contrib/python-zstandard/zstandard/cffi.py

python-zstandard: blacken at 80 characters

I made this change upstream and it will make it into the next
release of python-zstandard. I figured I'd send it Mercurial's
way because it will allow us to drop this directory from the black
exclusion list.

# skip-blame blackening

Differential Revision: https://phab.mercurial-scm.org/D7937

# Copyright (c) 2016-present, Gregory Szorc
# All rights reserved.
#
# This software may be modified and distributed under the terms
# of the BSD license. See the LICENSE file for details.

"""Python interface to the Zstandard (zstd) compression library."""

from __future__ import absolute_import, unicode_literals

# This should match what the C extension exports.
__all__ = [
    #'BufferSegment',
    #'BufferSegments',
    #'BufferWithSegments',
    #'BufferWithSegmentsCollection',
    "CompressionParameters",
    "ZstdCompressionDict",
    "ZstdCompressionParameters",
    "ZstdCompressor",
    "ZstdError",
    "ZstdDecompressor",
    "FrameParameters",
    "estimate_decompression_context_size",
    "frame_content_size",
    "frame_header_size",
    "get_frame_parameters",
    "train_dictionary",
    # Constants.
    "FLUSH_BLOCK",
    "FLUSH_FRAME",
    "COMPRESSOBJ_FLUSH_FINISH",
    "COMPRESSOBJ_FLUSH_BLOCK",
    "ZSTD_VERSION",
    "FRAME_HEADER",
    "CONTENTSIZE_UNKNOWN",
    "CONTENTSIZE_ERROR",
    "MAX_COMPRESSION_LEVEL",
    "COMPRESSION_RECOMMENDED_INPUT_SIZE",
    "COMPRESSION_RECOMMENDED_OUTPUT_SIZE",
    "DECOMPRESSION_RECOMMENDED_INPUT_SIZE",
    "DECOMPRESSION_RECOMMENDED_OUTPUT_SIZE",
    "MAGIC_NUMBER",
    "BLOCKSIZELOG_MAX",
    "BLOCKSIZE_MAX",
    "WINDOWLOG_MIN",
    "WINDOWLOG_MAX",
    "CHAINLOG_MIN",
    "CHAINLOG_MAX",
    "HASHLOG_MIN",
    "HASHLOG_MAX",
    "HASHLOG3_MAX",
    "MINMATCH_MIN",
    "MINMATCH_MAX",
    "SEARCHLOG_MIN",
    "SEARCHLOG_MAX",
    "SEARCHLENGTH_MIN",
    "SEARCHLENGTH_MAX",
    "TARGETLENGTH_MIN",
    "TARGETLENGTH_MAX",
    "LDM_MINMATCH_MIN",
    "LDM_MINMATCH_MAX",
    "LDM_BUCKETSIZELOG_MAX",
    "STRATEGY_FAST",
    "STRATEGY_DFAST",
    "STRATEGY_GREEDY",
    "STRATEGY_LAZY",
    "STRATEGY_LAZY2",
    "STRATEGY_BTLAZY2",
    "STRATEGY_BTOPT",
    "STRATEGY_BTULTRA",
    "STRATEGY_BTULTRA2",
    "DICT_TYPE_AUTO",
    "DICT_TYPE_RAWCONTENT",
    "DICT_TYPE_FULLDICT",
    "FORMAT_ZSTD1",
    "FORMAT_ZSTD1_MAGICLESS",
]

import io
import os
import sys

from _zstd_cffi import (
    ffi,
    lib,
)

if sys.version_info[0] == 2:
    bytes_type = str
    int_type = long
else:
    bytes_type = bytes
    int_type = int


COMPRESSION_RECOMMENDED_INPUT_SIZE = lib.ZSTD_CStreamInSize()
COMPRESSION_RECOMMENDED_OUTPUT_SIZE = lib.ZSTD_CStreamOutSize()
DECOMPRESSION_RECOMMENDED_INPUT_SIZE = lib.ZSTD_DStreamInSize()
DECOMPRESSION_RECOMMENDED_OUTPUT_SIZE = lib.ZSTD_DStreamOutSize()

new_nonzero = ffi.new_allocator(should_clear_after_alloc=False)


MAX_COMPRESSION_LEVEL = lib.ZSTD_maxCLevel()
MAGIC_NUMBER = lib.ZSTD_MAGICNUMBER
FRAME_HEADER = b"\x28\xb5\x2f\xfd"
CONTENTSIZE_UNKNOWN = lib.ZSTD_CONTENTSIZE_UNKNOWN
CONTENTSIZE_ERROR = lib.ZSTD_CONTENTSIZE_ERROR
ZSTD_VERSION = (
    lib.ZSTD_VERSION_MAJOR,
    lib.ZSTD_VERSION_MINOR,
    lib.ZSTD_VERSION_RELEASE,
)

BLOCKSIZELOG_MAX = lib.ZSTD_BLOCKSIZELOG_MAX
BLOCKSIZE_MAX = lib.ZSTD_BLOCKSIZE_MAX
WINDOWLOG_MIN = lib.ZSTD_WINDOWLOG_MIN
WINDOWLOG_MAX = lib.ZSTD_WINDOWLOG_MAX
CHAINLOG_MIN = lib.ZSTD_CHAINLOG_MIN
CHAINLOG_MAX = lib.ZSTD_CHAINLOG_MAX
HASHLOG_MIN = lib.ZSTD_HASHLOG_MIN
HASHLOG_MAX = lib.ZSTD_HASHLOG_MAX
HASHLOG3_MAX = lib.ZSTD_HASHLOG3_MAX
MINMATCH_MIN = lib.ZSTD_MINMATCH_MIN
MINMATCH_MAX = lib.ZSTD_MINMATCH_MAX
SEARCHLOG_MIN = lib.ZSTD_SEARCHLOG_MIN
SEARCHLOG_MAX = lib.ZSTD_SEARCHLOG_MAX
SEARCHLENGTH_MIN = lib.ZSTD_MINMATCH_MIN
SEARCHLENGTH_MAX = lib.ZSTD_MINMATCH_MAX
TARGETLENGTH_MIN = lib.ZSTD_TARGETLENGTH_MIN
TARGETLENGTH_MAX = lib.ZSTD_TARGETLENGTH_MAX
LDM_MINMATCH_MIN = lib.ZSTD_LDM_MINMATCH_MIN
LDM_MINMATCH_MAX = lib.ZSTD_LDM_MINMATCH_MAX
LDM_BUCKETSIZELOG_MAX = lib.ZSTD_LDM_BUCKETSIZELOG_MAX

STRATEGY_FAST = lib.ZSTD_fast
STRATEGY_DFAST = lib.ZSTD_dfast
STRATEGY_GREEDY = lib.ZSTD_greedy
STRATEGY_LAZY = lib.ZSTD_lazy
STRATEGY_LAZY2 = lib.ZSTD_lazy2
STRATEGY_BTLAZY2 = lib.ZSTD_btlazy2
STRATEGY_BTOPT = lib.ZSTD_btopt
STRATEGY_BTULTRA = lib.ZSTD_btultra
STRATEGY_BTULTRA2 = lib.ZSTD_btultra2

DICT_TYPE_AUTO = lib.ZSTD_dct_auto
DICT_TYPE_RAWCONTENT = lib.ZSTD_dct_rawContent
DICT_TYPE_FULLDICT = lib.ZSTD_dct_fullDict

FORMAT_ZSTD1 = lib.ZSTD_f_zstd1
FORMAT_ZSTD1_MAGICLESS = lib.ZSTD_f_zstd1_magicless

FLUSH_BLOCK = 0
FLUSH_FRAME = 1

COMPRESSOBJ_FLUSH_FINISH = 0
COMPRESSOBJ_FLUSH_BLOCK = 1


def _cpu_count():
    # os.cpu_count() was introducd in Python 3.4.
    try:
        return os.cpu_count() or 0
    except AttributeError:
        pass

    # Linux.
    try:
        if sys.version_info[0] == 2:
            return os.sysconf(b"SC_NPROCESSORS_ONLN")
        else:
            return os.sysconf("SC_NPROCESSORS_ONLN")
    except (AttributeError, ValueError):
        pass

    # TODO implement on other platforms.
    return 0


class ZstdError(Exception):
    pass


def _zstd_error(zresult):
    # Resolves to bytes on Python 2 and 3. We use the string for formatting
    # into error messages, which will be literal unicode. So convert it to
    # unicode.
    return ffi.string(lib.ZSTD_getErrorName(zresult)).decode("utf-8")


def _make_cctx_params(params):
    res = lib.ZSTD_createCCtxParams()
    if res == ffi.NULL:
        raise MemoryError()

    res = ffi.gc(res, lib.ZSTD_freeCCtxParams)

    attrs = [
        (lib.ZSTD_c_format, params.format),
        (lib.ZSTD_c_compressionLevel, params.compression_level),
        (lib.ZSTD_c_windowLog, params.window_log),
        (lib.ZSTD_c_hashLog, params.hash_log),
        (lib.ZSTD_c_chainLog, params.chain_log),
        (lib.ZSTD_c_searchLog, params.search_log),
        (lib.ZSTD_c_minMatch, params.min_match),
        (lib.ZSTD_c_targetLength, params.target_length),
        (lib.ZSTD_c_strategy, params.compression_strategy),
        (lib.ZSTD_c_contentSizeFlag, params.write_content_size),
        (lib.ZSTD_c_checksumFlag, params.write_checksum),
        (lib.ZSTD_c_dictIDFlag, params.write_dict_id),
        (lib.ZSTD_c_nbWorkers, params.threads),
        (lib.ZSTD_c_jobSize, params.job_size),
        (lib.ZSTD_c_overlapLog, params.overlap_log),
        (lib.ZSTD_c_forceMaxWindow, params.force_max_window),
        (lib.ZSTD_c_enableLongDistanceMatching, params.enable_ldm),
        (lib.ZSTD_c_ldmHashLog, params.ldm_hash_log),
        (lib.ZSTD_c_ldmMinMatch, params.ldm_min_match),
        (lib.ZSTD_c_ldmBucketSizeLog, params.ldm_bucket_size_log),
        (lib.ZSTD_c_ldmHashRateLog, params.ldm_hash_rate_log),
    ]

    for param, value in attrs:
        _set_compression_parameter(res, param, value)

    return res


class ZstdCompressionParameters(object):
    @staticmethod
    def from_level(level, source_size=0, dict_size=0, **kwargs):
        params = lib.ZSTD_getCParams(level, source_size, dict_size)

        args = {
            "window_log": "windowLog",
            "chain_log": "chainLog",
            "hash_log": "hashLog",
            "search_log": "searchLog",
            "min_match": "minMatch",
            "target_length": "targetLength",
            "compression_strategy": "strategy",
        }

        for arg, attr in args.items():
            if arg not in kwargs:
                kwargs[arg] = getattr(params, attr)

        return ZstdCompressionParameters(**kwargs)

    def __init__(
        self,
        format=0,
        compression_level=0,
        window_log=0,
        hash_log=0,
        chain_log=0,
        search_log=0,
        min_match=0,
        target_length=0,
        strategy=-1,
        compression_strategy=-1,
        write_content_size=1,
        write_checksum=0,
        write_dict_id=0,
        job_size=0,
        overlap_log=-1,
        overlap_size_log=-1,
        force_max_window=0,
        enable_ldm=0,
        ldm_hash_log=0,
        ldm_min_match=0,
        ldm_bucket_size_log=0,
        ldm_hash_rate_log=-1,
        ldm_hash_every_log=-1,
        threads=0,
    ):

        params = lib.ZSTD_createCCtxParams()
        if params == ffi.NULL:
            raise MemoryError()

        params = ffi.gc(params, lib.ZSTD_freeCCtxParams)

        self._params = params

        if threads < 0:
            threads = _cpu_count()

        # We need to set ZSTD_c_nbWorkers before ZSTD_c_jobSize and ZSTD_c_overlapLog
        # because setting ZSTD_c_nbWorkers resets the other parameters.
        _set_compression_parameter(params, lib.ZSTD_c_nbWorkers, threads)

        _set_compression_parameter(params, lib.ZSTD_c_format, format)
        _set_compression_parameter(
            params, lib.ZSTD_c_compressionLevel, compression_level
        )
        _set_compression_parameter(params, lib.ZSTD_c_windowLog, window_log)
        _set_compression_parameter(params, lib.ZSTD_c_hashLog, hash_log)
        _set_compression_parameter(params, lib.ZSTD_c_chainLog, chain_log)
        _set_compression_parameter(params, lib.ZSTD_c_searchLog, search_log)
        _set_compression_parameter(params, lib.ZSTD_c_minMatch, min_match)
        _set_compression_parameter(
            params, lib.ZSTD_c_targetLength, target_length
        )

        if strategy != -1 and compression_strategy != -1:
            raise ValueError(
                "cannot specify both compression_strategy and strategy"
            )

        if compression_strategy != -1:
            strategy = compression_strategy
        elif strategy == -1:
            strategy = 0

        _set_compression_parameter(params, lib.ZSTD_c_strategy, strategy)
        _set_compression_parameter(
            params, lib.ZSTD_c_contentSizeFlag, write_content_size
        )
        _set_compression_parameter(
            params, lib.ZSTD_c_checksumFlag, write_checksum
        )
        _set_compression_parameter(params, lib.ZSTD_c_dictIDFlag, write_dict_id)
        _set_compression_parameter(params, lib.ZSTD_c_jobSize, job_size)

        if overlap_log != -1 and overlap_size_log != -1:
            raise ValueError(
                "cannot specify both overlap_log and overlap_size_log"
            )

        if overlap_size_log != -1:
            overlap_log = overlap_size_log
        elif overlap_log == -1:
            overlap_log = 0

        _set_compression_parameter(params, lib.ZSTD_c_overlapLog, overlap_log)
        _set_compression_parameter(
            params, lib.ZSTD_c_forceMaxWindow, force_max_window
        )
        _set_compression_parameter(
            params, lib.ZSTD_c_enableLongDistanceMatching, enable_ldm
        )
        _set_compression_parameter(params, lib.ZSTD_c_ldmHashLog, ldm_hash_log)
        _set_compression_parameter(
            params, lib.ZSTD_c_ldmMinMatch, ldm_min_match
        )
        _set_compression_parameter(
            params, lib.ZSTD_c_ldmBucketSizeLog, ldm_bucket_size_log
        )

        if ldm_hash_rate_log != -1 and ldm_hash_every_log != -1:
            raise ValueError(
                "cannot specify both ldm_hash_rate_log and ldm_hash_every_log"
            )

        if ldm_hash_every_log != -1:
            ldm_hash_rate_log = ldm_hash_every_log
        elif ldm_hash_rate_log == -1:
            ldm_hash_rate_log = 0

        _set_compression_parameter(
            params, lib.ZSTD_c_ldmHashRateLog, ldm_hash_rate_log
        )

    @property
    def format(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_format)

    @property
    def compression_level(self):
        return _get_compression_parameter(
            self._params, lib.ZSTD_c_compressionLevel
        )

    @property
    def window_log(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_windowLog)

    @property
    def hash_log(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_hashLog)

    @property
    def chain_log(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_chainLog)

    @property
    def search_log(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_searchLog)

    @property
    def min_match(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_minMatch)

    @property
    def target_length(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_targetLength)

    @property
    def compression_strategy(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_strategy)

    @property
    def write_content_size(self):
        return _get_compression_parameter(
            self._params, lib.ZSTD_c_contentSizeFlag
        )

    @property
    def write_checksum(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_checksumFlag)

    @property
    def write_dict_id(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_dictIDFlag)

    @property
    def job_size(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_jobSize)

    @property
    def overlap_log(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_overlapLog)

    @property
    def overlap_size_log(self):
        return self.overlap_log

    @property
    def force_max_window(self):
        return _get_compression_parameter(
            self._params, lib.ZSTD_c_forceMaxWindow
        )

    @property
    def enable_ldm(self):
        return _get_compression_parameter(
            self._params, lib.ZSTD_c_enableLongDistanceMatching
        )

    @property
    def ldm_hash_log(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_ldmHashLog)

    @property
    def ldm_min_match(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_ldmMinMatch)

    @property
    def ldm_bucket_size_log(self):
        return _get_compression_parameter(
            self._params, lib.ZSTD_c_ldmBucketSizeLog
        )

    @property
    def ldm_hash_rate_log(self):
        return _get_compression_parameter(
            self._params, lib.ZSTD_c_ldmHashRateLog
        )

    @property
    def ldm_hash_every_log(self):
        return self.ldm_hash_rate_log

    @property
    def threads(self):
        return _get_compression_parameter(self._params, lib.ZSTD_c_nbWorkers)

    def estimated_compression_context_size(self):
        return lib.ZSTD_estimateCCtxSize_usingCCtxParams(self._params)


CompressionParameters = ZstdCompressionParameters


def estimate_decompression_context_size():
    return lib.ZSTD_estimateDCtxSize()


def _set_compression_parameter(params, param, value):
    zresult = lib.ZSTD_CCtxParams_setParameter(params, param, value)
    if lib.ZSTD_isError(zresult):
        raise ZstdError(
            "unable to set compression context parameter: %s"
            % _zstd_error(zresult)
        )


def _get_compression_parameter(params, param):
    result = ffi.new("int *")

    zresult = lib.ZSTD_CCtxParams_getParameter(params, param, result)
    if lib.ZSTD_isError(zresult):
        raise ZstdError(
            "unable to get compression context parameter: %s"
            % _zstd_error(zresult)
        )

    return result[0]


class ZstdCompressionWriter(object):
    def __init__(
        self, compressor, writer, source_size, write_size, write_return_read
    ):
        self._compressor = compressor
        self._writer = writer
        self._write_size = write_size
        self._write_return_read = bool(write_return_read)
        self._entered = False
        self._closed = False
        self._bytes_compressed = 0

        self._dst_buffer = ffi.new("char[]", write_size)
        self._out_buffer = ffi.new("ZSTD_outBuffer *")
        self._out_buffer.dst = self._dst_buffer
        self._out_buffer.size = len(self._dst_buffer)
        self._out_buffer.pos = 0

        zresult = lib.ZSTD_CCtx_setPledgedSrcSize(compressor._cctx, source_size)
        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "error setting source size: %s" % _zstd_error(zresult)
            )

    def __enter__(self):
        if self._closed:
            raise ValueError("stream is closed")

        if self._entered:
            raise ZstdError("cannot __enter__ multiple times")

        self._entered = True
        return self

    def __exit__(self, exc_type, exc_value, exc_tb):
        self._entered = False

        if not exc_type and not exc_value and not exc_tb:
            self.close()

        self._compressor = None

        return False

    def memory_size(self):
        return lib.ZSTD_sizeof_CCtx(self._compressor._cctx)

    def fileno(self):
        f = getattr(self._writer, "fileno", None)
        if f:
            return f()
        else:
            raise OSError("fileno not available on underlying writer")

    def close(self):
        if self._closed:
            return

        try:
            self.flush(FLUSH_FRAME)
        finally:
            self._closed = True

        # Call close() on underlying stream as well.
        f = getattr(self._writer, "close", None)
        if f:
            f()

    @property
    def closed(self):
        return self._closed

    def isatty(self):
        return False

    def readable(self):
        return False

    def readline(self, size=-1):
        raise io.UnsupportedOperation()

    def readlines(self, hint=-1):
        raise io.UnsupportedOperation()

    def seek(self, offset, whence=None):
        raise io.UnsupportedOperation()

    def seekable(self):
        return False

    def truncate(self, size=None):
        raise io.UnsupportedOperation()

    def writable(self):
        return True

    def writelines(self, lines):
        raise NotImplementedError("writelines() is not yet implemented")

    def read(self, size=-1):
        raise io.UnsupportedOperation()

    def readall(self):
        raise io.UnsupportedOperation()

    def readinto(self, b):
        raise io.UnsupportedOperation()

    def write(self, data):
        if self._closed:
            raise ValueError("stream is closed")

        total_write = 0

        data_buffer = ffi.from_buffer(data)

        in_buffer = ffi.new("ZSTD_inBuffer *")
        in_buffer.src = data_buffer
        in_buffer.size = len(data_buffer)
        in_buffer.pos = 0

        out_buffer = self._out_buffer
        out_buffer.pos = 0

        while in_buffer.pos < in_buffer.size:
            zresult = lib.ZSTD_compressStream2(
                self._compressor._cctx,
                out_buffer,
                in_buffer,
                lib.ZSTD_e_continue,
            )
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "zstd compress error: %s" % _zstd_error(zresult)
                )

            if out_buffer.pos:
                self._writer.write(
                    ffi.buffer(out_buffer.dst, out_buffer.pos)[:]
                )
                total_write += out_buffer.pos
                self._bytes_compressed += out_buffer.pos
                out_buffer.pos = 0

        if self._write_return_read:
            return in_buffer.pos
        else:
            return total_write

    def flush(self, flush_mode=FLUSH_BLOCK):
        if flush_mode == FLUSH_BLOCK:
            flush = lib.ZSTD_e_flush
        elif flush_mode == FLUSH_FRAME:
            flush = lib.ZSTD_e_end
        else:
            raise ValueError("unknown flush_mode: %r" % flush_mode)

        if self._closed:
            raise ValueError("stream is closed")

        total_write = 0

        out_buffer = self._out_buffer
        out_buffer.pos = 0

        in_buffer = ffi.new("ZSTD_inBuffer *")
        in_buffer.src = ffi.NULL
        in_buffer.size = 0
        in_buffer.pos = 0

        while True:
            zresult = lib.ZSTD_compressStream2(
                self._compressor._cctx, out_buffer, in_buffer, flush
            )
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "zstd compress error: %s" % _zstd_error(zresult)
                )

            if out_buffer.pos:
                self._writer.write(
                    ffi.buffer(out_buffer.dst, out_buffer.pos)[:]
                )
                total_write += out_buffer.pos
                self._bytes_compressed += out_buffer.pos
                out_buffer.pos = 0

            if not zresult:
                break

        return total_write

    def tell(self):
        return self._bytes_compressed


class ZstdCompressionObj(object):
    def compress(self, data):
        if self._finished:
            raise ZstdError("cannot call compress() after compressor finished")

        data_buffer = ffi.from_buffer(data)
        source = ffi.new("ZSTD_inBuffer *")
        source.src = data_buffer
        source.size = len(data_buffer)
        source.pos = 0

        chunks = []

        while source.pos < len(data):
            zresult = lib.ZSTD_compressStream2(
                self._compressor._cctx, self._out, source, lib.ZSTD_e_continue
            )
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "zstd compress error: %s" % _zstd_error(zresult)
                )

            if self._out.pos:
                chunks.append(ffi.buffer(self._out.dst, self._out.pos)[:])
                self._out.pos = 0

        return b"".join(chunks)

    def flush(self, flush_mode=COMPRESSOBJ_FLUSH_FINISH):
        if flush_mode not in (
            COMPRESSOBJ_FLUSH_FINISH,
            COMPRESSOBJ_FLUSH_BLOCK,
        ):
            raise ValueError("flush mode not recognized")

        if self._finished:
            raise ZstdError("compressor object already finished")

        if flush_mode == COMPRESSOBJ_FLUSH_BLOCK:
            z_flush_mode = lib.ZSTD_e_flush
        elif flush_mode == COMPRESSOBJ_FLUSH_FINISH:
            z_flush_mode = lib.ZSTD_e_end
            self._finished = True
        else:
            raise ZstdError("unhandled flush mode")

        assert self._out.pos == 0

        in_buffer = ffi.new("ZSTD_inBuffer *")
        in_buffer.src = ffi.NULL
        in_buffer.size = 0
        in_buffer.pos = 0

        chunks = []

        while True:
            zresult = lib.ZSTD_compressStream2(
                self._compressor._cctx, self._out, in_buffer, z_flush_mode
            )
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "error ending compression stream: %s" % _zstd_error(zresult)
                )

            if self._out.pos:
                chunks.append(ffi.buffer(self._out.dst, self._out.pos)[:])
                self._out.pos = 0

            if not zresult:
                break

        return b"".join(chunks)


class ZstdCompressionChunker(object):
    def __init__(self, compressor, chunk_size):
        self._compressor = compressor
        self._out = ffi.new("ZSTD_outBuffer *")
        self._dst_buffer = ffi.new("char[]", chunk_size)
        self._out.dst = self._dst_buffer
        self._out.size = chunk_size
        self._out.pos = 0

        self._in = ffi.new("ZSTD_inBuffer *")
        self._in.src = ffi.NULL
        self._in.size = 0
        self._in.pos = 0
        self._finished = False

    def compress(self, data):
        if self._finished:
            raise ZstdError("cannot call compress() after compression finished")

        if self._in.src != ffi.NULL:
            raise ZstdError(
                "cannot perform operation before consuming output "
                "from previous operation"
            )

        data_buffer = ffi.from_buffer(data)

        if not len(data_buffer):
            return

        self._in.src = data_buffer
        self._in.size = len(data_buffer)
        self._in.pos = 0

        while self._in.pos < self._in.size:
            zresult = lib.ZSTD_compressStream2(
                self._compressor._cctx, self._out, self._in, lib.ZSTD_e_continue
            )

            if self._in.pos == self._in.size:
                self._in.src = ffi.NULL
                self._in.size = 0
                self._in.pos = 0

            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "zstd compress error: %s" % _zstd_error(zresult)
                )

            if self._out.pos == self._out.size:
                yield ffi.buffer(self._out.dst, self._out.pos)[:]
                self._out.pos = 0

    def flush(self):
        if self._finished:
            raise ZstdError("cannot call flush() after compression finished")

        if self._in.src != ffi.NULL:
            raise ZstdError(
                "cannot call flush() before consuming output from "
                "previous operation"
            )

        while True:
            zresult = lib.ZSTD_compressStream2(
                self._compressor._cctx, self._out, self._in, lib.ZSTD_e_flush
            )
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "zstd compress error: %s" % _zstd_error(zresult)
                )

            if self._out.pos:
                yield ffi.buffer(self._out.dst, self._out.pos)[:]
                self._out.pos = 0

            if not zresult:
                return

    def finish(self):
        if self._finished:
            raise ZstdError("cannot call finish() after compression finished")

        if self._in.src != ffi.NULL:
            raise ZstdError(
                "cannot call finish() before consuming output from "
                "previous operation"
            )

        while True:
            zresult = lib.ZSTD_compressStream2(
                self._compressor._cctx, self._out, self._in, lib.ZSTD_e_end
            )
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "zstd compress error: %s" % _zstd_error(zresult)
                )

            if self._out.pos:
                yield ffi.buffer(self._out.dst, self._out.pos)[:]
                self._out.pos = 0

            if not zresult:
                self._finished = True
                return


class ZstdCompressionReader(object):
    def __init__(self, compressor, source, read_size):
        self._compressor = compressor
        self._source = source
        self._read_size = read_size
        self._entered = False
        self._closed = False
        self._bytes_compressed = 0
        self._finished_input = False
        self._finished_output = False

        self._in_buffer = ffi.new("ZSTD_inBuffer *")
        # Holds a ref so backing bytes in self._in_buffer stay alive.
        self._source_buffer = None

    def __enter__(self):
        if self._entered:
            raise ValueError("cannot __enter__ multiple times")

        self._entered = True
        return self

    def __exit__(self, exc_type, exc_value, exc_tb):
        self._entered = False
        self._closed = True
        self._source = None
        self._compressor = None

        return False

    def readable(self):
        return True

    def writable(self):
        return False

    def seekable(self):
        return False

    def readline(self):
        raise io.UnsupportedOperation()

    def readlines(self):
        raise io.UnsupportedOperation()

    def write(self, data):
        raise OSError("stream is not writable")

    def writelines(self, ignored):
        raise OSError("stream is not writable")

    def isatty(self):
        return False

    def flush(self):
        return None

    def close(self):
        self._closed = True
        return None

    @property
    def closed(self):
        return self._closed

    def tell(self):
        return self._bytes_compressed

    def readall(self):
        chunks = []

        while True:
            chunk = self.read(1048576)
            if not chunk:
                break

            chunks.append(chunk)

        return b"".join(chunks)

    def __iter__(self):
        raise io.UnsupportedOperation()

    def __next__(self):
        raise io.UnsupportedOperation()

    next = __next__

    def _read_input(self):
        if self._finished_input:
            return

        if hasattr(self._source, "read"):
            data = self._source.read(self._read_size)

            if not data:
                self._finished_input = True
                return

            self._source_buffer = ffi.from_buffer(data)
            self._in_buffer.src = self._source_buffer
            self._in_buffer.size = len(self._source_buffer)
            self._in_buffer.pos = 0
        else:
            self._source_buffer = ffi.from_buffer(self._source)
            self._in_buffer.src = self._source_buffer
            self._in_buffer.size = len(self._source_buffer)
            self._in_buffer.pos = 0

    def _compress_into_buffer(self, out_buffer):
        if self._in_buffer.pos >= self._in_buffer.size:
            return

        old_pos = out_buffer.pos

        zresult = lib.ZSTD_compressStream2(
            self._compressor._cctx,
            out_buffer,
            self._in_buffer,
            lib.ZSTD_e_continue,
        )

        self._bytes_compressed += out_buffer.pos - old_pos

        if self._in_buffer.pos == self._in_buffer.size:
            self._in_buffer.src = ffi.NULL
            self._in_buffer.pos = 0
            self._in_buffer.size = 0
            self._source_buffer = None

            if not hasattr(self._source, "read"):
                self._finished_input = True

        if lib.ZSTD_isError(zresult):
            raise ZstdError("zstd compress error: %s", _zstd_error(zresult))

        return out_buffer.pos and out_buffer.pos == out_buffer.size

    def read(self, size=-1):
        if self._closed:
            raise ValueError("stream is closed")

        if size < -1:
            raise ValueError("cannot read negative amounts less than -1")

        if size == -1:
            return self.readall()

        if self._finished_output or size == 0:
            return b""

        # Need a dedicated ref to dest buffer otherwise it gets collected.
        dst_buffer = ffi.new("char[]", size)
        out_buffer = ffi.new("ZSTD_outBuffer *")
        out_buffer.dst = dst_buffer
        out_buffer.size = size
        out_buffer.pos = 0

        if self._compress_into_buffer(out_buffer):
            return ffi.buffer(out_buffer.dst, out_buffer.pos)[:]

        while not self._finished_input:
            self._read_input()

            if self._compress_into_buffer(out_buffer):
                return ffi.buffer(out_buffer.dst, out_buffer.pos)[:]

        # EOF
        old_pos = out_buffer.pos

        zresult = lib.ZSTD_compressStream2(
            self._compressor._cctx, out_buffer, self._in_buffer, lib.ZSTD_e_end
        )

        self._bytes_compressed += out_buffer.pos - old_pos

        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "error ending compression stream: %s", _zstd_error(zresult)
            )

        if zresult == 0:
            self._finished_output = True

        return ffi.buffer(out_buffer.dst, out_buffer.pos)[:]

    def read1(self, size=-1):
        if self._closed:
            raise ValueError("stream is closed")

        if size < -1:
            raise ValueError("cannot read negative amounts less than -1")

        if self._finished_output or size == 0:
            return b""

        # -1 returns arbitrary number of bytes.
        if size == -1:
            size = COMPRESSION_RECOMMENDED_OUTPUT_SIZE

        dst_buffer = ffi.new("char[]", size)
        out_buffer = ffi.new("ZSTD_outBuffer *")
        out_buffer.dst = dst_buffer
        out_buffer.size = size
        out_buffer.pos = 0

        # read1() dictates that we can perform at most 1 call to the
        # underlying stream to get input. However, we can't satisfy this
        # restriction with compression because not all input generates output.
        # It is possible to perform a block flush in order to ensure output.
        # But this may not be desirable behavior. So we allow multiple read()
        # to the underlying stream. But unlike read(), we stop once we have
        # any output.

        self._compress_into_buffer(out_buffer)
        if out_buffer.pos:
            return ffi.buffer(out_buffer.dst, out_buffer.pos)[:]

        while not self._finished_input:
            self._read_input()

            # If we've filled the output buffer, return immediately.
            if self._compress_into_buffer(out_buffer):
                return ffi.buffer(out_buffer.dst, out_buffer.pos)[:]

            # If we've populated the output buffer and we're not at EOF,
            # also return, as we've satisfied the read1() limits.
            if out_buffer.pos and not self._finished_input:
                return ffi.buffer(out_buffer.dst, out_buffer.pos)[:]

            # Else if we're at EOS and we have room left in the buffer,
            # fall through to below and try to add more data to the output.

        # EOF.
        old_pos = out_buffer.pos

        zresult = lib.ZSTD_compressStream2(
            self._compressor._cctx, out_buffer, self._in_buffer, lib.ZSTD_e_end
        )

        self._bytes_compressed += out_buffer.pos - old_pos

        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "error ending compression stream: %s" % _zstd_error(zresult)
            )

        if zresult == 0:
            self._finished_output = True

        return ffi.buffer(out_buffer.dst, out_buffer.pos)[:]

    def readinto(self, b):
        if self._closed:
            raise ValueError("stream is closed")

        if self._finished_output:
            return 0

        # TODO use writable=True once we require CFFI >= 1.12.
        dest_buffer = ffi.from_buffer(b)
        ffi.memmove(b, b"", 0)
        out_buffer = ffi.new("ZSTD_outBuffer *")
        out_buffer.dst = dest_buffer
        out_buffer.size = len(dest_buffer)
        out_buffer.pos = 0

        if self._compress_into_buffer(out_buffer):
            return out_buffer.pos

        while not self._finished_input:
            self._read_input()
            if self._compress_into_buffer(out_buffer):
                return out_buffer.pos

        # EOF.
        old_pos = out_buffer.pos
        zresult = lib.ZSTD_compressStream2(
            self._compressor._cctx, out_buffer, self._in_buffer, lib.ZSTD_e_end
        )

        self._bytes_compressed += out_buffer.pos - old_pos

        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "error ending compression stream: %s", _zstd_error(zresult)
            )

        if zresult == 0:
            self._finished_output = True

        return out_buffer.pos

    def readinto1(self, b):
        if self._closed:
            raise ValueError("stream is closed")

        if self._finished_output:
            return 0

        # TODO use writable=True once we require CFFI >= 1.12.
        dest_buffer = ffi.from_buffer(b)
        ffi.memmove(b, b"", 0)

        out_buffer = ffi.new("ZSTD_outBuffer *")
        out_buffer.dst = dest_buffer
        out_buffer.size = len(dest_buffer)
        out_buffer.pos = 0

        self._compress_into_buffer(out_buffer)
        if out_buffer.pos:
            return out_buffer.pos

        while not self._finished_input:
            self._read_input()

            if self._compress_into_buffer(out_buffer):
                return out_buffer.pos

            if out_buffer.pos and not self._finished_input:
                return out_buffer.pos

        # EOF.
        old_pos = out_buffer.pos

        zresult = lib.ZSTD_compressStream2(
            self._compressor._cctx, out_buffer, self._in_buffer, lib.ZSTD_e_end
        )

        self._bytes_compressed += out_buffer.pos - old_pos

        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "error ending compression stream: %s" % _zstd_error(zresult)
            )

        if zresult == 0:
            self._finished_output = True

        return out_buffer.pos


class ZstdCompressor(object):
    def __init__(
        self,
        level=3,
        dict_data=None,
        compression_params=None,
        write_checksum=None,
        write_content_size=None,
        write_dict_id=None,
        threads=0,
    ):
        if level > lib.ZSTD_maxCLevel():
            raise ValueError(
                "level must be less than %d" % lib.ZSTD_maxCLevel()
            )

        if threads < 0:
            threads = _cpu_count()

        if compression_params and write_checksum is not None:
            raise ValueError(
                "cannot define compression_params and " "write_checksum"
            )

        if compression_params and write_content_size is not None:
            raise ValueError(
                "cannot define compression_params and " "write_content_size"
            )

        if compression_params and write_dict_id is not None:
            raise ValueError(
                "cannot define compression_params and " "write_dict_id"
            )

        if compression_params and threads:
            raise ValueError("cannot define compression_params and threads")

        if compression_params:
            self._params = _make_cctx_params(compression_params)
        else:
            if write_dict_id is None:
                write_dict_id = True

            params = lib.ZSTD_createCCtxParams()
            if params == ffi.NULL:
                raise MemoryError()

            self._params = ffi.gc(params, lib.ZSTD_freeCCtxParams)

            _set_compression_parameter(
                self._params, lib.ZSTD_c_compressionLevel, level
            )

            _set_compression_parameter(
                self._params,
                lib.ZSTD_c_contentSizeFlag,
                write_content_size if write_content_size is not None else 1,
            )

            _set_compression_parameter(
                self._params,
                lib.ZSTD_c_checksumFlag,
                1 if write_checksum else 0,
            )

            _set_compression_parameter(
                self._params, lib.ZSTD_c_dictIDFlag, 1 if write_dict_id else 0
            )

            if threads:
                _set_compression_parameter(
                    self._params, lib.ZSTD_c_nbWorkers, threads
                )

        cctx = lib.ZSTD_createCCtx()
        if cctx == ffi.NULL:
            raise MemoryError()

        self._cctx = cctx
        self._dict_data = dict_data

        # We defer setting up garbage collection until after calling
        # _setup_cctx() to ensure the memory size estimate is more accurate.
        try:
            self._setup_cctx()
        finally:
            self._cctx = ffi.gc(
                cctx, lib.ZSTD_freeCCtx, size=lib.ZSTD_sizeof_CCtx(cctx)
            )

    def _setup_cctx(self):
        zresult = lib.ZSTD_CCtx_setParametersUsingCCtxParams(
            self._cctx, self._params
        )
        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "could not set compression parameters: %s"
                % _zstd_error(zresult)
            )

        dict_data = self._dict_data

        if dict_data:
            if dict_data._cdict:
                zresult = lib.ZSTD_CCtx_refCDict(self._cctx, dict_data._cdict)
            else:
                zresult = lib.ZSTD_CCtx_loadDictionary_advanced(
                    self._cctx,
                    dict_data.as_bytes(),
                    len(dict_data),
                    lib.ZSTD_dlm_byRef,
                    dict_data._dict_type,
                )

            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "could not load compression dictionary: %s"
                    % _zstd_error(zresult)
                )

    def memory_size(self):
        return lib.ZSTD_sizeof_CCtx(self._cctx)

    def compress(self, data):
        lib.ZSTD_CCtx_reset(self._cctx, lib.ZSTD_reset_session_only)

        data_buffer = ffi.from_buffer(data)

        dest_size = lib.ZSTD_compressBound(len(data_buffer))
        out = new_nonzero("char[]", dest_size)

        zresult = lib.ZSTD_CCtx_setPledgedSrcSize(self._cctx, len(data_buffer))
        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "error setting source size: %s" % _zstd_error(zresult)
            )

        out_buffer = ffi.new("ZSTD_outBuffer *")
        in_buffer = ffi.new("ZSTD_inBuffer *")

        out_buffer.dst = out
        out_buffer.size = dest_size
        out_buffer.pos = 0

        in_buffer.src = data_buffer
        in_buffer.size = len(data_buffer)
        in_buffer.pos = 0

        zresult = lib.ZSTD_compressStream2(
            self._cctx, out_buffer, in_buffer, lib.ZSTD_e_end
        )

        if lib.ZSTD_isError(zresult):
            raise ZstdError("cannot compress: %s" % _zstd_error(zresult))
        elif zresult:
            raise ZstdError("unexpected partial frame flush")

        return ffi.buffer(out, out_buffer.pos)[:]

    def compressobj(self, size=-1):
        lib.ZSTD_CCtx_reset(self._cctx, lib.ZSTD_reset_session_only)

        if size < 0:
            size = lib.ZSTD_CONTENTSIZE_UNKNOWN

        zresult = lib.ZSTD_CCtx_setPledgedSrcSize(self._cctx, size)
        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "error setting source size: %s" % _zstd_error(zresult)
            )

        cobj = ZstdCompressionObj()
        cobj._out = ffi.new("ZSTD_outBuffer *")
        cobj._dst_buffer = ffi.new(
            "char[]", COMPRESSION_RECOMMENDED_OUTPUT_SIZE
        )
        cobj._out.dst = cobj._dst_buffer
        cobj._out.size = COMPRESSION_RECOMMENDED_OUTPUT_SIZE
        cobj._out.pos = 0
        cobj._compressor = self
        cobj._finished = False

        return cobj

    def chunker(self, size=-1, chunk_size=COMPRESSION_RECOMMENDED_OUTPUT_SIZE):
        lib.ZSTD_CCtx_reset(self._cctx, lib.ZSTD_reset_session_only)

        if size < 0:
            size = lib.ZSTD_CONTENTSIZE_UNKNOWN

        zresult = lib.ZSTD_CCtx_setPledgedSrcSize(self._cctx, size)
        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "error setting source size: %s" % _zstd_error(zresult)
            )

        return ZstdCompressionChunker(self, chunk_size=chunk_size)

    def copy_stream(
        self,
        ifh,
        ofh,
        size=-1,
        read_size=COMPRESSION_RECOMMENDED_INPUT_SIZE,
        write_size=COMPRESSION_RECOMMENDED_OUTPUT_SIZE,
    ):

        if not hasattr(ifh, "read"):
            raise ValueError("first argument must have a read() method")
        if not hasattr(ofh, "write"):
            raise ValueError("second argument must have a write() method")

        lib.ZSTD_CCtx_reset(self._cctx, lib.ZSTD_reset_session_only)

        if size < 0:
            size = lib.ZSTD_CONTENTSIZE_UNKNOWN

        zresult = lib.ZSTD_CCtx_setPledgedSrcSize(self._cctx, size)
        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "error setting source size: %s" % _zstd_error(zresult)
            )

        in_buffer = ffi.new("ZSTD_inBuffer *")
        out_buffer = ffi.new("ZSTD_outBuffer *")

        dst_buffer = ffi.new("char[]", write_size)
        out_buffer.dst = dst_buffer
        out_buffer.size = write_size
        out_buffer.pos = 0

        total_read, total_write = 0, 0

        while True:
            data = ifh.read(read_size)
            if not data:
                break

            data_buffer = ffi.from_buffer(data)
            total_read += len(data_buffer)
            in_buffer.src = data_buffer
            in_buffer.size = len(data_buffer)
            in_buffer.pos = 0

            while in_buffer.pos < in_buffer.size:
                zresult = lib.ZSTD_compressStream2(
                    self._cctx, out_buffer, in_buffer, lib.ZSTD_e_continue
                )
                if lib.ZSTD_isError(zresult):
                    raise ZstdError(
                        "zstd compress error: %s" % _zstd_error(zresult)
                    )

                if out_buffer.pos:
                    ofh.write(ffi.buffer(out_buffer.dst, out_buffer.pos))
                    total_write += out_buffer.pos
                    out_buffer.pos = 0

        # We've finished reading. Flush the compressor.
        while True:
            zresult = lib.ZSTD_compressStream2(
                self._cctx, out_buffer, in_buffer, lib.ZSTD_e_end
            )
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "error ending compression stream: %s" % _zstd_error(zresult)
                )

            if out_buffer.pos:
                ofh.write(ffi.buffer(out_buffer.dst, out_buffer.pos))
                total_write += out_buffer.pos
                out_buffer.pos = 0

            if zresult == 0:
                break

        return total_read, total_write

    def stream_reader(
        self, source, size=-1, read_size=COMPRESSION_RECOMMENDED_INPUT_SIZE
    ):
        lib.ZSTD_CCtx_reset(self._cctx, lib.ZSTD_reset_session_only)

        try:
            size = len(source)
        except Exception:
            pass

        if size < 0:
            size = lib.ZSTD_CONTENTSIZE_UNKNOWN

        zresult = lib.ZSTD_CCtx_setPledgedSrcSize(self._cctx, size)
        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "error setting source size: %s" % _zstd_error(zresult)
            )

        return ZstdCompressionReader(self, source, read_size)

    def stream_writer(
        self,
        writer,
        size=-1,
        write_size=COMPRESSION_RECOMMENDED_OUTPUT_SIZE,
        write_return_read=False,
    ):

        if not hasattr(writer, "write"):
            raise ValueError("must pass an object with a write() method")

        lib.ZSTD_CCtx_reset(self._cctx, lib.ZSTD_reset_session_only)

        if size < 0:
            size = lib.ZSTD_CONTENTSIZE_UNKNOWN

        return ZstdCompressionWriter(
            self, writer, size, write_size, write_return_read
        )

    write_to = stream_writer

    def read_to_iter(
        self,
        reader,
        size=-1,
        read_size=COMPRESSION_RECOMMENDED_INPUT_SIZE,
        write_size=COMPRESSION_RECOMMENDED_OUTPUT_SIZE,
    ):
        if hasattr(reader, "read"):
            have_read = True
        elif hasattr(reader, "__getitem__"):
            have_read = False
            buffer_offset = 0
            size = len(reader)
        else:
            raise ValueError(
                "must pass an object with a read() method or "
                "conforms to buffer protocol"
            )

        lib.ZSTD_CCtx_reset(self._cctx, lib.ZSTD_reset_session_only)

        if size < 0:
            size = lib.ZSTD_CONTENTSIZE_UNKNOWN

        zresult = lib.ZSTD_CCtx_setPledgedSrcSize(self._cctx, size)
        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "error setting source size: %s" % _zstd_error(zresult)
            )

        in_buffer = ffi.new("ZSTD_inBuffer *")
        out_buffer = ffi.new("ZSTD_outBuffer *")

        in_buffer.src = ffi.NULL
        in_buffer.size = 0
        in_buffer.pos = 0

        dst_buffer = ffi.new("char[]", write_size)
        out_buffer.dst = dst_buffer
        out_buffer.size = write_size
        out_buffer.pos = 0

        while True:
            # We should never have output data sitting around after a previous
            # iteration.
            assert out_buffer.pos == 0

            # Collect input data.
            if have_read:
                read_result = reader.read(read_size)
            else:
                remaining = len(reader) - buffer_offset
                slice_size = min(remaining, read_size)
                read_result = reader[buffer_offset : buffer_offset + slice_size]
                buffer_offset += slice_size

            # No new input data. Break out of the read loop.
            if not read_result:
                break

            # Feed all read data into the compressor and emit output until
            # exhausted.
            read_buffer = ffi.from_buffer(read_result)
            in_buffer.src = read_buffer
            in_buffer.size = len(read_buffer)
            in_buffer.pos = 0

            while in_buffer.pos < in_buffer.size:
                zresult = lib.ZSTD_compressStream2(
                    self._cctx, out_buffer, in_buffer, lib.ZSTD_e_continue
                )
                if lib.ZSTD_isError(zresult):
                    raise ZstdError(
                        "zstd compress error: %s" % _zstd_error(zresult)
                    )

                if out_buffer.pos:
                    data = ffi.buffer(out_buffer.dst, out_buffer.pos)[:]
                    out_buffer.pos = 0
                    yield data

            assert out_buffer.pos == 0

            # And repeat the loop to collect more data.
            continue

        # If we get here, input is exhausted. End the stream and emit what
        # remains.
        while True:
            assert out_buffer.pos == 0
            zresult = lib.ZSTD_compressStream2(
                self._cctx, out_buffer, in_buffer, lib.ZSTD_e_end
            )
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "error ending compression stream: %s" % _zstd_error(zresult)
                )

            if out_buffer.pos:
                data = ffi.buffer(out_buffer.dst, out_buffer.pos)[:]
                out_buffer.pos = 0
                yield data

            if zresult == 0:
                break

    read_from = read_to_iter

    def frame_progression(self):
        progression = lib.ZSTD_getFrameProgression(self._cctx)

        return progression.ingested, progression.consumed, progression.produced


class FrameParameters(object):
    def __init__(self, fparams):
        self.content_size = fparams.frameContentSize
        self.window_size = fparams.windowSize
        self.dict_id = fparams.dictID
        self.has_checksum = bool(fparams.checksumFlag)


def frame_content_size(data):
    data_buffer = ffi.from_buffer(data)

    size = lib.ZSTD_getFrameContentSize(data_buffer, len(data_buffer))

    if size == lib.ZSTD_CONTENTSIZE_ERROR:
        raise ZstdError("error when determining content size")
    elif size == lib.ZSTD_CONTENTSIZE_UNKNOWN:
        return -1
    else:
        return size


def frame_header_size(data):
    data_buffer = ffi.from_buffer(data)

    zresult = lib.ZSTD_frameHeaderSize(data_buffer, len(data_buffer))
    if lib.ZSTD_isError(zresult):
        raise ZstdError(
            "could not determine frame header size: %s" % _zstd_error(zresult)
        )

    return zresult


def get_frame_parameters(data):
    params = ffi.new("ZSTD_frameHeader *")

    data_buffer = ffi.from_buffer(data)
    zresult = lib.ZSTD_getFrameHeader(params, data_buffer, len(data_buffer))
    if lib.ZSTD_isError(zresult):
        raise ZstdError(
            "cannot get frame parameters: %s" % _zstd_error(zresult)
        )

    if zresult:
        raise ZstdError(
            "not enough data for frame parameters; need %d bytes" % zresult
        )

    return FrameParameters(params[0])


class ZstdCompressionDict(object):
    def __init__(self, data, dict_type=DICT_TYPE_AUTO, k=0, d=0):
        assert isinstance(data, bytes_type)
        self._data = data
        self.k = k
        self.d = d

        if dict_type not in (
            DICT_TYPE_AUTO,
            DICT_TYPE_RAWCONTENT,
            DICT_TYPE_FULLDICT,
        ):
            raise ValueError(
                "invalid dictionary load mode: %d; must use "
                "DICT_TYPE_* constants"
            )

        self._dict_type = dict_type
        self._cdict = None

    def __len__(self):
        return len(self._data)

    def dict_id(self):
        return int_type(lib.ZDICT_getDictID(self._data, len(self._data)))

    def as_bytes(self):
        return self._data

    def precompute_compress(self, level=0, compression_params=None):
        if level and compression_params:
            raise ValueError(
                "must only specify one of level or " "compression_params"
            )

        if not level and not compression_params:
            raise ValueError("must specify one of level or compression_params")

        if level:
            cparams = lib.ZSTD_getCParams(level, 0, len(self._data))
        else:
            cparams = ffi.new("ZSTD_compressionParameters")
            cparams.chainLog = compression_params.chain_log
            cparams.hashLog = compression_params.hash_log
            cparams.minMatch = compression_params.min_match
            cparams.searchLog = compression_params.search_log
            cparams.strategy = compression_params.compression_strategy
            cparams.targetLength = compression_params.target_length
            cparams.windowLog = compression_params.window_log

        cdict = lib.ZSTD_createCDict_advanced(
            self._data,
            len(self._data),
            lib.ZSTD_dlm_byRef,
            self._dict_type,
            cparams,
            lib.ZSTD_defaultCMem,
        )
        if cdict == ffi.NULL:
            raise ZstdError("unable to precompute dictionary")

        self._cdict = ffi.gc(
            cdict, lib.ZSTD_freeCDict, size=lib.ZSTD_sizeof_CDict(cdict)
        )

    @property
    def _ddict(self):
        ddict = lib.ZSTD_createDDict_advanced(
            self._data,
            len(self._data),
            lib.ZSTD_dlm_byRef,
            self._dict_type,
            lib.ZSTD_defaultCMem,
        )

        if ddict == ffi.NULL:
            raise ZstdError("could not create decompression dict")

        ddict = ffi.gc(
            ddict, lib.ZSTD_freeDDict, size=lib.ZSTD_sizeof_DDict(ddict)
        )
        self.__dict__["_ddict"] = ddict

        return ddict


def train_dictionary(
    dict_size,
    samples,
    k=0,
    d=0,
    notifications=0,
    dict_id=0,
    level=0,
    steps=0,
    threads=0,
):
    if not isinstance(samples, list):
        raise TypeError("samples must be a list")

    if threads < 0:
        threads = _cpu_count()

    total_size = sum(map(len, samples))

    samples_buffer = new_nonzero("char[]", total_size)
    sample_sizes = new_nonzero("size_t[]", len(samples))

    offset = 0
    for i, sample in enumerate(samples):
        if not isinstance(sample, bytes_type):
            raise ValueError("samples must be bytes")

        l = len(sample)
        ffi.memmove(samples_buffer + offset, sample, l)
        offset += l
        sample_sizes[i] = l

    dict_data = new_nonzero("char[]", dict_size)

    dparams = ffi.new("ZDICT_cover_params_t *")[0]
    dparams.k = k
    dparams.d = d
    dparams.steps = steps
    dparams.nbThreads = threads
    dparams.zParams.notificationLevel = notifications
    dparams.zParams.dictID = dict_id
    dparams.zParams.compressionLevel = level

    if (
        not dparams.k
        and not dparams.d
        and not dparams.steps
        and not dparams.nbThreads
        and not dparams.zParams.notificationLevel
        and not dparams.zParams.dictID
        and not dparams.zParams.compressionLevel
    ):
        zresult = lib.ZDICT_trainFromBuffer(
            ffi.addressof(dict_data),
            dict_size,
            ffi.addressof(samples_buffer),
            ffi.addressof(sample_sizes, 0),
            len(samples),
        )
    elif dparams.steps or dparams.nbThreads:
        zresult = lib.ZDICT_optimizeTrainFromBuffer_cover(
            ffi.addressof(dict_data),
            dict_size,
            ffi.addressof(samples_buffer),
            ffi.addressof(sample_sizes, 0),
            len(samples),
            ffi.addressof(dparams),
        )
    else:
        zresult = lib.ZDICT_trainFromBuffer_cover(
            ffi.addressof(dict_data),
            dict_size,
            ffi.addressof(samples_buffer),
            ffi.addressof(sample_sizes, 0),
            len(samples),
            dparams,
        )

    if lib.ZDICT_isError(zresult):
        msg = ffi.string(lib.ZDICT_getErrorName(zresult)).decode("utf-8")
        raise ZstdError("cannot train dict: %s" % msg)

    return ZstdCompressionDict(
        ffi.buffer(dict_data, zresult)[:],
        dict_type=DICT_TYPE_FULLDICT,
        k=dparams.k,
        d=dparams.d,
    )


class ZstdDecompressionObj(object):
    def __init__(self, decompressor, write_size):
        self._decompressor = decompressor
        self._write_size = write_size
        self._finished = False

    def decompress(self, data):
        if self._finished:
            raise ZstdError("cannot use a decompressobj multiple times")

        in_buffer = ffi.new("ZSTD_inBuffer *")
        out_buffer = ffi.new("ZSTD_outBuffer *")

        data_buffer = ffi.from_buffer(data)

        if len(data_buffer) == 0:
            return b""

        in_buffer.src = data_buffer
        in_buffer.size = len(data_buffer)
        in_buffer.pos = 0

        dst_buffer = ffi.new("char[]", self._write_size)
        out_buffer.dst = dst_buffer
        out_buffer.size = len(dst_buffer)
        out_buffer.pos = 0

        chunks = []

        while True:
            zresult = lib.ZSTD_decompressStream(
                self._decompressor._dctx, out_buffer, in_buffer
            )
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "zstd decompressor error: %s" % _zstd_error(zresult)
                )

            if zresult == 0:
                self._finished = True
                self._decompressor = None

            if out_buffer.pos:
                chunks.append(ffi.buffer(out_buffer.dst, out_buffer.pos)[:])

            if zresult == 0 or (
                in_buffer.pos == in_buffer.size and out_buffer.pos == 0
            ):
                break

            out_buffer.pos = 0

        return b"".join(chunks)

    def flush(self, length=0):
        pass


class ZstdDecompressionReader(object):
    def __init__(self, decompressor, source, read_size, read_across_frames):
        self._decompressor = decompressor
        self._source = source
        self._read_size = read_size
        self._read_across_frames = bool(read_across_frames)
        self._entered = False
        self._closed = False
        self._bytes_decompressed = 0
        self._finished_input = False
        self._finished_output = False
        self._in_buffer = ffi.new("ZSTD_inBuffer *")
        # Holds a ref to self._in_buffer.src.
        self._source_buffer = None

    def __enter__(self):
        if self._entered:
            raise ValueError("cannot __enter__ multiple times")

        self._entered = True
        return self

    def __exit__(self, exc_type, exc_value, exc_tb):
        self._entered = False
        self._closed = True
        self._source = None
        self._decompressor = None

        return False

    def readable(self):
        return True

    def writable(self):
        return False

    def seekable(self):
        return True

    def readline(self):
        raise io.UnsupportedOperation()

    def readlines(self):
        raise io.UnsupportedOperation()

    def write(self, data):
        raise io.UnsupportedOperation()

    def writelines(self, lines):
        raise io.UnsupportedOperation()

    def isatty(self):
        return False

    def flush(self):
        return None

    def close(self):
        self._closed = True
        return None

    @property
    def closed(self):
        return self._closed

    def tell(self):
        return self._bytes_decompressed

    def readall(self):
        chunks = []

        while True:
            chunk = self.read(1048576)
            if not chunk:
                break

            chunks.append(chunk)

        return b"".join(chunks)

    def __iter__(self):
        raise io.UnsupportedOperation()

    def __next__(self):
        raise io.UnsupportedOperation()

    next = __next__

    def _read_input(self):
        # We have data left over in the input buffer. Use it.
        if self._in_buffer.pos < self._in_buffer.size:
            return

        # All input data exhausted. Nothing to do.
        if self._finished_input:
            return

        # Else populate the input buffer from our source.
        if hasattr(self._source, "read"):
            data = self._source.read(self._read_size)

            if not data:
                self._finished_input = True
                return

            self._source_buffer = ffi.from_buffer(data)
            self._in_buffer.src = self._source_buffer
            self._in_buffer.size = len(self._source_buffer)
            self._in_buffer.pos = 0
        else:
            self._source_buffer = ffi.from_buffer(self._source)
            self._in_buffer.src = self._source_buffer
            self._in_buffer.size = len(self._source_buffer)
            self._in_buffer.pos = 0

    def _decompress_into_buffer(self, out_buffer):
        """Decompress available input into an output buffer.

        Returns True if data in output buffer should be emitted.
        """
        zresult = lib.ZSTD_decompressStream(
            self._decompressor._dctx, out_buffer, self._in_buffer
        )

        if self._in_buffer.pos == self._in_buffer.size:
            self._in_buffer.src = ffi.NULL
            self._in_buffer.pos = 0
            self._in_buffer.size = 0
            self._source_buffer = None

            if not hasattr(self._source, "read"):
                self._finished_input = True

        if lib.ZSTD_isError(zresult):
            raise ZstdError("zstd decompress error: %s" % _zstd_error(zresult))

        # Emit data if there is data AND either:
        # a) output buffer is full (read amount is satisfied)
        # b) we're at end of a frame and not in frame spanning mode
        return out_buffer.pos and (
            out_buffer.pos == out_buffer.size
            or zresult == 0
            and not self._read_across_frames
        )

    def read(self, size=-1):
        if self._closed:
            raise ValueError("stream is closed")

        if size < -1:
            raise ValueError("cannot read negative amounts less than -1")

        if size == -1:
            # This is recursive. But it gets the job done.
            return self.readall()

        if self._finished_output or size == 0:
            return b""

        # We /could/ call into readinto() here. But that introduces more
        # overhead.
        dst_buffer = ffi.new("char[]", size)
        out_buffer = ffi.new("ZSTD_outBuffer *")
        out_buffer.dst = dst_buffer
        out_buffer.size = size
        out_buffer.pos = 0

        self._read_input()
        if self._decompress_into_buffer(out_buffer):
            self._bytes_decompressed += out_buffer.pos
            return ffi.buffer(out_buffer.dst, out_buffer.pos)[:]

        while not self._finished_input:
            self._read_input()
            if self._decompress_into_buffer(out_buffer):
                self._bytes_decompressed += out_buffer.pos
                return ffi.buffer(out_buffer.dst, out_buffer.pos)[:]

        self._bytes_decompressed += out_buffer.pos
        return ffi.buffer(out_buffer.dst, out_buffer.pos)[:]

    def readinto(self, b):
        if self._closed:
            raise ValueError("stream is closed")

        if self._finished_output:
            return 0

        # TODO use writable=True once we require CFFI >= 1.12.
        dest_buffer = ffi.from_buffer(b)
        ffi.memmove(b, b"", 0)
        out_buffer = ffi.new("ZSTD_outBuffer *")
        out_buffer.dst = dest_buffer
        out_buffer.size = len(dest_buffer)
        out_buffer.pos = 0

        self._read_input()
        if self._decompress_into_buffer(out_buffer):
            self._bytes_decompressed += out_buffer.pos
            return out_buffer.pos

        while not self._finished_input:
            self._read_input()
            if self._decompress_into_buffer(out_buffer):
                self._bytes_decompressed += out_buffer.pos
                return out_buffer.pos

        self._bytes_decompressed += out_buffer.pos
        return out_buffer.pos

    def read1(self, size=-1):
        if self._closed:
            raise ValueError("stream is closed")

        if size < -1:
            raise ValueError("cannot read negative amounts less than -1")

        if self._finished_output or size == 0:
            return b""

        # -1 returns arbitrary number of bytes.
        if size == -1:
            size = DECOMPRESSION_RECOMMENDED_OUTPUT_SIZE

        dst_buffer = ffi.new("char[]", size)
        out_buffer = ffi.new("ZSTD_outBuffer *")
        out_buffer.dst = dst_buffer
        out_buffer.size = size
        out_buffer.pos = 0

        # read1() dictates that we can perform at most 1 call to underlying
        # stream to get input. However, we can't satisfy this restriction with
        # decompression because not all input generates output. So we allow
        # multiple read(). But unlike read(), we stop once we have any output.
        while not self._finished_input:
            self._read_input()
            self._decompress_into_buffer(out_buffer)

            if out_buffer.pos:
                break

        self._bytes_decompressed += out_buffer.pos
        return ffi.buffer(out_buffer.dst, out_buffer.pos)[:]

    def readinto1(self, b):
        if self._closed:
            raise ValueError("stream is closed")

        if self._finished_output:
            return 0

        # TODO use writable=True once we require CFFI >= 1.12.
        dest_buffer = ffi.from_buffer(b)
        ffi.memmove(b, b"", 0)

        out_buffer = ffi.new("ZSTD_outBuffer *")
        out_buffer.dst = dest_buffer
        out_buffer.size = len(dest_buffer)
        out_buffer.pos = 0

        while not self._finished_input and not self._finished_output:
            self._read_input()
            self._decompress_into_buffer(out_buffer)

            if out_buffer.pos:
                break

        self._bytes_decompressed += out_buffer.pos
        return out_buffer.pos

    def seek(self, pos, whence=os.SEEK_SET):
        if self._closed:
            raise ValueError("stream is closed")

        read_amount = 0

        if whence == os.SEEK_SET:
            if pos < 0:
                raise ValueError(
                    "cannot seek to negative position with SEEK_SET"
                )

            if pos < self._bytes_decompressed:
                raise ValueError(
                    "cannot seek zstd decompression stream " "backwards"
                )

            read_amount = pos - self._bytes_decompressed

        elif whence == os.SEEK_CUR:
            if pos < 0:
                raise ValueError(
                    "cannot seek zstd decompression stream " "backwards"
                )

            read_amount = pos
        elif whence == os.SEEK_END:
            raise ValueError(
                "zstd decompression streams cannot be seeked " "with SEEK_END"
            )

        while read_amount:
            result = self.read(
                min(read_amount, DECOMPRESSION_RECOMMENDED_OUTPUT_SIZE)
            )

            if not result:
                break

            read_amount -= len(result)

        return self._bytes_decompressed


class ZstdDecompressionWriter(object):
    def __init__(self, decompressor, writer, write_size, write_return_read):
        decompressor._ensure_dctx()

        self._decompressor = decompressor
        self._writer = writer
        self._write_size = write_size
        self._write_return_read = bool(write_return_read)
        self._entered = False
        self._closed = False

    def __enter__(self):
        if self._closed:
            raise ValueError("stream is closed")

        if self._entered:
            raise ZstdError("cannot __enter__ multiple times")

        self._entered = True

        return self

    def __exit__(self, exc_type, exc_value, exc_tb):
        self._entered = False
        self.close()

    def memory_size(self):
        return lib.ZSTD_sizeof_DCtx(self._decompressor._dctx)

    def close(self):
        if self._closed:
            return

        try:
            self.flush()
        finally:
            self._closed = True

        f = getattr(self._writer, "close", None)
        if f:
            f()

    @property
    def closed(self):
        return self._closed

    def fileno(self):
        f = getattr(self._writer, "fileno", None)
        if f:
            return f()
        else:
            raise OSError("fileno not available on underlying writer")

    def flush(self):
        if self._closed:
            raise ValueError("stream is closed")

        f = getattr(self._writer, "flush", None)
        if f:
            return f()

    def isatty(self):
        return False

    def readable(self):
        return False

    def readline(self, size=-1):
        raise io.UnsupportedOperation()

    def readlines(self, hint=-1):
        raise io.UnsupportedOperation()

    def seek(self, offset, whence=None):
        raise io.UnsupportedOperation()

    def seekable(self):
        return False

    def tell(self):
        raise io.UnsupportedOperation()

    def truncate(self, size=None):
        raise io.UnsupportedOperation()

    def writable(self):
        return True

    def writelines(self, lines):
        raise io.UnsupportedOperation()

    def read(self, size=-1):
        raise io.UnsupportedOperation()

    def readall(self):
        raise io.UnsupportedOperation()

    def readinto(self, b):
        raise io.UnsupportedOperation()

    def write(self, data):
        if self._closed:
            raise ValueError("stream is closed")

        total_write = 0

        in_buffer = ffi.new("ZSTD_inBuffer *")
        out_buffer = ffi.new("ZSTD_outBuffer *")

        data_buffer = ffi.from_buffer(data)
        in_buffer.src = data_buffer
        in_buffer.size = len(data_buffer)
        in_buffer.pos = 0

        dst_buffer = ffi.new("char[]", self._write_size)
        out_buffer.dst = dst_buffer
        out_buffer.size = len(dst_buffer)
        out_buffer.pos = 0

        dctx = self._decompressor._dctx

        while in_buffer.pos < in_buffer.size:
            zresult = lib.ZSTD_decompressStream(dctx, out_buffer, in_buffer)
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "zstd decompress error: %s" % _zstd_error(zresult)
                )

            if out_buffer.pos:
                self._writer.write(
                    ffi.buffer(out_buffer.dst, out_buffer.pos)[:]
                )
                total_write += out_buffer.pos
                out_buffer.pos = 0

        if self._write_return_read:
            return in_buffer.pos
        else:
            return total_write


class ZstdDecompressor(object):
    def __init__(self, dict_data=None, max_window_size=0, format=FORMAT_ZSTD1):
        self._dict_data = dict_data
        self._max_window_size = max_window_size
        self._format = format

        dctx = lib.ZSTD_createDCtx()
        if dctx == ffi.NULL:
            raise MemoryError()

        self._dctx = dctx

        # Defer setting up garbage collection until full state is loaded so
        # the memory size is more accurate.
        try:
            self._ensure_dctx()
        finally:
            self._dctx = ffi.gc(
                dctx, lib.ZSTD_freeDCtx, size=lib.ZSTD_sizeof_DCtx(dctx)
            )

    def memory_size(self):
        return lib.ZSTD_sizeof_DCtx(self._dctx)

    def decompress(self, data, max_output_size=0):
        self._ensure_dctx()

        data_buffer = ffi.from_buffer(data)

        output_size = lib.ZSTD_getFrameContentSize(
            data_buffer, len(data_buffer)
        )

        if output_size == lib.ZSTD_CONTENTSIZE_ERROR:
            raise ZstdError("error determining content size from frame header")
        elif output_size == 0:
            return b""
        elif output_size == lib.ZSTD_CONTENTSIZE_UNKNOWN:
            if not max_output_size:
                raise ZstdError(
                    "could not determine content size in frame header"
                )

            result_buffer = ffi.new("char[]", max_output_size)
            result_size = max_output_size
            output_size = 0
        else:
            result_buffer = ffi.new("char[]", output_size)
            result_size = output_size

        out_buffer = ffi.new("ZSTD_outBuffer *")
        out_buffer.dst = result_buffer
        out_buffer.size = result_size
        out_buffer.pos = 0

        in_buffer = ffi.new("ZSTD_inBuffer *")
        in_buffer.src = data_buffer
        in_buffer.size = len(data_buffer)
        in_buffer.pos = 0

        zresult = lib.ZSTD_decompressStream(self._dctx, out_buffer, in_buffer)
        if lib.ZSTD_isError(zresult):
            raise ZstdError("decompression error: %s" % _zstd_error(zresult))
        elif zresult:
            raise ZstdError(
                "decompression error: did not decompress full frame"
            )
        elif output_size and out_buffer.pos != output_size:
            raise ZstdError(
                "decompression error: decompressed %d bytes; expected %d"
                % (zresult, output_size)
            )

        return ffi.buffer(result_buffer, out_buffer.pos)[:]

    def stream_reader(
        self,
        source,
        read_size=DECOMPRESSION_RECOMMENDED_INPUT_SIZE,
        read_across_frames=False,
    ):
        self._ensure_dctx()
        return ZstdDecompressionReader(
            self, source, read_size, read_across_frames
        )

    def decompressobj(self, write_size=DECOMPRESSION_RECOMMENDED_OUTPUT_SIZE):
        if write_size < 1:
            raise ValueError("write_size must be positive")

        self._ensure_dctx()
        return ZstdDecompressionObj(self, write_size=write_size)

    def read_to_iter(
        self,
        reader,
        read_size=DECOMPRESSION_RECOMMENDED_INPUT_SIZE,
        write_size=DECOMPRESSION_RECOMMENDED_OUTPUT_SIZE,
        skip_bytes=0,
    ):
        if skip_bytes >= read_size:
            raise ValueError("skip_bytes must be smaller than read_size")

        if hasattr(reader, "read"):
            have_read = True
        elif hasattr(reader, "__getitem__"):
            have_read = False
            buffer_offset = 0
            size = len(reader)
        else:
            raise ValueError(
                "must pass an object with a read() method or "
                "conforms to buffer protocol"
            )

        if skip_bytes:
            if have_read:
                reader.read(skip_bytes)
            else:
                if skip_bytes > size:
                    raise ValueError("skip_bytes larger than first input chunk")

                buffer_offset = skip_bytes

        self._ensure_dctx()

        in_buffer = ffi.new("ZSTD_inBuffer *")
        out_buffer = ffi.new("ZSTD_outBuffer *")

        dst_buffer = ffi.new("char[]", write_size)
        out_buffer.dst = dst_buffer
        out_buffer.size = len(dst_buffer)
        out_buffer.pos = 0

        while True:
            assert out_buffer.pos == 0

            if have_read:
                read_result = reader.read(read_size)
            else:
                remaining = size - buffer_offset
                slice_size = min(remaining, read_size)
                read_result = reader[buffer_offset : buffer_offset + slice_size]
                buffer_offset += slice_size

            # No new input. Break out of read loop.
            if not read_result:
                break

            # Feed all read data into decompressor and emit output until
            # exhausted.
            read_buffer = ffi.from_buffer(read_result)
            in_buffer.src = read_buffer
            in_buffer.size = len(read_buffer)
            in_buffer.pos = 0

            while in_buffer.pos < in_buffer.size:
                assert out_buffer.pos == 0

                zresult = lib.ZSTD_decompressStream(
                    self._dctx, out_buffer, in_buffer
                )
                if lib.ZSTD_isError(zresult):
                    raise ZstdError(
                        "zstd decompress error: %s" % _zstd_error(zresult)
                    )

                if out_buffer.pos:
                    data = ffi.buffer(out_buffer.dst, out_buffer.pos)[:]
                    out_buffer.pos = 0
                    yield data

                if zresult == 0:
                    return

            # Repeat loop to collect more input data.
            continue

        # If we get here, input is exhausted.

    read_from = read_to_iter

    def stream_writer(
        self,
        writer,
        write_size=DECOMPRESSION_RECOMMENDED_OUTPUT_SIZE,
        write_return_read=False,
    ):
        if not hasattr(writer, "write"):
            raise ValueError("must pass an object with a write() method")

        return ZstdDecompressionWriter(
            self, writer, write_size, write_return_read
        )

    write_to = stream_writer

    def copy_stream(
        self,
        ifh,
        ofh,
        read_size=DECOMPRESSION_RECOMMENDED_INPUT_SIZE,
        write_size=DECOMPRESSION_RECOMMENDED_OUTPUT_SIZE,
    ):
        if not hasattr(ifh, "read"):
            raise ValueError("first argument must have a read() method")
        if not hasattr(ofh, "write"):
            raise ValueError("second argument must have a write() method")

        self._ensure_dctx()

        in_buffer = ffi.new("ZSTD_inBuffer *")
        out_buffer = ffi.new("ZSTD_outBuffer *")

        dst_buffer = ffi.new("char[]", write_size)
        out_buffer.dst = dst_buffer
        out_buffer.size = write_size
        out_buffer.pos = 0

        total_read, total_write = 0, 0

        # Read all available input.
        while True:
            data = ifh.read(read_size)
            if not data:
                break

            data_buffer = ffi.from_buffer(data)
            total_read += len(data_buffer)
            in_buffer.src = data_buffer
            in_buffer.size = len(data_buffer)
            in_buffer.pos = 0

            # Flush all read data to output.
            while in_buffer.pos < in_buffer.size:
                zresult = lib.ZSTD_decompressStream(
                    self._dctx, out_buffer, in_buffer
                )
                if lib.ZSTD_isError(zresult):
                    raise ZstdError(
                        "zstd decompressor error: %s" % _zstd_error(zresult)
                    )

                if out_buffer.pos:
                    ofh.write(ffi.buffer(out_buffer.dst, out_buffer.pos))
                    total_write += out_buffer.pos
                    out_buffer.pos = 0

            # Continue loop to keep reading.

        return total_read, total_write

    def decompress_content_dict_chain(self, frames):
        if not isinstance(frames, list):
            raise TypeError("argument must be a list")

        if not frames:
            raise ValueError("empty input chain")

        # First chunk should not be using a dictionary. We handle it specially.
        chunk = frames[0]
        if not isinstance(chunk, bytes_type):
            raise ValueError("chunk 0 must be bytes")

        # All chunks should be zstd frames and should have content size set.
        chunk_buffer = ffi.from_buffer(chunk)
        params = ffi.new("ZSTD_frameHeader *")
        zresult = lib.ZSTD_getFrameHeader(
            params, chunk_buffer, len(chunk_buffer)
        )
        if lib.ZSTD_isError(zresult):
            raise ValueError("chunk 0 is not a valid zstd frame")
        elif zresult:
            raise ValueError("chunk 0 is too small to contain a zstd frame")

        if params.frameContentSize == lib.ZSTD_CONTENTSIZE_UNKNOWN:
            raise ValueError("chunk 0 missing content size in frame")

        self._ensure_dctx(load_dict=False)

        last_buffer = ffi.new("char[]", params.frameContentSize)

        out_buffer = ffi.new("ZSTD_outBuffer *")
        out_buffer.dst = last_buffer
        out_buffer.size = len(last_buffer)
        out_buffer.pos = 0

        in_buffer = ffi.new("ZSTD_inBuffer *")
        in_buffer.src = chunk_buffer
        in_buffer.size = len(chunk_buffer)
        in_buffer.pos = 0

        zresult = lib.ZSTD_decompressStream(self._dctx, out_buffer, in_buffer)
        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "could not decompress chunk 0: %s" % _zstd_error(zresult)
            )
        elif zresult:
            raise ZstdError("chunk 0 did not decompress full frame")

        # Special case of chain length of 1
        if len(frames) == 1:
            return ffi.buffer(last_buffer, len(last_buffer))[:]

        i = 1
        while i < len(frames):
            chunk = frames[i]
            if not isinstance(chunk, bytes_type):
                raise ValueError("chunk %d must be bytes" % i)

            chunk_buffer = ffi.from_buffer(chunk)
            zresult = lib.ZSTD_getFrameHeader(
                params, chunk_buffer, len(chunk_buffer)
            )
            if lib.ZSTD_isError(zresult):
                raise ValueError("chunk %d is not a valid zstd frame" % i)
            elif zresult:
                raise ValueError(
                    "chunk %d is too small to contain a zstd frame" % i
                )

            if params.frameContentSize == lib.ZSTD_CONTENTSIZE_UNKNOWN:
                raise ValueError("chunk %d missing content size in frame" % i)

            dest_buffer = ffi.new("char[]", params.frameContentSize)

            out_buffer.dst = dest_buffer
            out_buffer.size = len(dest_buffer)
            out_buffer.pos = 0

            in_buffer.src = chunk_buffer
            in_buffer.size = len(chunk_buffer)
            in_buffer.pos = 0

            zresult = lib.ZSTD_decompressStream(
                self._dctx, out_buffer, in_buffer
            )
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "could not decompress chunk %d: %s" % _zstd_error(zresult)
                )
            elif zresult:
                raise ZstdError("chunk %d did not decompress full frame" % i)

            last_buffer = dest_buffer
            i += 1

        return ffi.buffer(last_buffer, len(last_buffer))[:]

    def _ensure_dctx(self, load_dict=True):
        lib.ZSTD_DCtx_reset(self._dctx, lib.ZSTD_reset_session_only)

        if self._max_window_size:
            zresult = lib.ZSTD_DCtx_setMaxWindowSize(
                self._dctx, self._max_window_size
            )
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "unable to set max window size: %s" % _zstd_error(zresult)
                )

        zresult = lib.ZSTD_DCtx_setFormat(self._dctx, self._format)
        if lib.ZSTD_isError(zresult):
            raise ZstdError(
                "unable to set decoding format: %s" % _zstd_error(zresult)
            )

        if self._dict_data and load_dict:
            zresult = lib.ZSTD_DCtx_refDDict(self._dctx, self._dict_data._ddict)
            if lib.ZSTD_isError(zresult):
                raise ZstdError(
                    "unable to reference prepared dictionary: %s"
                    % _zstd_error(zresult)
                )