Mon 21 Jul 22:43:21 CEST 2025

js/sql/random.js

@@ -0,0 +1,87 @@
+open('c2');
+sqlite3OsRandomSeed =function(buf) {
+  var i=buf.length;
+  while (i--) buf[i]=(Math.random()*256)|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.
+*/
+
+/* All threads share a single random number generator.
+** This structure is the current state of the generator.
+*/
+var prng = {
+    isInit:false,          /* True if initialized */
+    i:U8(0), 
+    j:U8(0),            /* State variables */
+    s: Buffer(256)          /* State variables */
+};
+
+
+function randomByte(){
+  // TODO
+ var t=U8(0);
+
+  /* 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 ){
+    var i;
+    var k=Buffer(256);
+    prng.j = U8(0);
+    prng.i = U8(0);
+    sqlite3OsRandomSeed(k);
+    for(i=0; i<256; i++){
+      prng.s[i] = i;
+    }
+    for(i=0; i<256; i++){
+      prng.j = U8(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 = true;
+  }
+
+  /* Generate and return single random byte
+  */
+  prng.i = U8(prng.i+1);
+  t = prng.s[prng.i];
+  prng.j = U8(prng.j+t);
+  prng.s[prng.i] = prng.s[prng.j];
+  prng.s[prng.j] = t;
+  t = U8(t+prng.s[prng.i]);
+  return prng.s[t];
+}
+/*
+** Return N random bytes.
+** void sqlite3Randomness(int N, void *pBuf)
+*/
+sqlite3Randomness = function(N,pBuf) {
+  if (pBuf.ref != undefined && typeof pBuf.ref == 'number') {
+    pBuf.ref=0;
+    while(N--) {
+      pBuf.ref = pBuf.ref << 8;
+      pBuf.ref = pBuf.ref | randomByte();
+    }
+  }
+}