Source Code for Module skytools.gzlog

 1   
 2  """Atomic append of gzipped data. 
 3   
 4  The point is - if several gzip streams are concated, they 
 5  are read back as one whose stream. 
 6  """ 
 7   
 8  import gzip 
 9  from cStringIO import StringIO 
10   
11  __all__ = ['gzip_append'] 
12   
13  # 
14  # gzip storage 
15  # 
16 -def gzip_append(filename, data, level = 6): 
17      """Append a block of data to file with safety checks.""" 
18   
19      # compress data 
20      buf = StringIO() 
21      g = gzip.GzipFile(fileobj = buf, compresslevel = level, mode = "w") 
22      g.write(data) 
23      g.close() 
24      zdata = buf.getvalue() 
25       
26      # append, safely 
27      f = open(filename, "a+", 0) 
28      f.seek(0, 2) 
29      pos = f.tell() 
30      try: 
31          f.write(zdata) 
32          f.close() 
33      except Exception, ex: 
34          # rollback on error 
35          f.seek(pos, 0) 
36          f.truncate() 
37          f.close() 
38          raise ex 
39