summaryrefslogtreecommitdiffstats
path: root/kopete/plugins/statistics/sqlite/random.c
diff options
context:
space:
mode:
Diffstat (limited to 'kopete/plugins/statistics/sqlite/random.c')
-rw-r--r--kopete/plugins/statistics/sqlite/random.c100
1 files changed, 100 insertions, 0 deletions
diff --git a/kopete/plugins/statistics/sqlite/random.c b/kopete/plugins/statistics/sqlite/random.c
new file mode 100644
index 00000000..de74e291
--- /dev/null
+++ b/kopete/plugins/statistics/sqlite/random.c
@@ -0,0 +1,100 @@
+/*
+** 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(){
+ 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 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;
+ sqlite3OsRandomSeed(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 sqlite3Randomness(int N, void *pBuf){
+ unsigned char *zBuf = pBuf;
+ sqlite3OsEnterMutex();
+ while( N-- ){
+ *(zBuf++) = randomByte();
+ }
+ sqlite3OsLeaveMutex();
+}
+
+
+