Refactor the sqlite3_randomness() implementation for improved performance.
FossilOrigin-Name: 4144dffb57b5ed791d7a6d2f26fab5e7dc77fbd1
diff --git a/src/random.c b/src/random.c
index 234ebdf..7afff50 100644
--- a/src/random.c
+++ b/src/random.c
@@ -28,24 +28,11 @@
} sqlite3Prng;
/*
-** Get a single 8-bit random value from the RC4 PRNG. The Mutex
-** must be held while executing this routine.
-**
-** Why not just use a library random generator like lrand48() for this?
-** Because the OP_NewRowid opcode in the VDBE depends on having a very
-** good source of random numbers. The lrand48() library function may
-** well be good enough. But maybe not. Or maybe lrand48() has some
-** subtle problems on some systems that could cause problems. It is hard
-** to know. To minimize the risk of problems due to bad lrand48()
-** implementations, SQLite uses this random number generator based
-** on RC4, which we know works very well.
-**
-** (Later): Actually, OP_NewRowid does not depend on a good source of
-** randomness any more. But we will leave this code in all the same.
+** Return N random bytes.
*/
-static u8 randomByte(void){
+void sqlite3_randomness(int N, void *pBuf){
unsigned char t;
-
+ unsigned char *zBuf = pBuf;
/* The "wsdPrng" macro will resolve to the pseudo-random number generator
** state vector. If writable static data is unsupported on the target,
@@ -60,6 +47,10 @@
# 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
@@ -88,28 +79,14 @@
wsdPrng.isInit = 1;
}
- /* Generate and return single random byte
- */
- 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];
- return wsdPrng.s[t];
-}
-
-/*
-** Return N random bytes.
-*/
-void sqlite3_randomness(int N, void *pBuf){
- unsigned char *zBuf = pBuf;
-#if SQLITE_THREADSAFE
- sqlite3_mutex *mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_PRNG);
-#endif
- sqlite3_mutex_enter(mutex);
while( N-- ){
- *(zBuf++) = randomByte();
+ 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);
}