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Diffstat (limited to 'ext/sqlite/libsqlite/src/random.c')
-rw-r--r-- | ext/sqlite/libsqlite/src/random.c | 113 |
1 files changed, 0 insertions, 113 deletions
diff --git a/ext/sqlite/libsqlite/src/random.c b/ext/sqlite/libsqlite/src/random.c deleted file mode 100644 index d18bebff6b..0000000000 --- a/ext/sqlite/libsqlite/src/random.c +++ /dev/null @@ -1,113 +0,0 @@ -/* -** 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. -** -** $Id$ -*/ -#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, SQLite uses this random number generator based -** on RC4, which we know works very well. -*/ -static int randomByte(){ - int t; - - /* All threads share a single random number generator. - ** This structure is the current state of the generator. - */ - static struct { - int isInit; /* True if initialized */ - int i, j; /* State variables */ - int 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 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( !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++){ - int t; - prng.j = (prng.j + prng.s[i] + k[i]) & 0xff; - 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 = (prng.i + 1) & 0xff; - prng.j = (prng.j + prng.s[prng.i]) & 0xff; - t = prng.s[prng.i]; - prng.s[prng.i] = prng.s[prng.j]; - prng.s[prng.j] = t; - t = prng.s[prng.i] + prng.s[prng.j]; - return prng.s[t & 0xff]; -} - -/* -** Return an random 8-bit integer. -*/ -int sqliteRandomByte(){ - int r; - sqliteOsEnterMutex(); - r = randomByte(); - sqliteOsLeaveMutex(); - return r; -} - -/* -** Return a random 32-bit integer. The integer is generated by making -** 4 calls to sqliteRandomByte(). -*/ -int sqliteRandomInteger(){ - int r; - int i; - sqliteOsEnterMutex(); - r = randomByte(); - for(i=1; i<4; i++){ - r = (r<<8) + randomByte(); - } - sqliteOsLeaveMutex(); - return r; -} |