# Source code for dask.bytes.core

    from __future__ import annotations

    import copy
    import os

    from fsspec.core import OpenFile, get_fs_token_paths
    from fsspec.utils import infer_compression, read_block

    from dask.base import tokenize
    from dask.delayed import delayed
    from dask.utils import is_integer, parse_bytes

    def read_bytes(
        urlpath,
        delimiter=None,
        not_zero=False,
        blocksize="128 MiB",
        sample="10 kiB",
        compression=None,
        include_path=False,
        **kwargs,
    ):
        """Given a path or paths, return delayed objects that read from those paths.

        The path may be a filename like ``'2015-01-01.csv'`` or a globstring
        like ``'2015-*-*.csv'``.

        The path may be preceded by a protocol, like ``s3://`` or ``hdfs://`` if
        those libraries are installed.

        This cleanly breaks data by a delimiter if given, so that block boundaries
        start directly after a delimiter and end on the delimiter.

        Parameters
        ----------
        urlpath : string or list
            Absolute or relative filepath(s). Prefix with a protocol like ``s3://``
            to read from alternative filesystems. To read from multiple files you
            can pass a globstring or a list of paths, with the caveat that they
            must all have the same protocol.
        delimiter : bytes
            An optional delimiter, like ``b'\\n'`` on which to split blocks of
            bytes.
        not_zero : bool
            Force seek of start-of-file delimiter, discarding header.
        blocksize : int, str
            Chunk size in bytes, defaults to "128 MiB"
        compression : string or None
            String like 'gzip' or 'xz'.  Must support efficient random access.
        sample : int, string, or boolean
            Whether or not to return a header sample.
            Values can be ``False`` for "no sample requested"
            Or an integer or string value like ``2**20`` or ``"1 MiB"``
        include_path : bool
            Whether or not to include the path with the bytes representing a particular file.
            Default is False.
        **kwargs : dict
            Extra options that make sense to a particular storage connection, e.g.
            host, port, username, password, etc.

        Examples
        --------
        >>> sample, blocks = read_bytes('2015-*-*.csv', delimiter=b'\\n')  # doctest: +SKIP
        >>> sample, blocks = read_bytes('s3://bucket/2015-*-*.csv', delimiter=b'\\n')  # doctest: +SKIP
        >>> sample, paths, blocks = read_bytes('2015-*-*.csv', include_path=True)  # doctest: +SKIP

        Returns
        -------
        sample : bytes
            The sample header
        blocks : list of lists of ``dask.Delayed``
            Each list corresponds to a file, and each delayed object computes to a
            block of bytes from that file.
        paths : list of strings, only included if include_path is True
            List of same length as blocks, where each item is the path to the file
            represented in the corresponding block.

        """
        if not isinstance(urlpath, (str, list, tuple, os.PathLike)):
            raise TypeError("Path should be a string, os.PathLike, list or tuple")

        fs, fs_token, paths = get_fs_token_paths(urlpath, mode="rb", storage_options=kwargs)

        if len(paths) == 0:
            raise OSError("%s resolved to no files" % urlpath)

        if blocksize is not None:
            if isinstance(blocksize, str):
                blocksize = parse_bytes(blocksize)
            if not is_integer(blocksize):
                raise TypeError("blocksize must be an integer")
            blocksize = int(blocksize)

        if blocksize is None:
            offsets = [[0]] * len(paths)
            lengths = [[None]] * len(paths)
        else:
            offsets = []
            lengths = []
            for path in paths:
                if compression == "infer":
                    comp = infer_compression(path)
                else:
                    comp = compression
                if comp is not None:
                    raise ValueError(
                        "Cannot do chunked reads on compressed files. "
                        "To read, set blocksize=None"
                    )
                size = fs.info(path)["size"]
                if size is None:
                    raise ValueError(
                        "Backing filesystem couldn't determine file size, cannot "
                        "do chunked reads. To read, set blocksize=None."
                    )

                elif size == 0:
                    # skip empty
                    offsets.append([])
                    lengths.append([])
                else:
                    # shrink blocksize to give same number of parts
                    if size % blocksize and size > blocksize:
                        blocksize1 = size / (size // blocksize)
                    else:
                        blocksize1 = blocksize
                    place = 0
                    off = [0]
                    length = []

                    # figure out offsets, spreading around spare bytes
                    while size - place > (blocksize1 * 2) - 1:
                        place += blocksize1
                        off.append(int(place))
                        length.append(off[-1] - off[-2])
                    length.append(size - off[-1])

                    if not_zero:
                        off[0] = 1
                        length[0] -= 1
                    offsets.append(off)
                    lengths.append(length)

        delayed_read = delayed(read_block_from_file)

        out = []
        for path, offset, length in zip(paths, offsets, lengths):
            token = tokenize(fs_token, delimiter, path, fs.ukey(path), compression, offset)
            keys = [f"read-block-{o}-{token}" for o in offset]
            values = [
                delayed_read(
                    OpenFile(fs, path, compression=compression),
                    o,
                    l,
                    delimiter,
                    dask_key_name=key,
                )
                for o, key, l in zip(offset, keys, length)
            ]
            out.append(values)

        if sample:
            if sample is True:
                sample = "10 kiB"  # backwards compatibility
            if isinstance(sample, str):
                sample = parse_bytes(sample)
            with OpenFile(fs, paths[0], compression=compression) as f:
                # read block without seek (because we start at zero)
                if delimiter is None:
                    sample = f.read(sample)
                else:
                    sample_buff = f.read(sample)
                    while True:
                        new = f.read(sample)
                        if not new:
                            break
                        if delimiter in new:
                            sample_buff = (
                                sample_buff + new.split(delimiter, 1)[0] + delimiter
                            )
                            break
                        sample_buff = sample_buff + new
                    sample = sample_buff
        if include_path:
            return sample, out, paths
        return sample, out

    def read_block_from_file(lazy_file, off, bs, delimiter):
        with copy.copy(lazy_file) as f:
            if off == 0 and bs is None:
                return f.read()
            return read_block(f, off, bs, delimiter)