engine/sqlite/src/random.cpp
changeset 97 3903521a36da
parent 96 87e863f6f840
child 98 5f9e7e14eb11
--- a/engine/sqlite/src/random.cpp	Wed May 26 10:44:32 2010 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,103 +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: random.cpp 1282 2008-11-13 09:31:33Z LarsPson $
-*/
-#include "sqliteInt.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_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;
-
-  /* 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;
-    sqlite3OsRandomness(sqlite3_vfs_find(0), 256, 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 = (unsigned char*)pBuf;
-  static sqlite3_mutex *mutex = 0;
-  if( mutex==0 ){
-    mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PRNG);
-  }
-  sqlite3_mutex_enter(mutex);
-  while( N-- ){
-    *(zBuf++) = randomByte();
-  }
-  sqlite3_mutex_leave(mutex);
-}