Synnefo

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from os import SEEK_CUR, SEEK_SET

from rados import Ioctx, ObjectNotFound

_zeros = ''

def zeros(nr):

    global _zeros

    size = len(_zeros)

    if nr == size:

        return _zeros

    if nr > size:

        _zeros += '\0' * (nr - size)

        return _zeros

    if nr < size:

        _zeros = _zeros[:nr]

        return _zeros

def file_sync_write_chunks(radosobject, chunksize, offset, chunks, size=None):

    """Write given chunks to the given buffered file object.

       Writes never span across chunk boundaries.

       If size is given stop after or pad until size bytes have been written.

    """

    padding = 0

    cursize = chunksize * offset

    radosobject.seek(cursize)

    for chunk in chunks:

        if padding:

            radosobject.sync_write(buffer(zeros(chunksize), 0, padding))

        if size is not None and cursize + chunksize >= size:

            chunk = chunk[:chunksize - (cursize - size)]

            radosobject.sync_write(chunk)

            cursize += len(chunk)

            break

        radosobject.sync_write(chunk)

        padding = chunksize - len(chunk)

    padding = size - cursize if size is not None else 0

    if padding <= 0:

        return

    q, r = divmod(padding, chunksize)

    for x in xrange(q):

        radosobject.sunc_write(zeros(chunksize))

    radosobject.sync_write(buffer(zeros(chunksize), 0, r))

def file_sync_read_chunks(radosobject, chunksize, nr, offset=0):

    """Read and yield groups of chunks from a buffered file object at offset.

       Reads never span accros chunksize boundaries.

    """

    radosobject.seek(offset * chunksize)

    while nr:

        remains = chunksize

        chunk = ''

        while 1:

            s = radosobject.sync_read(remains)

            if not s:

                if chunk:

                    yield chunk

                return

            chunk += s

            remains -= len(s)

            if remains <= 0:

                break

        yield chunk

        nr -= 1

class RadosObject(object):

    __slots__ = ("name", "ioctx", "create", "offset")

    def __init__(self, name, ioctx, create=0):

        self.name = name

        self.ioctx = ioctx

        self.create = create

        self.offset = 0

        #self.dirty = 0

    def __enter__(self):

        return self

    def __exit__(self, exc, arg, trace):

        return False

    def seek(self, offset, whence=SEEK_SET):

        if whence == SEEK_CUR:

            offset += self.offset

        self.offset = offset

        return offset

    def tell(self):

        return self.offset

    def truncate(self, size):

        self.ioctx.trunc(self.name, size)

    def sync_write(self, data):

        #self.dirty = 1

        self.ioctx.write(self.name, data, self.offset)

        self.offset += len(data)

    def sync_write_chunks(self, chunksize, offset, chunks, size=None):

        #self.dirty = 1

        return file_sync_write_chunks(self, chunksize, offset, chunks, size)

    def sync_read(self, size):

        read = self.ioctx.read

        data = ''

        datalen = 0

        while 1:

            try:

                s = read(self.name, size-datalen, self.offset)

            except ObjectNotFound:

                s = None

            if not s:

                break

            data += s

            datalen += len(s)

            self.offset += len(s)

            if datalen >= size:

                break

        return data

    def sync_read_chunks(self, chunksize, nr, offset=0):

        return file_sync_read_chunks(self, chunksize, nr, offset)