File:
[LON-CAPA] /
loncom /
ConfigFileEdit.pm
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1.1:
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Tue Nov 25 12:09:57 2003 UTC (20 years, 10 months ago) by
foxr
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CVS tags:
version_1_0_99,
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Configuration file editor: This module maintains a file consisting of colon
separated fields as an array of lines that is indexed by a single selected field
The indexing is done by maintaining a hash of index value -> line array index.
This allows keyed lookups in constant time as well as editing that preserves
lines with comments and so on. Still to do:
- Write modified file.
See the cfgedittests directory for the test suite associated with this module.
Please add to those tests if you add functionality.
1: #
2: #
3: #
4: # Copyright Michigan State University Board of Trustees
5: #
6: # This file is part of the LearningOnline Network with CAPA (LON-CAPA).
7: #
8: # LON-CAPA is free software; you can redistribute it and/or modify
9: # it under the terms of the GNU General Public License as published by
10: # the Free Software Foundation; either version 2 of the License, or
11: # (at your option) any later version.
12: #
13: # LON-CAPA is distributed in the hope that it will be useful,
14: # but WITHOUT ANY WARRANTY; without even the implied warranty of
15: # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16: # GNU General Public License for more details.
17: #
18: # You should have received a copy of the GNU General Public License
19: # along with LON-CAPA; if not, write to the Free Software
20: # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21: #
22: # /home/httpd/html/adm/gpl.txt
23: #
24: # http://www.lon-capa.org/
25: #
26:
27: package ConfigFileEdit;
28:
29: #
30: # Module to read/edit configuration files.
31: # See the POD at the bottom of the file for more information.
32:
33: #------------------------------ internal utility functions ----------
34:
35: #
36: # Comment
37: # Returns true if the line is completely a comment.
38: # Paramter:
39: # line
40: # Contents of a configuration file line.
41: #
42: sub Comment {
43: my $line = shift;
44:
45: # Leading whitespace followed by a #..
46:
47: if ($line =~ /^[' ',\t]*\#/) {
48: return 1;
49: }
50: # Solely whitespace or empty line.
51:
52: $line =~ s/[' ',\t]//g;
53: return ($line eq "");
54:
55: }
56:
57: #
58: # Field
59: # Return the value of a field in the line. Leading whitespace is trimmed
60: # from the first key (key 0).
61: # Parameters:
62: # line
63: # Line from which to extract the field.
64: #
65: # idx
66: # Index of the field to extract.
67: #
68: sub Field {
69: my $line = shift;
70: my $idx = shift;
71:
72: $line =~ s/(^ *)|(^\t*)//;
73:
74: my @fields = split(/:/, $line);
75:
76: return $fields[$idx];
77: }
78: #
79: # Index:
80: # Return a reference to a hash that indexes a line array.
81: # The hash is keyed on a field in the line array lines
82: # Each hash entry is the line number of the line in which
83: # that key value appears. Note that at present, keys must be
84: # unique.
85: # Parameters:
86: # $array - Reference to a line array.
87: # $idxfield - Field number to index on (0 is the first field).
88: # Returns:
89: # Reference to the index hash:
90: sub Index {
91: my $array = shift;
92: my $idxfield = shift;
93:
94: my %hash;
95: for(my $l = 0; $l < scalar(@$array); $l++) {
96: chomp $array->[$l]; # Ensure lines have no \n's.
97: my $line = $array->[$l];
98: if(!Comment($line)) {
99: my $keyvalue = Field($line, $idxfield);
100: $hash{$keyvalue} = $l;
101: }
102: }
103:
104:
105: return \%hash;
106: }
107:
108:
109: #------------------------------- public functions --------------------
110: #
111: # new
112: # Create a new configuration file editor object.
113: # configuration files are : separated fields that
114: # may have comments, blank lines and trailing comments.
115: # comments are indicated by #"s.
116: # Parameters:
117: # filename
118: # Name of file to open.
119: # indexfield
120: # Select the field to index the file by.
121: #
122: #
123: sub new {
124: my $class = shift;
125: my $filename = shift;
126: my $indexfield = shift;
127:
128: # Open the configuration file. Failure results in the return
129: # of an undef.
130: # Note we dont' need to hold on to the file handle after the file
131: # is read in.
132:
133: open(CONFIGFILE, "< $filename")
134: or return undef;
135:
136:
137: # Read the file into a line array:
138:
139: my @linearray = <CONFIGFILE>;
140: close(CONFIGFILE);
141:
142:
143: # Build the key to lines hash: this hash
144: # is keyed on item $indexfield of the line
145: # and contains the line number of the actual line.
146:
147: my $hashref = Index(\@linearray, $indexfield);
148:
149:
150: # Build the object hash, bless it and return.
151:
152: my $self = { Filename => $filename,
153: Indexfield => $indexfield,
154: LineArray => \@linearray,
155: KeyToLines => $hashref};
156:
157: bless ($self, $class);
158:
159: return $self;
160:
161: }
162: #
163: # Append an element to the configuration file array.
164: # The element is placed at the end of the array. If the element is not
165: # a comment. The key is added to the index.
166: #
167: # Parameters:
168: # $self - Reference to our member hash.
169: # $line - A line to add to the config file.
170: sub Append {
171: my $self = shift;
172: my $line = shift;
173:
174: # Regardless, the line is added to the config file.
175:
176: my $linearray = ($self->{LineArray});
177: push(@$linearray, $line); # Append the line.
178: my $newindex = @$linearray - 1; # Index of new line.
179:
180: # If the line is not a comment, pull out the desired field and add
181: # it to the line index hash.
182:
183: if(!Comment($line)) {
184: my $field = Field($line, $self->{Indexfield});
185: $self->{KeyToLines}->{$field} = $newindex;
186: }
187: }
188: #
189: # Find a non comment line by looking it up by key.
190: # Parameters:
191: # $self - Reference to our member hash.
192: # $key - Lookup key.
193: # Returns:
194: # Contents of the line or undef if there is no match.
195: #
196: sub Find {
197: my $self = shift;
198: my $key = shift;
199:
200: my $hash = $self->{KeyToLines};
201: if(defined($hash->{$key})) {
202: my $lines = $self->{LineArray};
203: return $lines->[$hash->{$key}];
204: } else {
205: return undef;
206: }
207: }
208: #
209: # Return the number of lines in the current configuration file.
210: # Note that this count includes the comment lines. To
211: # Get the non comment lines the best thing is to iterate through the
212: # keys of the KeyToLines hash.
213: # Parameters:
214: # $self - Reference to member data hash for the object.
215: #
216: sub LineCount {
217: my $self = shift;
218: my $lines = $self->{LineArray};
219: my $count = @$lines;
220: return $count;
221: }
222: #
223: # Delete a line from the configuration file.
224: # Note at present, there is no support for deleting comment lines.
225: # The line is deleted, from the array. All lines following are slid back
226: # one index and the index hash is rebuilt.
227: # Parameters:
228: # $self - Reference to the member data hash for the object.
229: # $key - key value of the line to delete.
230: # NOTE:
231: # If a line matching this key does not exist, this is a no-op.
232: #
233: sub DeleteLine {
234: my $self = shift;
235: my $key = shift;
236:
237: my $lines = $self->{LineArray};
238: my $index = $self->{KeyToLines};
239: my $lastidx = $self->LineCount() - 1; # Index of last item.
240:
241:
242: my @temp = @$lines;
243:
244:
245: if(! defined($index->{$key})) { # bail if no match.
246: return;
247: }
248: my $itemno = $index->{$key}; # Index of item to delete.
249:
250: if ($itemno != $lastidx) { # need to slide and reindex.
251: @$temp[$itemno..($lastidx-1)] =
252: @$temp[$itemno+1..$lastidx];
253: $#temp = $lastidx - 1;
254: $self->{KeyToLines} = Index(\@temp, $self->{Indexfield});
255: } else { # just need to truncate
256: $#temp = $lastidx-1; # the line array...
257: delete($index->{$key}); # and remove from index hash.
258: }
259: $self->{LineArray} = \@temp;
260:
261:
262: }
263: #
264: # Replace a line in the configuration file:
265: # The line is looked up by index.
266: # The line is replaced by the one passed in... note if the line
267: # is a comment, the index is just deleted!!
268: # The index for the line is replaced with the new value of the key field
269: # (it's possible the key field changed).
270: #
271: # Parameters:
272: # $self - Reference to the object's member data hash.
273: # $key - Lookup key.
274: # $line - New line.
275: # NOTE:
276: # If there is no line with the key $key, this reduces to an append.
277: #
278: sub ReplaceLine {
279: my $self = shift;
280: my $key = shift;
281: my $line = shift;
282:
283: my $hashref = $self->{KeyToLines};
284: if(!defined $hashref->{$key}) {
285: $self->Append($line);
286: } else {
287: my $l = $hashref->{$key};
288: my $lines = $self->{LineArray};
289: $lines->[$l] = $line; # Replace old line.
290: delete $hashref->{$key}; # get rid of the old index.
291: if(!Comment($line)) { # Index this line only if not comment!
292: my $newkey = Field($line, $self->{Indexfield});
293: $hashref->{$newkey} = $l;
294: }
295: }
296: }
297: 1;
298:
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