beagled/TextCache.cs

   1 //
   2 // TextCache.cs
   3 //
   4 // Copyright (C) 2004 Novell, Inc.
   5 //
   6
   7 //
   8 // Permission is hereby granted, free of charge, to any person obtaining a
   9 // copy of this software and associated documentation files (the "Software"),
  10 // to deal in the Software without restriction, including without limitation
  11 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
  12 // and/or sell copies of the Software, and to permit persons to whom the
  13 // Software is furnished to do so, subject to the following conditions:
  14 //
  15 // The above copyright notice and this permission notice shall be included in
  16 // all copies or substantial portions of the Software.
  17 //
  18 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  19 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  21 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  22 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  23 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  24 // DEALINGS IN THE SOFTWARE.
  25 //
  26
  27
  28 using System;
  29 using System.Collections;
  30 using System.IO;
  31 using System.Threading;
  32
  33 using Mono.Data.SqliteClient;
  34
  35 using Beagle.Util;
  36
  37 namespace Beagle.Daemon {
  38
  39         public class TextCache {
  40
  41                 public const string SELF_CACHE_TAG = "*self*";
  42
  43                 private string text_cache_dir;
  44                 private SqliteConnection connection;
  45
  46                 private enum TransactionState {
  47                         None,
  48                         Requested,
  49                         Started
  50                 }
  51                 private TransactionState transaction_state;
  52
  53                 private static TextCache user_cache = null;
  54
  55                 public static TextCache UserCache {
  56                         get {
  57                                 if (user_cache == null)
  58                                         user_cache = new TextCache (PathFinder.StorageDir);
  59
  60                                 return user_cache;
  61                         }
  62                 }
  63
  64                 public TextCache (string storage_dir)
  65                 {
  66                         text_cache_dir = Path.Combine (storage_dir, "TextCache");
  67                         if (! Directory.Exists (text_cache_dir)) {
  68                                 Directory.CreateDirectory (text_cache_dir);
  69
  70                                 // Create our cache subdirectories.
  71                                 for (int i = 0; i < 256; ++i) {
  72                                         string subdir = i.ToString ("x");
  73                                         if (i < 16)
  74                                                 subdir = "0" + subdir;
  75                                         subdir = Path.Combine (text_cache_dir, subdir);
  76                                         Directory.CreateDirectory (subdir);
  77                                 }
  78                         }
  79
  80                         // Create our Sqlite database
  81                         string db_filename = Path.Combine (text_cache_dir, "TextCache.db");
  82                         bool create_new_db = false;
  83                         if (! File.Exists (db_filename))
  84                                 create_new_db = true;
  85
  86                         connection = new SqliteConnection ();
  87                         connection.ConnectionString = "URI=file:" + db_filename;
  88                         connection.Open ();
  89
  90                         if (create_new_db) {
  91                                 DoNonQuery ("CREATE TABLE uri_index (            " +
  92                                             "  uri      STRING UNIQUE NOT NULL,  " +
  93                                             "  filename STRING NOT NULL          " +
  94                                             ")");
  95                         }
  96                 }
  97
  98                 private static string UriToString (Uri uri)
  99                 {
 100                         return uri.ToString ().Replace ("'", "''");
 101                 }
 102
 103                 private SqliteCommand NewCommand (string format, params object [] args)
 104                 {
 105                         SqliteCommand command;
 106                         command = new SqliteCommand ();
 107                         command.Connection = connection;
 108                         command.CommandText = String.Format (format, args);
 109                         return command;
 110                 }
 111
 112                 private void DoNonQuery (string format, params object [] args)
 113                 {
 114                         SqliteCommand command = NewCommand (format, args);
 115                         while (true) {
 116                                 try {
 117                                         command.ExecuteNonQuery ();
 118                                         break;
 119                                 } catch (SqliteException ex) {
 120                                         // FIXME: should we eventually time out?
 121                                         if (ex.SqliteError == SqliteError.BUSY)
 122                                                 Thread.Sleep (50);
 123                                         else
 124                                                 throw ex;
 125                                 }
 126                         }
 127                         command.Dispose ();
 128                 }
 129
 130                 private SqliteDataReader ExecuteReaderOrWait (SqliteCommand command)
 131                 {
 132                         SqliteDataReader reader = null;
 133                         while (reader == null) {
 134                                 try {
 135                                         reader = command.ExecuteReader ();
 136                                 } catch (SqliteException ex) {
 137                                         if (ex.SqliteError == SqliteError.BUSY)
 138                                                 Thread.Sleep (50);
 139                                         else
 140                                                 throw ex;
 141                                 }
 142                         }
 143                         return reader;
 144                 }
 145
 146                 private bool ReadOrWait (SqliteDataReader reader)
 147                 {
 148                         while (true) {
 149                                 try {
 150                                         return reader.Read ();
 151                                 } catch (SqliteException ex) {
 152                                         if (ex.SqliteError == SqliteError.BUSY)
 153                                                 Thread.Sleep (50);
 154                                         else
 155                                                 throw ex;
 156                                 }
 157                         }
 158                 }
 159
 160                 private void Insert (Uri uri, string filename)
 161                 {
 162                         MaybeStartTransaction ();
 163                         DoNonQuery ("INSERT OR REPLACE INTO uri_index (uri, filename) VALUES ('{0}', '{1}')",
 164                                     UriToString (uri), filename);
 165                 }
 166
 167                 private string LookupPathRawUnlocked (Uri uri, bool create_if_not_found)
 168                 {
 169                         SqliteCommand command;
 170                         SqliteDataReader reader = null;
 171                         string path = null;
 172
 173                         command = NewCommand ("SELECT filename FROM uri_index WHERE uri='{0}'",
 174                                               UriToString (uri));
 175                         reader = ExecuteReaderOrWait (command);
 176                         if (ReadOrWait (reader))
 177                                 path = reader.GetString (0);
 178                         reader.Close ();
 179                         command.Dispose ();
 180
 181                         if (path == null && create_if_not_found) {
 182                                 string guid = Guid.NewGuid ().ToString ();
 183                                 path = Path.Combine (guid.Substring (0, 2), guid.Substring (2));
 184                                 Insert (uri, path);
 185                         }
 186
 187                         if (path == SELF_CACHE_TAG)
 188                                 return SELF_CACHE_TAG;
 189
 190                         return path != null ? Path.Combine (text_cache_dir, path) : null;
 191                 }
 192
 193                 // Don't do this unless you know what you are doing!  If you
 194                 // do anything to the path you get back other than open and
 195                 // read the file, you will almost certainly break something.
 196                 // And it will be evidence that you are a bad person and that
 197                 // you deserve whatever horrible fate befalls you.
 198                 public string LookupPathRaw (Uri uri)
 199                 {
 200                         lock (connection)
 201                                 return LookupPathRawUnlocked (uri, false);
 202                 }
 203
 204                 private string LookupPath (Uri uri, bool create_if_not_found)
 205                 {
 206                         lock (connection) {
 207                                 string path = LookupPathRawUnlocked (uri, create_if_not_found);
 208                                 if (path == SELF_CACHE_TAG) {
 209                                         // FIXME: How do we handle URI remapping for self-cached items?
 210 #if false
 211                                         if (uri_remapper != null)
 212                                                 uri = uri_remapper (uri);
 213 #endif
 214                                         if (! uri.IsFile) {
 215                                                 string msg = String.Format ("Non-file uri {0} flagged as self-cached", uri);
 216                                                 throw new Exception (msg);
 217                                         }
 218                                         return uri.LocalPath;
 219                                 }
 220                                 return path;
 221                         }
 222                 }
 223
 224                 public void MarkAsSelfCached (Uri uri)
 225                 {
 226                         lock (connection)
 227                                 Insert (uri, SELF_CACHE_TAG);
 228                 }
 229
 230                 public TextWriter GetWriter (Uri uri)
 231                 {
 232                         // FIXME: Uri remapping?
 233                         string path = LookupPath (uri, true);
 234
 235                         FileStream stream;
 236                         stream = new FileStream (path, FileMode.Create, FileAccess.Write, FileShare.ReadWrite);
 237
 238                         // We don't expect to need this again in the near future.
 239                         FileAdvise.FlushCache (stream);
 240
 241                         StreamWriter writer;
 242                         writer = new StreamWriter (stream);
 243                         return writer;
 244                 }
 245
 246                 public void WriteFromReader (Uri uri, TextReader reader)
 247                 {
 248                         TextWriter writer;
 249                         writer = GetWriter (uri);
 250                         string line;
 251                         while ((line = reader.ReadLine ()) != null)
 252                                 writer.WriteLine (line);
 253                         writer.Close ();
 254                 }
 255
 256                 public void WriteFromString (Uri uri, string str)
 257                 {
 258                         if (str == null) {
 259                                 Delete (uri);
 260                                 return;
 261                         }
 262
 263                         TextWriter writer;
 264                         writer = GetWriter (uri);
 265                         writer.WriteLine (str);
 266                         writer.Close ();
 267                 }
 268
 269                 // FIXME: Uri remapping?
 270                 public TextReader GetReader (Uri uri)
 271                 {
 272                         string path = LookupPath (uri, false);
 273                         if (path == null)
 274                                 return null;
 275
 276                         FileStream stream;
 277                         try {
 278                                 stream = new FileStream (path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
 279                         } catch (FileNotFoundException ex) {
 280                                 return null;
 281                         }
 282
 283                         StreamReader reader;
 284                         reader = new StreamReader (stream);
 285                         return reader;
 286                 }
 287
 288                 public void Delete (Uri uri)
 289                 {
 290                         lock (connection) {
 291                                 string path = LookupPathRawUnlocked (uri, false);
 292                                 if (path != null) {
 293                                         MaybeStartTransaction ();
 294                                         DoNonQuery ("DELETE FROM uri_index WHERE uri='{0}' AND filename='{1}'",
 295                                                     UriToString (uri), path);
 296                                         if (path != SELF_CACHE_TAG)
 297                                                 File.Delete (path);
 298                                 }
 299                         }
 300                 }
 301
 302                 private void MaybeStartTransaction ()
 303                 {
 304                         if (transaction_state == TransactionState.Requested) {
 305                                 DoNonQuery ("BEGIN");
 306                                 transaction_state = TransactionState.Started;
 307                         }
 308                 }
 309
 310                 public void BeginTransaction ()
 311                 {
 312                         if (transaction_state == TransactionState.None)
 313                                 transaction_state = TransactionState.Requested;
 314                 }
 315
 316                 public void CommitTransaction ()
 317                 {
 318                         if (transaction_state == TransactionState.Started) {
 319                                 lock (connection)
 320                                         DoNonQuery ("COMMIT");
 321                         }
 322                         transaction_state = TransactionState.None;
 323                 }
 324         }
 325 }