diff -r 000000000000 -r 08ec8eefde2f persistentstorage/sql/SQLite364/random.c --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/persistentstorage/sql/SQLite364/random.c Fri Jan 22 11:06:30 2010 +0200 @@ -0,0 +1,147 @@ +/* +** 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 find forgiveness for yourself and forgive others. +** May you share freely, never taking more than you give. +** +************************************************************************* +** This file contains code to implement a pseudo-random number +** generator (PRNG) for SQLite. +** +** 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 1.27 2008/10/07 15:25:48 drh Exp $ +*/ +#include "sqliteInt.h" + + +/* All threads share a single random number generator. +** This structure is the current state of the generator. +*/ +static SQLITE_WSD struct sqlite3PrngType { + unsigned char isInit; /* True if initialized */ + unsigned char i, j; /* State variables */ + unsigned char s[256]; /* State variables */ +} sqlite3Prng = { 0, }; + +/* +** 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. +*/ +static int randomByte(void){ + unsigned char t; + + + /* The "wsdPrng" macro will resolve to the pseudo-random number generator + ** state vector. If writable static data is unsupported on the target, + ** we have to locate the state vector at run-time. In the more common + ** case where writable static data is supported, wsdPrng can refer directly + ** to the "sqlite3Prng" state vector declared above. + */ +#ifdef SQLITE_OMIT_WSD + struct sqlite3PrngType *p = &GLOBAL(struct sqlite3PrngType, sqlite3Prng); +# define wsdPrng p[0] +#else +# define wsdPrng sqlite3Prng +#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 + ** encryption. The RC4 algorithm is being used as a PRNG (pseudo-random + ** number generator) not as an encryption device. + */ + if( !wsdPrng.isInit ){ + int i; + char k[256]; + wsdPrng.j = 0; + wsdPrng.i = 0; + sqlite3OsRandomness(sqlite3_vfs_find(0), 256, k); + for(i=0; i<256; i++){ + wsdPrng.s[i] = i; + } + for(i=0; i<256; i++){ + wsdPrng.j += wsdPrng.s[i] + k[i]; + t = wsdPrng.s[wsdPrng.j]; + wsdPrng.s[wsdPrng.j] = wsdPrng.s[i]; + wsdPrng.s[i] = t; + } + 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(); + } + 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 +** to reset the PRNG to its initial state. These routines accomplish +** those tasks. +** +** The sqlite3_test_control() interface calls these routines to +** control the PRNG. +*/ +static SQLITE_WSD struct sqlite3PrngType sqlite3SavedPrng = { 0, }; +void sqlite3PrngSaveState(void){ + memcpy( + &GLOBAL(struct sqlite3PrngType, sqlite3SavedPrng), + &GLOBAL(struct sqlite3PrngType, sqlite3Prng), + sizeof(sqlite3Prng) + ); +} +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 */