Enhance sqlite3_randomness(N,P) such that it resets the internal PRNG

drh · drh · commit fe98081e18e0 · 2014-01-01T14:00:13.000Z
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.

FossilOrigin-Name: a221aa82bb5496885fd0bf76e4601443799511de
diff --git a/manifest b/manifest
@@ -1,5 +1,5 @@
-C Add\s-I.\sto\sthe\smain.mk\smakefile\sfor\sbuilding\ssqlite3.o\sand\sspeedtest1.
-D 2013-12-24T12:04:24.811
+C Enhance\ssqlite3_randomness(N,P)\ssuch\sthat\sit\sresets\sthe\sinternal\sPRNG\nif\sN\sis\sless\sthan\s1.\s\sSubsequent\scalls\sto\ssqlite3_randomness()\swill\sreinitialize\nthe\sinternal\sPRNG\sby\scalling\sthe\sxRandomness()\smethod\sof\sthe\sdefault\sVFS.
+D 2014-01-01T14:00:13.905
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 2ef13430cd359f7b361bb863504e227b25cc7f81
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -188,7 +188,7 @@ F src/journal.c b4124532212b6952f42eb2c12fa3c25701d8ba8d
 F src/legacy.c 0df0b1550b9cc1f58229644735e317ac89131f12
 F src/lempar.c cdf0a000315332fc9b50b62f3b5e22e080a0952b
 F src/loadext.c 867c7b330b740c6c917af9956b13b81d0a048303
-F src/main.c 5307601c58b6e08153a15846098399a59c166d8d
+F src/main.c 37f55de2000f6c882414ad3e1bcdb751c531fddd
 F src/malloc.c 0203ebce9152c6a0e5de520140b8ba65187350be
 F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
 F src/mem1.c c0c990fcaddff810ea277b4fb5d9138603dd5d4b
@@ -216,15 +216,15 @@ F src/pcache1.c 57fee9a9a617218f5037afbbe49b09da65bde56b
 F src/pragma.c 5ab7279d132143feb77f773688a24ab05da75fd7
 F src/prepare.c 677521ab7132615a8a26107a1d1c3132f44ae337
 F src/printf.c 85d07756e45d7496d19439dcae3e6e9e0090f269
-F src/random.c 0b2dbc37fdfbfa6bd455b091dfcef5bdb32dba68
+F src/random.c d10c1f85b6709ca97278428fd5db5bbb9c74eece
 F src/resolve.c 7eda9097b29fcf3d2b42fdc17d1de672134e09b6
 F src/rowset.c 64655f1a627c9c212d9ab497899e7424a34222e0
 F src/select.c 819bb090c9a348d17f69f136cad2bfa9ee9cbb41
 F src/shell.c a3541193d5fce37e91dad8ef46a9505aa7c9b344
-F src/sqlite.h.in 4ef56464aeaa3785a2c5ca37fb3a0fb229d68b2e
+F src/sqlite.h.in d94a8b89522f526ba711182ee161e06f8669bcc9
 F src/sqlite3.rc 11094cc6a157a028b301a9f06b3d03089ea37c3e
 F src/sqlite3ext.h 886f5a34de171002ad46fae8c36a7d8051c190fc
-F src/sqliteInt.h fdb8c1e4bc5424ad82a9394a845781abf0d7d849
+F src/sqliteInt.h 62664868458b53a815380733f059ff9d92cb08be
 F src/sqliteLimit.h 164b0e6749d31e0daa1a4589a169d31c0dec7b3d
 F src/status.c 7ac05a5c7017d0b9f0b4bcd701228b784f987158
 F src/table.c 2cd62736f845d82200acfa1287e33feb3c15d62e
@@ -1147,7 +1147,7 @@ F tool/vdbe-compress.tcl 0cf56e9263a152b84da86e75a5c0cdcdb7a47891
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh d1a6de74685f360ab718efda6265994b99bbea01
 F tool/win/sqlite.vsix 030f3eeaf2cb811a3692ab9c14d021a75ce41fff
-P c289a253c0c053ac8fc344efe138262c327d8096
-R 2bb3d3295c5bbe58e528a8069b6e67b9
+P cc72c5aec7fe93d4a1368517aab949dc98d33003
+R 4dbb82094f79fe324b8594c5661b9532
 U drh
-Z 2be15cf525011fea6a70c12bcaf2ac37
+Z 7f33812905741a2d8942dba59b43dd66
diff --git a/manifest.uuid b/manifest.uuid
@@ -1 +1 @@
-cc72c5aec7fe93d4a1368517aab949dc98d33003
+a221aa82bb5496885fd0bf76e4601443799511de
diff --git a/src/main.c b/src/main.c
@@ -3101,7 +3101,7 @@ int sqlite3_test_control(int op, ...){
     ** to the xRandomness method of the default VFS.
     */
     case SQLITE_TESTCTRL_PRNG_RESET: {
-      sqlite3PrngResetState();
+      sqlite3_randomness(0,0);
       break;
     }
 
diff --git a/src/random.c b/src/random.c
@@ -52,6 +52,12 @@ void sqlite3_randomness(int N, void *pBuf){
   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
@@ -79,15 +85,16 @@ void sqlite3_randomness(int N, void *pBuf){
     wsdPrng.isInit = 1;
   }
 
-  while( N-- ){
+  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);
 }
 
@@ -116,7 +123,4 @@ void sqlite3PrngRestoreState(void){
     sizeof(sqlite3Prng)
   );
 }
-void sqlite3PrngResetState(void){
-  GLOBAL(struct sqlite3PrngType, sqlite3Prng).isInit = 0;
-}
 #endif /* SQLITE_OMIT_BUILTIN_TEST */
diff --git a/src/sqlite.h.in b/src/sqlite.h.in
@@ -2395,11 +2395,13 @@ sqlite3_int64 sqlite3_memory_highwater(int resetFlag);
 ** 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.
 **
-** ^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
+** ^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.
 */
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
@@ -2972,7 +2972,6 @@ 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);

Original file line number	Diff line number	Diff line change
`@@ -1 +1 @@`
`1`		`-cc72c5aec7fe93d4a1368517aab949dc98d33003`
	`1`	`+a221aa82bb5496885fd0bf76e4601443799511de`
Original file line number	Diff line number	Diff line change
`@@ -3101,7 +3101,7 @@ int sqlite3_test_control(int op, ...){`
`3101`	`3101`	`** to the xRandomness method of the default VFS.`
`3102`	`3102`	`*/`
`3103`	`3103`	`case SQLITE_TESTCTRL_PRNG_RESET: {`
`3104`		`- sqlite3PrngResetState();`
	`3104`	`+ sqlite3_randomness(0,0);`
`3105`	`3105`	`break;`
`3106`	`3106`	`}`
`3107`	`3107`