src/test_multiplex.c

   1 /*
   2 ** 2010 October 28
   3 **
   4 ** The author disclaims copyright to this source code.  In place of
   5 ** a legal notice, here is a blessing:
   6 **
   7 **    May you do good and not evil.
   8 **    May you find forgiveness for yourself and forgive others.
   9 **    May you share freely, never taking more than you give.
  10 **
  11 *************************************************************************
  12 **
  13 ** This file contains a VFS "shim" - a layer that sits in between the
  14 ** pager and the real VFS - that breaks up a very large database file
  15 ** into two or more smaller files on disk.  This is useful, for example,
  16 ** in order to support large, multi-gigabyte databases on older filesystems
  17 ** that limit the maximum file size to 2 GiB.
  18 **
  19 ** USAGE:
  20 **
  21 ** Compile this source file and link it with your application.  Then
  22 ** at start-time, invoke the following procedure:
  23 **
  24 **   int sqlite3_multiplex_initialize(
  25 **      const char *zOrigVfsName,    // The underlying real VFS
  26 **      int makeDefault              // True to make multiplex the default VFS
  27 **   );
  28 **
  29 ** The procedure call above will create and register a new VFS shim named
  30 ** "multiplex".  The multiplex VFS will use the VFS named by zOrigVfsName to
  31 ** do the actual disk I/O.  (The zOrigVfsName parameter may be NULL, in
  32 ** which case the default VFS at the moment sqlite3_multiplex_initialize()
  33 ** is called will be used as the underlying real VFS.)
  34 **
  35 ** If the makeDefault parameter is TRUE then multiplex becomes the new
  36 ** default VFS.  Otherwise, you can use the multiplex VFS by specifying
  37 ** "multiplex" as the 4th parameter to sqlite3_open_v2() or by employing
  38 ** URI filenames and adding "vfs=multiplex" as a parameter to the filename
  39 ** URI.
  40 **
  41 ** The multiplex VFS allows databases up to 32 GiB in size.  But it splits
  42 ** the files up into smaller pieces, so that they will work even on
  43 ** filesystems that do not support large files.  The default chunk size
  44 ** is 2147418112 bytes (which is 64KiB less than 2GiB) but this can be
  45 ** changed at compile-time by defining the SQLITE_MULTIPLEX_CHUNK_SIZE
  46 ** macro.  Use the "chunksize=NNNN" query parameter with a URI filename
  47 ** in order to select an alternative chunk size for individual connections
  48 ** at run-time.
  49 */
  50 #include "sqlite3.h"
  51 #include <string.h>
  52 #include <assert.h>
  53 #include <stdlib.h>
  54 #include "test_multiplex.h"
  55
  56 #ifndef SQLITE_CORE
  57   #define SQLITE_CORE 1  /* Disable the API redefinition in sqlite3ext.h */
  58 #endif
  59 #include "sqlite3ext.h"
  60
  61 /*
  62 ** These should be defined to be the same as the values in
  63 ** sqliteInt.h.  They are defined separately here so that
  64 ** the multiplex VFS shim can be built as a loadable
  65 ** module.
  66 */
  67 #define UNUSED_PARAMETER(x) (void)(x)
  68 #define MAX_PAGE_SIZE       0x10000
  69 #define DEFAULT_SECTOR_SIZE 0x1000
  70
  71 /* Maximum chunk number */
  72 #define MX_CHUNK_NUMBER 299
  73
  74 /* First chunk for rollback journal files */
  75 #define SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET 400
  76 #define SQLITE_MULTIPLEX_WAL_8_3_OFFSET 700
  77
  78
  79 /************************ Shim Definitions ******************************/
  80
  81 #ifndef SQLITE_MULTIPLEX_VFS_NAME
  82 # define SQLITE_MULTIPLEX_VFS_NAME "multiplex"
  83 #endif
  84
  85 /* This is the limit on the chunk size.  It may be changed by calling
  86 ** the xFileControl() interface.  It will be rounded up to a
  87 ** multiple of MAX_PAGE_SIZE.  We default it here to 2GiB less 64KiB.
  88 */
  89 #ifndef SQLITE_MULTIPLEX_CHUNK_SIZE
  90 # define SQLITE_MULTIPLEX_CHUNK_SIZE 2147418112
  91 #endif
  92
  93 /* This used to be the default limit on number of chunks, but
  94 ** it is no longer enforced. There is currently no limit to the
  95 ** number of chunks.
  96 **
  97 ** May be changed by calling the xFileControl() interface.
  98 */
  99 #ifndef SQLITE_MULTIPLEX_MAX_CHUNKS
 100 # define SQLITE_MULTIPLEX_MAX_CHUNKS 12
 101 #endif
 102
 103 /************************ Object Definitions ******************************/
 104
 105 /* Forward declaration of all object types */
 106 typedef struct multiplexGroup multiplexGroup;
 107 typedef struct multiplexConn multiplexConn;
 108
 109 /*
 110 ** A "multiplex group" is a collection of files that collectively
 111 ** makeup a single SQLite DB file.  This allows the size of the DB
 112 ** to exceed the limits imposed by the file system.
 113 **
 114 ** There is an instance of the following object for each defined multiplex
 115 ** group.
 116 */
 117 struct multiplexGroup {
 118   struct multiplexReal {           /* For each chunk */
 119     sqlite3_file *p;                  /* Handle for the chunk */
 120     char *z;                          /* Name of this chunk */
 121   } *aReal;                        /* list of all chunks */
 122   int nReal;                       /* Number of chunks */
 123   char *zName;                     /* Base filename of this group */
 124   int nName;                       /* Length of base filename */
 125   int flags;                       /* Flags used for original opening */
 126   unsigned int szChunk;            /* Chunk size used for this group */
 127   unsigned char bEnabled;          /* TRUE to use Multiplex VFS for this file */
 128   unsigned char bTruncate;         /* TRUE to enable truncation of databases */
 129 };
 130
 131 /*
 132 ** An instance of the following object represents each open connection
 133 ** to a file that is multiplex'ed.  This object is a
 134 ** subclass of sqlite3_file.  The sqlite3_file object for the underlying
 135 ** VFS is appended to this structure.
 136 */
 137 struct multiplexConn {
 138   sqlite3_file base;              /* Base class - must be first */
 139   multiplexGroup *pGroup;         /* The underlying group of files */
 140 };
 141
 142 /************************* Global Variables **********************************/
 143 /*
 144 ** All global variables used by this file are containing within the following
 145 ** gMultiplex structure.
 146 */
 147 static struct {
 148   /* The pOrigVfs is the real, original underlying VFS implementation.
 149   ** Most operations pass-through to the real VFS.  This value is read-only
 150   ** during operation.  It is only modified at start-time and thus does not
 151   ** require a mutex.
 152   */
 153   sqlite3_vfs *pOrigVfs;
 154
 155   /* The sThisVfs is the VFS structure used by this shim.  It is initialized
 156   ** at start-time and thus does not require a mutex
 157   */
 158   sqlite3_vfs sThisVfs;
 159
 160   /* The sIoMethods defines the methods used by sqlite3_file objects
 161   ** associated with this shim.  It is initialized at start-time and does
 162   ** not require a mutex.
 163   **
 164   ** When the underlying VFS is called to open a file, it might return
 165   ** either a version 1 or a version 2 sqlite3_file object.  This shim
 166   ** has to create a wrapper sqlite3_file of the same version.  Hence
 167   ** there are two I/O method structures, one for version 1 and the other
 168   ** for version 2.
 169   */
 170   sqlite3_io_methods sIoMethodsV1;
 171   sqlite3_io_methods sIoMethodsV2;
 172
 173   /* True when this shim has been initialized.
 174   */
 175   int isInitialized;
 176 } gMultiplex;
 177
 178 /************************* Utility Routines *********************************/
 179 /*
 180 ** Compute a string length that is limited to what can be stored in
 181 ** lower 30 bits of a 32-bit signed integer.
 182 **
 183 ** The value returned will never be negative.  Nor will it ever be greater
 184 ** than the actual length of the string.  For very long strings (greater
 185 ** than 1GiB) the value returned might be less than the true string length.
 186 */
 187 static int multiplexStrlen30(const char *z){
 188   const char *z2 = z;
 189   if( z==0 ) return 0;
 190   while( *z2 ){ z2++; }
 191   return 0x3fffffff & (int)(z2 - z);
 192 }
 193
 194 /*
 195 ** Generate the file-name for chunk iChunk of the group with base name
 196 ** zBase. The file-name is written to buffer zOut before returning. Buffer
 197 ** zOut must be allocated by the caller so that it is at least (nBase+5)
 198 ** bytes in size, where nBase is the length of zBase, not including the
 199 ** nul-terminator.
 200 **
 201 ** If iChunk is 0 (or 400 - the number for the first journal file chunk),
 202 ** the output is a copy of the input string. Otherwise, if
 203 ** SQLITE_ENABLE_8_3_NAMES is not defined or the input buffer does not contain
 204 ** a "." character, then the output is a copy of the input string with the
 205 ** three-digit zero-padded decimal representation if iChunk appended to it.
 206 ** For example:
 207 **
 208 **   zBase="test.db", iChunk=4  ->  zOut="test.db004"
 209 **
 210 ** Or, if SQLITE_ENABLE_8_3_NAMES is defined and the input buffer contains
 211 ** a "." character, then everything after the "." is replaced by the
 212 ** three-digit representation of iChunk.
 213 **
 214 **   zBase="test.db", iChunk=4  ->  zOut="test.004"
 215 **
 216 ** The output buffer string is terminated by 2 0x00 bytes. This makes it safe
 217 ** to pass to sqlite3_uri_parameter() and similar.
 218 */
 219 static void multiplexFilename(
 220   const char *zBase,              /* Filename for chunk 0 */
 221   int nBase,                      /* Size of zBase in bytes (without \0) */
 222   int flags,                      /* Flags used to open file */
 223   int iChunk,                     /* Chunk to generate filename for */
 224   char *zOut                      /* Buffer to write generated name to */
 225 ){
 226   int n = nBase;
 227   memcpy(zOut, zBase, n+1);
 228   if( iChunk!=0 && iChunk<=MX_CHUNK_NUMBER ){
 229 #ifdef SQLITE_ENABLE_8_3_NAMES
 230     int i;
 231     for(i=n-1; i>0 && i>=n-4 && zOut[i]!='.'; i--){}
 232     if( i>=n-4 ) n = i+1;
 233     if( flags & SQLITE_OPEN_MAIN_JOURNAL ){
 234       /* The extensions on overflow files for main databases are 001, 002,
 235       ** 003 and so forth.  To avoid name collisions, add 400 to the
 236       ** extensions of journal files so that they are 401, 402, 403, ....
 237       */
 238       iChunk += SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET;
 239     }else if( flags & SQLITE_OPEN_WAL ){
 240       /* To avoid name collisions, add 700 to the
 241       ** extensions of WAL files so that they are 701, 702, 703, ....
 242       */
 243       iChunk += SQLITE_MULTIPLEX_WAL_8_3_OFFSET;
 244     }
 245 #endif
 246     sqlite3_snprintf(4,&zOut[n],"%03d",iChunk);
 247     n += 3;
 248   }
 249
 250   assert( zOut[n]=='\0' );
 251   zOut[n+1] = '\0';
 252 }
 253
 254 /* Compute the filename for the iChunk-th chunk
 255 */
 256 static int multiplexSubFilename(multiplexGroup *pGroup, int iChunk){
 257   if( iChunk>=pGroup->nReal ){
 258     struct multiplexReal *p;
 259     p = sqlite3_realloc64(pGroup->aReal, (iChunk+1)*sizeof(*p));
 260     if( p==0 ){
 261       return SQLITE_NOMEM;
 262     }
 263     memset(&p[pGroup->nReal], 0, sizeof(p[0])*(iChunk+1-pGroup->nReal));
 264     pGroup->aReal = p;
 265     pGroup->nReal = iChunk+1;
 266   }
 267   if( pGroup->zName && pGroup->aReal[iChunk].z==0 ){
 268     char *z;
 269     int n = pGroup->nName;
 270     z = sqlite3_malloc64( n+5 );
 271     if( z==0 ){
 272       return SQLITE_NOMEM;
 273     }
 274     multiplexFilename(pGroup->zName, pGroup->nName, pGroup->flags, iChunk, z);
 275     pGroup->aReal[iChunk].z = (char*)sqlite3_create_filename(z,"","",0,0);
 276     sqlite3_free(z);
 277     if( pGroup->aReal[iChunk].z==0 ) return SQLITE_NOMEM;
 278   }
 279   return SQLITE_OK;
 280 }
 281
 282 /* Translate an sqlite3_file* that is really a multiplexGroup* into
 283 ** the sqlite3_file* for the underlying original VFS.
 284 **
 285 ** For chunk 0, the pGroup->flags determines whether or not a new file
 286 ** is created if it does not already exist.  For chunks 1 and higher, the
 287 ** file is created only if createFlag is 1.
 288 */
 289 static sqlite3_file *multiplexSubOpen(
 290   multiplexGroup *pGroup,    /* The multiplexor group */
 291   int iChunk,                /* Which chunk to open.  0==original file */
 292   int *rc,                   /* Result code in and out */
 293   int *pOutFlags,            /* Output flags */
 294   int createFlag             /* True to create if iChunk>0 */
 295 ){
 296   sqlite3_file *pSubOpen = 0;
 297   sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;        /* Real VFS */
 298
 299 #ifdef SQLITE_ENABLE_8_3_NAMES
 300   /* If JOURNAL_8_3_OFFSET is set to (say) 400, then any overflow files are
 301   ** part of a database journal are named db.401, db.402, and so on. A
 302   ** database may therefore not grow to larger than 400 chunks. Attempting
 303   ** to open chunk 401 indicates the database is full. */
 304   if( iChunk>=SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET ){
 305     sqlite3_log(SQLITE_FULL, "multiplexed chunk overflow: %s", pGroup->zName);
 306     *rc = SQLITE_FULL;
 307     return 0;
 308   }
 309 #endif
 310
 311   *rc = multiplexSubFilename(pGroup, iChunk);
 312   if( (*rc)==SQLITE_OK && (pSubOpen = pGroup->aReal[iChunk].p)==0 ){
 313     int flags, bExists;
 314     flags = pGroup->flags;
 315     if( createFlag ){
 316       flags |= SQLITE_OPEN_CREATE;
 317     }else if( iChunk==0 ){
 318       /* Fall through */
 319     }else if( pGroup->aReal[iChunk].z==0 ){
 320       return 0;
 321     }else{
 322       *rc = pOrigVfs->xAccess(pOrigVfs, pGroup->aReal[iChunk].z,
 323                               SQLITE_ACCESS_EXISTS, &bExists);
 324      if( *rc || !bExists ){
 325         if( *rc ){
 326           sqlite3_log(*rc, "multiplexor.xAccess failure on %s",
 327                       pGroup->aReal[iChunk].z);
 328         }
 329         return 0;
 330       }
 331       flags &= ~SQLITE_OPEN_CREATE;
 332     }
 333     pSubOpen = sqlite3_malloc64( pOrigVfs->szOsFile );
 334     if( pSubOpen==0 ){
 335       *rc = SQLITE_IOERR_NOMEM;
 336       return 0;
 337     }
 338     pGroup->aReal[iChunk].p = pSubOpen;
 339     *rc = pOrigVfs->xOpen(pOrigVfs, pGroup->aReal[iChunk].z, pSubOpen,
 340                           flags, pOutFlags);
 341     if( (*rc)!=SQLITE_OK ){
 342       sqlite3_log(*rc, "multiplexor.xOpen failure on %s",
 343                   pGroup->aReal[iChunk].z);
 344       sqlite3_free(pSubOpen);
 345       pGroup->aReal[iChunk].p = 0;
 346       return 0;
 347     }
 348   }
 349   return pSubOpen;
 350 }
 351
 352 /*
 353 ** Return the size, in bytes, of chunk number iChunk.  If that chunk
 354 ** does not exist, then return 0.  This function does not distingish between
 355 ** non-existant files and zero-length files.
 356 */
 357 static sqlite3_int64 multiplexSubSize(
 358   multiplexGroup *pGroup,    /* The multiplexor group */
 359   int iChunk,                /* Which chunk to open.  0==original file */
 360   int *rc                    /* Result code in and out */
 361 ){
 362   sqlite3_file *pSub;
 363   sqlite3_int64 sz = 0;
 364
 365   if( *rc ) return 0;
 366   pSub = multiplexSubOpen(pGroup, iChunk, rc, NULL, 0);
 367   if( pSub==0 ) return 0;
 368   *rc = pSub->pMethods->xFileSize(pSub, &sz);
 369   return sz;
 370 }
 371
 372 /*
 373 ** This is the implementation of the multiplex_control() SQL function.
 374 */
 375 static void multiplexControlFunc(
 376   sqlite3_context *context,
 377   int argc,
 378   sqlite3_value **argv
 379 ){
 380   int rc = SQLITE_OK;
 381   sqlite3 *db = sqlite3_context_db_handle(context);
 382   int op = 0;
 383   int iVal;
 384
 385   if( !db || argc!=2 ){
 386     rc = SQLITE_ERROR;
 387   }else{
 388     /* extract params */
 389     op = sqlite3_value_int(argv[0]);
 390     iVal = sqlite3_value_int(argv[1]);
 391     /* map function op to file_control op */
 392     switch( op ){
 393       case 1:
 394         op = MULTIPLEX_CTRL_ENABLE;
 395         break;
 396       case 2:
 397         op = MULTIPLEX_CTRL_SET_CHUNK_SIZE;
 398         break;
 399       case 3:
 400         op = MULTIPLEX_CTRL_SET_MAX_CHUNKS;
 401         break;
 402       default:
 403         rc = SQLITE_NOTFOUND;
 404         break;
 405     }
 406   }
 407   if( rc==SQLITE_OK ){
 408     rc = sqlite3_file_control(db, 0, op, &iVal);
 409   }
 410   sqlite3_result_error_code(context, rc);
 411 }
 412
 413 /*
 414 ** This is the entry point to register the auto-extension for the
 415 ** multiplex_control() function.
 416 */
 417 static int multiplexFuncInit(
 418   sqlite3 *db,
 419   char **pzErrMsg,
 420   const sqlite3_api_routines *pApi
 421 ){
 422   int rc;
 423   rc = sqlite3_create_function(db, "multiplex_control", 2, SQLITE_ANY,
 424       0, multiplexControlFunc, 0, 0);
 425   return rc;
 426 }
 427
 428 /*
 429 ** Close a single sub-file in the connection group.
 430 */
 431 static void multiplexSubClose(
 432   multiplexGroup *pGroup,
 433   int iChunk,
 434   sqlite3_vfs *pOrigVfs
 435 ){
 436   sqlite3_file *pSubOpen = pGroup->aReal[iChunk].p;
 437   if( pSubOpen ){
 438     pSubOpen->pMethods->xClose(pSubOpen);
 439     if( pOrigVfs && pGroup->aReal[iChunk].z ){
 440       pOrigVfs->xDelete(pOrigVfs, pGroup->aReal[iChunk].z, 0);
 441     }
 442     sqlite3_free(pGroup->aReal[iChunk].p);
 443   }
 444   sqlite3_free_filename(pGroup->aReal[iChunk].z);
 445   memset(&pGroup->aReal[iChunk], 0, sizeof(pGroup->aReal[iChunk]));
 446 }
 447
 448 /*
 449 ** Deallocate memory held by a multiplexGroup
 450 */
 451 static void multiplexFreeComponents(multiplexGroup *pGroup){
 452   int i;
 453   for(i=0; i<pGroup->nReal; i++){ multiplexSubClose(pGroup, i, 0); }
 454   sqlite3_free(pGroup->aReal);
 455   pGroup->aReal = 0;
 456   pGroup->nReal = 0;
 457 }
 458
 459
 460 /************************* VFS Method Wrappers *****************************/
 461
 462 /*
 463 ** This is the xOpen method used for the "multiplex" VFS.
 464 **
 465 ** Most of the work is done by the underlying original VFS.  This method
 466 ** simply links the new file into the appropriate multiplex group if it is a
 467 ** file that needs to be tracked.
 468 */
 469 static int multiplexOpen(
 470   sqlite3_vfs *pVfs,         /* The multiplex VFS */
 471   const char *zName,         /* Name of file to be opened */
 472   sqlite3_file *pConn,       /* Fill in this file descriptor */
 473   int flags,                 /* Flags to control the opening */
 474   int *pOutFlags             /* Flags showing results of opening */
 475 ){
 476   int rc = SQLITE_OK;                  /* Result code */
 477   multiplexConn *pMultiplexOpen;       /* The new multiplex file descriptor */
 478   multiplexGroup *pGroup = 0;          /* Corresponding multiplexGroup object */
 479   sqlite3_file *pSubOpen = 0;                    /* Real file descriptor */
 480   sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
 481   int nName = 0;
 482   int sz = 0;
 483   char *zToFree = 0;
 484
 485   UNUSED_PARAMETER(pVfs);
 486   memset(pConn, 0, pVfs->szOsFile);
 487   assert( zName || (flags & SQLITE_OPEN_DELETEONCLOSE) );
 488
 489   /* We need to create a group structure and manage
 490   ** access to this group of files.
 491   */
 492   pMultiplexOpen = (multiplexConn*)pConn;
 493
 494   if( rc==SQLITE_OK ){
 495     /* allocate space for group */
 496     nName = zName ? multiplexStrlen30(zName) : 0;
 497     sz = sizeof(multiplexGroup)                             /* multiplexGroup */
 498        + nName + 1;                                         /* zName */
 499     pGroup = sqlite3_malloc64( sz );
 500     if( pGroup==0 ){
 501       rc = SQLITE_NOMEM;
 502     }
 503   }
 504
 505   if( rc==SQLITE_OK ){
 506     const char *zUri = (flags & SQLITE_OPEN_URI) ? zName : 0;
 507     /* assign pointers to extra space allocated */
 508     memset(pGroup, 0, sz);
 509     pMultiplexOpen->pGroup = pGroup;
 510     pGroup->bEnabled = (unsigned char)-1;
 511     pGroup->bTruncate = (unsigned char)sqlite3_uri_boolean(zUri, "truncate",
 512                                    (flags & SQLITE_OPEN_MAIN_DB)==0);
 513     pGroup->szChunk = (int)sqlite3_uri_int64(zUri, "chunksize",
 514                                         SQLITE_MULTIPLEX_CHUNK_SIZE);
 515     pGroup->szChunk = (pGroup->szChunk+0xffff)&~0xffff;
 516     if( zName ){
 517       char *p = (char *)&pGroup[1];
 518       pGroup->zName = p;
 519       memcpy(pGroup->zName, zName, nName+1);
 520       pGroup->nName = nName;
 521     }
 522     if( pGroup->bEnabled ){
 523       /* Make sure that the chunksize is such that the pending byte does not
 524       ** falls at the end of a chunk.  A region of up to 64K following
 525       ** the pending byte is never written, so if the pending byte occurs
 526       ** near the end of a chunk, that chunk will be too small. */
 527 #ifndef SQLITE_OMIT_WSD
 528       extern int sqlite3PendingByte;
 529 #else
 530       int sqlite3PendingByte = 0x40000000;
 531 #endif
 532       while( (sqlite3PendingByte % pGroup->szChunk)>=(pGroup->szChunk-65536) ){
 533         pGroup->szChunk += 65536;
 534       }
 535     }
 536     pGroup->flags = (flags & ~SQLITE_OPEN_URI);
 537     rc = multiplexSubFilename(pGroup, 1);
 538     if( rc==SQLITE_OK ){
 539       pSubOpen = multiplexSubOpen(pGroup, 0, &rc, pOutFlags, 0);
 540       if( pSubOpen==0 && rc==SQLITE_OK ) rc = SQLITE_CANTOPEN;
 541     }
 542     if( rc==SQLITE_OK ){
 543       sqlite3_int64 sz64;
 544
 545       rc = pSubOpen->pMethods->xFileSize(pSubOpen, &sz64);
 546       if( rc==SQLITE_OK && zName ){
 547         int bExists;
 548         if( flags & SQLITE_OPEN_SUPER_JOURNAL ){
 549           pGroup->bEnabled = 0;
 550         }else
 551         if( sz64==0 ){
 552           if( flags & SQLITE_OPEN_MAIN_JOURNAL ){
 553             /* If opening a main journal file and the first chunk is zero
 554             ** bytes in size, delete any subsequent chunks from the
 555             ** file-system. */
 556             int iChunk = 1;
 557             do {
 558               rc = pOrigVfs->xAccess(pOrigVfs,
 559                   pGroup->aReal[iChunk].z, SQLITE_ACCESS_EXISTS, &bExists
 560               );
 561               if( rc==SQLITE_OK && bExists ){
 562                 rc = pOrigVfs->xDelete(pOrigVfs, pGroup->aReal[iChunk].z, 0);
 563                 if( rc==SQLITE_OK ){
 564                   rc = multiplexSubFilename(pGroup, ++iChunk);
 565                 }
 566               }
 567             }while( rc==SQLITE_OK && bExists );
 568           }
 569         }else{
 570           /* If the first overflow file exists and if the size of the main file
 571           ** is different from the chunk size, that means the chunk size is set
 572           ** set incorrectly.  So fix it.
 573           **
 574           ** Or, if the first overflow file does not exist and the main file is
 575           ** larger than the chunk size, that means the chunk size is too small.
 576           ** But we have no way of determining the intended chunk size, so
 577           ** just disable the multiplexor all togethre.
 578           */
 579           rc = pOrigVfs->xAccess(pOrigVfs, pGroup->aReal[1].z,
 580               SQLITE_ACCESS_EXISTS, &bExists);
 581           bExists = multiplexSubSize(pGroup, 1, &rc)>0;
 582           if( rc==SQLITE_OK && bExists && sz64==(sz64&0xffff0000) && sz64>0
 583               && sz64!=pGroup->szChunk ){
 584             pGroup->szChunk = (int)sz64;
 585           }else if( rc==SQLITE_OK && !bExists && sz64>pGroup->szChunk ){
 586             pGroup->bEnabled = 0;
 587           }
 588         }
 589       }
 590     }
 591
 592     if( rc==SQLITE_OK ){
 593       if( pSubOpen->pMethods->iVersion==1 ){
 594         pConn->pMethods = &gMultiplex.sIoMethodsV1;
 595       }else{
 596         pConn->pMethods = &gMultiplex.sIoMethodsV2;
 597       }
 598     }else{
 599       multiplexFreeComponents(pGroup);
 600       sqlite3_free(pGroup);
 601     }
 602   }
 603   sqlite3_free(zToFree);
 604   return rc;
 605 }
 606
 607 /*
 608 ** This is the xDelete method used for the "multiplex" VFS.
 609 ** It attempts to delete the filename specified.
 610 */
 611 static int multiplexDelete(
 612   sqlite3_vfs *pVfs,         /* The multiplex VFS */
 613   const char *zName,         /* Name of file to delete */
 614   int syncDir
 615 ){
 616   int rc;
 617   sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
 618   rc = pOrigVfs->xDelete(pOrigVfs, zName, syncDir);
 619   if( rc==SQLITE_OK ){
 620     /* If the main chunk was deleted successfully, also delete any subsequent
 621     ** chunks - starting with the last (highest numbered).
 622     */
 623     int nName = (int)strlen(zName);
 624     char *z;
 625     z = sqlite3_malloc64(nName + 5);
 626     if( z==0 ){
 627       rc = SQLITE_IOERR_NOMEM;
 628     }else{
 629       int iChunk = 0;
 630       int bExists;
 631       do{
 632         multiplexFilename(zName, nName, SQLITE_OPEN_MAIN_JOURNAL, ++iChunk, z);
 633         rc = pOrigVfs->xAccess(pOrigVfs, z, SQLITE_ACCESS_EXISTS, &bExists);
 634       }while( rc==SQLITE_OK && bExists );
 635       while( rc==SQLITE_OK && iChunk>1 ){
 636         multiplexFilename(zName, nName, SQLITE_OPEN_MAIN_JOURNAL, --iChunk, z);
 637         rc = pOrigVfs->xDelete(pOrigVfs, z, syncDir);
 638       }
 639       if( rc==SQLITE_OK ){
 640         iChunk = 0;
 641         do{
 642           multiplexFilename(zName, nName, SQLITE_OPEN_WAL, ++iChunk, z);
 643           rc = pOrigVfs->xAccess(pOrigVfs, z, SQLITE_ACCESS_EXISTS, &bExists);
 644         }while( rc==SQLITE_OK && bExists );
 645         while( rc==SQLITE_OK && iChunk>1 ){
 646           multiplexFilename(zName, nName, SQLITE_OPEN_WAL, --iChunk, z);
 647           rc = pOrigVfs->xDelete(pOrigVfs, z, syncDir);
 648         }
 649       }
 650     }
 651     sqlite3_free(z);
 652   }
 653   return rc;
 654 }
 655
 656 static int multiplexAccess(sqlite3_vfs *a, const char *b, int c, int *d){
 657   return gMultiplex.pOrigVfs->xAccess(gMultiplex.pOrigVfs, b, c, d);
 658 }
 659 static int multiplexFullPathname(sqlite3_vfs *a, const char *b, int c, char *d){
 660   return gMultiplex.pOrigVfs->xFullPathname(gMultiplex.pOrigVfs, b, c, d);
 661 }
 662 static void *multiplexDlOpen(sqlite3_vfs *a, const char *b){
 663   return gMultiplex.pOrigVfs->xDlOpen(gMultiplex.pOrigVfs, b);
 664 }
 665 static void multiplexDlError(sqlite3_vfs *a, int b, char *c){
 666   gMultiplex.pOrigVfs->xDlError(gMultiplex.pOrigVfs, b, c);
 667 }
 668 static void (*multiplexDlSym(sqlite3_vfs *a, void *b, const char *c))(void){
 669   return gMultiplex.pOrigVfs->xDlSym(gMultiplex.pOrigVfs, b, c);
 670 }
 671 static void multiplexDlClose(sqlite3_vfs *a, void *b){
 672   gMultiplex.pOrigVfs->xDlClose(gMultiplex.pOrigVfs, b);
 673 }
 674 static int multiplexRandomness(sqlite3_vfs *a, int b, char *c){
 675   return gMultiplex.pOrigVfs->xRandomness(gMultiplex.pOrigVfs, b, c);
 676 }
 677 static int multiplexSleep(sqlite3_vfs *a, int b){
 678   return gMultiplex.pOrigVfs->xSleep(gMultiplex.pOrigVfs, b);
 679 }
 680 static int multiplexCurrentTime(sqlite3_vfs *a, double *b){
 681   return gMultiplex.pOrigVfs->xCurrentTime(gMultiplex.pOrigVfs, b);
 682 }
 683 static int multiplexGetLastError(sqlite3_vfs *a, int b, char *c){
 684   if( gMultiplex.pOrigVfs->xGetLastError ){
 685     return gMultiplex.pOrigVfs->xGetLastError(gMultiplex.pOrigVfs, b, c);
 686   }else{
 687     return 0;
 688   }
 689 }
 690 static int multiplexCurrentTimeInt64(sqlite3_vfs *a, sqlite3_int64 *b){
 691   return gMultiplex.pOrigVfs->xCurrentTimeInt64(gMultiplex.pOrigVfs, b);
 692 }
 693
 694 /************************ I/O Method Wrappers *******************************/
 695
 696 /* xClose requests get passed through to the original VFS.
 697 ** We loop over all open chunk handles and close them.
 698 ** The group structure for this file is unlinked from
 699 ** our list of groups and freed.
 700 */
 701 static int multiplexClose(sqlite3_file *pConn){
 702   multiplexConn *p = (multiplexConn*)pConn;
 703   multiplexGroup *pGroup = p->pGroup;
 704   int rc = SQLITE_OK;
 705   multiplexFreeComponents(pGroup);
 706   sqlite3_free(pGroup);
 707   return rc;
 708 }
 709
 710 /* Pass xRead requests thru to the original VFS after
 711 ** determining the correct chunk to operate on.
 712 ** Break up reads across chunk boundaries.
 713 */
 714 static int multiplexRead(
 715   sqlite3_file *pConn,
 716   void *pBuf,
 717   int iAmt,
 718   sqlite3_int64 iOfst
 719 ){
 720   multiplexConn *p = (multiplexConn*)pConn;
 721   multiplexGroup *pGroup = p->pGroup;
 722   int rc = SQLITE_OK;
 723   if( !pGroup->bEnabled ){
 724     sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
 725     if( pSubOpen==0 ){
 726       rc = SQLITE_IOERR_READ;
 727     }else{
 728       rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt, iOfst);
 729     }
 730   }else{
 731     while( iAmt > 0 ){
 732       int i = (int)(iOfst / pGroup->szChunk);
 733       sqlite3_file *pSubOpen;
 734       pSubOpen = multiplexSubOpen(pGroup, i, &rc, NULL, 1);
 735       if( pSubOpen ){
 736         int extra = ((int)(iOfst % pGroup->szChunk) + iAmt) - pGroup->szChunk;
 737         if( extra<0 ) extra = 0;
 738         iAmt -= extra;
 739         rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt,
 740                                        iOfst % pGroup->szChunk);
 741         if( rc!=SQLITE_OK ) break;
 742         pBuf = (char *)pBuf + iAmt;
 743         iOfst += iAmt;
 744         iAmt = extra;
 745       }else{
 746         rc = SQLITE_IOERR_READ;
 747         break;
 748       }
 749     }
 750   }
 751
 752   return rc;
 753 }
 754
 755 /* Pass xWrite requests thru to the original VFS after
 756 ** determining the correct chunk to operate on.
 757 ** Break up writes across chunk boundaries.
 758 */
 759 static int multiplexWrite(
 760   sqlite3_file *pConn,
 761   const void *pBuf,
 762   int iAmt,
 763   sqlite3_int64 iOfst
 764 ){
 765   multiplexConn *p = (multiplexConn*)pConn;
 766   multiplexGroup *pGroup = p->pGroup;
 767   int rc = SQLITE_OK;
 768   if( !pGroup->bEnabled ){
 769     sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
 770     if( pSubOpen==0 ){
 771       rc = SQLITE_IOERR_WRITE;
 772     }else{
 773       rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt, iOfst);
 774     }
 775   }else{
 776     while( rc==SQLITE_OK && iAmt>0 ){
 777       int i = (int)(iOfst / pGroup->szChunk);
 778       sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, i, &rc, NULL, 1);
 779       if( pSubOpen ){
 780         int extra = ((int)(iOfst % pGroup->szChunk) + iAmt) -
 781                     pGroup->szChunk;
 782         if( extra<0 ) extra = 0;
 783         iAmt -= extra;
 784         rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt,
 785                                         iOfst % pGroup->szChunk);
 786         pBuf = (char *)pBuf + iAmt;
 787         iOfst += iAmt;
 788         iAmt = extra;
 789       }
 790     }
 791   }
 792   return rc;
 793 }
 794
 795 /* Pass xTruncate requests thru to the original VFS after
 796 ** determining the correct chunk to operate on.  Delete any
 797 ** chunks above the truncate mark.
 798 */
 799 static int multiplexTruncate(sqlite3_file *pConn, sqlite3_int64 size){
 800   multiplexConn *p = (multiplexConn*)pConn;
 801   multiplexGroup *pGroup = p->pGroup;
 802   int rc = SQLITE_OK;
 803   if( !pGroup->bEnabled ){
 804     sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
 805     if( pSubOpen==0 ){
 806       rc = SQLITE_IOERR_TRUNCATE;
 807     }else{
 808       rc = pSubOpen->pMethods->xTruncate(pSubOpen, size);
 809     }
 810   }else{
 811     int i;
 812     int iBaseGroup = (int)(size / pGroup->szChunk);
 813     sqlite3_file *pSubOpen;
 814     sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
 815     /* delete the chunks above the truncate limit */
 816     for(i = pGroup->nReal-1; i>iBaseGroup && rc==SQLITE_OK; i--){
 817       if( pGroup->bTruncate ){
 818         multiplexSubClose(pGroup, i, pOrigVfs);
 819       }else{
 820         pSubOpen = multiplexSubOpen(pGroup, i, &rc, 0, 0);
 821         if( pSubOpen ){
 822           rc = pSubOpen->pMethods->xTruncate(pSubOpen, 0);
 823         }
 824       }
 825     }
 826     if( rc==SQLITE_OK ){
 827       pSubOpen = multiplexSubOpen(pGroup, iBaseGroup, &rc, 0, 0);
 828       if( pSubOpen ){
 829         rc = pSubOpen->pMethods->xTruncate(pSubOpen, size % pGroup->szChunk);
 830       }
 831     }
 832     if( rc ) rc = SQLITE_IOERR_TRUNCATE;
 833   }
 834   return rc;
 835 }
 836
 837 /* Pass xSync requests through to the original VFS without change
 838 */
 839 static int multiplexSync(sqlite3_file *pConn, int flags){
 840   multiplexConn *p = (multiplexConn*)pConn;
 841   multiplexGroup *pGroup = p->pGroup;
 842   int rc = SQLITE_OK;
 843   int i;
 844   for(i=0; i<pGroup->nReal; i++){
 845     sqlite3_file *pSubOpen = pGroup->aReal[i].p;
 846     if( pSubOpen ){
 847       int rc2 = pSubOpen->pMethods->xSync(pSubOpen, flags);
 848       if( rc2!=SQLITE_OK ) rc = rc2;
 849     }
 850   }
 851   return rc;
 852 }
 853
 854 /* Pass xFileSize requests through to the original VFS.
 855 ** Aggregate the size of all the chunks before returning.
 856 */
 857 static int multiplexFileSize(sqlite3_file *pConn, sqlite3_int64 *pSize){
 858   multiplexConn *p = (multiplexConn*)pConn;
 859   multiplexGroup *pGroup = p->pGroup;
 860   int rc = SQLITE_OK;
 861   int i;
 862   if( !pGroup->bEnabled ){
 863     sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
 864     if( pSubOpen==0 ){
 865       rc = SQLITE_IOERR_FSTAT;
 866     }else{
 867       rc = pSubOpen->pMethods->xFileSize(pSubOpen, pSize);
 868     }
 869   }else{
 870     *pSize = 0;
 871     for(i=0; rc==SQLITE_OK; i++){
 872       sqlite3_int64 sz = multiplexSubSize(pGroup, i, &rc);
 873       if( sz==0 ) break;
 874       *pSize = i*(sqlite3_int64)pGroup->szChunk + sz;
 875     }
 876   }
 877   return rc;
 878 }
 879
 880 /* Pass xLock requests through to the original VFS unchanged.
 881 */
 882 static int multiplexLock(sqlite3_file *pConn, int lock){
 883   multiplexConn *p = (multiplexConn*)pConn;
 884   int rc;
 885   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
 886   if( pSubOpen ){
 887     return pSubOpen->pMethods->xLock(pSubOpen, lock);
 888   }
 889   return SQLITE_BUSY;
 890 }
 891
 892 /* Pass xUnlock requests through to the original VFS unchanged.
 893 */
 894 static int multiplexUnlock(sqlite3_file *pConn, int lock){
 895   multiplexConn *p = (multiplexConn*)pConn;
 896   int rc;
 897   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
 898   if( pSubOpen ){
 899     return pSubOpen->pMethods->xUnlock(pSubOpen, lock);
 900   }
 901   return SQLITE_IOERR_UNLOCK;
 902 }
 903
 904 /* Pass xCheckReservedLock requests through to the original VFS unchanged.
 905 */
 906 static int multiplexCheckReservedLock(sqlite3_file *pConn, int *pResOut){
 907   multiplexConn *p = (multiplexConn*)pConn;
 908   int rc;
 909   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
 910   if( pSubOpen ){
 911     return pSubOpen->pMethods->xCheckReservedLock(pSubOpen, pResOut);
 912   }
 913   return SQLITE_IOERR_CHECKRESERVEDLOCK;
 914 }
 915
 916 /* Pass xFileControl requests through to the original VFS unchanged,
 917 ** except for any MULTIPLEX_CTRL_* requests here.
 918 */
 919 static int multiplexFileControl(sqlite3_file *pConn, int op, void *pArg){
 920   multiplexConn *p = (multiplexConn*)pConn;
 921   multiplexGroup *pGroup = p->pGroup;
 922   int rc = SQLITE_ERROR;
 923   sqlite3_file *pSubOpen;
 924
 925   if( !gMultiplex.isInitialized ) return SQLITE_MISUSE;
 926   switch( op ){
 927     case MULTIPLEX_CTRL_ENABLE:
 928       if( pArg ) {
 929         int bEnabled = *(int *)pArg;
 930         pGroup->bEnabled = (unsigned char)bEnabled;
 931         rc = SQLITE_OK;
 932       }
 933       break;
 934     case MULTIPLEX_CTRL_SET_CHUNK_SIZE:
 935       if( pArg ) {
 936         unsigned int szChunk = *(unsigned*)pArg;
 937         if( szChunk<1 ){
 938           rc = SQLITE_MISUSE;
 939         }else{
 940           /* Round up to nearest multiple of MAX_PAGE_SIZE. */
 941           szChunk = (szChunk + (MAX_PAGE_SIZE-1));
 942           szChunk &= ~(MAX_PAGE_SIZE-1);
 943           pGroup->szChunk = szChunk;
 944           rc = SQLITE_OK;
 945         }
 946       }
 947       break;
 948     case MULTIPLEX_CTRL_SET_MAX_CHUNKS:
 949       rc = SQLITE_OK;
 950       break;
 951     case SQLITE_FCNTL_SIZE_HINT:
 952     case SQLITE_FCNTL_CHUNK_SIZE:
 953       /* no-op these */
 954       rc = SQLITE_OK;
 955       break;
 956     case SQLITE_FCNTL_PRAGMA: {
 957       char **aFcntl = (char**)pArg;
 958       /*
 959       ** EVIDENCE-OF: R-29875-31678 The argument to the SQLITE_FCNTL_PRAGMA
 960       ** file control is an array of pointers to strings (char**) in which the
 961       ** second element of the array is the name of the pragma and the third
 962       ** element is the argument to the pragma or NULL if the pragma has no
 963       ** argument.
 964       */
 965       if( aFcntl[1] && sqlite3_strnicmp(aFcntl[1],"multiplex_",10)==0 ){
 966         sqlite3_int64 sz = 0;
 967         (void)multiplexFileSize(pConn, &sz);
 968         /*
 969         ** PRAGMA multiplex_truncate=BOOLEAN;
 970         ** PRAGMA multiplex_truncate;
 971         **
 972         ** Turn the multiplexor truncate feature on or off.  Return either
 973         ** "on" or "off" to indicate the new setting.  If the BOOLEAN argument
 974         ** is omitted, just return the current value for the truncate setting.
 975         */
 976         if( sqlite3_stricmp(aFcntl[1],"multiplex_truncate")==0 ){
 977           if( aFcntl[2] && aFcntl[2][0] ){
 978             if( sqlite3_stricmp(aFcntl[2], "on")==0
 979              || sqlite3_stricmp(aFcntl[2], "1")==0 ){
 980               pGroup->bTruncate = 1;
 981             }else
 982             if( sqlite3_stricmp(aFcntl[2], "off")==0
 983              || sqlite3_stricmp(aFcntl[2], "0")==0 ){
 984               pGroup->bTruncate = 0;
 985             }
 986           }
 987           /* EVIDENCE-OF: R-27806-26076 The handler for an SQLITE_FCNTL_PRAGMA
 988           ** file control can optionally make the first element of the char**
 989           ** argument point to a string obtained from sqlite3_mprintf() or the
 990           ** equivalent and that string will become the result of the pragma
 991           ** or the error message if the pragma fails.
 992           */
 993           aFcntl[0] = sqlite3_mprintf(pGroup->bTruncate ? "on" : "off");
 994           rc = SQLITE_OK;
 995           break;
 996         }
 997         /*
 998         ** PRAGMA multiplex_enabled;
 999         **
1000         ** Return 0 or 1 depending on whether the multiplexor is enabled or
1001         ** disabled, respectively.
1002         */
1003         if( sqlite3_stricmp(aFcntl[1],"multiplex_enabled")==0 ){
1004           aFcntl[0] = sqlite3_mprintf("%d", pGroup->bEnabled!=0);
1005           rc = SQLITE_OK;
1006           break;
1007         }
1008         /*
1009         ** PRAGMA multiplex_chunksize;
1010         **
1011         ** Return the chunksize for the multiplexor, or no-op if the
1012         ** multiplexor is not active.
1013         */
1014         if( sqlite3_stricmp(aFcntl[1],"multiplex_chunksize")==0
1015          && pGroup->bEnabled
1016         ){
1017           aFcntl[0] = sqlite3_mprintf("%u", pGroup->szChunk);
1018           rc = SQLITE_OK;
1019           break;
1020         }
1021         /*
1022         ** PRAGMA multiplex_filecount;
1023         **
1024         ** Return the number of disk files currently in use by the
1025         ** multiplexor.  This should be the total database size size
1026         ** divided by the chunksize and rounded up.
1027         */
1028         if( sqlite3_stricmp(aFcntl[1],"multiplex_filecount")==0 ){
1029           int n = 0;
1030           int ii;
1031           for(ii=0; ii<pGroup->nReal; ii++){
1032             if( pGroup->aReal[ii].p!=0 ) n++;
1033           }
1034           aFcntl[0] = sqlite3_mprintf("%d", n);
1035           rc = SQLITE_OK;
1036           break;
1037         }
1038       }
1039       /* If the multiplexor does not handle the pragma, pass it through
1040       ** into the default case. */
1041     }
1042     default:
1043       pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
1044       if( pSubOpen ){
1045         rc = pSubOpen->pMethods->xFileControl(pSubOpen, op, pArg);
1046         if( op==SQLITE_FCNTL_VFSNAME && rc==SQLITE_OK ){
1047          *(char**)pArg = sqlite3_mprintf("multiplex/%z", *(char**)pArg);
1048         }
1049       }
1050       break;
1051   }
1052   return rc;
1053 }
1054
1055 /* Pass xSectorSize requests through to the original VFS unchanged.
1056 */
1057 static int multiplexSectorSize(sqlite3_file *pConn){
1058   multiplexConn *p = (multiplexConn*)pConn;
1059   int rc;
1060   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
1061   if( pSubOpen && pSubOpen->pMethods->xSectorSize ){
1062     return pSubOpen->pMethods->xSectorSize(pSubOpen);
1063   }
1064   return DEFAULT_SECTOR_SIZE;
1065 }
1066
1067 /* Pass xDeviceCharacteristics requests through to the original VFS unchanged.
1068 */
1069 static int multiplexDeviceCharacteristics(sqlite3_file *pConn){
1070   multiplexConn *p = (multiplexConn*)pConn;
1071   int rc;
1072   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
1073   if( pSubOpen ){
1074     return pSubOpen->pMethods->xDeviceCharacteristics(pSubOpen);
1075   }
1076   return 0;
1077 }
1078
1079 /* Pass xShmMap requests through to the original VFS unchanged.
1080 */
1081 static int multiplexShmMap(
1082   sqlite3_file *pConn,            /* Handle open on database file */
1083   int iRegion,                    /* Region to retrieve */
1084   int szRegion,                   /* Size of regions */
1085   int bExtend,                    /* True to extend file if necessary */
1086   void volatile **pp              /* OUT: Mapped memory */
1087 ){
1088   multiplexConn *p = (multiplexConn*)pConn;
1089   int rc;
1090   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
1091   if( pSubOpen ){
1092     return pSubOpen->pMethods->xShmMap(pSubOpen, iRegion, szRegion, bExtend,pp);
1093   }
1094   return SQLITE_IOERR;
1095 }
1096
1097 /* Pass xShmLock requests through to the original VFS unchanged.
1098 */
1099 static int multiplexShmLock(
1100   sqlite3_file *pConn,       /* Database file holding the shared memory */
1101   int ofst,                  /* First lock to acquire or release */
1102   int n,                     /* Number of locks to acquire or release */
1103   int flags                  /* What to do with the lock */
1104 ){
1105   multiplexConn *p = (multiplexConn*)pConn;
1106   int rc;
1107   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
1108   if( pSubOpen ){
1109     return pSubOpen->pMethods->xShmLock(pSubOpen, ofst, n, flags);
1110   }
1111   return SQLITE_BUSY;
1112 }
1113
1114 /* Pass xShmBarrier requests through to the original VFS unchanged.
1115 */
1116 static void multiplexShmBarrier(sqlite3_file *pConn){
1117   multiplexConn *p = (multiplexConn*)pConn;
1118   int rc;
1119   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
1120   if( pSubOpen ){
1121     pSubOpen->pMethods->xShmBarrier(pSubOpen);
1122   }
1123 }
1124
1125 /* Pass xShmUnmap requests through to the original VFS unchanged.
1126 */
1127 static int multiplexShmUnmap(sqlite3_file *pConn, int deleteFlag){
1128   multiplexConn *p = (multiplexConn*)pConn;
1129   int rc;
1130   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
1131   if( pSubOpen ){
1132     return pSubOpen->pMethods->xShmUnmap(pSubOpen, deleteFlag);
1133   }
1134   return SQLITE_OK;
1135 }
1136
1137 /************************** Public Interfaces *****************************/
1138 /*
1139 ** CAPI: Initialize the multiplex VFS shim - sqlite3_multiplex_initialize()
1140 **
1141 ** Use the VFS named zOrigVfsName as the VFS that does the actual work.
1142 ** Use the default if zOrigVfsName==NULL.
1143 **
1144 ** The multiplex VFS shim is named "multiplex".  It will become the default
1145 ** VFS if makeDefault is non-zero.
1146 **
1147 ** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once
1148 ** during start-up.
1149 */
1150 int sqlite3_multiplex_initialize(const char *zOrigVfsName, int makeDefault){
1151   sqlite3_vfs *pOrigVfs;
1152   if( gMultiplex.isInitialized ) return SQLITE_MISUSE;
1153   pOrigVfs = sqlite3_vfs_find(zOrigVfsName);
1154   if( pOrigVfs==0 ) return SQLITE_ERROR;
1155   assert( pOrigVfs!=&gMultiplex.sThisVfs );
1156   gMultiplex.isInitialized = 1;
1157   gMultiplex.pOrigVfs = pOrigVfs;
1158   gMultiplex.sThisVfs = *pOrigVfs;
1159   gMultiplex.sThisVfs.szOsFile += sizeof(multiplexConn);
1160   gMultiplex.sThisVfs.zName = SQLITE_MULTIPLEX_VFS_NAME;
1161   gMultiplex.sThisVfs.xOpen = multiplexOpen;
1162   gMultiplex.sThisVfs.xDelete = multiplexDelete;
1163   gMultiplex.sThisVfs.xAccess = multiplexAccess;
1164   gMultiplex.sThisVfs.xFullPathname = multiplexFullPathname;
1165   gMultiplex.sThisVfs.xDlOpen = multiplexDlOpen;
1166   gMultiplex.sThisVfs.xDlError = multiplexDlError;
1167   gMultiplex.sThisVfs.xDlSym = multiplexDlSym;
1168   gMultiplex.sThisVfs.xDlClose = multiplexDlClose;
1169   gMultiplex.sThisVfs.xRandomness = multiplexRandomness;
1170   gMultiplex.sThisVfs.xSleep = multiplexSleep;
1171   gMultiplex.sThisVfs.xCurrentTime = multiplexCurrentTime;
1172   gMultiplex.sThisVfs.xGetLastError = multiplexGetLastError;
1173   gMultiplex.sThisVfs.xCurrentTimeInt64 = multiplexCurrentTimeInt64;
1174
1175   gMultiplex.sIoMethodsV1.iVersion = 1;
1176   gMultiplex.sIoMethodsV1.xClose = multiplexClose;
1177   gMultiplex.sIoMethodsV1.xRead = multiplexRead;
1178   gMultiplex.sIoMethodsV1.xWrite = multiplexWrite;
1179   gMultiplex.sIoMethodsV1.xTruncate = multiplexTruncate;
1180   gMultiplex.sIoMethodsV1.xSync = multiplexSync;
1181   gMultiplex.sIoMethodsV1.xFileSize = multiplexFileSize;
1182   gMultiplex.sIoMethodsV1.xLock = multiplexLock;
1183   gMultiplex.sIoMethodsV1.xUnlock = multiplexUnlock;
1184   gMultiplex.sIoMethodsV1.xCheckReservedLock = multiplexCheckReservedLock;
1185   gMultiplex.sIoMethodsV1.xFileControl = multiplexFileControl;
1186   gMultiplex.sIoMethodsV1.xSectorSize = multiplexSectorSize;
1187   gMultiplex.sIoMethodsV1.xDeviceCharacteristics =
1188                                             multiplexDeviceCharacteristics;
1189   gMultiplex.sIoMethodsV2 = gMultiplex.sIoMethodsV1;
1190   gMultiplex.sIoMethodsV2.iVersion = 2;
1191   gMultiplex.sIoMethodsV2.xShmMap = multiplexShmMap;
1192   gMultiplex.sIoMethodsV2.xShmLock = multiplexShmLock;
1193   gMultiplex.sIoMethodsV2.xShmBarrier = multiplexShmBarrier;
1194   gMultiplex.sIoMethodsV2.xShmUnmap = multiplexShmUnmap;
1195   sqlite3_vfs_register(&gMultiplex.sThisVfs, makeDefault);
1196
1197   sqlite3_auto_extension((void(*)(void))multiplexFuncInit);
1198
1199   return SQLITE_OK;
1200 }
1201
1202 /*
1203 ** CAPI: Shutdown the multiplex system - sqlite3_multiplex_shutdown()
1204 **
1205 ** All SQLite database connections must be closed before calling this
1206 ** routine.
1207 **
1208 ** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
1209 ** shutting down in order to free all remaining multiplex groups.
1210 */
1211 int sqlite3_multiplex_shutdown(int eForce){
1212   int rc = SQLITE_OK;
1213   if( gMultiplex.isInitialized==0 ) return SQLITE_MISUSE;
1214   gMultiplex.isInitialized = 0;
1215   sqlite3_vfs_unregister(&gMultiplex.sThisVfs);
1216   memset(&gMultiplex, 0, sizeof(gMultiplex));
1217   return rc;
1218 }
1219
1220 /***************************** Test Code ***********************************/
1221 #ifdef SQLITE_TEST
1222 #if defined(INCLUDE_SQLITE_TCL_H)
1223 #  include "sqlite_tcl.h"
1224 #else
1225 #  include "tcl.h"
1226 #  ifndef SQLITE_TCLAPI
1227 #    define SQLITE_TCLAPI
1228 #  endif
1229 #endif
1230 extern const char *sqlite3ErrName(int);
1231
1232
1233 /*
1234 ** tclcmd: sqlite3_multiplex_initialize NAME MAKEDEFAULT
1235 */
1236 static int SQLITE_TCLAPI test_multiplex_initialize(
1237   void * clientData,
1238   Tcl_Interp *interp,
1239   int objc,
1240   Tcl_Obj *CONST objv[]
1241 ){
1242   const char *zName;              /* Name of new multiplex VFS */
1243   int makeDefault;                /* True to make the new VFS the default */
1244   int rc;                         /* Value returned by multiplex_initialize() */
1245
1246   UNUSED_PARAMETER(clientData);
1247
1248   /* Process arguments */
1249   if( objc!=3 ){
1250     Tcl_WrongNumArgs(interp, 1, objv, "NAME MAKEDEFAULT");
1251     return TCL_ERROR;
1252   }
1253   zName = Tcl_GetString(objv[1]);
1254   if( Tcl_GetBooleanFromObj(interp, objv[2], &makeDefault) ) return TCL_ERROR;
1255   if( zName[0]=='\0' ) zName = 0;
1256
1257   /* Call sqlite3_multiplex_initialize() */
1258   rc = sqlite3_multiplex_initialize(zName, makeDefault);
1259   Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
1260
1261   return TCL_OK;
1262 }
1263
1264 /*
1265 ** tclcmd: sqlite3_multiplex_shutdown
1266 */
1267 static int SQLITE_TCLAPI test_multiplex_shutdown(
1268   void * clientData,
1269   Tcl_Interp *interp,
1270   int objc,
1271   Tcl_Obj *CONST objv[]
1272 ){
1273   int rc;                         /* Value returned by multiplex_shutdown() */
1274
1275   UNUSED_PARAMETER(clientData);
1276
1277   if( objc==2 && strcmp(Tcl_GetString(objv[1]),"-force")!=0 ){
1278     objc = 3;
1279   }
1280   if( (objc!=1 && objc!=2) ){
1281     Tcl_WrongNumArgs(interp, 1, objv, "?-force?");
1282     return TCL_ERROR;
1283   }
1284
1285   /* Call sqlite3_multiplex_shutdown() */
1286   rc = sqlite3_multiplex_shutdown(objc==2);
1287   Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
1288
1289   return TCL_OK;
1290 }
1291
1292 /*
1293 ** Tclcmd: test_multiplex_control HANDLE DBNAME SUB-COMMAND ?INT-VALUE?
1294 */
1295 static int SQLITE_TCLAPI test_multiplex_control(
1296   ClientData cd,
1297   Tcl_Interp *interp,
1298   int objc,
1299   Tcl_Obj *CONST objv[]
1300 ){
1301   int rc;                         /* Return code from file_control() */
1302   int idx;                        /* Index in aSub[] */
1303   Tcl_CmdInfo cmdInfo;            /* Command info structure for HANDLE */
1304   sqlite3 *db;                    /* Underlying db handle for HANDLE */
1305   int iValue = 0;
1306   void *pArg = 0;
1307
1308   struct SubCommand {
1309     const char *zName;
1310     int op;
1311     int argtype;
1312   } aSub[] = {
1313     { "enable",       MULTIPLEX_CTRL_ENABLE,           1 },
1314     { "chunk_size",   MULTIPLEX_CTRL_SET_CHUNK_SIZE,   1 },
1315     { "max_chunks",   MULTIPLEX_CTRL_SET_MAX_CHUNKS,   1 },
1316     { 0, 0, 0 }
1317   };
1318
1319   if( objc!=5 ){
1320     Tcl_WrongNumArgs(interp, 1, objv, "HANDLE DBNAME SUB-COMMAND INT-VALUE");
1321     return TCL_ERROR;
1322   }
1323
1324   if( 0==Tcl_GetCommandInfo(interp, Tcl_GetString(objv[1]), &cmdInfo) ){
1325     Tcl_AppendResult(interp, "expected database handle, got \"", 0);
1326     Tcl_AppendResult(interp, Tcl_GetString(objv[1]), "\"", 0);
1327     return TCL_ERROR;
1328   }else{
1329     db = *(sqlite3 **)cmdInfo.objClientData;
1330   }
1331
1332   rc = Tcl_GetIndexFromObjStruct(
1333       interp, objv[3], aSub, sizeof(aSub[0]), "sub-command", 0, &idx
1334   );
1335   if( rc!=TCL_OK ) return rc;
1336
1337   switch( aSub[idx].argtype ){
1338     case 1:
1339       if( Tcl_GetIntFromObj(interp, objv[4], &iValue) ){
1340         return TCL_ERROR;
1341       }
1342       pArg = (void *)&iValue;
1343       break;
1344     default:
1345       Tcl_WrongNumArgs(interp, 4, objv, "SUB-COMMAND");
1346       return TCL_ERROR;
1347   }
1348
1349   rc = sqlite3_file_control(db, Tcl_GetString(objv[2]), aSub[idx].op, pArg);
1350   Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
1351   return (rc==SQLITE_OK) ? TCL_OK : TCL_ERROR;
1352 }
1353
1354 /*
1355 ** This routine registers the custom TCL commands defined in this
1356 ** module.  This should be the only procedure visible from outside
1357 ** of this module.
1358 */
1359 int Sqlitemultiplex_Init(Tcl_Interp *interp){
1360   static struct {
1361      char *zName;
1362      Tcl_ObjCmdProc *xProc;
1363   } aCmd[] = {
1364     { "sqlite3_multiplex_initialize", test_multiplex_initialize },
1365     { "sqlite3_multiplex_shutdown", test_multiplex_shutdown },
1366     { "sqlite3_multiplex_control", test_multiplex_control },
1367   };
1368   int i;
1369
1370   for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
1371     Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
1372   }
1373
1374   return TCL_OK;
1375 }
1376 #endif