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     pGroup->aReal[iChunk].z = 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   }
 276   return SQLITE_OK;
 277 }
 278
 279 /* Translate an sqlite3_file* that is really a multiplexGroup* into
 280 ** the sqlite3_file* for the underlying original VFS.
 281 **
 282 ** For chunk 0, the pGroup->flags determines whether or not a new file
 283 ** is created if it does not already exist.  For chunks 1 and higher, the
 284 ** file is created only if createFlag is 1.
 285 */
 286 static sqlite3_file *multiplexSubOpen(
 287   multiplexGroup *pGroup,    /* The multiplexor group */
 288   int iChunk,                /* Which chunk to open.  0==original file */
 289   int *rc,                   /* Result code in and out */
 290   int *pOutFlags,            /* Output flags */
 291   int createFlag             /* True to create if iChunk>0 */
 292 ){
 293   sqlite3_file *pSubOpen = 0;
 294   sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;        /* Real VFS */
 295
 296 #ifdef SQLITE_ENABLE_8_3_NAMES
 297   /* If JOURNAL_8_3_OFFSET is set to (say) 400, then any overflow files are
 298   ** part of a database journal are named db.401, db.402, and so on. A
 299   ** database may therefore not grow to larger than 400 chunks. Attempting
 300   ** to open chunk 401 indicates the database is full. */
 301   if( iChunk>=SQLITE_MULTIPLEX_JOURNAL_8_3_OFFSET ){
 302     sqlite3_log(SQLITE_FULL, "multiplexed chunk overflow: %s", pGroup->zName);
 303     *rc = SQLITE_FULL;
 304     return 0;
 305   }
 306 #endif
 307
 308   *rc = multiplexSubFilename(pGroup, iChunk);
 309   if( (*rc)==SQLITE_OK && (pSubOpen = pGroup->aReal[iChunk].p)==0 ){
 310     int flags, bExists;
 311     flags = pGroup->flags;
 312     if( createFlag ){
 313       flags |= SQLITE_OPEN_CREATE;
 314     }else if( iChunk==0 ){
 315       /* Fall through */
 316     }else if( pGroup->aReal[iChunk].z==0 ){
 317       return 0;
 318     }else{
 319       *rc = pOrigVfs->xAccess(pOrigVfs, pGroup->aReal[iChunk].z,
 320                               SQLITE_ACCESS_EXISTS, &bExists);
 321      if( *rc || !bExists ){
 322         if( *rc ){
 323           sqlite3_log(*rc, "multiplexor.xAccess failure on %s",
 324                       pGroup->aReal[iChunk].z);
 325         }
 326         return 0;
 327       }
 328       flags &= ~SQLITE_OPEN_CREATE;
 329     }
 330     pSubOpen = sqlite3_malloc64( pOrigVfs->szOsFile );
 331     if( pSubOpen==0 ){
 332       *rc = SQLITE_IOERR_NOMEM;
 333       return 0;
 334     }
 335     pGroup->aReal[iChunk].p = pSubOpen;
 336     *rc = pOrigVfs->xOpen(pOrigVfs, pGroup->aReal[iChunk].z, pSubOpen,
 337                           flags, pOutFlags);
 338     if( (*rc)!=SQLITE_OK ){
 339       sqlite3_log(*rc, "multiplexor.xOpen failure on %s",
 340                   pGroup->aReal[iChunk].z);
 341       sqlite3_free(pSubOpen);
 342       pGroup->aReal[iChunk].p = 0;
 343       return 0;
 344     }
 345   }
 346   return pSubOpen;
 347 }
 348
 349 /*
 350 ** Return the size, in bytes, of chunk number iChunk.  If that chunk
 351 ** does not exist, then return 0.  This function does not distingish between
 352 ** non-existant files and zero-length files.
 353 */
 354 static sqlite3_int64 multiplexSubSize(
 355   multiplexGroup *pGroup,    /* The multiplexor group */
 356   int iChunk,                /* Which chunk to open.  0==original file */
 357   int *rc                    /* Result code in and out */
 358 ){
 359   sqlite3_file *pSub;
 360   sqlite3_int64 sz = 0;
 361
 362   if( *rc ) return 0;
 363   pSub = multiplexSubOpen(pGroup, iChunk, rc, NULL, 0);
 364   if( pSub==0 ) return 0;
 365   *rc = pSub->pMethods->xFileSize(pSub, &sz);
 366   return sz;
 367 }
 368
 369 /*
 370 ** This is the implementation of the multiplex_control() SQL function.
 371 */
 372 static void multiplexControlFunc(
 373   sqlite3_context *context,
 374   int argc,
 375   sqlite3_value **argv
 376 ){
 377   int rc = SQLITE_OK;
 378   sqlite3 *db = sqlite3_context_db_handle(context);
 379   int op = 0;
 380   int iVal;
 381
 382   if( !db || argc!=2 ){
 383     rc = SQLITE_ERROR;
 384   }else{
 385     /* extract params */
 386     op = sqlite3_value_int(argv[0]);
 387     iVal = sqlite3_value_int(argv[1]);
 388     /* map function op to file_control op */
 389     switch( op ){
 390       case 1:
 391         op = MULTIPLEX_CTRL_ENABLE;
 392         break;
 393       case 2:
 394         op = MULTIPLEX_CTRL_SET_CHUNK_SIZE;
 395         break;
 396       case 3:
 397         op = MULTIPLEX_CTRL_SET_MAX_CHUNKS;
 398         break;
 399       default:
 400         rc = SQLITE_NOTFOUND;
 401         break;
 402     }
 403   }
 404   if( rc==SQLITE_OK ){
 405     rc = sqlite3_file_control(db, 0, op, &iVal);
 406   }
 407   sqlite3_result_error_code(context, rc);
 408 }
 409
 410 /*
 411 ** This is the entry point to register the auto-extension for the
 412 ** multiplex_control() function.
 413 */
 414 static int multiplexFuncInit(
 415   sqlite3 *db,
 416   char **pzErrMsg,
 417   const sqlite3_api_routines *pApi
 418 ){
 419   int rc;
 420   rc = sqlite3_create_function(db, "multiplex_control", 2, SQLITE_ANY,
 421       0, multiplexControlFunc, 0, 0);
 422   return rc;
 423 }
 424
 425 /*
 426 ** Close a single sub-file in the connection group.
 427 */
 428 static void multiplexSubClose(
 429   multiplexGroup *pGroup,
 430   int iChunk,
 431   sqlite3_vfs *pOrigVfs
 432 ){
 433   sqlite3_file *pSubOpen = pGroup->aReal[iChunk].p;
 434   if( pSubOpen ){
 435     pSubOpen->pMethods->xClose(pSubOpen);
 436     if( pOrigVfs && pGroup->aReal[iChunk].z ){
 437       pOrigVfs->xDelete(pOrigVfs, pGroup->aReal[iChunk].z, 0);
 438     }
 439     sqlite3_free(pGroup->aReal[iChunk].p);
 440   }
 441   sqlite3_free(pGroup->aReal[iChunk].z);
 442   memset(&pGroup->aReal[iChunk], 0, sizeof(pGroup->aReal[iChunk]));
 443 }
 444
 445 /*
 446 ** Deallocate memory held by a multiplexGroup
 447 */
 448 static void multiplexFreeComponents(multiplexGroup *pGroup){
 449   int i;
 450   for(i=0; i<pGroup->nReal; i++){ multiplexSubClose(pGroup, i, 0); }
 451   sqlite3_free(pGroup->aReal);
 452   pGroup->aReal = 0;
 453   pGroup->nReal = 0;
 454 }
 455
 456
 457 /************************* VFS Method Wrappers *****************************/
 458
 459 /*
 460 ** This is the xOpen method used for the "multiplex" VFS.
 461 **
 462 ** Most of the work is done by the underlying original VFS.  This method
 463 ** simply links the new file into the appropriate multiplex group if it is a
 464 ** file that needs to be tracked.
 465 */
 466 static int multiplexOpen(
 467   sqlite3_vfs *pVfs,         /* The multiplex VFS */
 468   const char *zName,         /* Name of file to be opened */
 469   sqlite3_file *pConn,       /* Fill in this file descriptor */
 470   int flags,                 /* Flags to control the opening */
 471   int *pOutFlags             /* Flags showing results of opening */
 472 ){
 473   int rc = SQLITE_OK;                  /* Result code */
 474   multiplexConn *pMultiplexOpen;       /* The new multiplex file descriptor */
 475   multiplexGroup *pGroup = 0;          /* Corresponding multiplexGroup object */
 476   sqlite3_file *pSubOpen = 0;                    /* Real file descriptor */
 477   sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
 478   int nName = 0;
 479   int sz = 0;
 480   char *zToFree = 0;
 481
 482   UNUSED_PARAMETER(pVfs);
 483   memset(pConn, 0, pVfs->szOsFile);
 484   assert( zName || (flags & SQLITE_OPEN_DELETEONCLOSE) );
 485
 486   /* We need to create a group structure and manage
 487   ** access to this group of files.
 488   */
 489   pMultiplexOpen = (multiplexConn*)pConn;
 490
 491   if( rc==SQLITE_OK ){
 492     /* allocate space for group */
 493     nName = zName ? multiplexStrlen30(zName) : 0;
 494     sz = sizeof(multiplexGroup)                             /* multiplexGroup */
 495        + nName + 1;                                         /* zName */
 496     pGroup = sqlite3_malloc64( sz );
 497     if( pGroup==0 ){
 498       rc = SQLITE_NOMEM;
 499     }
 500   }
 501
 502   if( rc==SQLITE_OK ){
 503     const char *zUri = (flags & SQLITE_OPEN_URI) ? zName : 0;
 504     /* assign pointers to extra space allocated */
 505     memset(pGroup, 0, sz);
 506     pMultiplexOpen->pGroup = pGroup;
 507     pGroup->bEnabled = (unsigned char)-1;
 508     pGroup->bTruncate = (unsigned char)sqlite3_uri_boolean(zUri, "truncate",
 509                                    (flags & SQLITE_OPEN_MAIN_DB)==0);
 510     pGroup->szChunk = (int)sqlite3_uri_int64(zUri, "chunksize",
 511                                         SQLITE_MULTIPLEX_CHUNK_SIZE);
 512     pGroup->szChunk = (pGroup->szChunk+0xffff)&~0xffff;
 513     if( zName ){
 514       char *p = (char *)&pGroup[1];
 515       pGroup->zName = p;
 516       memcpy(pGroup->zName, zName, nName+1);
 517       pGroup->nName = nName;
 518     }
 519     if( pGroup->bEnabled ){
 520       /* Make sure that the chunksize is such that the pending byte does not
 521       ** falls at the end of a chunk.  A region of up to 64K following
 522       ** the pending byte is never written, so if the pending byte occurs
 523       ** near the end of a chunk, that chunk will be too small. */
 524 #ifndef SQLITE_OMIT_WSD
 525       extern int sqlite3PendingByte;
 526 #else
 527       int sqlite3PendingByte = 0x40000000;
 528 #endif
 529       while( (sqlite3PendingByte % pGroup->szChunk)>=(pGroup->szChunk-65536) ){
 530         pGroup->szChunk += 65536;
 531       }
 532     }
 533     pGroup->flags = flags;
 534     rc = multiplexSubFilename(pGroup, 1);
 535     if( rc==SQLITE_OK ){
 536       pSubOpen = multiplexSubOpen(pGroup, 0, &rc, pOutFlags, 0);
 537       if( pSubOpen==0 && rc==SQLITE_OK ) rc = SQLITE_CANTOPEN;
 538     }
 539     if( rc==SQLITE_OK ){
 540       sqlite3_int64 sz64;
 541
 542       rc = pSubOpen->pMethods->xFileSize(pSubOpen, &sz64);
 543       if( rc==SQLITE_OK && zName ){
 544         int bExists;
 545         if( flags & SQLITE_OPEN_MASTER_JOURNAL ){
 546           pGroup->bEnabled = 0;
 547         }else
 548         if( sz64==0 ){
 549           if( flags & SQLITE_OPEN_MAIN_JOURNAL ){
 550             /* If opening a main journal file and the first chunk is zero
 551             ** bytes in size, delete any subsequent chunks from the
 552             ** file-system. */
 553             int iChunk = 1;
 554             do {
 555               rc = pOrigVfs->xAccess(pOrigVfs,
 556                   pGroup->aReal[iChunk].z, SQLITE_ACCESS_EXISTS, &bExists
 557               );
 558               if( rc==SQLITE_OK && bExists ){
 559                 rc = pOrigVfs->xDelete(pOrigVfs, pGroup->aReal[iChunk].z, 0);
 560                 if( rc==SQLITE_OK ){
 561                   rc = multiplexSubFilename(pGroup, ++iChunk);
 562                 }
 563               }
 564             }while( rc==SQLITE_OK && bExists );
 565           }
 566         }else{
 567           /* If the first overflow file exists and if the size of the main file
 568           ** is different from the chunk size, that means the chunk size is set
 569           ** set incorrectly.  So fix it.
 570           **
 571           ** Or, if the first overflow file does not exist and the main file is
 572           ** larger than the chunk size, that means the chunk size is too small.
 573           ** But we have no way of determining the intended chunk size, so
 574           ** just disable the multiplexor all togethre.
 575           */
 576           rc = pOrigVfs->xAccess(pOrigVfs, pGroup->aReal[1].z,
 577               SQLITE_ACCESS_EXISTS, &bExists);
 578           bExists = multiplexSubSize(pGroup, 1, &rc)>0;
 579           if( rc==SQLITE_OK && bExists && sz64==(sz64&0xffff0000) && sz64>0
 580               && sz64!=pGroup->szChunk ){
 581             pGroup->szChunk = (int)sz64;
 582           }else if( rc==SQLITE_OK && !bExists && sz64>pGroup->szChunk ){
 583             pGroup->bEnabled = 0;
 584           }
 585         }
 586       }
 587     }
 588
 589     if( rc==SQLITE_OK ){
 590       if( pSubOpen->pMethods->iVersion==1 ){
 591         pMultiplexOpen->base.pMethods = &gMultiplex.sIoMethodsV1;
 592       }else{
 593         pMultiplexOpen->base.pMethods = &gMultiplex.sIoMethodsV2;
 594       }
 595     }else{
 596       multiplexFreeComponents(pGroup);
 597       sqlite3_free(pGroup);
 598     }
 599   }
 600   sqlite3_free(zToFree);
 601   return rc;
 602 }
 603
 604 /*
 605 ** This is the xDelete method used for the "multiplex" VFS.
 606 ** It attempts to delete the filename specified.
 607 */
 608 static int multiplexDelete(
 609   sqlite3_vfs *pVfs,         /* The multiplex VFS */
 610   const char *zName,         /* Name of file to delete */
 611   int syncDir
 612 ){
 613   int rc;
 614   sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
 615   rc = pOrigVfs->xDelete(pOrigVfs, zName, syncDir);
 616   if( rc==SQLITE_OK ){
 617     /* If the main chunk was deleted successfully, also delete any subsequent
 618     ** chunks - starting with the last (highest numbered).
 619     */
 620     int nName = (int)strlen(zName);
 621     char *z;
 622     z = sqlite3_malloc64(nName + 5);
 623     if( z==0 ){
 624       rc = SQLITE_IOERR_NOMEM;
 625     }else{
 626       int iChunk = 0;
 627       int bExists;
 628       do{
 629         multiplexFilename(zName, nName, SQLITE_OPEN_MAIN_JOURNAL, ++iChunk, z);
 630         rc = pOrigVfs->xAccess(pOrigVfs, z, SQLITE_ACCESS_EXISTS, &bExists);
 631       }while( rc==SQLITE_OK && bExists );
 632       while( rc==SQLITE_OK && iChunk>1 ){
 633         multiplexFilename(zName, nName, SQLITE_OPEN_MAIN_JOURNAL, --iChunk, z);
 634         rc = pOrigVfs->xDelete(pOrigVfs, z, syncDir);
 635       }
 636       if( rc==SQLITE_OK ){
 637         iChunk = 0;
 638         do{
 639           multiplexFilename(zName, nName, SQLITE_OPEN_WAL, ++iChunk, z);
 640           rc = pOrigVfs->xAccess(pOrigVfs, z, SQLITE_ACCESS_EXISTS, &bExists);
 641         }while( rc==SQLITE_OK && bExists );
 642         while( rc==SQLITE_OK && iChunk>1 ){
 643           multiplexFilename(zName, nName, SQLITE_OPEN_WAL, --iChunk, z);
 644           rc = pOrigVfs->xDelete(pOrigVfs, z, syncDir);
 645         }
 646       }
 647     }
 648     sqlite3_free(z);
 649   }
 650   return rc;
 651 }
 652
 653 static int multiplexAccess(sqlite3_vfs *a, const char *b, int c, int *d){
 654   return gMultiplex.pOrigVfs->xAccess(gMultiplex.pOrigVfs, b, c, d);
 655 }
 656 static int multiplexFullPathname(sqlite3_vfs *a, const char *b, int c, char *d){
 657   return gMultiplex.pOrigVfs->xFullPathname(gMultiplex.pOrigVfs, b, c, d);
 658 }
 659 static void *multiplexDlOpen(sqlite3_vfs *a, const char *b){
 660   return gMultiplex.pOrigVfs->xDlOpen(gMultiplex.pOrigVfs, b);
 661 }
 662 static void multiplexDlError(sqlite3_vfs *a, int b, char *c){
 663   gMultiplex.pOrigVfs->xDlError(gMultiplex.pOrigVfs, b, c);
 664 }
 665 static void (*multiplexDlSym(sqlite3_vfs *a, void *b, const char *c))(void){
 666   return gMultiplex.pOrigVfs->xDlSym(gMultiplex.pOrigVfs, b, c);
 667 }
 668 static void multiplexDlClose(sqlite3_vfs *a, void *b){
 669   gMultiplex.pOrigVfs->xDlClose(gMultiplex.pOrigVfs, b);
 670 }
 671 static int multiplexRandomness(sqlite3_vfs *a, int b, char *c){
 672   return gMultiplex.pOrigVfs->xRandomness(gMultiplex.pOrigVfs, b, c);
 673 }
 674 static int multiplexSleep(sqlite3_vfs *a, int b){
 675   return gMultiplex.pOrigVfs->xSleep(gMultiplex.pOrigVfs, b);
 676 }
 677 static int multiplexCurrentTime(sqlite3_vfs *a, double *b){
 678   return gMultiplex.pOrigVfs->xCurrentTime(gMultiplex.pOrigVfs, b);
 679 }
 680 static int multiplexGetLastError(sqlite3_vfs *a, int b, char *c){
 681   if( gMultiplex.pOrigVfs->xGetLastError ){
 682     return gMultiplex.pOrigVfs->xGetLastError(gMultiplex.pOrigVfs, b, c);
 683   }else{
 684     return 0;
 685   }
 686 }
 687 static int multiplexCurrentTimeInt64(sqlite3_vfs *a, sqlite3_int64 *b){
 688   return gMultiplex.pOrigVfs->xCurrentTimeInt64(gMultiplex.pOrigVfs, b);
 689 }
 690
 691 /************************ I/O Method Wrappers *******************************/
 692
 693 /* xClose requests get passed through to the original VFS.
 694 ** We loop over all open chunk handles and close them.
 695 ** The group structure for this file is unlinked from
 696 ** our list of groups and freed.
 697 */
 698 static int multiplexClose(sqlite3_file *pConn){
 699   multiplexConn *p = (multiplexConn*)pConn;
 700   multiplexGroup *pGroup = p->pGroup;
 701   int rc = SQLITE_OK;
 702   multiplexFreeComponents(pGroup);
 703   sqlite3_free(pGroup);
 704   return rc;
 705 }
 706
 707 /* Pass xRead requests thru to the original VFS after
 708 ** determining the correct chunk to operate on.
 709 ** Break up reads across chunk boundaries.
 710 */
 711 static int multiplexRead(
 712   sqlite3_file *pConn,
 713   void *pBuf,
 714   int iAmt,
 715   sqlite3_int64 iOfst
 716 ){
 717   multiplexConn *p = (multiplexConn*)pConn;
 718   multiplexGroup *pGroup = p->pGroup;
 719   int rc = SQLITE_OK;
 720   if( !pGroup->bEnabled ){
 721     sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
 722     if( pSubOpen==0 ){
 723       rc = SQLITE_IOERR_READ;
 724     }else{
 725       rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt, iOfst);
 726     }
 727   }else{
 728     while( iAmt > 0 ){
 729       int i = (int)(iOfst / pGroup->szChunk);
 730       sqlite3_file *pSubOpen;
 731       pSubOpen = multiplexSubOpen(pGroup, i, &rc, NULL, 1);
 732       if( pSubOpen ){
 733         int extra = ((int)(iOfst % pGroup->szChunk) + iAmt) - pGroup->szChunk;
 734         if( extra<0 ) extra = 0;
 735         iAmt -= extra;
 736         rc = pSubOpen->pMethods->xRead(pSubOpen, pBuf, iAmt,
 737                                        iOfst % pGroup->szChunk);
 738         if( rc!=SQLITE_OK ) break;
 739         pBuf = (char *)pBuf + iAmt;
 740         iOfst += iAmt;
 741         iAmt = extra;
 742       }else{
 743         rc = SQLITE_IOERR_READ;
 744         break;
 745       }
 746     }
 747   }
 748
 749   return rc;
 750 }
 751
 752 /* Pass xWrite requests thru to the original VFS after
 753 ** determining the correct chunk to operate on.
 754 ** Break up writes across chunk boundaries.
 755 */
 756 static int multiplexWrite(
 757   sqlite3_file *pConn,
 758   const void *pBuf,
 759   int iAmt,
 760   sqlite3_int64 iOfst
 761 ){
 762   multiplexConn *p = (multiplexConn*)pConn;
 763   multiplexGroup *pGroup = p->pGroup;
 764   int rc = SQLITE_OK;
 765   if( !pGroup->bEnabled ){
 766     sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
 767     if( pSubOpen==0 ){
 768       rc = SQLITE_IOERR_WRITE;
 769     }else{
 770       rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt, iOfst);
 771     }
 772   }else{
 773     while( rc==SQLITE_OK && iAmt>0 ){
 774       int i = (int)(iOfst / pGroup->szChunk);
 775       sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, i, &rc, NULL, 1);
 776       if( pSubOpen ){
 777         int extra = ((int)(iOfst % pGroup->szChunk) + iAmt) -
 778                     pGroup->szChunk;
 779         if( extra<0 ) extra = 0;
 780         iAmt -= extra;
 781         rc = pSubOpen->pMethods->xWrite(pSubOpen, pBuf, iAmt,
 782                                         iOfst % pGroup->szChunk);
 783         pBuf = (char *)pBuf + iAmt;
 784         iOfst += iAmt;
 785         iAmt = extra;
 786       }
 787     }
 788   }
 789   return rc;
 790 }
 791
 792 /* Pass xTruncate requests thru to the original VFS after
 793 ** determining the correct chunk to operate on.  Delete any
 794 ** chunks above the truncate mark.
 795 */
 796 static int multiplexTruncate(sqlite3_file *pConn, sqlite3_int64 size){
 797   multiplexConn *p = (multiplexConn*)pConn;
 798   multiplexGroup *pGroup = p->pGroup;
 799   int rc = SQLITE_OK;
 800   if( !pGroup->bEnabled ){
 801     sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
 802     if( pSubOpen==0 ){
 803       rc = SQLITE_IOERR_TRUNCATE;
 804     }else{
 805       rc = pSubOpen->pMethods->xTruncate(pSubOpen, size);
 806     }
 807   }else{
 808     int i;
 809     int iBaseGroup = (int)(size / pGroup->szChunk);
 810     sqlite3_file *pSubOpen;
 811     sqlite3_vfs *pOrigVfs = gMultiplex.pOrigVfs;   /* Real VFS */
 812     /* delete the chunks above the truncate limit */
 813     for(i = pGroup->nReal-1; i>iBaseGroup && rc==SQLITE_OK; i--){
 814       if( pGroup->bTruncate ){
 815         multiplexSubClose(pGroup, i, pOrigVfs);
 816       }else{
 817         pSubOpen = multiplexSubOpen(pGroup, i, &rc, 0, 0);
 818         if( pSubOpen ){
 819           rc = pSubOpen->pMethods->xTruncate(pSubOpen, 0);
 820         }
 821       }
 822     }
 823     if( rc==SQLITE_OK ){
 824       pSubOpen = multiplexSubOpen(pGroup, iBaseGroup, &rc, 0, 0);
 825       if( pSubOpen ){
 826         rc = pSubOpen->pMethods->xTruncate(pSubOpen, size % pGroup->szChunk);
 827       }
 828     }
 829     if( rc ) rc = SQLITE_IOERR_TRUNCATE;
 830   }
 831   return rc;
 832 }
 833
 834 /* Pass xSync requests through to the original VFS without change
 835 */
 836 static int multiplexSync(sqlite3_file *pConn, int flags){
 837   multiplexConn *p = (multiplexConn*)pConn;
 838   multiplexGroup *pGroup = p->pGroup;
 839   int rc = SQLITE_OK;
 840   int i;
 841   for(i=0; i<pGroup->nReal; i++){
 842     sqlite3_file *pSubOpen = pGroup->aReal[i].p;
 843     if( pSubOpen ){
 844       int rc2 = pSubOpen->pMethods->xSync(pSubOpen, flags);
 845       if( rc2!=SQLITE_OK ) rc = rc2;
 846     }
 847   }
 848   return rc;
 849 }
 850
 851 /* Pass xFileSize requests through to the original VFS.
 852 ** Aggregate the size of all the chunks before returning.
 853 */
 854 static int multiplexFileSize(sqlite3_file *pConn, sqlite3_int64 *pSize){
 855   multiplexConn *p = (multiplexConn*)pConn;
 856   multiplexGroup *pGroup = p->pGroup;
 857   int rc = SQLITE_OK;
 858   int i;
 859   if( !pGroup->bEnabled ){
 860     sqlite3_file *pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
 861     if( pSubOpen==0 ){
 862       rc = SQLITE_IOERR_FSTAT;
 863     }else{
 864       rc = pSubOpen->pMethods->xFileSize(pSubOpen, pSize);
 865     }
 866   }else{
 867     *pSize = 0;
 868     for(i=0; rc==SQLITE_OK; i++){
 869       sqlite3_int64 sz = multiplexSubSize(pGroup, i, &rc);
 870       if( sz==0 ) break;
 871       *pSize = i*(sqlite3_int64)pGroup->szChunk + sz;
 872     }
 873   }
 874   return rc;
 875 }
 876
 877 /* Pass xLock requests through to the original VFS unchanged.
 878 */
 879 static int multiplexLock(sqlite3_file *pConn, int lock){
 880   multiplexConn *p = (multiplexConn*)pConn;
 881   int rc;
 882   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
 883   if( pSubOpen ){
 884     return pSubOpen->pMethods->xLock(pSubOpen, lock);
 885   }
 886   return SQLITE_BUSY;
 887 }
 888
 889 /* Pass xUnlock requests through to the original VFS unchanged.
 890 */
 891 static int multiplexUnlock(sqlite3_file *pConn, int lock){
 892   multiplexConn *p = (multiplexConn*)pConn;
 893   int rc;
 894   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
 895   if( pSubOpen ){
 896     return pSubOpen->pMethods->xUnlock(pSubOpen, lock);
 897   }
 898   return SQLITE_IOERR_UNLOCK;
 899 }
 900
 901 /* Pass xCheckReservedLock requests through to the original VFS unchanged.
 902 */
 903 static int multiplexCheckReservedLock(sqlite3_file *pConn, int *pResOut){
 904   multiplexConn *p = (multiplexConn*)pConn;
 905   int rc;
 906   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
 907   if( pSubOpen ){
 908     return pSubOpen->pMethods->xCheckReservedLock(pSubOpen, pResOut);
 909   }
 910   return SQLITE_IOERR_CHECKRESERVEDLOCK;
 911 }
 912
 913 /* Pass xFileControl requests through to the original VFS unchanged,
 914 ** except for any MULTIPLEX_CTRL_* requests here.
 915 */
 916 static int multiplexFileControl(sqlite3_file *pConn, int op, void *pArg){
 917   multiplexConn *p = (multiplexConn*)pConn;
 918   multiplexGroup *pGroup = p->pGroup;
 919   int rc = SQLITE_ERROR;
 920   sqlite3_file *pSubOpen;
 921
 922   if( !gMultiplex.isInitialized ) return SQLITE_MISUSE;
 923   switch( op ){
 924     case MULTIPLEX_CTRL_ENABLE:
 925       if( pArg ) {
 926         int bEnabled = *(int *)pArg;
 927         pGroup->bEnabled = (unsigned char)bEnabled;
 928         rc = SQLITE_OK;
 929       }
 930       break;
 931     case MULTIPLEX_CTRL_SET_CHUNK_SIZE:
 932       if( pArg ) {
 933         unsigned int szChunk = *(unsigned*)pArg;
 934         if( szChunk<1 ){
 935           rc = SQLITE_MISUSE;
 936         }else{
 937           /* Round up to nearest multiple of MAX_PAGE_SIZE. */
 938           szChunk = (szChunk + (MAX_PAGE_SIZE-1));
 939           szChunk &= ~(MAX_PAGE_SIZE-1);
 940           pGroup->szChunk = szChunk;
 941           rc = SQLITE_OK;
 942         }
 943       }
 944       break;
 945     case MULTIPLEX_CTRL_SET_MAX_CHUNKS:
 946       rc = SQLITE_OK;
 947       break;
 948     case SQLITE_FCNTL_SIZE_HINT:
 949     case SQLITE_FCNTL_CHUNK_SIZE:
 950       /* no-op these */
 951       rc = SQLITE_OK;
 952       break;
 953     case SQLITE_FCNTL_PRAGMA: {
 954       char **aFcntl = (char**)pArg;
 955       /*
 956       ** EVIDENCE-OF: R-29875-31678 The argument to the SQLITE_FCNTL_PRAGMA
 957       ** file control is an array of pointers to strings (char**) in which the
 958       ** second element of the array is the name of the pragma and the third
 959       ** element is the argument to the pragma or NULL if the pragma has no
 960       ** argument.
 961       */
 962       if( aFcntl[1] && sqlite3_stricmp(aFcntl[1],"multiplex_truncate")==0 ){
 963         if( aFcntl[2] && aFcntl[2][0] ){
 964           if( sqlite3_stricmp(aFcntl[2], "on")==0
 965            || sqlite3_stricmp(aFcntl[2], "1")==0 ){
 966             pGroup->bTruncate = 1;
 967           }else
 968           if( sqlite3_stricmp(aFcntl[2], "off")==0
 969            || sqlite3_stricmp(aFcntl[2], "0")==0 ){
 970             pGroup->bTruncate = 0;
 971           }
 972         }
 973         /* EVIDENCE-OF: R-27806-26076 The handler for an SQLITE_FCNTL_PRAGMA
 974         ** file control can optionally make the first element of the char**
 975         ** argument point to a string obtained from sqlite3_mprintf() or the
 976         ** equivalent and that string will become the result of the pragma
 977         ** or the error message if the pragma fails.
 978         */
 979         aFcntl[0] = sqlite3_mprintf(pGroup->bTruncate ? "on" : "off");
 980         rc = SQLITE_OK;
 981         break;
 982       }
 983       /* If the multiplexor does not handle the pragma, pass it through
 984       ** into the default case. */
 985     }
 986     default:
 987       pSubOpen = multiplexSubOpen(pGroup, 0, &rc, NULL, 0);
 988       if( pSubOpen ){
 989         rc = pSubOpen->pMethods->xFileControl(pSubOpen, op, pArg);
 990         if( op==SQLITE_FCNTL_VFSNAME && rc==SQLITE_OK ){
 991          *(char**)pArg = sqlite3_mprintf("multiplex/%z", *(char**)pArg);
 992         }
 993       }
 994       break;
 995   }
 996   return rc;
 997 }
 998
 999 /* Pass xSectorSize requests through to the original VFS unchanged.
1000 */
1001 static int multiplexSectorSize(sqlite3_file *pConn){
1002   multiplexConn *p = (multiplexConn*)pConn;
1003   int rc;
1004   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
1005   if( pSubOpen && pSubOpen->pMethods->xSectorSize ){
1006     return pSubOpen->pMethods->xSectorSize(pSubOpen);
1007   }
1008   return DEFAULT_SECTOR_SIZE;
1009 }
1010
1011 /* Pass xDeviceCharacteristics requests through to the original VFS unchanged.
1012 */
1013 static int multiplexDeviceCharacteristics(sqlite3_file *pConn){
1014   multiplexConn *p = (multiplexConn*)pConn;
1015   int rc;
1016   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
1017   if( pSubOpen ){
1018     return pSubOpen->pMethods->xDeviceCharacteristics(pSubOpen);
1019   }
1020   return 0;
1021 }
1022
1023 /* Pass xShmMap requests through to the original VFS unchanged.
1024 */
1025 static int multiplexShmMap(
1026   sqlite3_file *pConn,            /* Handle open on database file */
1027   int iRegion,                    /* Region to retrieve */
1028   int szRegion,                   /* Size of regions */
1029   int bExtend,                    /* True to extend file if necessary */
1030   void volatile **pp              /* OUT: Mapped memory */
1031 ){
1032   multiplexConn *p = (multiplexConn*)pConn;
1033   int rc;
1034   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
1035   if( pSubOpen ){
1036     return pSubOpen->pMethods->xShmMap(pSubOpen, iRegion, szRegion, bExtend,pp);
1037   }
1038   return SQLITE_IOERR;
1039 }
1040
1041 /* Pass xShmLock requests through to the original VFS unchanged.
1042 */
1043 static int multiplexShmLock(
1044   sqlite3_file *pConn,       /* Database file holding the shared memory */
1045   int ofst,                  /* First lock to acquire or release */
1046   int n,                     /* Number of locks to acquire or release */
1047   int flags                  /* What to do with the lock */
1048 ){
1049   multiplexConn *p = (multiplexConn*)pConn;
1050   int rc;
1051   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
1052   if( pSubOpen ){
1053     return pSubOpen->pMethods->xShmLock(pSubOpen, ofst, n, flags);
1054   }
1055   return SQLITE_BUSY;
1056 }
1057
1058 /* Pass xShmBarrier requests through to the original VFS unchanged.
1059 */
1060 static void multiplexShmBarrier(sqlite3_file *pConn){
1061   multiplexConn *p = (multiplexConn*)pConn;
1062   int rc;
1063   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
1064   if( pSubOpen ){
1065     pSubOpen->pMethods->xShmBarrier(pSubOpen);
1066   }
1067 }
1068
1069 /* Pass xShmUnmap requests through to the original VFS unchanged.
1070 */
1071 static int multiplexShmUnmap(sqlite3_file *pConn, int deleteFlag){
1072   multiplexConn *p = (multiplexConn*)pConn;
1073   int rc;
1074   sqlite3_file *pSubOpen = multiplexSubOpen(p->pGroup, 0, &rc, NULL, 0);
1075   if( pSubOpen ){
1076     return pSubOpen->pMethods->xShmUnmap(pSubOpen, deleteFlag);
1077   }
1078   return SQLITE_OK;
1079 }
1080
1081 /************************** Public Interfaces *****************************/
1082 /*
1083 ** CAPI: Initialize the multiplex VFS shim - sqlite3_multiplex_initialize()
1084 **
1085 ** Use the VFS named zOrigVfsName as the VFS that does the actual work.
1086 ** Use the default if zOrigVfsName==NULL.
1087 **
1088 ** The multiplex VFS shim is named "multiplex".  It will become the default
1089 ** VFS if makeDefault is non-zero.
1090 **
1091 ** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once
1092 ** during start-up.
1093 */
1094 int sqlite3_multiplex_initialize(const char *zOrigVfsName, int makeDefault){
1095   sqlite3_vfs *pOrigVfs;
1096   if( gMultiplex.isInitialized ) return SQLITE_MISUSE;
1097   pOrigVfs = sqlite3_vfs_find(zOrigVfsName);
1098   if( pOrigVfs==0 ) return SQLITE_ERROR;
1099   assert( pOrigVfs!=&gMultiplex.sThisVfs );
1100   gMultiplex.isInitialized = 1;
1101   gMultiplex.pOrigVfs = pOrigVfs;
1102   gMultiplex.sThisVfs = *pOrigVfs;
1103   gMultiplex.sThisVfs.szOsFile += sizeof(multiplexConn);
1104   gMultiplex.sThisVfs.zName = SQLITE_MULTIPLEX_VFS_NAME;
1105   gMultiplex.sThisVfs.xOpen = multiplexOpen;
1106   gMultiplex.sThisVfs.xDelete = multiplexDelete;
1107   gMultiplex.sThisVfs.xAccess = multiplexAccess;
1108   gMultiplex.sThisVfs.xFullPathname = multiplexFullPathname;
1109   gMultiplex.sThisVfs.xDlOpen = multiplexDlOpen;
1110   gMultiplex.sThisVfs.xDlError = multiplexDlError;
1111   gMultiplex.sThisVfs.xDlSym = multiplexDlSym;
1112   gMultiplex.sThisVfs.xDlClose = multiplexDlClose;
1113   gMultiplex.sThisVfs.xRandomness = multiplexRandomness;
1114   gMultiplex.sThisVfs.xSleep = multiplexSleep;
1115   gMultiplex.sThisVfs.xCurrentTime = multiplexCurrentTime;
1116   gMultiplex.sThisVfs.xGetLastError = multiplexGetLastError;
1117   gMultiplex.sThisVfs.xCurrentTimeInt64 = multiplexCurrentTimeInt64;
1118
1119   gMultiplex.sIoMethodsV1.iVersion = 1;
1120   gMultiplex.sIoMethodsV1.xClose = multiplexClose;
1121   gMultiplex.sIoMethodsV1.xRead = multiplexRead;
1122   gMultiplex.sIoMethodsV1.xWrite = multiplexWrite;
1123   gMultiplex.sIoMethodsV1.xTruncate = multiplexTruncate;
1124   gMultiplex.sIoMethodsV1.xSync = multiplexSync;
1125   gMultiplex.sIoMethodsV1.xFileSize = multiplexFileSize;
1126   gMultiplex.sIoMethodsV1.xLock = multiplexLock;
1127   gMultiplex.sIoMethodsV1.xUnlock = multiplexUnlock;
1128   gMultiplex.sIoMethodsV1.xCheckReservedLock = multiplexCheckReservedLock;
1129   gMultiplex.sIoMethodsV1.xFileControl = multiplexFileControl;
1130   gMultiplex.sIoMethodsV1.xSectorSize = multiplexSectorSize;
1131   gMultiplex.sIoMethodsV1.xDeviceCharacteristics =
1132                                             multiplexDeviceCharacteristics;
1133   gMultiplex.sIoMethodsV2 = gMultiplex.sIoMethodsV1;
1134   gMultiplex.sIoMethodsV2.iVersion = 2;
1135   gMultiplex.sIoMethodsV2.xShmMap = multiplexShmMap;
1136   gMultiplex.sIoMethodsV2.xShmLock = multiplexShmLock;
1137   gMultiplex.sIoMethodsV2.xShmBarrier = multiplexShmBarrier;
1138   gMultiplex.sIoMethodsV2.xShmUnmap = multiplexShmUnmap;
1139   sqlite3_vfs_register(&gMultiplex.sThisVfs, makeDefault);
1140
1141   sqlite3_auto_extension((void(*)(void))multiplexFuncInit);
1142
1143   return SQLITE_OK;
1144 }
1145
1146 /*
1147 ** CAPI: Shutdown the multiplex system - sqlite3_multiplex_shutdown()
1148 **
1149 ** All SQLite database connections must be closed before calling this
1150 ** routine.
1151 **
1152 ** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
1153 ** shutting down in order to free all remaining multiplex groups.
1154 */
1155 int sqlite3_multiplex_shutdown(int eForce){
1156   int rc = SQLITE_OK;
1157   if( gMultiplex.isInitialized==0 ) return SQLITE_MISUSE;
1158   gMultiplex.isInitialized = 0;
1159   sqlite3_vfs_unregister(&gMultiplex.sThisVfs);
1160   memset(&gMultiplex, 0, sizeof(gMultiplex));
1161   return rc;
1162 }
1163
1164 /***************************** Test Code ***********************************/
1165 #ifdef SQLITE_TEST
1166 #if defined(INCLUDE_SQLITE_TCL_H)
1167 #  include "sqlite_tcl.h"
1168 #else
1169 #  include "tcl.h"
1170 #  ifndef SQLITE_TCLAPI
1171 #    define SQLITE_TCLAPI
1172 #  endif
1173 #endif
1174 extern const char *sqlite3ErrName(int);
1175
1176
1177 /*
1178 ** tclcmd: sqlite3_multiplex_initialize NAME MAKEDEFAULT
1179 */
1180 static int SQLITE_TCLAPI test_multiplex_initialize(
1181   void * clientData,
1182   Tcl_Interp *interp,
1183   int objc,
1184   Tcl_Obj *CONST objv[]
1185 ){
1186   const char *zName;              /* Name of new multiplex VFS */
1187   int makeDefault;                /* True to make the new VFS the default */
1188   int rc;                         /* Value returned by multiplex_initialize() */
1189
1190   UNUSED_PARAMETER(clientData);
1191
1192   /* Process arguments */
1193   if( objc!=3 ){
1194     Tcl_WrongNumArgs(interp, 1, objv, "NAME MAKEDEFAULT");
1195     return TCL_ERROR;
1196   }
1197   zName = Tcl_GetString(objv[1]);
1198   if( Tcl_GetBooleanFromObj(interp, objv[2], &makeDefault) ) return TCL_ERROR;
1199   if( zName[0]=='\0' ) zName = 0;
1200
1201   /* Call sqlite3_multiplex_initialize() */
1202   rc = sqlite3_multiplex_initialize(zName, makeDefault);
1203   Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
1204
1205   return TCL_OK;
1206 }
1207
1208 /*
1209 ** tclcmd: sqlite3_multiplex_shutdown
1210 */
1211 static int SQLITE_TCLAPI test_multiplex_shutdown(
1212   void * clientData,
1213   Tcl_Interp *interp,
1214   int objc,
1215   Tcl_Obj *CONST objv[]
1216 ){
1217   int rc;                         /* Value returned by multiplex_shutdown() */
1218
1219   UNUSED_PARAMETER(clientData);
1220
1221   if( objc==2 && strcmp(Tcl_GetString(objv[1]),"-force")!=0 ){
1222     objc = 3;
1223   }
1224   if( (objc!=1 && objc!=2) ){
1225     Tcl_WrongNumArgs(interp, 1, objv, "?-force?");
1226     return TCL_ERROR;
1227   }
1228
1229   /* Call sqlite3_multiplex_shutdown() */
1230   rc = sqlite3_multiplex_shutdown(objc==2);
1231   Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
1232
1233   return TCL_OK;
1234 }
1235
1236 /*
1237 ** Tclcmd: test_multiplex_control HANDLE DBNAME SUB-COMMAND ?INT-VALUE?
1238 */
1239 static int SQLITE_TCLAPI test_multiplex_control(
1240   ClientData cd,
1241   Tcl_Interp *interp,
1242   int objc,
1243   Tcl_Obj *CONST objv[]
1244 ){
1245   int rc;                         /* Return code from file_control() */
1246   int idx;                        /* Index in aSub[] */
1247   Tcl_CmdInfo cmdInfo;            /* Command info structure for HANDLE */
1248   sqlite3 *db;                    /* Underlying db handle for HANDLE */
1249   int iValue = 0;
1250   void *pArg = 0;
1251
1252   struct SubCommand {
1253     const char *zName;
1254     int op;
1255     int argtype;
1256   } aSub[] = {
1257     { "enable",       MULTIPLEX_CTRL_ENABLE,           1 },
1258     { "chunk_size",   MULTIPLEX_CTRL_SET_CHUNK_SIZE,   1 },
1259     { "max_chunks",   MULTIPLEX_CTRL_SET_MAX_CHUNKS,   1 },
1260     { 0, 0, 0 }
1261   };
1262
1263   if( objc!=5 ){
1264     Tcl_WrongNumArgs(interp, 1, objv, "HANDLE DBNAME SUB-COMMAND INT-VALUE");
1265     return TCL_ERROR;
1266   }
1267
1268   if( 0==Tcl_GetCommandInfo(interp, Tcl_GetString(objv[1]), &cmdInfo) ){
1269     Tcl_AppendResult(interp, "expected database handle, got \"", 0);
1270     Tcl_AppendResult(interp, Tcl_GetString(objv[1]), "\"", 0);
1271     return TCL_ERROR;
1272   }else{
1273     db = *(sqlite3 **)cmdInfo.objClientData;
1274   }
1275
1276   rc = Tcl_GetIndexFromObjStruct(
1277       interp, objv[3], aSub, sizeof(aSub[0]), "sub-command", 0, &idx
1278   );
1279   if( rc!=TCL_OK ) return rc;
1280
1281   switch( aSub[idx].argtype ){
1282     case 1:
1283       if( Tcl_GetIntFromObj(interp, objv[4], &iValue) ){
1284         return TCL_ERROR;
1285       }
1286       pArg = (void *)&iValue;
1287       break;
1288     default:
1289       Tcl_WrongNumArgs(interp, 4, objv, "SUB-COMMAND");
1290       return TCL_ERROR;
1291   }
1292
1293   rc = sqlite3_file_control(db, Tcl_GetString(objv[2]), aSub[idx].op, pArg);
1294   Tcl_SetResult(interp, (char *)sqlite3ErrName(rc), TCL_STATIC);
1295   return (rc==SQLITE_OK) ? TCL_OK : TCL_ERROR;
1296 }
1297
1298 /*
1299 ** This routine registers the custom TCL commands defined in this
1300 ** module.  This should be the only procedure visible from outside
1301 ** of this module.
1302 */
1303 int Sqlitemultiplex_Init(Tcl_Interp *interp){
1304   static struct {
1305      char *zName;
1306      Tcl_ObjCmdProc *xProc;
1307   } aCmd[] = {
1308     { "sqlite3_multiplex_initialize", test_multiplex_initialize },
1309     { "sqlite3_multiplex_shutdown", test_multiplex_shutdown },
1310     { "sqlite3_multiplex_control", test_multiplex_control },
1311   };
1312   int i;
1313
1314   for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
1315     Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xProc, 0, 0);
1316   }
1317
1318   return TCL_OK;
1319 }
1320 #endif