ext/misc/scrub.c

   1 /*
   2 ** 2016-05-05
   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 implements a utility function (and a utility program) that
  14 ** makes a copy of an SQLite database while simultaneously zeroing out all
  15 ** deleted content.
  16 **
  17 ** Normally (when PRAGMA secure_delete=OFF, which is the default) when SQLite
  18 ** deletes content, it does not overwrite the deleted content but rather marks
  19 ** the region of the file that held that content as being reusable.  This can
  20 ** cause deleted content to recoverable from the database file.  This stale
  21 ** content is removed by the VACUUM command, but VACUUM can be expensive for
  22 ** large databases.  When in PRAGMA secure_delete=ON mode, the deleted content
  23 ** is zeroed, but secure_delete=ON has overhead as well.
  24 **
  25 ** This utility attempts to make a copy of a complete SQLite database where
  26 ** all of the deleted content is zeroed out in the copy, and it attempts to
  27 ** do so while being faster than running VACUUM.
  28 **
  29 ** Usage:
  30 **
  31 **   int sqlite3_scrub_backup(
  32 **       const char *zSourceFile,   // Source database filename
  33 **       const char *zDestFile,     // Destination database filename
  34 **       char **pzErrMsg            // Write error message here
  35 **   );
  36 **
  37 ** Simply call the API above specifying the filename of the source database
  38 ** and the name of the backup copy.  The source database must already exist
  39 ** and can be in active use. (A read lock is held during the backup.)  The
  40 ** destination file should not previously exist.  If the pzErrMsg parameter
  41 ** is non-NULL and if an error occurs, then an error message might be written
  42 ** into memory obtained from sqlite3_malloc() and *pzErrMsg made to point to
  43 ** that error message.  But if the error is an OOM, the error might not be
  44 ** reported.  The routine always returns non-zero if there is an error.
  45 **
  46 ** If compiled with -DSCRUB_STANDALONE then a main() procedure is added and
  47 ** this file becomes a standalone program that can be run as follows:
  48 **
  49 **      ./sqlite3scrub SOURCE DEST
  50 */
  51 #include "sqlite3.h"
  52 #include <assert.h>
  53 #include <stdio.h>
  54 #include <stdlib.h>
  55 #include <stdarg.h>
  56 #include <string.h>
  57
  58 typedef struct ScrubState ScrubState;
  59 typedef unsigned char u8;
  60 typedef unsigned short u16;
  61 typedef unsigned int u32;
  62
  63
  64 /* State information for a scrub-and-backup operation */
  65 struct ScrubState {
  66   const char *zSrcFile;    /* Name of the source file */
  67   const char *zDestFile;   /* Name of the destination file */
  68   int rcErr;               /* Error code */
  69   char *zErr;              /* Error message text */
  70   sqlite3 *dbSrc;          /* Source database connection */
  71   sqlite3_file *pSrc;      /* Source file handle */
  72   sqlite3 *dbDest;         /* Destination database connection */
  73   sqlite3_file *pDest;     /* Destination file handle */
  74   u32 szPage;              /* Page size */
  75   u32 szUsable;            /* Usable bytes on each page */
  76   u32 nPage;               /* Number of pages */
  77   u32 iLastPage;           /* Page number of last page written so far*/
  78   u8 *page1;               /* Content of page 1 */
  79 };
  80
  81 /* Store an error message */
  82 static void scrubBackupErr(ScrubState *p, const char *zFormat, ...){
  83   va_list ap;
  84   sqlite3_free(p->zErr);
  85   va_start(ap, zFormat);
  86   p->zErr = sqlite3_vmprintf(zFormat, ap);
  87   va_end(ap);
  88   if( p->rcErr==0 ) p->rcErr = SQLITE_ERROR;
  89 }
  90
  91 /* Allocate memory to hold a single page of content */
  92 static u8 *scrubBackupAllocPage(ScrubState *p){
  93   u8 *pPage;
  94   if( p->rcErr ) return 0;
  95   pPage = sqlite3_malloc( p->szPage );
  96   if( pPage==0 ) p->rcErr = SQLITE_NOMEM;
  97   return pPage;
  98 }
  99
 100 /* Read a page from the source database into memory.  Use the memory
 101 ** provided by pBuf if not NULL or allocate a new page if pBuf==NULL.
 102 */
 103 static u8 *scrubBackupRead(ScrubState *p, int pgno, u8 *pBuf){
 104   int rc;
 105   sqlite3_int64 iOff;
 106   u8 *pOut = pBuf;
 107   if( p->rcErr ) return 0;
 108   if( pOut==0 ){
 109     pOut = scrubBackupAllocPage(p);
 110     if( pOut==0 ) return 0;
 111   }
 112   iOff = (pgno-1)*(sqlite3_int64)p->szPage;
 113   rc = p->pSrc->pMethods->xRead(p->pSrc, pOut, p->szPage, iOff);
 114   if( rc!=SQLITE_OK ){
 115     if( pBuf==0 ) sqlite3_free(pOut);
 116     pOut = 0;
 117     scrubBackupErr(p, "read failed for page %d", pgno);
 118     p->rcErr = SQLITE_IOERR;
 119   }
 120   return pOut;
 121 }
 122
 123 /* Write a page to the destination database */
 124 static void scrubBackupWrite(ScrubState *p, int pgno, const u8 *pData){
 125   int rc;
 126   sqlite3_int64 iOff;
 127   if( p->rcErr ) return;
 128   iOff = (pgno-1)*(sqlite3_int64)p->szPage;
 129   rc = p->pDest->pMethods->xWrite(p->pDest, pData, p->szPage, iOff);
 130   if( rc!=SQLITE_OK ){
 131     scrubBackupErr(p, "write failed for page %d", pgno);
 132     p->rcErr = SQLITE_IOERR;
 133   }
 134   if( (u32)pgno>p->iLastPage ) p->iLastPage = pgno;
 135 }
 136
 137 /* Prepare a statement against the "db" database. */
 138 static sqlite3_stmt *scrubBackupPrepare(
 139   ScrubState *p,      /* Backup context */
 140   sqlite3 *db,        /* Database to prepare against */
 141   const char *zSql    /* SQL statement */
 142 ){
 143   sqlite3_stmt *pStmt;
 144   if( p->rcErr ) return 0;
 145   p->rcErr = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
 146   if( p->rcErr ){
 147     scrubBackupErr(p, "SQL error \"%s\" on \"%s\"",
 148                    sqlite3_errmsg(db), zSql);
 149     sqlite3_finalize(pStmt);
 150     return 0;
 151   }
 152   return pStmt;
 153 }
 154
 155
 156 /* Open the source database file */
 157 static void scrubBackupOpenSrc(ScrubState *p){
 158   sqlite3_stmt *pStmt;
 159   int rc;
 160   /* Open the source database file */
 161   p->rcErr = sqlite3_open_v2(p->zSrcFile, &p->dbSrc,
 162                  SQLITE_OPEN_READWRITE |
 163                  SQLITE_OPEN_URI | SQLITE_OPEN_PRIVATECACHE, 0);
 164   if( p->rcErr ){
 165     scrubBackupErr(p, "cannot open source database: %s",
 166                       sqlite3_errmsg(p->dbSrc));
 167     return;
 168   }
 169   p->rcErr = sqlite3_exec(p->dbSrc, "SELECT 1 FROM sqlite_master; BEGIN;",
 170                           0, 0, 0);
 171   if( p->rcErr ){
 172     scrubBackupErr(p,
 173        "cannot start a read transaction on the source database: %s",
 174        sqlite3_errmsg(p->dbSrc));
 175     return;
 176   }
 177   rc = sqlite3_wal_checkpoint_v2(p->dbSrc, "main", SQLITE_CHECKPOINT_FULL,
 178                                  0, 0);
 179   if( rc ){
 180     scrubBackupErr(p, "cannot checkpoint the source database");
 181     return;
 182   }
 183   pStmt = scrubBackupPrepare(p, p->dbSrc, "PRAGMA page_size");
 184   if( pStmt==0 ) return;
 185   rc = sqlite3_step(pStmt);
 186   if( rc==SQLITE_ROW ){
 187     p->szPage = sqlite3_column_int(pStmt, 0);
 188   }else{
 189     scrubBackupErr(p, "unable to determine the page size");
 190   }
 191   sqlite3_finalize(pStmt);
 192   if( p->rcErr ) return;
 193   pStmt = scrubBackupPrepare(p, p->dbSrc, "PRAGMA page_count");
 194   if( pStmt==0 ) return;
 195   rc = sqlite3_step(pStmt);
 196   if( rc==SQLITE_ROW ){
 197     p->nPage = sqlite3_column_int(pStmt, 0);
 198   }else{
 199     scrubBackupErr(p, "unable to determine the size of the source database");
 200   }
 201   sqlite3_finalize(pStmt);
 202   sqlite3_file_control(p->dbSrc, "main", SQLITE_FCNTL_FILE_POINTER, &p->pSrc);
 203   if( p->pSrc==0 || p->pSrc->pMethods==0 ){
 204     scrubBackupErr(p, "cannot get the source file handle");
 205     p->rcErr = SQLITE_ERROR;
 206   }
 207 }
 208
 209 /* Create and open the destination file */
 210 static void scrubBackupOpenDest(ScrubState *p){
 211   sqlite3_stmt *pStmt;
 212   int rc;
 213   char *zSql;
 214   if( p->rcErr ) return;
 215   p->rcErr = sqlite3_open_v2(p->zDestFile, &p->dbDest,
 216                  SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
 217                  SQLITE_OPEN_URI | SQLITE_OPEN_PRIVATECACHE, 0);
 218   if( p->rcErr ){
 219     scrubBackupErr(p, "cannot open destination database: %s",
 220                       sqlite3_errmsg(p->dbDest));
 221     return;
 222   }
 223   zSql = sqlite3_mprintf("PRAGMA page_size(%u);", p->szPage);
 224   if( zSql==0 ){
 225     p->rcErr = SQLITE_NOMEM;
 226     return;
 227   }
 228   p->rcErr = sqlite3_exec(p->dbDest, zSql, 0, 0, 0);
 229   sqlite3_free(zSql);
 230   if( p->rcErr ){
 231     scrubBackupErr(p,
 232        "cannot set the page size on the destination database: %s",
 233        sqlite3_errmsg(p->dbDest));
 234     return;
 235   }
 236   sqlite3_exec(p->dbDest, "PRAGMA journal_mode=OFF;", 0, 0, 0);
 237   p->rcErr = sqlite3_exec(p->dbDest, "BEGIN EXCLUSIVE;", 0, 0, 0);
 238   if( p->rcErr ){
 239     scrubBackupErr(p,
 240        "cannot start a write transaction on the destination database: %s",
 241        sqlite3_errmsg(p->dbDest));
 242     return;
 243   }
 244   pStmt = scrubBackupPrepare(p, p->dbDest, "PRAGMA page_count;");
 245   if( pStmt==0 ) return;
 246   rc = sqlite3_step(pStmt);
 247   if( rc!=SQLITE_ROW ){
 248     scrubBackupErr(p, "cannot measure the size of the destination");
 249   }else if( sqlite3_column_int(pStmt, 0)>1 ){
 250     scrubBackupErr(p, "destination database is not empty - holds %d pages",
 251                    sqlite3_column_int(pStmt, 0));
 252   }
 253   sqlite3_finalize(pStmt);
 254   sqlite3_file_control(p->dbDest, "main", SQLITE_FCNTL_FILE_POINTER, &p->pDest);
 255   if( p->pDest==0 || p->pDest->pMethods==0 ){
 256     scrubBackupErr(p, "cannot get the destination file handle");
 257     p->rcErr = SQLITE_ERROR;
 258   }
 259 }
 260
 261 /* Read a 32-bit big-endian integer */
 262 static u32 scrubBackupInt32(const u8 *a){
 263   u32 v = a[3];
 264   v += ((u32)a[2])<<8;
 265   v += ((u32)a[1])<<16;
 266   v += ((u32)a[0])<<24;
 267   return v;
 268 }
 269
 270 /* Read a 16-bit big-endian integer */
 271 static u32 scrubBackupInt16(const u8 *a){
 272   return (a[0]<<8) + a[1];
 273 }
 274
 275 /*
 276 ** Read a varint.  Put the value in *pVal and return the number of bytes.
 277 */
 278 static int scrubBackupVarint(const u8 *z, sqlite3_int64 *pVal){
 279   sqlite3_int64 v = 0;
 280   int i;
 281   for(i=0; i<8; i++){
 282     v = (v<<7) + (z[i]&0x7f);
 283     if( (z[i]&0x80)==0 ){ *pVal = v; return i+1; }
 284   }
 285   v = (v<<8) + (z[i]&0xff);
 286   *pVal = v;
 287   return 9;
 288 }
 289
 290 /*
 291 ** Return the number of bytes in a varint.
 292 */
 293 static int scrubBackupVarintSize(const u8 *z){
 294   int i;
 295   for(i=0; i<8; i++){
 296     if( (z[i]&0x80)==0 ){ return i+1; }
 297   }
 298   return 9;
 299 }
 300
 301 /*
 302 ** Copy the freelist trunk page given, and all its descendents,
 303 ** zeroing out as much as possible in the process.
 304 */
 305 static void scrubBackupFreelist(ScrubState *p, int pgno, u32 nFree){
 306   u8 *a, *aBuf;
 307   u32 n, mx;
 308
 309   if( p->rcErr ) return;
 310   aBuf = scrubBackupAllocPage(p);
 311   if( aBuf==0 ) return;
 312
 313   while( pgno && nFree){
 314     a = scrubBackupRead(p, pgno, aBuf);
 315     if( a==0 ) break;
 316     n = scrubBackupInt32(&a[4]);
 317     mx = p->szUsable/4 - 2;
 318     if( n<mx ){
 319       memset(&a[n*4+8], 0, 4*(mx-n));
 320     }
 321     scrubBackupWrite(p, pgno, a);
 322     pgno = scrubBackupInt32(a);
 323 #if 0
 324     /* There is really no point in copying the freelist leaf pages.
 325     ** Simply leave them uninitialized in the destination database.  The
 326     ** OS filesystem should zero those pages for us automatically.
 327     */
 328     for(i=0; i<n && nFree; i++){
 329       u32 iLeaf = scrubBackupInt32(&a[i*4+8]);
 330       if( aZero==0 ){
 331         aZero = scrubBackupAllocPage(p);
 332         if( aZero==0 ){ pgno = 0; break; }
 333         memset(aZero, 0, p->szPage);
 334       }
 335       scrubBackupWrite(p, iLeaf, aZero);
 336       nFree--;
 337     }
 338 #endif
 339   }
 340   sqlite3_free(aBuf);
 341 }
 342
 343 /*
 344 ** Copy an overflow chain from source to destination.  Zero out any
 345 ** unused tail at the end of the overflow chain.
 346 */
 347 static void scrubBackupOverflow(ScrubState *p, int pgno, u32 nByte){
 348   u8 *a, *aBuf;
 349
 350   aBuf = scrubBackupAllocPage(p);
 351   if( aBuf==0 ) return;
 352   while( nByte>0 && pgno!=0 ){
 353     a = scrubBackupRead(p, pgno, aBuf);
 354     if( a==0 ) break;
 355     if( nByte >= (p->szUsable)-4 ){
 356       nByte -= (p->szUsable) - 4;
 357     }else{
 358       u32 x = (p->szUsable - 4) - nByte;
 359       u32 i = p->szUsable - x;
 360       memset(&a[i], 0, x);
 361       nByte = 0;
 362     }
 363     scrubBackupWrite(p, pgno, a);
 364     pgno = scrubBackupInt32(a);
 365   }
 366   sqlite3_free(aBuf);
 367 }
 368
 369
 370 /*
 371 ** Copy B-Tree page pgno, and all of its children, from source to destination.
 372 ** Zero out deleted content during the copy.
 373 */
 374 static void scrubBackupBtree(ScrubState *p, int pgno, int iDepth){
 375   u8 *a;
 376   u32 i, n, pc;
 377   u32 nCell;
 378   u32 nPrefix;
 379   u32 szHdr;
 380   u32 iChild;
 381   u8 *aTop;
 382   u8 *aCell;
 383   u32 x, y;
 384   int ln = 0;
 385
 386
 387   if( p->rcErr ) return;
 388   if( iDepth>50 ){
 389     scrubBackupErr(p, "corrupt: b-tree too deep at page %d", pgno);
 390     return;
 391   }
 392   if( pgno==1 ){
 393     a = p->page1;
 394   }else{
 395     a = scrubBackupRead(p, pgno, 0);
 396     if( a==0 ) return;
 397   }
 398   nPrefix = pgno==1 ? 100 : 0;
 399   aTop = &a[nPrefix];
 400   szHdr = 8 + 4*(aTop[0]==0x02 || aTop[0]==0x05);
 401   aCell = aTop + szHdr;
 402   nCell = scrubBackupInt16(&aTop[3]);
 403
 404   /* Zero out the gap between the cell index and the start of the
 405   ** cell content area */
 406   x = scrubBackupInt16(&aTop[5]);  /* First byte of cell content area */
 407   if( x>p->szUsable ){ ln=__LINE__; goto btree_corrupt; }
 408   y = szHdr + nPrefix + nCell*2;
 409   if( y>x ){ ln=__LINE__; goto btree_corrupt; }
 410   if( y<x ) memset(a+y, 0, x-y);  /* Zero the gap */
 411
 412   /* Zero out all the free blocks */
 413   pc = scrubBackupInt16(&aTop[1]);
 414   if( pc>0 && pc<x ){ ln=__LINE__; goto btree_corrupt; }
 415   while( pc ){
 416     if( pc>(p->szUsable)-4 ){ ln=__LINE__; goto btree_corrupt; }
 417     n = scrubBackupInt16(&a[pc+2]);
 418     if( pc+n>(p->szUsable) ){ ln=__LINE__; goto btree_corrupt; }
 419     if( n>4 ) memset(&a[pc+4], 0, n-4);
 420     x = scrubBackupInt16(&a[pc]);
 421     if( x<pc+4 && x>0 ){ ln=__LINE__; goto btree_corrupt; }
 422     pc = x;
 423   }
 424
 425   /* Write this one page */
 426   scrubBackupWrite(p, pgno, a);
 427
 428   /* Walk the tree and process child pages */
 429   for(i=0; i<nCell; i++){
 430     u32 X, M, K, nLocal;
 431     sqlite3_int64 P;
 432     pc = scrubBackupInt16(&aCell[i*2]);
 433     if( pc <= szHdr ){ ln=__LINE__; goto btree_corrupt; }
 434     if( pc > p->szUsable-3 ){ ln=__LINE__; goto btree_corrupt; }
 435     if( aTop[0]==0x05 || aTop[0]==0x02 ){
 436       if( pc+4 > p->szUsable ){ ln=__LINE__; goto btree_corrupt; }
 437       iChild = scrubBackupInt32(&a[pc]);
 438       pc += 4;
 439       scrubBackupBtree(p, iChild, iDepth+1);
 440       if( aTop[0]==0x05 ) continue;
 441     }
 442     pc += scrubBackupVarint(&a[pc], &P);
 443     if( pc >= p->szUsable ){ ln=__LINE__; goto btree_corrupt; }
 444     if( aTop[0]==0x0d ){
 445       X = p->szUsable - 35;
 446     }else{
 447       X = ((p->szUsable - 12)*64/255) - 23;
 448     }
 449     if( P<=X ){
 450       /* All content is local.  No overflow */
 451       continue;
 452     }
 453     M = ((p->szUsable - 12)*32/255)-23;
 454     K = M + ((P-M)%(p->szUsable-4));
 455     if( aTop[0]==0x0d ){
 456       pc += scrubBackupVarintSize(&a[pc]);
 457       if( pc > (p->szUsable-4) ){ ln=__LINE__; goto btree_corrupt; }
 458     }
 459     nLocal = K<=X ? K : M;
 460     if( pc+nLocal > p->szUsable-4 ){ ln=__LINE__; goto btree_corrupt; }
 461     iChild = scrubBackupInt32(&a[pc+nLocal]);
 462     scrubBackupOverflow(p, iChild, (u32)(P-nLocal));
 463   }
 464
 465   /* Walk the right-most tree */
 466   if( aTop[0]==0x05 || aTop[0]==0x02 ){
 467     iChild = scrubBackupInt32(&aTop[8]);
 468     scrubBackupBtree(p, iChild, iDepth+1);
 469   }
 470
 471   /* All done */
 472   if( pgno>1 ) sqlite3_free(a);
 473   return;
 474
 475 btree_corrupt:
 476   scrubBackupErr(p, "corruption on page %d of source database (errid=%d)",
 477                  pgno, ln);
 478   if( pgno>1 ) sqlite3_free(a);
 479 }
 480
 481 /*
 482 ** Copy all ptrmap pages from source to destination.
 483 ** This routine is only called if the source database is in autovacuum
 484 ** or incremental vacuum mode.
 485 */
 486 static void scrubBackupPtrmap(ScrubState *p){
 487   u32 pgno = 2;
 488   u32 J = p->szUsable/5;
 489   u32 iLock = (1073742335/p->szPage)+1;
 490   u8 *a, *pBuf;
 491   if( p->rcErr ) return;
 492   pBuf = scrubBackupAllocPage(p);
 493   if( pBuf==0 ) return;
 494   while( pgno<=p->nPage ){
 495     a = scrubBackupRead(p, pgno, pBuf);
 496     if( a==0 ) break;
 497     scrubBackupWrite(p, pgno, a);
 498     pgno += J+1;
 499     if( pgno==iLock ) pgno++;
 500   }
 501   sqlite3_free(pBuf);
 502 }
 503
 504 int sqlite3_scrub_backup(
 505   const char *zSrcFile,    /* Source file */
 506   const char *zDestFile,   /* Destination file */
 507   char **pzErr             /* Write error here if non-NULL */
 508 ){
 509   ScrubState s;
 510   u32 n, i;
 511   sqlite3_stmt *pStmt;
 512
 513   memset(&s, 0, sizeof(s));
 514   s.zSrcFile = zSrcFile;
 515   s.zDestFile = zDestFile;
 516
 517   /* Open both source and destination databases */
 518   scrubBackupOpenSrc(&s);
 519   scrubBackupOpenDest(&s);
 520
 521   /* Read in page 1 */
 522   s.page1 = scrubBackupRead(&s, 1, 0);
 523   if( s.page1==0 ) goto scrub_abort;
 524   s.szUsable = s.szPage - s.page1[20];
 525
 526   /* Copy the freelist */
 527   n = scrubBackupInt32(&s.page1[36]);
 528   i = scrubBackupInt32(&s.page1[32]);
 529   if( n ) scrubBackupFreelist(&s, i, n);
 530
 531   /* Copy ptrmap pages */
 532   n = scrubBackupInt32(&s.page1[52]);
 533   if( n ) scrubBackupPtrmap(&s);
 534
 535   /* Copy all of the btrees */
 536   scrubBackupBtree(&s, 1, 0);
 537   pStmt = scrubBackupPrepare(&s, s.dbSrc,
 538        "SELECT rootpage FROM sqlite_master WHERE coalesce(rootpage,0)>0");
 539   if( pStmt==0 ) goto scrub_abort;
 540   while( sqlite3_step(pStmt)==SQLITE_ROW ){
 541     i = (u32)sqlite3_column_int(pStmt, 0);
 542     scrubBackupBtree(&s, i, 0);
 543   }
 544   sqlite3_finalize(pStmt);
 545
 546   /* If the last page of the input db file is a free-list leaf, then the
 547   ** backup file on disk is still smaller than the size indicated within
 548   ** the database header. In this case, write a page of zeroes to the
 549   ** last page of the backup database so that SQLite does not mistakenly
 550   ** think the db is corrupt.  */
 551   if( s.iLastPage<s.nPage ){
 552     u8 *aZero = scrubBackupAllocPage(&s);
 553     if( aZero ){
 554       memset(aZero, 0, s.szPage);
 555       scrubBackupWrite(&s, s.nPage, aZero);
 556       sqlite3_free(aZero);
 557     }
 558   }
 559
 560 scrub_abort:
 561   /* Close the destination database without closing the transaction. If we
 562   ** commit, page zero will be overwritten. */
 563   sqlite3_close(s.dbDest);
 564
 565   /* But do close out the read-transaction on the source database */
 566   sqlite3_exec(s.dbSrc, "COMMIT;", 0, 0, 0);
 567   sqlite3_close(s.dbSrc);
 568   sqlite3_free(s.page1);
 569   if( pzErr ){
 570     *pzErr = s.zErr;
 571   }else{
 572     sqlite3_free(s.zErr);
 573   }
 574   return s.rcErr;
 575 }
 576
 577 #ifdef SCRUB_STANDALONE
 578 /* Error and warning log */
 579 static void errorLogCallback(void *pNotUsed, int iErr, const char *zMsg){
 580   const char *zType;
 581   switch( iErr&0xff ){
 582     case SQLITE_WARNING: zType = "WARNING";  break;
 583     case SQLITE_NOTICE:  zType = "NOTICE";   break;
 584     default:             zType = "ERROR";    break;
 585   }
 586   fprintf(stderr, "%s: %s\n", zType, zMsg);
 587 }
 588
 589 /* The main() routine when this utility is run as a stand-alone program */
 590 int main(int argc, char **argv){
 591   char *zErr = 0;
 592   int rc;
 593   if( argc!=3 ){
 594     fprintf(stderr,"Usage: %s SOURCE DESTINATION\n", argv[0]);
 595     exit(1);
 596   }
 597   sqlite3_config(SQLITE_CONFIG_LOG, errorLogCallback, 0);
 598   rc = sqlite3_scrub_backup(argv[1], argv[2], &zErr);
 599   if( rc==SQLITE_NOMEM ){
 600     fprintf(stderr, "%s: out of memory\n", argv[0]);
 601     exit(1);
 602   }
 603   if( zErr ){
 604     fprintf(stderr, "%s: %s\n", argv[0], zErr);
 605     sqlite3_free(zErr);
 606     exit(1);
 607   }
 608   return 0;
 609 }
 610 #endif