Add a simple /dev/random.

VirtualFileSystem/RandomDevice.cpp

@@ -0,0 +1,47 @@
+#include "RandomDevice.h"
+#include "Limits.h"
+#include <AK/StdLib.h>
+#include <cstring>
+#include <cstdio>
+
+RandomDevice::RandomDevice()
+{
+}
+
+RandomDevice::~RandomDevice()
+{
+}
+
+// Simple rand() and srand() borrowed from the POSIX standard:
+
+static unsigned long next = 1;
+
+#define MY_RAND_MAX 32767
+static int myrand()
+{
+    next = next * 1103515245 + 12345;
+    return((unsigned)(next/((MY_RAND_MAX + 1) * 2)) % (MY_RAND_MAX + 1));
+}
+
+static void mysrand(unsigned seed)
+{
+    next = seed;
+}
+
+Unix::ssize_t RandomDevice::read(byte* buffer, Unix::size_t bufferSize)
+{
+    const int range = 'z' - 'a';
+    Unix::ssize_t nread = min(bufferSize, GoodBufferSize);
+    for (Unix::ssize_t i = 0; i < nread; ++i) {
+        double r = ((double)myrand() / (double)MY_RAND_MAX) * (double)range;
+        buffer[i] = 'a' + r;
+    }
+    return nread;
+}
+
+Unix::ssize_t RandomDevice::write(const byte*, Unix::size_t bufferSize)
+{
+    // FIXME: Use input for entropy? I guess that could be a neat feature?
+    return min(GoodBufferSize, bufferSize);
+}
+