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4 # without modification, are permitted provided that the following
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12 # copyright notice, this list of conditions and the following
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32 # or implied, of GRNET S.A.
34 from os import SEEK_CUR, SEEK_SET, fsync
35 from errno import ENOENT
48 _zeros += '\0' * (nr - size)
56 def file_sync_write_chunks(openfile, chunksize, offset, chunks, size=None):
57 """Write given chunks to the given buffered file object.
58 Writes never span across chunk boundaries.
59 If size is given stop after or pad until size bytes have been written.
61 fwrite = openfile.write
66 seek(offset * chunksize)
69 for x in xrange(offset):
70 fwrite(zeros(chunksize))
72 cursize = offset * chunksize
77 seek(padding -1, SEEK_CUR)
80 fwrite(buffer(zeros(chunksize), 0, padding))
81 if size is not None and cursize + chunksize >= size:
82 chunk = chunk[:chunksize - (cursize - size)]
87 padding = chunksize - len(chunk)
89 padding = size - cursize if size is not None else 0
93 q, r = divmod(padding, chunksize)
95 fwrite(zeros(chunksize))
96 fwrite(buffer(zeros(chunksize), 0, r))
99 def file_sync_read_chunks(openfile, chunksize, nr, offset=0):
100 """Read and yield groups of chunks from a buffered file object at offset.
101 Reads never span accros chunksize boundaries.
103 fread = openfile.read
104 remains = offset * chunksize
133 class ContextFile(object):
134 __slots__ = ("name", "fdesc", "create")
136 def __init__(self, name, create=0):
145 fdesc = open(name, 'rb+')
147 if not self.create or e.errno != ENOENT:
149 fdesc = open(name, 'w+')
154 def __exit__(self, exc, arg, trace):
156 if fdesc is not None:
158 # fsync(fdesc.fileno())
160 return False # propagate exceptions
162 def seek(self, offset, whence=SEEK_SET):
163 return self.fdesc.seek(offset, whence)
166 return self.fdesc.tell()
168 def truncate(self, size):
169 self.fdesc.truncate(size)
171 def sync_write(self, data):
173 self.fdesc.write(data)
175 def sync_write_chunks(self, chunksize, offset, chunks, size=None):
177 return file_sync_write_chunks(self.fdesc, chunksize, offset, chunks, size)
179 def sync_read(self, size):
180 read = self.fdesc.read
189 def sync_read_chunks(self, chunksize, nr, offset=0):
190 return file_sync_read_chunks(self.fdesc, chunksize, nr, offset)