diff options
Diffstat (limited to 'experimental/tqtinterface/qt4/src/3rdparty/sqlite/random.c')
-rw-r--r-- | experimental/tqtinterface/qt4/src/3rdparty/sqlite/random.c | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/experimental/tqtinterface/qt4/src/3rdparty/sqlite/random.c b/experimental/tqtinterface/qt4/src/3rdparty/sqlite/random.c new file mode 100644 index 000000000..7182ad1c3 --- /dev/null +++ b/experimental/tqtinterface/qt4/src/3rdparty/sqlite/random.c @@ -0,0 +1,97 @@ +/* +** 2001 September 15 +** +** The author disclaims copyright to this source code. In place of +** a legal notice, here is a blessing: +** +** May you do good and not evil. +** May you tqfind forgiveness for yourself and forgive others. +** May you share freely, never taking more than you give. +** +************************************************************************* +** This file tqcontains code to implement a pseudo-random number +** generator (PRNG) for STQLite. +** +** Random numbers are used by some of the database backends in order +** to generate random integer keys for tables or random filenames. +** +** $Id: random.c,v 1.11 2004/02/11 09:46:33 drh Exp $ +*/ +#include "sqliteInt.h" +#include "os.h" + + +/* +** 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_NewRecno 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, STQLite uses this random number generator based +** on RC4, which we know works very well. +*/ +static int randomByte(){ + unsigned char t; + + /* All threads share a single random number generator. + ** This structure is the current state of the generator. + */ + static struct { + unsigned char isInit; /* True if initialized */ + unsigned char i, j; /* State variables */ + unsigned char s[256]; /* State variables */ + } prng; + + /* 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 STQLite does any kind of + ** encryption. The RC4 algorithm is being used as a PRNG (pseudo-random + ** number generator) not as an encryption tqdevice. + */ + if( !prng.isInit ){ + int i; + char k[256]; + prng.j = 0; + prng.i = 0; + sqliteOsRandomSeed(k); + for(i=0; i<256; i++){ + prng.s[i] = i; + } + for(i=0; i<256; i++){ + prng.j += prng.s[i] + k[i]; + t = prng.s[prng.j]; + prng.s[prng.j] = prng.s[i]; + prng.s[i] = t; + } + prng.isInit = 1; + } + + /* Generate and return single random byte + */ + prng.i++; + t = prng.s[prng.i]; + prng.j += t; + prng.s[prng.i] = prng.s[prng.j]; + prng.s[prng.j] = t; + t += prng.s[prng.i]; + return prng.s[t]; +} + +/* +** Return N random bytes. +*/ +void sqliteRandomness(int N, void *pBuf){ + unsigned char *zBuf = pBuf; + sqliteOsEnterMutex(); + while( N-- ){ + *(zBuf++) = randomByte(); + } + sqliteOsLeaveMutex(); +} |