bes  Updated for version 3.19.1
BESUncompressManager3.cc
1 // BESUncompressManager3.cc
2 
3 // This file is part of bes, A C++ back-end server implementation framework
4 // for the OPeNDAP Data Access Protocol.
5 
6 // Copyright (c) 2012 OPeNDAP, Inc
7 // Author: James Gallagher <jgallagher@opendap.org>
8 // Patrick West <pwest@ucar.edu> and
9 // Jose Garcia <jgarcia@ucar.edu>
10 //
11 // This library is free software; you can redistribute it and/or
12 // modify it under the terms of the GNU Lesser General Public
13 // License as published by the Free Software Foundation; either
14 // version 2.1 of the License, or (at your option) any later version.
15 //
16 // This library is distributed in the hope that it will be useful,
17 // but WITHOUT ANY WARRANTY; without even the implied warranty of
18 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 // Lesser General Public License for more details.
20 //
21 // You should have received a copy of the GNU Lesser General Public
22 // License along with this library; if not, write to the Free Software
23 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 //
25 // You can contact University Corporation for Atmospheric Research at
26 // 3080 Center Green Drive, Boulder, CO 80301
27 
28 #include <sstream>
29 
30 using std::istringstream;
31 
32 #include "BESUncompressManager3.h"
33 #include "BESUncompress3GZ.h"
34 #include "BESUncompress3BZ2.h"
35 #include "BESUncompress3Z.h"
36 
37 #include "BESFileLockingCache.h"
38 
39 #include "BESInternalError.h"
40 #include "BESDebug.h"
41 
42 #include "TheBESKeys.h"
43 
44 BESUncompressManager3 *BESUncompressManager3::_instance = 0;
45 
55 BESUncompressManager3::BESUncompressManager3()
56 {
60 }
61 
71 bool BESUncompressManager3::add_method(const string &name, p_bes_uncompress method)
72 {
73  BESUncompressManager3::UCIter i;
74  i = _uncompress_list.find(name);
75  if (i == _uncompress_list.end()) {
76  _uncompress_list[name] = method;
77  return true;
78  }
79  return false;
80 }
81 
90 p_bes_uncompress BESUncompressManager3::find_method(const string &name)
91 {
92  BESUncompressManager3::UCIter i;
93  i = _uncompress_list.find(name);
94  if (i != _uncompress_list.end()) {
95  return (*i).second;
96  }
97  return 0;
98 }
99 
132 bool BESUncompressManager3::uncompress(const string &src, string &cache_file, BESFileLockingCache *cache)
133 {
134  BESDEBUG( "uncompress2", "BESUncompressManager3::uncompress() - src: " << src << endl );
135 
146  if (cache == NULL) {
147  std::ostringstream oss;
148  oss << "BESUncompressManager3::" << __func__ << "() - ";
149  oss << "The supplied Cache object is NULL. Decompression Requires An Operational Cache.";
150  throw BESInternalError(oss.str(), __FILE__, __LINE__);
151  }
152 
153  // All compressed files have a 'dot extension'.
154  string::size_type dot = src.rfind(".");
155  if (dot == string::npos) {
156  BESDEBUG( "uncompress2", "BESUncompressManager3::uncompress() - no file extension" << endl );
157  return false;
158  }
159 
160  string ext = src.substr(dot + 1, src.length() - dot);
161 
162  // If there's no match for the extension, the file is not compressed and we return false.
163  // Otherwise, 'p' points to a function that uncompresses the data.
164  p_bes_uncompress p = find_method(ext);
165  if (!p) {
166  BESDEBUG( "uncompress2", "BESUncompressManager3::uncompress() - not compressed " << endl );
167  return false;
168  }
169 
170  // Get the name of the file in the cache (either the code finds this file or
171  // or it makes it).
172  cache_file = cache->get_cache_file_name(src);
173 
174  try {
175  BESDEBUG( "uncompress2", "BESUncompressManager3::uncompress() - is cached? " << src << endl );
176 
177  int fd;
178  if (cache->get_read_lock(cache_file, fd)) {
179  BESDEBUG( "uncompress", "BESUncompressManager3::uncompress() - cached hit: " << cache_file << endl );
180  return true;
181  }
182 
183  // Now we actually try to uncompress the file, given that there's not a decomp'd version
184  // in the cache. First make an empty file and get an exclusive lock on it.
185  if (cache->create_and_lock(cache_file, fd)) {
186  BESDEBUG( "uncompress", "BESUncompressManager3::uncompress() - caching " << cache_file << endl );
187 
188  // uncompress. Make sure that the decompression function does not close
189  // the file descriptor.
190  p(src, fd);
191 
192  // Change the exclusive lock on the new file to a shared lock. This keeps
193  // other processes from purging the new file and ensures that the reading
194  // process can use it.
195  cache->exclusive_to_shared_lock(fd);
196 
197  // Now update the total cache size info and purge if needed. The new file's
198  // name is passed into the purge method because this process cannot detect its
199  // own lock on the file.
200  unsigned long long size = cache->update_cache_info(cache_file);
201  if (cache->cache_too_big(size))
202  cache->update_and_purge(cache_file);
203 
204  return true;
205  }
206  else {
207  if (cache->get_read_lock(cache_file, fd)) {
208  BESDEBUG( "uncompress", "BESUncompressManager3::uncompress() - cached hit: " << cache_file << endl );
209  return true;
210  }
211  }
212 
213  return false;
214  }
215  catch (...) {
216  BESDEBUG( "uncompress", "BESUncompressManager3::uncompress() - caught exception, unlocking cache and re-throw." << endl );
217  cache->unlock_cache();
218  throw;
219  }
220 
221  return false; // gcc warns without this
222 }
223 
231 void BESUncompressManager3::dump(ostream &strm) const
232 {
233  strm << BESIndent::LMarg << "BESUncompressManager3::dump - (" << (void *) this << ")" << endl;
234  BESIndent::Indent();
235  if (_uncompress_list.size()) {
236  strm << BESIndent::LMarg << "registered uncompression methods:" << endl;
237  BESIndent::Indent();
238  BESUncompressManager3::UCIter i = _uncompress_list.begin();
239  BESUncompressManager3::UCIter ie = _uncompress_list.end();
240  for (; i != ie; i++) {
241  strm << BESIndent::LMarg << (*i).first << endl;
242  }
243  BESIndent::UnIndent();
244  }
245  else {
246  strm << BESIndent::LMarg << "registered uncompress methods: none" << endl;
247  }
248  BESIndent::UnIndent();
249 }
250 
252 BESUncompressManager3::TheManager()
253 {
254  if (_instance == 0) {
255  _instance = new BESUncompressManager3;
256  }
257  return _instance;
258 }
virtual bool cache_too_big(unsigned long long current_size) const
look at the cache size; is it too large? Look at the cache size and see if it is too big...
virtual void dump(ostream &strm) const
dumps information about this object
exception thrown if inernal error encountered
virtual bool create_and_lock(const string &target, int &fd)
Create a file in the cache and lock it for write access.
static void uncompress(const string &src, int fd)
uncompress a file with the .gz file extension
virtual bool uncompress(const string &src, string &target, BESFileLockingCache *cache)
If the file &#39;src&#39; should be uncompressed, do so and return a new file name on the value-result param ...
Implementation of a caching mechanism for compressed data.
List of all registered decompression methods.
virtual p_bes_uncompress find_method(const string &name)
returns the uncompression method specified
virtual string get_cache_file_name(const string &src, bool mangle=true)
virtual bool get_read_lock(const string &target, int &fd)
Get a read-only lock on the file if it exists.
virtual void update_and_purge(const string &new_file)
Purge files from the cache.
virtual unsigned long long update_cache_info(const string &target)
Update the cache info file to include &#39;target&#39;.
virtual void exclusive_to_shared_lock(int fd)
Transfer from an exclusive lock to a shared lock.
static void uncompress(const string &src, int dest_fd)
uncompress a file with the .gz file extension
virtual bool add_method(const string &name, p_bes_uncompress method)
create_and_lock a uncompress method to the list
static void uncompress(const string &src, int fd)
uncompress a file with the .bz2 file extension