1 files changed, 99 insertions, 0 deletions
diff --git a/Crypto/src/crypto/prng/ThreadedSeedGenerator.cs b/Crypto/src/crypto/prng/ThreadedSeedGenerator.cs
new file mode 100644
index 000000000..9f918ea6e
--- /dev/null
+++ b/Crypto/src/crypto/prng/ThreadedSeedGenerator.cs
@@ -0,0 +1,99 @@
+using System;
+using System.Threading;
+
+namespace Org.BouncyCastle.Crypto.Prng
+{
+ /**
+ * A thread based seed generator - one source of randomness.
+ * <p>
+ * Based on an idea from Marcus Lippert.
+ * </p>
+ */
+ public class ThreadedSeedGenerator
+ {
+ private class SeedGenerator
+ {
+#if NETCF_1_0
+ // No volatile keyword, but all fields implicitly volatile anyway
+ private int counter = 0;
+ private bool stop = false;
+#else
+ private volatile int counter = 0;
+ private volatile bool stop = false;
+#endif
+
+ private void Run(object ignored)
+ {
+ while (!this.stop)
+ {
+ this.counter++;
+ }
+ }
+
+ public byte[] GenerateSeed(
+ int numBytes,
+ bool fast)
+ {
+ this.counter = 0;
+ this.stop = false;
+
+ byte[] result = new byte[numBytes];
+ int last = 0;
+ int end = fast ? numBytes : numBytes * 8;
+
+ ThreadPool.QueueUserWorkItem(new WaitCallback(Run));
+
+ for (int i = 0; i < end; i++)
+ {
+ var waitEvent = new ManualResetEvent(false);
+
+ while (this.counter == last)
+ {
+ try
+ {
+ waitEvent.WaitOne(1);
+ }
+ catch (Exception)
+ {
+ // ignore
+ }
+ }
+
+ last = this.counter;
+
+ if (fast)
+ {
+ result[i] = (byte) last;
+ }
+ else
+ {
+ int bytepos = i / 8;
+ result[bytepos] = (byte) ((result[bytepos] << 1) | (last & 1));
+ }
+ }
+
+ this.stop = true;
+
+ return result;
+ }
+ }
+
+ /**
+ * Generate seed bytes. Set fast to false for best quality.
+ * <p>
+ * If fast is set to true, the code should be round about 8 times faster when
+ * generating a long sequence of random bytes. 20 bytes of random values using
+ * the fast mode take less than half a second on a Nokia e70. If fast is set to false,
+ * it takes round about 2500 ms.
+ * </p>
+ * @param numBytes the number of bytes to generate
+ * @param fast true if fast mode should be used
+ */
+ public byte[] GenerateSeed(
+ int numBytes,
+ bool fast)
+ {
+ return new SeedGenerator().GenerateSeed(numBytes, fast);
+ }
+ }
+}
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