# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.

# Cython wrappers for IO interfaces defined in arrow::io and messaging in
# arrow::ipc

from libc.stdlib cimport malloc, free

import re
import six
import sys
import threading
import time
import warnings
from io import BufferedIOBase, IOBase, TextIOBase, UnsupportedOperation

from pyarrow.util import _stringify_path
from pyarrow.compat import (
    builtin_pickle, frombytes, tobytes, encode_file_path, file_type)


# 64K
DEFAULT_BUFFER_SIZE = 2 ** 16


# To let us get a PyObject* and avoid Cython auto-ref-counting
cdef extern from "Python.h":
    PyObject* PyBytes_FromStringAndSizeNative" PyBytes_FromStringAndSize"(
        char *v, Py_ssize_t len) except NULL


cdef class NativeFile:
    """
    The base class for all Arrow streams.

    Streams are either readable, writable, or both.
    They optionally support seeking.

    While this class exposes methods to read or write data from Python, the
    primary intent of using a Arrow stream is to pass it to other Arrow
    facilities that will make use of it, such as Arrow IPC routines.
    """

    def __cinit__(self):
        self.own_file = False
        self.is_readable = False
        self.is_writable = False
        self.is_seekable = False

    def __dealloc__(self):
        if self.own_file:
            self.close()

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, tb):
        self.close()

    @property
    def mode(self):
        """
        The file mode. Currently instances of NativeFile may support:

        * rb: binary read
        * wb: binary write
        * rb+: binary read and write
        """
        # Emulate built-in file modes
        if self.is_readable and self.is_writable:
            return 'rb+'
        elif self.is_readable:
            return 'rb'
        elif self.is_writable:
            return 'wb'
        else:
            raise ValueError('File object is malformed, has no mode')

    def readable(self):
        self._assert_open()
        return self.is_readable

    def writable(self):
        self._assert_open()
        return self.is_writable

    def seekable(self):
        self._assert_open()
        return self.is_seekable

    def isatty(self):
        self._assert_open()
        return False

    def fileno(self):
        """
        NOT IMPLEMENTED
        """
        raise UnsupportedOperation()

    @property
    def closed(self):
        if self.is_readable:
            return self.input_stream.get().closed()
        elif self.is_writable:
            return self.output_stream.get().closed()
        else:
            return True

    def close(self):
        if not self.closed:
            with nogil:
                if self.is_readable:
                    check_status(self.input_stream.get().Close())
                else:
                    check_status(self.output_stream.get().Close())

    def flush(self):
        """Flush the buffer stream, if applicable.

        No-op to match the IOBase interface."""
        self._assert_open()

    cdef set_random_access_file(self, shared_ptr[RandomAccessFile] handle):
        self.input_stream = <shared_ptr[InputStream]> handle
        self.random_access = handle
        self.is_seekable = True

    cdef set_input_stream(self, shared_ptr[InputStream] handle):
        self.input_stream = handle
        self.random_access.reset()
        self.is_seekable = False

    cdef set_output_stream(self, shared_ptr[OutputStream] handle):
        self.output_stream = handle

    cdef shared_ptr[RandomAccessFile] get_random_access_file(self) except *:
        self._assert_readable()
        self._assert_seekable()
        return self.random_access

    cdef shared_ptr[InputStream] get_input_stream(self) except *:
        self._assert_readable()
        return self.input_stream

    cdef shared_ptr[OutputStream] get_output_stream(self) except *:
        self._assert_writable()
        return self.output_stream

    def _assert_open(self):
        if self.closed:
            raise ValueError("I/O operation on closed file")

    def _assert_readable(self):
        self._assert_open()
        if not self.is_readable:
            # XXX UnsupportedOperation
            raise IOError("only valid on readonly files")

    def _assert_writable(self):
        self._assert_open()
        if not self.is_writable:
            raise IOError("only valid on writable files")

    def _assert_seekable(self):
        self._assert_open()
        if not self.is_seekable:
            raise IOError("only valid on seekable files")

    def size(self):
        """
        Return file size
        """
        cdef int64_t size

        handle = self.get_random_access_file()
        with nogil:
            check_status(handle.get().GetSize(&size))
        return size

    def tell(self):
        """
        Return current stream position
        """
        cdef int64_t position

        if self.is_readable:
            rd_handle = self.get_random_access_file()
            with nogil:
                check_status(rd_handle.get().Tell(&position))
        else:
            wr_handle = self.get_output_stream()
            with nogil:
                check_status(wr_handle.get().Tell(&position))
        return position

    def seek(self, int64_t position, int whence=0):
        """
        Change current file stream position

        Parameters
        ----------
        position : int
            Byte offset, interpreted relative to value of whence argument
        whence : int, default 0
            Point of reference for seek offset

        Notes
        -----
        Values of whence:
        * 0 -- start of stream (the default); offset should be zero or positive
        * 1 -- current stream position; offset may be negative
        * 2 -- end of stream; offset is usually negative

        Returns
        -------
        new_position : the new absolute stream position
        """
        cdef int64_t offset
        handle = self.get_random_access_file()

        with nogil:
            if whence == 0:
                offset = position
            elif whence == 1:
                check_status(handle.get().Tell(&offset))
                offset = offset + position
            elif whence == 2:
                check_status(handle.get().GetSize(&offset))
                offset = offset + position
            else:
                with gil:
                    raise ValueError("Invalid value of whence: {0}"
                                     .format(whence))
            check_status(handle.get().Seek(offset))

        return self.tell()

    def write(self, data):
        """
        Write byte from any object implementing buffer protocol (bytes,
        bytearray, ndarray, pyarrow.Buffer)

        Parameters
        ----------
        data : bytes-like object or exporter of buffer protocol

        Returns
        -------
        nbytes : number of bytes written
        """
        self._assert_writable()

        cdef Buffer arrow_buffer = py_buffer(data)

        cdef const uint8_t* buf = arrow_buffer.buffer.get().data()
        cdef int64_t bufsize = len(arrow_buffer)
        handle = self.get_output_stream()

        with nogil:
            check_status(handle.get().Write(buf, bufsize))
        return bufsize

    def read(self, nbytes=None):
        """
        Read indicated number of bytes from file, or read all remaining bytes
        if no argument passed

        Parameters
        ----------
        nbytes : int, default None

        Returns
        -------
        data : bytes
        """
        cdef:
            int64_t c_nbytes
            int64_t bytes_read = 0
            PyObject* obj

        if nbytes is None:
            if not self.is_seekable:
                # Cannot get file size => read chunkwise
                bs = 16384
                chunks = []
                while True:
                    chunk = self.read(bs)
                    if not chunk:
                        break
                    chunks.append(chunk)
                return b"".join(chunks)

            c_nbytes = self.size() - self.tell()
        else:
            c_nbytes = nbytes

        handle = self.get_input_stream()

        # Allocate empty write space
        obj = PyBytes_FromStringAndSizeNative(NULL, c_nbytes)

        cdef uint8_t* buf = <uint8_t*> cp.PyBytes_AS_STRING(<object> obj)
        with nogil:
            check_status(handle.get().Read(c_nbytes, &bytes_read, buf))

        if bytes_read < c_nbytes:
            cp._PyBytes_Resize(&obj, <Py_ssize_t> bytes_read)

        return PyObject_to_object(obj)

    def read_at(self, nbytes, offset):
        """
        Read indicated number of bytes at offset from the file

        Parameters
        ----------
        nbytes : int
        offset : int

        Returns
        -------
        data : bytes
        """
        cdef:
            int64_t c_nbytes
            int64_t c_offset
            int64_t bytes_read = 0
            PyObject* obj

        c_nbytes = nbytes

        c_offset = offset

        handle = self.get_random_access_file()

        # Allocate empty write space
        obj = PyBytes_FromStringAndSizeNative(NULL, c_nbytes)

        cdef uint8_t* buf = <uint8_t*> cp.PyBytes_AS_STRING(<object> obj)
        with nogil:
            check_status(handle.get().
                         ReadAt(c_offset, c_nbytes, &bytes_read, buf))

        if bytes_read < c_nbytes:
            cp._PyBytes_Resize(&obj, <Py_ssize_t> bytes_read)

        return PyObject_to_object(obj)

    def read1(self, nbytes=None):
        """Read and return up to n bytes.

        Alias for read, needed to match the IOBase interface."""
        return self.read(nbytes=None)

    def readall(self):
        return self.read()

    def readinto(self, b):
        """
        Read into the supplied buffer

        Parameters
        -----------
        b: any python object supporting buffer interface

        Returns
        --------
        number of bytes written
        """

        cdef:
            int64_t bytes_read
            uint8_t* buf
            Buffer py_buf
            int64_t buf_len

        handle = self.get_input_stream()

        py_buf = py_buffer(b)
        buf_len = py_buf.size
        buf = py_buf.buffer.get().mutable_data()

        with nogil:
            check_status(handle.get().Read(buf_len, &bytes_read, buf))

        return bytes_read

    def readline(self, size=None):
        """NOT IMPLEMENTED. Read and return a line of bytes from the file.

        If size is specified, read at most size bytes.

        Line terminator is always b"\\n".
        """

        raise UnsupportedOperation()

    def readlines(self, hint=None):
        """NOT IMPLEMENTED. Read lines of the file

        Parameters
        -----------

        hint: int maximum number of bytes read until we stop
        """

        raise UnsupportedOperation()

    def __iter__(self):
        self._assert_readable()
        return self

    def __next__(self):
        line = self.readline()
        if not line:
            raise StopIteration
        return line

    def read_buffer(self, nbytes=None):
        cdef:
            int64_t c_nbytes
            int64_t bytes_read = 0
            shared_ptr[CBuffer] output

        handle = self.get_input_stream()

        if nbytes is None:
            if not self.is_seekable:
                # Cannot get file size => read chunkwise
                return py_buffer(self.read())
            c_nbytes = self.size() - self.tell()
        else:
            c_nbytes = nbytes

        with nogil:
            check_status(handle.get().ReadB(c_nbytes, &output))

        return pyarrow_wrap_buffer(output)

    def truncate(self):
        """
        NOT IMPLEMENTED
        """
        raise UnsupportedOperation()

    def writelines(self, lines):
        self._assert_writable()

        for line in lines:
            self.write(line)

    def download(self, stream_or_path, buffer_size=None):
        """
        Read file completely to local path (rather than reading completely into
        memory). First seeks to the beginning of the file.
        """
        cdef:
            int64_t bytes_read = 0
            uint8_t* buf

        handle = self.get_input_stream()

        buffer_size = buffer_size or DEFAULT_BUFFER_SIZE

        write_queue = Queue(50)

        if not hasattr(stream_or_path, 'read'):
            stream = open(stream_or_path, 'wb')

            def cleanup():
                stream.close()
        else:
            stream = stream_or_path

            def cleanup():
                pass

        done = False
        exc_info = None

        def bg_write():
            try:
                while not done or write_queue.qsize() > 0:
                    try:
                        buf = write_queue.get(timeout=0.01)
                    except QueueEmpty:
                        continue
                    stream.write(buf)
            except Exception as e:
                exc_info = sys.exc_info()
            finally:
                cleanup()

        self.seek(0)

        writer_thread = threading.Thread(target=bg_write)

        # This isn't ideal -- PyBytes_FromStringAndSize copies the data from
        # the passed buffer, so it's hard for us to avoid doubling the memory
        buf = <uint8_t*> malloc(buffer_size)
        if buf == NULL:
            raise MemoryError("Failed to allocate {0} bytes"
                              .format(buffer_size))

        writer_thread.start()

        cdef int64_t total_bytes = 0
        cdef int32_t c_buffer_size = buffer_size

        try:
            while True:
                with nogil:
                    check_status(handle.get()
                                 .Read(c_buffer_size, &bytes_read, buf))

                total_bytes += bytes_read

                # EOF
                if bytes_read == 0:
                    break

                pybuf = cp.PyBytes_FromStringAndSize(<const char*>buf,
                                                     bytes_read)

                if writer_thread.is_alive():
                    while write_queue.full():
                        time.sleep(0.01)
                else:
                    break

                write_queue.put_nowait(pybuf)
        finally:
            free(buf)
            done = True

        writer_thread.join()
        if exc_info is not None:
            raise exc_info[0], exc_info[1], exc_info[2]

    def upload(self, stream, buffer_size=None):
        """
        Pipe file-like object to file
        """
        write_queue = Queue(50)
        self._assert_writable()

        buffer_size = buffer_size or DEFAULT_BUFFER_SIZE

        done = False
        exc_info = None

        def bg_write():
            try:
                while not done or write_queue.qsize() > 0:
                    try:
                        buf = write_queue.get(timeout=0.01)
                    except QueueEmpty:
                        continue

                    self.write(buf)

            except Exception as e:
                exc_info = sys.exc_info()

        writer_thread = threading.Thread(target=bg_write)
        writer_thread.start()

        try:
            while True:
                buf = stream.read(buffer_size)
                if not buf:
                    break

                if writer_thread.is_alive():
                    while write_queue.full():
                        time.sleep(0.01)
                else:
                    break

                write_queue.put_nowait(buf)
        finally:
            done = True

        writer_thread.join()
        if exc_info is not None:
            raise exc_info[0], exc_info[1], exc_info[2]

BufferedIOBase.register(NativeFile)

# ----------------------------------------------------------------------
# Python file-like objects


cdef class PythonFile(NativeFile):
    """
    A stream backed by a Python file object.

    This class allows using Python file objects with arbitrary Arrow
    functions, including functions written in another language than Python.

    As a downside, there is a non-zero redirection cost in translating
    Arrow stream calls to Python method calls.  Furthermore, Python's
    Global Interpreter Lock may limit parallelism in some situations.
    """
    cdef:
        object handle

    def __cinit__(self, handle, mode=None):
        self.handle = handle

        if mode is None:
            try:
                inferred_mode = handle.mode
            except AttributeError:
                # Not all file-like objects have a mode attribute
                # (e.g. BytesIO)
                try:
                    inferred_mode = 'w' if handle.writable() else 'r'
                except AttributeError:
                    raise ValueError("could not infer open mode for file-like "
                                     "object %r, please pass it explicitly"
                                     % (handle,))
        else:
            inferred_mode = mode

        if inferred_mode.startswith('w'):
            kind = 'w'
        elif inferred_mode.startswith('r'):
            kind = 'r'
        else:
            raise ValueError('Invalid file mode: {0}'.format(mode))

        # If mode was given, check it matches the given file
        if mode is not None:
            if isinstance(handle, IOBase):
                # Python 3 IO object
                if kind == 'r':
                    if not handle.readable():
                        raise TypeError("readable file expected")
                else:
                    if not handle.writable():
                        raise TypeError("writable file expected")
            elif file_type is not None and isinstance(handle, file_type):
                # Python 2 file type
                if kind == 'r':
                    if 'r' not in handle.mode and '+' not in handle.mode:
                        raise TypeError("readable file expected")
                else:
                    if 'w' not in handle.mode and '+' not in handle.mode:
                        raise TypeError("writable file expected")
            # (other duck-typed file-like objects are possible)

        # If possible, check the file is a binary file
        if isinstance(handle, TextIOBase):
            raise TypeError("binary file expected, got text file")

        if kind == 'r':
            self.set_random_access_file(
                shared_ptr[RandomAccessFile](new PyReadableFile(handle)))
            self.is_readable = True
        else:
            self.set_output_stream(
                shared_ptr[OutputStream](new PyOutputStream(handle)))
            self.is_writable = True

    def truncate(self, pos=None):
        self.handle.truncate(pos)

    def readline(self, size=None):
        return self.handle.readline(size)

    def readlines(self, hint=None):
        return self.handle.readlines(hint)


cdef class MemoryMappedFile(NativeFile):
    """
    A stream that represents a memory-mapped file.

    Supports 'r', 'r+', 'w' modes.
    """
    cdef:
        shared_ptr[CMemoryMappedFile] handle
        object path

    @staticmethod
    def create(path, size):
        cdef:
            shared_ptr[CMemoryMappedFile] handle
            c_string c_path = encode_file_path(path)
            int64_t c_size = size

        with nogil:
            check_status(CMemoryMappedFile.Create(c_path, c_size, &handle))

        cdef MemoryMappedFile result = MemoryMappedFile()
        result.path = path
        result.is_readable = True
        result.is_writable = True
        result.set_output_stream(<shared_ptr[OutputStream]> handle)
        result.set_random_access_file(<shared_ptr[RandomAccessFile]> handle)
        result.handle = handle

        return result

    def _open(self, path, mode='r'):
        self.path = path

        cdef:
            FileMode c_mode
            shared_ptr[CMemoryMappedFile] handle
            c_string c_path = encode_file_path(path)

        if mode in ('r', 'rb'):
            c_mode = FileMode_READ
            self.is_readable = True
        elif mode in ('w', 'wb'):
            c_mode = FileMode_WRITE
            self.is_writable = True
        elif mode in ('r+', 'r+b', 'rb+'):
            c_mode = FileMode_READWRITE
            self.is_readable = True
            self.is_writable = True
        else:
            raise ValueError('Invalid file mode: {0}'.format(mode))

        with nogil:
            check_status(CMemoryMappedFile.Open(c_path, c_mode, &handle))

        self.set_output_stream(<shared_ptr[OutputStream]> handle)
        self.set_random_access_file(<shared_ptr[RandomAccessFile]> handle)
        self.handle = handle

    def resize(self, new_size):
        """
        Resize the map and underlying file.

        Parameters
        ----------
        new_size : new size in bytes
        """
        check_status(self.handle.get().Resize(new_size))

    def fileno(self):
        self._assert_open()
        return self.handle.get().file_descriptor()


def memory_map(path, mode='r'):
    """
    Open memory map at file path. Size of the memory map cannot change

    Parameters
    ----------
    path : string
    mode : {'r', 'r+', 'w'}, default 'r'
        Whether the file is opened for reading ('r+'), writing ('w')
        or both ('r+').

    Returns
    -------
    mmap : MemoryMappedFile
    """
    cdef MemoryMappedFile mmap = MemoryMappedFile()
    mmap._open(path, mode)
    return mmap


def create_memory_map(path, size):
    """
    Create a file of the given size and memory-map it.

    Parameters
    ----------
    path : string
        The file path to create, on the local filesystem.
    size : int
        The file size to create.

    Returns
    -------
    mmap : MemoryMappedFile
    """
    return MemoryMappedFile.create(path, size)


cdef class OSFile(NativeFile):
    """
    A stream backed by a regular file descriptor.
    """
    cdef:
        object path

    def __cinit__(self, path, mode='r', MemoryPool memory_pool=None):
        self.path = path

        cdef:
            FileMode c_mode
            shared_ptr[Readable] handle
            c_string c_path = encode_file_path(path)

        if mode in ('r', 'rb'):
            self._open_readable(c_path, maybe_unbox_memory_pool(memory_pool))
        elif mode in ('w', 'wb'):
            self._open_writable(c_path)
        else:
            raise ValueError('Invalid file mode: {0}'.format(mode))

    cdef _open_readable(self, c_string path, CMemoryPool* pool):
        cdef shared_ptr[ReadableFile] handle

        with nogil:
            check_status(ReadableFile.Open(path, pool, &handle))

        self.is_readable = True
        self.set_random_access_file(<shared_ptr[RandomAccessFile]> handle)

    cdef _open_writable(self, c_string path):
        with nogil:
            check_status(FileOutputStream.Open(path, &self.output_stream))
        self.is_writable = True

    def fileno(self):
        self._assert_open()
        return self.handle.file_descriptor()


cdef class FixedSizeBufferWriter(NativeFile):
    """
    A stream writing to a Arrow buffer.
    """

    def __cinit__(self, Buffer buffer):
        self.output_stream.reset(new CFixedSizeBufferWriter(buffer.buffer))
        self.is_writable = True

    def set_memcopy_threads(self, int num_threads):
        cdef CFixedSizeBufferWriter* writer = \
            <CFixedSizeBufferWriter*> self.output_stream.get()
        writer.set_memcopy_threads(num_threads)

    def set_memcopy_blocksize(self, int64_t blocksize):
        cdef CFixedSizeBufferWriter* writer = \
            <CFixedSizeBufferWriter*> self.output_stream.get()
        writer.set_memcopy_blocksize(blocksize)

    def set_memcopy_threshold(self, int64_t threshold):
        cdef CFixedSizeBufferWriter* writer = \
            <CFixedSizeBufferWriter*> self.output_stream.get()
        writer.set_memcopy_threshold(threshold)


# ----------------------------------------------------------------------
# Arrow buffers


cdef class Buffer:
    """
    The base class for all Arrow buffers.

    A buffer represents a contiguous memory area.  Many buffers will own
    their memory, though not all of them do.
    """

    def __cinit__(self):
        pass

    def __init__(self):
        raise TypeError("Do not call Buffer's constructor directly, use "
                        "`pyarrow.py_buffer` function instead.")

    cdef void init(self, const shared_ptr[CBuffer]& buffer):
        self.buffer = buffer
        self.shape[0] = self.size
        self.strides[0] = <Py_ssize_t>(1)

    def __len__(self):
        return self.size

    @property
    def size(self):
        """
        The buffer size in bytes.
        """
        return self.buffer.get().size()

    @property
    def address(self):
        """
        The buffer's address, as an integer.
        """
        return <uintptr_t> self.buffer.get().data()

    def hex(self):
        """
        Compute hexadecimal representation of the buffer.

        Returns
        -------
        : bytes
        """
        return self.buffer.get().ToHexString()

    @property
    def is_mutable(self):
        """
        Whether the buffer is mutable.
        """
        return self.buffer.get().is_mutable()

    @property
    def parent(self):
        cdef shared_ptr[CBuffer] parent_buf = self.buffer.get().parent()

        if parent_buf.get() == NULL:
            return None
        else:
            return pyarrow_wrap_buffer(parent_buf)

    def __getitem__(self, key):
        if PySlice_Check(key):
            return _normalize_slice(self, key)

        return self.getitem(_normalize_index(key, self.size))

    cdef getitem(self, int64_t i):
        return self.buffer.get().data()[i]

    def slice(self, offset=0, length=None):
        """
        Slice this buffer.  Memory is not copied.

        You can also use the Python slice notation ``buffer[start:stop]``.

        Parameters
        ----------
        offset : int, default 0
            Offset from start of buffer to slice
        length : int, default None
            Length of slice (default is until end of Buffer starting from
            offset)

        Returns
        -------
        sliced : Buffer
            A logical view over this buffer.
        """
        cdef shared_ptr[CBuffer] result

        if offset < 0:
            raise IndexError('Offset must be non-negative')

        if length is None:
            result = SliceBuffer(self.buffer, offset)
        else:
            result = SliceBuffer(self.buffer, offset, max(length, 0))

        return pyarrow_wrap_buffer(result)

    def equals(self, Buffer other):
        """
        Determine if two buffers contain exactly the same data.

        Parameters
        ----------
        other : Buffer

        Returns
        -------
        are_equal : True if buffer contents and size are equal
        """
        cdef c_bool result = False
        with nogil:
            result = self.buffer.get().Equals(deref(other.buffer.get()))
        return result

    def __eq__(self, other):
        if isinstance(other, Buffer):
            return self.equals(other)
        else:
            return NotImplemented

    def __reduce_ex__(self, protocol):
        if protocol >= 5:
            return py_buffer, (builtin_pickle.PickleBuffer(self),)
        else:
            return py_buffer, (self.to_pybytes(),)

    def to_pybytes(self):
        """
        Return this buffer as a Python bytes object.  Memory is copied.
        """
        return cp.PyBytes_FromStringAndSize(
            <const char*>self.buffer.get().data(),
            self.buffer.get().size())

    def __getbuffer__(self, cp.Py_buffer* buffer, int flags):
        if self.buffer.get().is_mutable():
            buffer.readonly = 0
        else:
            if flags & cp.PyBUF_WRITABLE:
                raise BufferError("Writable buffer requested but Arrow "
                                  "buffer was not mutable")
            buffer.readonly = 1
        buffer.buf = <char *>self.buffer.get().data()
        buffer.format = 'b'
        buffer.internal = NULL
        buffer.itemsize = 1
        buffer.len = self.size
        buffer.ndim = 1
        buffer.obj = self
        buffer.shape = self.shape
        buffer.strides = self.strides
        buffer.suboffsets = NULL

    def __getsegcount__(self, Py_ssize_t *len_out):
        if len_out != NULL:
            len_out[0] = <Py_ssize_t>self.size
        return 1

    def __getreadbuffer__(self, Py_ssize_t idx, void **p):
        if idx != 0:
            raise SystemError("accessing non-existent buffer segment")
        if p != NULL:
            p[0] = <void*> self.buffer.get().data()
        return self.size

    def __getwritebuffer__(self, Py_ssize_t idx, void **p):
        if not self.buffer.get().is_mutable():
            raise SystemError("trying to write an immutable buffer")
        if idx != 0:
            raise SystemError("accessing non-existent buffer segment")
        if p != NULL:
            p[0] = <void*> self.buffer.get().data()
        return self.size


cdef class ResizableBuffer(Buffer):
    """
    A base class for buffers that can be resized.
    """

    cdef void init_rz(self, const shared_ptr[CResizableBuffer]& buffer):
        self.init(<shared_ptr[CBuffer]> buffer)

    def resize(self, int64_t new_size, shrink_to_fit=False):
        """
        Resize buffer to indicated size.

        Parameters
        ----------
        new_size : int
            New size of buffer (padding may be added internally)
        shrink_to_fit : boolean, default False
            If this is true, the buffer is shrunk when new_size is less
            than the current size.
            If this is false, the buffer is never shrunk.
        """
        cdef c_bool c_shrink_to_fit = shrink_to_fit
        with nogil:
            check_status((<CResizableBuffer*> self.buffer.get())
                         .Resize(new_size, c_shrink_to_fit))


cdef shared_ptr[CResizableBuffer] _allocate_buffer(CMemoryPool* pool):
    cdef shared_ptr[CResizableBuffer] result
    with nogil:
        check_status(AllocateResizableBuffer(pool, 0, &result))
    return result


def allocate_buffer(int64_t size, MemoryPool memory_pool=None,
                    resizable=False):
    """
    Allocate a mutable buffer.

    Parameters
    ----------
    size : int
        Number of bytes to allocate (plus internal padding)
    memory_pool : MemoryPool, optional
        The pool to allocate memory from.
        If not given, the default memory pool is used.
    resizable : boolean, default False
        If true, the returned buffer is resizable.

    Returns
    -------
    buffer : Buffer or ResizableBuffer
    """
    cdef:
        shared_ptr[CBuffer] buffer
        shared_ptr[CResizableBuffer] rz_buffer
        CMemoryPool* cpool = maybe_unbox_memory_pool(memory_pool)

    if resizable:
        with nogil:
            check_status(AllocateResizableBuffer(cpool, size, &rz_buffer))
        return pyarrow_wrap_resizable_buffer(rz_buffer)
    else:
        with nogil:
            check_status(AllocateBuffer(cpool, size, &buffer))
        return pyarrow_wrap_buffer(buffer)


cdef class BufferOutputStream(NativeFile):

    cdef:
        shared_ptr[CResizableBuffer] buffer

    def __cinit__(self, MemoryPool memory_pool=None):
        self.buffer = _allocate_buffer(maybe_unbox_memory_pool(memory_pool))
        self.output_stream.reset(new CBufferOutputStream(
            <shared_ptr[CResizableBuffer]> self.buffer))
        self.is_writable = True

    def getvalue(self):
        """
        Finalize output stream and return result as pyarrow.Buffer.

        Returns
        -------
        value : Buffer
        """
        with nogil:
            check_status(self.output_stream.get().Close())
        return pyarrow_wrap_buffer(<shared_ptr[CBuffer]> self.buffer)


cdef class MockOutputStream(NativeFile):

    def __cinit__(self):
        self.output_stream.reset(new CMockOutputStream())
        self.is_writable = True

    def size(self):
        handle = <CMockOutputStream*> self.output_stream.get()
        return handle.GetExtentBytesWritten()


cdef class BufferReader(NativeFile):
    """
    Zero-copy reader from objects convertible to Arrow buffer

    Parameters
    ----------
    obj : Python bytes or pyarrow.Buffer
    """
    cdef:
        Buffer buffer

    def __cinit__(self, object obj):
        self.buffer = as_buffer(obj)
        self.set_random_access_file(shared_ptr[RandomAccessFile](
            new CBufferReader(self.buffer.buffer)))
        self.is_readable = True


cdef class CompressedInputStream(NativeFile):
    """
    An input stream wrapper which decompresses data on the fly.

    Parameters
    ----------
    stream : pa.NativeFile
    compression : str
        The compression type ("bz2", "brotli", "gzip", "lz4", "snappy"
        or "zstd")
    """
    def __init__(self, NativeFile stream, compression):
        cdef:
            CompressionType compression_type
            unique_ptr[CCodec] codec
            shared_ptr[CCompressedInputStream] compressed_stream

        compression_type = _get_compression_type(compression)
        if compression_type == CompressionType_UNCOMPRESSED:
            raise ValueError('Invalid value for compression: {!r}'
                             .format(compression))

        check_status(CCodec.Create(compression_type, &codec))
        check_status(CCompressedInputStream.Make(
            codec.get(), stream.get_input_stream(), &compressed_stream))

        self.set_input_stream(<shared_ptr[InputStream]> compressed_stream)
        self.is_readable = True


cdef class CompressedOutputStream(NativeFile):
    """
    An output stream wrapper which compresses data on the fly.

    Parameters
    ----------
    stream : pa.NativeFile
    compression : str
        The compression type ("bz2", "brotli", "gzip", "lz4", "snappy"
        or "zstd")
    """

    def __init__(self, NativeFile stream, compression):
        cdef:
            CompressionType compression_type
            unique_ptr[CCodec] codec
            shared_ptr[CCompressedOutputStream] compressed_stream

        compression_type = _get_compression_type(compression)
        if compression_type == CompressionType_UNCOMPRESSED:
            raise ValueError('Invalid value for compression: {!r}'
                             .format(compression))

        check_status(CCodec.Create(compression_type, &codec))
        check_status(CCompressedOutputStream.Make(
            codec.get(), stream.get_output_stream(), &compressed_stream))

        self.set_output_stream(<shared_ptr[OutputStream]> compressed_stream)
        self.is_writable = True


cdef class BufferedInputStream(NativeFile):

    def __init__(self, NativeFile stream, int buffer_size,
                 MemoryPool memory_pool=None):
        cdef shared_ptr[CBufferedInputStream] buffered_stream

        if buffer_size <= 0:
            raise ValueError('Buffer size must be larger than zero')
        check_status(CBufferedInputStream.Create(
            buffer_size, maybe_unbox_memory_pool(memory_pool),
            stream.get_input_stream(), &buffered_stream))

        self.set_input_stream(<shared_ptr[InputStream]> buffered_stream)
        self.is_readable = True


cdef class BufferedOutputStream(NativeFile):

    def __init__(self, NativeFile stream, int buffer_size,
                 MemoryPool memory_pool=None):
        cdef shared_ptr[CBufferedOutputStream] buffered_stream

        if buffer_size <= 0:
            raise ValueError('Buffer size must be larger than zero')
        check_status(CBufferedOutputStream.Create(
            buffer_size, maybe_unbox_memory_pool(memory_pool),
            stream.get_output_stream(), &buffered_stream))

        self.set_output_stream(<shared_ptr[OutputStream]> buffered_stream)
        self.is_writable = True


def py_buffer(object obj):
    """
    Construct an Arrow buffer from a Python bytes-like or buffer-like object
    """
    cdef shared_ptr[CBuffer] buf
    check_status(PyBuffer.FromPyObject(obj, &buf))
    return pyarrow_wrap_buffer(buf)


def foreign_buffer(address, size, base=None):
    """
    Construct an Arrow buffer with the given *address* and *size*,
    optionally backed by the Python *base* object.

    The *base* object, if given, will be kept alive as long as this buffer
    is alive, including accross language boundaries (for example if the
    buffer is referenced by C++ code).
    """
    cdef:
        intptr_t c_addr = address
        int64_t c_size = size
        shared_ptr[CBuffer] buf

    check_status(PyForeignBuffer.Make(<uint8_t*> c_addr, c_size,
                                      base, &buf))
    return pyarrow_wrap_buffer(buf)


def as_buffer(object o):
    if isinstance(o, Buffer):
        return o
    return py_buffer(o)


cdef NativeFile _get_native_file(object source, c_bool use_memory_map):
    try:
        source_path = _stringify_path(source)
    except TypeError:
        if isinstance(source, Buffer):
            source = BufferReader(source)
        elif not isinstance(source, NativeFile) and hasattr(source, 'read'):
            # Optimistically hope this is file-like
            source = PythonFile(source, mode='r')
    else:
        if use_memory_map:
            source = memory_map(source_path, mode='r')
        else:
            source = OSFile(source_path, mode='r')

    return source


cdef get_reader(object source, c_bool use_memory_map,
                shared_ptr[RandomAccessFile]* reader):
    cdef NativeFile nf

    nf = _get_native_file(source, use_memory_map)
    reader[0] = nf.get_random_access_file()


cdef get_input_stream(object source, c_bool use_memory_map,
                      shared_ptr[InputStream]* out):
    """
    Like get_reader(), but can automatically decompress, and returns
    an InputStream.
    """
    cdef:
        NativeFile nf
        unique_ptr[CCodec] codec
        shared_ptr[InputStream] input_stream
        shared_ptr[CCompressedInputStream] compressed_stream
        CompressionType compression_type

    try:
        source_path = _stringify_path(source)
    except TypeError:
        compression = None
    else:
        compression = _detect_compression(source_path)

    compression_type = _get_compression_type(compression)
    nf = _get_native_file(source, use_memory_map)
    input_stream = nf.get_input_stream()

    if compression_type != CompressionType_UNCOMPRESSED:
        check_status(CCodec.Create(compression_type, &codec))
        check_status(CCompressedInputStream.Make(codec.get(), input_stream,
                                                 &compressed_stream))
        input_stream = <shared_ptr[InputStream]> compressed_stream

    out[0] = input_stream


cdef get_writer(object source, shared_ptr[OutputStream]* writer):
    cdef NativeFile nf

    try:
        source_path = _stringify_path(source)
    except TypeError:
        if not isinstance(source, NativeFile) and hasattr(source, 'write'):
            # Optimistically hope this is file-like
            source = PythonFile(source, mode='w')
    else:
        source = OSFile(source_path, mode='w')

    if isinstance(source, NativeFile):
        nf = source
        writer[0] = nf.get_output_stream()
    else:
        raise TypeError('Unable to read from object of type: {0}'
                        .format(type(source)))


# ---------------------------------------------------------------------

cdef CompressionType _get_compression_type(object name) except *:
    if name is None or name == 'uncompressed':
        return CompressionType_UNCOMPRESSED
    elif name == 'bz2':
        return CompressionType_BZ2
    elif name == 'brotli':
        return CompressionType_BROTLI
    elif name == 'gzip':
        return CompressionType_GZIP
    elif name == 'lz4':
        return CompressionType_LZ4
    elif name == 'snappy':
        return CompressionType_SNAPPY
    elif name == 'zstd':
        return CompressionType_ZSTD
    else:
        raise ValueError('Unrecognized compression type: {}'.format(name))


def _detect_compression(path):
    if isinstance(path, six.string_types):
        if path.endswith('.bz2'):
            return 'bz2'
        elif path.endswith('.gz'):
            return 'gzip'
        elif path.endswith('.lz4'):
            return 'lz4'
        elif path.endswith('.zst'):
            return 'zstd'


def compress(object buf, codec='lz4', asbytes=False, memory_pool=None):
    """
    Compress data from buffer-like object.

    Parameters
    ----------
    buf : pyarrow.Buffer, bytes, or other object supporting buffer protocol
    codec : string, default 'lz4'
        Compression codec.
        Supported types: {'brotli, 'gzip', 'lz4', 'snappy', 'zstd'}
    asbytes : boolean, default False
        Return result as Python bytes object, otherwise Buffer
    memory_pool : MemoryPool, default None
        Memory pool to use for buffer allocations, if any

    Returns
    -------
    compressed : pyarrow.Buffer or bytes (if asbytes=True)
    """
    cdef:
        CompressionType c_codec = _get_compression_type(codec)
        unique_ptr[CCodec] compressor
        cdef CBuffer* c_buf
        cdef PyObject* pyobj
        cdef ResizableBuffer out_buf

    with nogil:
        check_status(CCodec.Create(c_codec, &compressor))

    buf = as_buffer(buf)
    c_buf = (<Buffer> buf).buffer.get()

    cdef int64_t max_output_size = (compressor.get()
                                    .MaxCompressedLen(c_buf.size(),
                                                      c_buf.data()))
    cdef uint8_t* output_buffer = NULL

    if asbytes:
        pyobj = PyBytes_FromStringAndSizeNative(NULL, max_output_size)
        output_buffer = <uint8_t*> cp.PyBytes_AS_STRING(<object> pyobj)
    else:
        out_buf = allocate_buffer(max_output_size, memory_pool=memory_pool,
                                  resizable=True)
        output_buffer = out_buf.buffer.get().mutable_data()

    cdef int64_t output_length = 0
    with nogil:
        check_status(compressor.get()
                     .Compress(c_buf.size(), c_buf.data(),
                               max_output_size, output_buffer,
                               &output_length))

    if asbytes:
        cp._PyBytes_Resize(&pyobj, <Py_ssize_t> output_length)
        return PyObject_to_object(pyobj)
    else:
        out_buf.resize(output_length)
        return out_buf


def decompress(object buf, decompressed_size=None, codec='lz4',
               asbytes=False, memory_pool=None):
    """
    Decompress data from buffer-like object.

    Parameters
    ----------
    buf : pyarrow.Buffer, bytes, or memoryview-compatible object
    decompressed_size : int64_t, default None
        If not specified, will be computed if the codec is able to determine
        the uncompressed buffer size
    codec : string, default 'lz4'
        Compression codec.
        Supported types: {'brotli, 'gzip', 'lz4', 'snappy', 'zstd'}
    asbytes : boolean, default False
        Return result as Python bytes object, otherwise Buffer
    memory_pool : MemoryPool, default None
        Memory pool to use for buffer allocations, if any

    Returns
    -------
    uncompressed : pyarrow.Buffer or bytes (if asbytes=True)
    """
    cdef:
        CompressionType c_codec = _get_compression_type(codec)
        unique_ptr[CCodec] compressor
        cdef CBuffer* c_buf
        cdef Buffer out_buf

    with nogil:
        check_status(CCodec.Create(c_codec, &compressor))

    buf = as_buffer(buf)
    c_buf = (<Buffer> buf).buffer.get()

    if decompressed_size is None:
        raise ValueError("Must pass decompressed_size for {0} codec"
                         .format(codec))

    cdef int64_t output_size = decompressed_size
    cdef uint8_t* output_buffer = NULL

    if asbytes:
        pybuf = cp.PyBytes_FromStringAndSize(NULL, output_size)
        output_buffer = <uint8_t*> cp.PyBytes_AS_STRING(pybuf)
    else:
        out_buf = allocate_buffer(output_size, memory_pool=memory_pool)
        output_buffer = out_buf.buffer.get().mutable_data()

    with nogil:
        check_status(compressor.get()
                     .Decompress(c_buf.size(), c_buf.data(),
                                 output_size, output_buffer))

    return pybuf if asbytes else out_buf


def input_stream(source, compression='detect', buffer_size=None):
    """
    Create an Arrow input stream.

    Parameters
    ----------
    source: str, Path, buffer, file-like object, ...
        The source to open for reading
    compression: str or None
        The compression algorithm to use for on-the-fly decompression.
        If "detect" and source is a file path, then compression will be
        chosen based on the file extension.
        If None, no compression will be applied.
        Otherwise, a well-known algorithm name must be supplied (e.g. "gzip")
    buffer_size: int, default None
        If None or 0, no buffering will happen.  Otherwise the size of the
        temporary read buffer.
    """
    cdef NativeFile stream

    try:
        source_path = _stringify_path(source)
    except TypeError:
        source_path = None

    if isinstance(source, NativeFile):
        stream = source
    elif source_path is not None:
        stream = OSFile(source_path, 'r')
    elif isinstance(source, (Buffer, memoryview)):
        stream = BufferReader(as_buffer(source))
    elif isinstance(source, BufferedIOBase):
        stream = PythonFile(source, 'r')
    elif file_type is not None and isinstance(source, file_type):
        # Python 2 file type
        stream = PythonFile(source, 'r')
    else:
        raise TypeError("pa.input_stream() called with instance of '{}'"
                        .format(source.__class__))

    if compression == 'detect':
        compression = _detect_compression(source_path)

    if buffer_size is not None and buffer_size != 0:
        stream = BufferedInputStream(stream, buffer_size)

    if compression is not None:
        stream = CompressedInputStream(stream, compression)

    return stream


def output_stream(source, compression='detect', buffer_size=None):
    """
    Create an Arrow output stream.

    Parameters
    ----------
    source: str, Path, buffer, file-like object, ...
        The source to open for writing
    compression: str or None
        The compression algorithm to use for on-the-fly compression.
        If "detect" and source is a file path, then compression will be
        chosen based on the file extension.
        If None, no compression will be applied.
        Otherwise, a well-known algorithm name must be supplied (e.g. "gzip")
    buffer_size: int, default None
        If None or 0, no buffering will happen.  Otherwise the size of the
        temporary write buffer.
    """
    cdef NativeFile stream

    try:
        source_path = _stringify_path(source)
    except TypeError:
        source_path = None

    if isinstance(source, NativeFile):
        stream = source
    elif source_path is not None:
        stream = OSFile(source_path, 'w')
    elif isinstance(source, (Buffer, memoryview)):
        stream = FixedSizeBufferWriter(as_buffer(source))
    elif isinstance(source, BufferedIOBase):
        stream = PythonFile(source, 'w')
    elif file_type is not None and isinstance(source, file_type):
        # Python 2 file type
        stream = PythonFile(source, 'w')
    else:
        raise TypeError("pa.output_stream() called with instance of '{}'"
                        .format(source.__class__))

    if compression == 'detect':
        compression = _detect_compression(source_path)

    if buffer_size is not None and buffer_size != 0:
        stream = BufferedOutputStream(stream, buffer_size)

    if compression is not None:
        stream = CompressedOutputStream(stream, compression)

    return stream