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Overview
Comment:Enhance sqlite3_randomness(N,P) such that it resets the internal PRNG if N is less than 1. Subsequent calls to sqlite3_randomness() will reinitialize the internal PRNG by calling the xRandomness() method of the default VFS.
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SHA1: a221aa82bb5496885fd0bf76e4601443799511de
User & Date: drh 2014-01-01 14:00:13
References
2014-01-15
00:24
Merge recent fixes from trunk. Cherrypick of [c43b59dac1], [a221aa82bb], [e1eba1fb09], and [1e131094b5]. check-in: c697d2f8 user: mistachkin tags: branch-3.8.2
Context
2014-01-15
00:24
Merge recent fixes from trunk. Cherrypick of [c43b59dac1], [a221aa82bb], [e1eba1fb09], and [1e131094b5]. check-in: c697d2f8 user: mistachkin tags: branch-3.8.2
2014-01-01
15:18
Try to detect process ID changes due to fork() calls in os_unix.c and reset the PRNG when a process ID change is detected. check-in: e1eba1fb user: drh tags: trunk
14:00
Enhance sqlite3_randomness(N,P) such that it resets the internal PRNG if N is less than 1. Subsequent calls to sqlite3_randomness() will reinitialize the internal PRNG by calling the xRandomness() method of the default VFS. check-in: a221aa82 user: drh tags: trunk
2013-12-24
12:04
Add -I. to the main.mk makefile for building sqlite3.o and speedtest1. check-in: cc72c5ae user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/main.c.

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    /*
    ** Reset the PRNG back to its uninitialized state.  The next call
    ** to sqlite3_randomness() will reseed the PRNG using a single call
    ** to the xRandomness method of the default VFS.
    */
    case SQLITE_TESTCTRL_PRNG_RESET: {
      sqlite3PrngResetState();
      break;
    }

    /*
    **  sqlite3_test_control(BITVEC_TEST, size, program)
    **
    ** Run a test against a Bitvec object of size.  The program argument







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    /*
    ** Reset the PRNG back to its uninitialized state.  The next call
    ** to sqlite3_randomness() will reseed the PRNG using a single call
    ** to the xRandomness method of the default VFS.
    */
    case SQLITE_TESTCTRL_PRNG_RESET: {
      sqlite3_randomness(0,0);
      break;
    }

    /*
    **  sqlite3_test_control(BITVEC_TEST, size, program)
    **
    ** Run a test against a Bitvec object of size.  The program argument

Changes to src/random.c.

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# define wsdPrng sqlite3Prng
#endif

#if SQLITE_THREADSAFE
  sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_PRNG);
  sqlite3_mutex_enter(mutex);
#endif







  /* Initialize the state of the random number generator once,
  ** the first time this routine is called.  The seed value does
  ** not need to contain a lot of randomness since we are not
  ** trying to do secure encryption or anything like that...
  **
  ** Nothing in this file or anywhere else in SQLite does any kind of
................................................................................
      t = wsdPrng.s[wsdPrng.j];
      wsdPrng.s[wsdPrng.j] = wsdPrng.s[i];
      wsdPrng.s[i] = t;
    }
    wsdPrng.isInit = 1;
  }

  while( N-- ){

    wsdPrng.i++;
    t = wsdPrng.s[wsdPrng.i];
    wsdPrng.j += t;
    wsdPrng.s[wsdPrng.i] = wsdPrng.s[wsdPrng.j];
    wsdPrng.s[wsdPrng.j] = t;
    t += wsdPrng.s[wsdPrng.i];
    *(zBuf++) = wsdPrng.s[t];
  }
  sqlite3_mutex_leave(mutex);
}

#ifndef SQLITE_OMIT_BUILTIN_TEST
/*
** For testing purposes, we sometimes want to preserve the state of
** PRNG and restore the PRNG to its saved state at a later time, or
................................................................................
void sqlite3PrngRestoreState(void){
  memcpy(
    &GLOBAL(struct sqlite3PrngType, sqlite3Prng),
    &GLOBAL(struct sqlite3PrngType, sqlite3SavedPrng),
    sizeof(sqlite3Prng)
  );
}
void sqlite3PrngResetState(void){
  GLOBAL(struct sqlite3PrngType, sqlite3Prng).isInit = 0;
}
#endif /* SQLITE_OMIT_BUILTIN_TEST */







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# define wsdPrng sqlite3Prng
#endif

#if SQLITE_THREADSAFE
  sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_PRNG);
  sqlite3_mutex_enter(mutex);
#endif

  if( N<=0 ){
    wsdPrng.isInit = 0;
    sqlite3_mutex_leave(mutex);
    return;
  }

  /* Initialize the state of the random number generator once,
  ** the first time this routine is called.  The seed value does
  ** not need to contain a lot of randomness since we are not
  ** trying to do secure encryption or anything like that...
  **
  ** Nothing in this file or anywhere else in SQLite does any kind of
................................................................................
      t = wsdPrng.s[wsdPrng.j];
      wsdPrng.s[wsdPrng.j] = wsdPrng.s[i];
      wsdPrng.s[i] = t;
    }
    wsdPrng.isInit = 1;
  }

  assert( N>0 );
  do{
    wsdPrng.i++;
    t = wsdPrng.s[wsdPrng.i];
    wsdPrng.j += t;
    wsdPrng.s[wsdPrng.i] = wsdPrng.s[wsdPrng.j];
    wsdPrng.s[wsdPrng.j] = t;
    t += wsdPrng.s[wsdPrng.i];
    *(zBuf++) = wsdPrng.s[t];
  }while( --N );
  sqlite3_mutex_leave(mutex);
}

#ifndef SQLITE_OMIT_BUILTIN_TEST
/*
** For testing purposes, we sometimes want to preserve the state of
** PRNG and restore the PRNG to its saved state at a later time, or
................................................................................
void sqlite3PrngRestoreState(void){
  memcpy(
    &GLOBAL(struct sqlite3PrngType, sqlite3Prng),
    &GLOBAL(struct sqlite3PrngType, sqlite3SavedPrng),
    sizeof(sqlite3Prng)
  );
}



#endif /* SQLITE_OMIT_BUILTIN_TEST */

Changes to src/sqlite.h.in.

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** SQLite contains a high-quality pseudo-random number generator (PRNG) used to
** select random [ROWID | ROWIDs] when inserting new records into a table that
** already uses the largest possible [ROWID].  The PRNG is also used for
** the build-in random() and randomblob() SQL functions.  This interface allows
** applications to access the same PRNG for other purposes.
**
** ^A call to this routine stores N bytes of randomness into buffer P.

**
** ^The first time this routine is invoked (either internally or by

** the application) the PRNG is seeded using randomness obtained
** from the xRandomness method of the default [sqlite3_vfs] object.

** ^On all subsequent invocations, the pseudo-randomness is generated
** internally and without recourse to the [sqlite3_vfs] xRandomness
** method.
*/
void sqlite3_randomness(int N, void *P);

/*
** CAPI3REF: Compile-Time Authorization Callbacks







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** SQLite contains a high-quality pseudo-random number generator (PRNG) used to
** select random [ROWID | ROWIDs] when inserting new records into a table that
** already uses the largest possible [ROWID].  The PRNG is also used for
** the build-in random() and randomblob() SQL functions.  This interface allows
** applications to access the same PRNG for other purposes.
**
** ^A call to this routine stores N bytes of randomness into buffer P.
** ^If N is less than one, then P can be a NULL pointer.
**

** ^If this routine has not been previously called or if the previous
** call had N less than one, then the PRNG is seeded using randomness
** obtained from the xRandomness method of the default [sqlite3_vfs] object.
** ^If the previous call to this routine had an N of 1 or more then
** the pseudo-randomness is generated
** internally and without recourse to the [sqlite3_vfs] xRandomness
** method.
*/
void sqlite3_randomness(int N, void *P);

/*
** CAPI3REF: Compile-Time Authorization Callbacks

Changes to src/sqliteInt.h.

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int sqlite3ExprImpliesExpr(Expr*, Expr*, int);
void sqlite3ExprAnalyzeAggregates(NameContext*, Expr*);
void sqlite3ExprAnalyzeAggList(NameContext*,ExprList*);
int sqlite3FunctionUsesThisSrc(Expr*, SrcList*);
Vdbe *sqlite3GetVdbe(Parse*);
void sqlite3PrngSaveState(void);
void sqlite3PrngRestoreState(void);
void sqlite3PrngResetState(void);
void sqlite3RollbackAll(sqlite3*,int);
void sqlite3CodeVerifySchema(Parse*, int);
void sqlite3CodeVerifyNamedSchema(Parse*, const char *zDb);
void sqlite3BeginTransaction(Parse*, int);
void sqlite3CommitTransaction(Parse*);
void sqlite3RollbackTransaction(Parse*);
void sqlite3Savepoint(Parse*, int, Token*);







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int sqlite3ExprImpliesExpr(Expr*, Expr*, int);
void sqlite3ExprAnalyzeAggregates(NameContext*, Expr*);
void sqlite3ExprAnalyzeAggList(NameContext*,ExprList*);
int sqlite3FunctionUsesThisSrc(Expr*, SrcList*);
Vdbe *sqlite3GetVdbe(Parse*);
void sqlite3PrngSaveState(void);
void sqlite3PrngRestoreState(void);

void sqlite3RollbackAll(sqlite3*,int);
void sqlite3CodeVerifySchema(Parse*, int);
void sqlite3CodeVerifyNamedSchema(Parse*, const char *zDb);
void sqlite3BeginTransaction(Parse*, int);
void sqlite3CommitTransaction(Parse*);
void sqlite3RollbackTransaction(Parse*);
void sqlite3Savepoint(Parse*, int, Token*);