = []
        for group in range(self["huffman_groups"].value):

yield Enum(Bits(self, "method", 2), NAME)
        elif method == 14:  # LZMA
            yield Bit(self, "lzma_eos", "LZMA stream is ended with a EndOfStream marker")
            yield Bit(self, "unused[]")
        else:
            yield Bits(self, "compression_info", 2)
        yield Bit(self, "has_descriptor",
                  "Compressed data followed by descriptor?")
        yield Bit(self, "enhanced_deflate", "Reserved for use with method 8")
        yield Bit(self, "is_patched", "File is compressed with patched data?")
        yield Bit(self, "strong_encrypt", "Strong encryption (version >= 50)")
        yield Bits(self, "unused[]", 4, "Unused")
        yield Bit(self, "uses_unicode", "Filename and comments are in UTF-8")
        yield Bit(self, "incomplete", "Reserved by PKWARE for enhanced compression.")
        yield Bit(self, "encrypted_central_dir", "Selected data values in the Local Header are masked")
        yield Bits(self, "unused[]", 2, "Unused")

yield RealBit(self, "is_extended")
        if self["is_extended"].value:
            info = NoteInfo(self, "info")
            yield info
            if info["has_note"].value:
                yield Enum(UInt8(self, "note"), NOTE_NAME)
            if info["has_instrument"].value:
                yield UInt8(self, "instrument")
            if info["has_volume"].value:
                yield textHandler(UInt8(self, "volume"), parseVolume)
            if info["has_type"].value:
                yield Effect(self, "effect_type")
            if info["has_parameter"].value:
                yield textHandler(UInt8(self, "effect_parameter"), hexadecimal)
        else:
            yield Enum(Bits(self, "note", 7), NOTE_NAME)
            yield UInt8(self, "instrument")
            yield textHandler(UInt8(self, "volume"), parseVolume)
            yield Effect(self, "effect_type")
            yield textHandler(UInt8(self, "effect_parameter"), hexadecimal)

def createFields(self):
        yield Bits(self, "mantissa_high", 20)
        yield FloatExponent(self, "exponent", 11)
        yield Bit(self, "negative")
        yield Bits(self, "mantissa_low", 32)

def __init__(self, parent, name, size, description=None):
        Bits.__init__(self, parent, name, size, description)

yield UInt16(parent, "height", "Height*16 in pixel")

    yield UInt24(parent, "frame_width")
    yield UInt24(parent, "frame_height")
    yield UInt8(parent, "offset_x")
    yield UInt8(parent, "offset_y")

    yield UInt32(parent, "fps_num", "Frame per second numerator")
    yield UInt32(parent, "fps_den", "Frame per second denominator")
    yield UInt24(parent, "aspect_ratio_num", "Aspect ratio numerator")
    yield UInt24(parent, "aspect_ratio_den", "Aspect ratio denominator")

    yield UInt8(parent, "color_space")
    yield UInt24(parent, "target_bitrate")
    yield Bits(parent, "quality", 6)
    yield Bits(parent, "gp_shift", 5)
    yield Enum(Bits(parent, "pixel_format", 2), PIXEL_FORMATS)
    yield Bits(parent, "spare_config", 3)

def createFields(self):
        yield Bits(self, "block_type", 3)
        yield Bits(self, "block_size", 24)
        self.uncompressed_size = self["block_size"].value
        self.compression_level = self.root.compr_level
        self.window_size = self.WINDOW_SIZE[self.compression_level]
        self.block_type = self["block_type"].value
        curlen = len(self.parent.uncompressed_data)
        if self.block_type in (1, 2):  # Verbatim or aligned offset block
            if self.block_type == 2:
                for i in range(8):
                    yield Bits(self, "aligned_len[]", 3)
                aligned_tree = build_tree(
                    [self['aligned_len[%d]' % i].value for i in range(8)])
            yield LZXPreTreeEncodedTree(self, "main_tree_start", 256)
            yield LZXPreTreeEncodedTree(self, "main_tree_rest", self.window_size * 8)
            main_tree = build_tree(
                self["main_tree_start"].lengths + self["main_tree_rest"].lengths)
            yield LZXPreTreeEncodedTree(self, "length_tree", 249)
            length_tree = build_tree(self["length_tree"].lengths)
            current_decoded_size = 0
            while current_decoded_size < self.uncompressed_size:
                if (curlen + current_decoded_size) % 32768 == 0 and (curlen + current_decoded_size) != 0:
                    padding = paddingSize(self.address + self.current_size, 16)
                    if padding:
                        yield PaddingBits(self, "padding[]", padding)
                field = HuffmanCode(self, "main_code[]", main_tree)
                if field.realvalue < 256: