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[auf_roundup.git] / roundup / cgi / ZTUtils / .svn / text-base / Batch.py.svn-base
1 ##############################################################################
2 #
3 # Copyright (c) 2001 Zope Corporation and Contributors. All Rights Reserved.
4
5 # This software is subject to the provisions of the Zope Public License,
6 # Version 2.0 (ZPL).  A copy of the ZPL should accompany this distribution.
7 # THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
8 # WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
9 # WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
10 # FOR A PARTICULAR PURPOSE
11
12 ##############################################################################
13 __doc__='''Batch class, for iterating over a sequence in batches
14
15 $Id: Batch.py,v 1.3 2004-02-11 23:55:09 richard Exp $'''
16 __docformat__ = 'restructuredtext'
17 __version__='$Revision: 1.3 $'[11:-2]
18
19 class LazyPrevBatch:
20     def __of__(self, parent):
21         return Batch(parent._sequence, parent._size,
22                      parent.first - parent._size + parent.overlap, 0,
23                      parent.orphan, parent.overlap)
24
25 class LazyNextBatch:
26     def __of__(self, parent):
27         try: parent._sequence[parent.end]
28         except IndexError: return None
29         return Batch(parent._sequence, parent._size,
30                      parent.end - parent.overlap, 0,
31                      parent.orphan, parent.overlap)
32
33 class LazySequenceLength:
34     def __of__(self, parent):
35         parent.sequence_length = l = len(parent._sequence)
36         return l
37
38 class Batch:
39     """Create a sequence batch"""
40     __allow_access_to_unprotected_subobjects__ = 1
41
42     previous = LazyPrevBatch()
43     next = LazyNextBatch()
44     sequence_length = LazySequenceLength()
45
46     def __init__(self, sequence, size, start=0, end=0,
47                  orphan=0, overlap=0):
48         '''Encapsulate "sequence" in batches of "size".
49
50         Arguments: "start" and "end" are 0-based indexes into the
51         sequence.  If the next batch would contain no more than
52         "orphan" elements, it is combined with the current batch.
53         "overlap" is the number of elements shared by adjacent
54         batches.  If "size" is not specified, it is computed from
55         "start" and "end".  Failing that, it is 7.
56
57         Attributes: Note that the "start" attribute, unlike the
58         argument, is a 1-based index (I know, lame).  "first" is the
59         0-based index.  "length" is the actual number of elements in
60         the batch.
61
62         "sequence_length" is the length of the original, unbatched, sequence
63         '''
64
65         start = start + 1
66
67         start,end,sz = opt(start,end,size,orphan,sequence)
68
69         self._sequence = sequence
70         self.size = sz
71         self._size = size
72         self.start = start
73         self.end = end
74         self.orphan = orphan
75         self.overlap = overlap
76         self.first = max(start - 1, 0)
77         self.length = self.end - self.first
78         if self.first == 0:
79             self.previous = None
80
81
82     def __getitem__(self, index):
83         if index < 0:
84             if index + self.end < self.first: raise IndexError, index
85             return self._sequence[index + self.end]
86         
87         if index >= self.length: raise IndexError, index
88         return self._sequence[index + self.first]
89
90     def __len__(self):
91         return self.length
92
93 def opt(start,end,size,orphan,sequence):
94     if size < 1:
95         if start > 0 and end > 0 and end >= start:
96             size=end+1-start
97         else: size=7
98
99     if start > 0:
100
101         try: sequence[start-1]
102         except IndexError: start=len(sequence)
103
104         if end > 0:
105             if end < start: end=start
106         else:
107             end=start+size-1
108             try: sequence[end+orphan-1]
109             except IndexError: end=len(sequence)
110     elif end > 0:
111         try: sequence[end-1]
112         except IndexError: end=len(sequence)
113         start=end+1-size
114         if start - 1 < orphan: start=1
115     else:
116         start=1
117         end=start+size-1
118         try: sequence[end+orphan-1]
119         except IndexError: end=len(sequence)
120     return start,end,size