libs/pbd/file_manager.cc

   1 /*
   2     Copyright (C) 2010 Paul Davis
   3
   4     This program is free software; you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation; either version 2 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12     GNU General Public License for more details.
  13
  14     You should have received a copy of the GNU General Public License
  15     along with this program; if not, write to the Free Software
  16     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17
  18 */
  19
  20 #include <sys/time.h>
  21 #include <sys/resource.h>
  22 #include <sys/types.h>
  23 #include <sys/stat.h>
  24 #include <fcntl.h>
  25 #include <cassert>
  26 #include <iostream>
  27 #include <cstdio>
  28
  29 #ifdef __APPLE__
  30 #include <mach/mach_time.h>
  31 #endif
  32
  33 #include "pbd/compose.h"
  34 #include "pbd/file_manager.h"
  35 #include "pbd/debug.h"
  36
  37 using namespace std;
  38 using namespace PBD;
  39
  40 FileManager* FileDescriptor::_manager;
  41
  42 FileManager::FileManager ()
  43         : _open (0)
  44 {
  45         struct rlimit rl;
  46         int const r = getrlimit (RLIMIT_NOFILE, &rl);
  47
  48         /* XXX: this is a bit arbitrary */
  49         if (r == 0) {
  50                 _max_open = rl.rlim_cur - 64;
  51         } else {
  52                 _max_open = 256;
  53         }
  54
  55         DEBUG_TRACE (DEBUG::FileManager, string_compose ("FileManager can open up to %1 files.\n", _max_open));
  56 }
  57
  58 void
  59 FileManager::add (FileDescriptor* d)
  60 {
  61         Glib::Mutex::Lock lm (_mutex);
  62         _files.push_back (d);
  63 }
  64
  65 /** @return true on error, otherwise false */
  66 bool
  67 FileManager::allocate (FileDescriptor* d)
  68 {
  69         Glib::Mutex::Lock lm (_mutex);
  70
  71         if (!d->is_open()) {
  72
  73                 /* this file needs to be opened */
  74
  75                 if (_open == _max_open) {
  76
  77                         /* We already have the maximum allowed number of files opened, so we must try to close one.
  78                            Find the unallocated, open file with the lowest last_used time.
  79                         */
  80
  81                         double lowest_last_used = DBL_MAX;
  82                         list<FileDescriptor*>::iterator oldest = _files.end ();
  83
  84                         for (list<FileDescriptor*>::iterator i = _files.begin(); i != _files.end(); ++i) {
  85                                 if ((*i)->is_open() && (*i)->_refcount == 0) {
  86                                         if ((*i)->_last_used < lowest_last_used) {
  87                                                 lowest_last_used = (*i)->_last_used;
  88                                                 oldest = i;
  89                                         }
  90                                 }
  91                         }
  92
  93                         if (oldest == _files.end()) {
  94                                 /* no unallocated and open files exist, so there's nothing we can do */
  95                                 return true;
  96                         }
  97
  98                         close (*oldest);
  99                         DEBUG_TRACE (
 100                                 DEBUG::FileManager,
 101                                 string_compose (
 102                                         "closed file for %1 to release file handle; now have %2 of %3 open\n",
 103                                         (*oldest)->_path, _open, _max_open
 104                                         )
 105                                 );
 106                 }
 107
 108                 if (d->open ()) {
 109                         DEBUG_TRACE (DEBUG::FileManager, string_compose ("open of %1 failed.\n", d->_path));
 110                         return true;
 111                 }
 112
 113                 _open++;
 114
 115                 DEBUG_TRACE (DEBUG::FileManager, string_compose ("opened file for %1; now have %2 of %3 open.\n", d->_path, _open, _max_open));
 116         }
 117
 118 #ifdef __APPLE__
 119         d->_last_used = mach_absolute_time();
 120 #else
 121         struct timespec t;
 122         clock_gettime (CLOCK_MONOTONIC, &t);
 123         d->_last_used = t.tv_sec + (double) t.tv_nsec / 10e9;
 124 #endif
 125
 126         d->_refcount++;
 127
 128         return false;
 129 }
 130
 131 /** Tell FileManager that a FileDescriptor is no longer needed for a given handle */
 132 void
 133 FileManager::release (FileDescriptor* d)
 134 {
 135         Glib::Mutex::Lock lm (_mutex);
 136
 137         d->_refcount--;
 138         assert (d->_refcount >= 0);
 139 }
 140
 141 /** Remove a file from our lists.  It will be closed if it is currently open. */
 142 void
 143 FileManager::remove (FileDescriptor* d)
 144 {
 145         Glib::Mutex::Lock lm (_mutex);
 146
 147         if (d->is_open ()) {
 148                 close (d);
 149                 DEBUG_TRACE (
 150                         DEBUG::FileManager,
 151                         string_compose ("closed file for %1; file is being removed; now have %2 of %3 open\n", d->_path, _open, _max_open)
 152                         );
 153         }
 154
 155         _files.remove (d);
 156 }
 157
 158 void
 159 FileManager::close (FileDescriptor* d)
 160 {
 161         /* we must have a lock on our mutex */
 162
 163         d->close ();
 164         d->Closed (); /* EMIT SIGNAL */
 165         _open--;
 166 }
 167
 168 FileDescriptor::FileDescriptor (string const & n, bool w)
 169         : _refcount (0)
 170         , _last_used (0)
 171         , _path (n)
 172         , _writeable (w)
 173 {
 174
 175 }
 176
 177 FileManager*
 178 FileDescriptor::manager ()
 179 {
 180         if (_manager == 0) {
 181                 _manager = new FileManager;
 182         }
 183
 184         return _manager;
 185 }
 186
 187 /** Release a previously allocated handle to this file */
 188 void
 189 FileDescriptor::release ()
 190 {
 191         manager()->release (this);
 192 }
 193
 194
 195
 196 /** @param n Filename.
 197  *  @param w true to open writeable, otherwise false.
 198  *  @param m Open mode for the file.
 199  */
 200
 201 FdFileDescriptor::FdFileDescriptor (string const & n, bool w, mode_t m)
 202         : FileDescriptor (n, w)
 203         , _fd (-1)
 204         , _mode (m)
 205 {
 206         manager()->add (this);
 207 }
 208
 209 FdFileDescriptor::~FdFileDescriptor ()
 210 {
 211         manager()->remove (this);
 212 }
 213
 214 bool
 215 FdFileDescriptor::is_open () const
 216 {
 217         /* we must have a lock on the FileManager's mutex */
 218
 219         return _fd != -1;
 220 }
 221
 222 bool
 223 FdFileDescriptor::open ()
 224 {
 225         /* we must have a lock on the FileManager's mutex */
 226
 227         _fd = ::open (_path.c_str(), _writeable ? (O_RDWR | O_CREAT) : O_RDONLY, _mode);
 228         return (_fd == -1);
 229 }
 230
 231 void
 232 FdFileDescriptor::close ()
 233 {
 234         /* we must have a lock on the FileManager's mutex */
 235
 236         ::close (_fd);
 237         _fd = -1;
 238 }
 239
 240 /** @return fd, or -1 on error */
 241 int
 242 FdFileDescriptor::allocate ()
 243 {
 244         bool const f = manager()->allocate (this);
 245         if (f) {
 246                 return -1;
 247         }
 248
 249         /* this is ok thread-wise because allocate () has incremented
 250            the Descriptor's refcount, so the file will not be closed
 251         */
 252         return _fd;
 253 }
 254
 255
 256 void
 257 FileDescriptor::set_path (const string& p)
 258 {
 259         _path = p;
 260 }
 261
 262 /** @param n Filename.
 263  *  @param w true to open writeable, otherwise false.
 264  */
 265
 266 StdioFileDescriptor::StdioFileDescriptor (string const & n, std::string const & m)
 267         : FileDescriptor (n, false)
 268         , _file (0)
 269         , _mode (m)
 270 {
 271         manager()->add (this);
 272 }
 273
 274 StdioFileDescriptor::~StdioFileDescriptor ()
 275 {
 276         manager()->remove (this);
 277 }
 278
 279 bool
 280 StdioFileDescriptor::is_open () const
 281 {
 282         /* we must have a lock on the FileManager's mutex */
 283
 284         return _file != 0;
 285 }
 286
 287 bool
 288 StdioFileDescriptor::open ()
 289 {
 290         /* we must have a lock on the FileManager's mutex */
 291
 292         _file = fopen (_path.c_str(), _mode.c_str());
 293         return (_file == 0);
 294 }
 295
 296 void
 297 StdioFileDescriptor::close ()
 298 {
 299         /* we must have a lock on the FileManager's mutex */
 300
 301         fclose (_file);
 302         _file = 0;
 303 }
 304
 305 /** @return FILE*, or 0 on error */
 306 FILE*
 307 StdioFileDescriptor::allocate ()
 308 {
 309         bool const f = manager()->allocate (this);
 310         if (f) {
 311                 return 0;
 312         }
 313
 314         /* this is ok thread-wise because allocate () has incremented
 315            the Descriptor's refcount, so the file will not be closed
 316         */
 317         return _file;
 318 }