From 05b088ee2f033120e7f1299a1c7ec123fc3c57c9 Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Mon, 15 Oct 2018 00:44:54 +0200
Subject: [PATCH] Add a simple /dev/random.

---
 VirtualFileSystem/Makefile         |   1 +
 VirtualFileSystem/RandomDevice.cpp |  47 +++++++++++++++++++++++++++++
 VirtualFileSystem/RandomDevice.h   |  13 ++++++++
 VirtualFileSystem/small.fs         | Bin 2048000 -> 2048000 bytes
 VirtualFileSystem/test.cpp         |   5 ++-
 5 files changed, 65 insertions(+), 1 deletion(-)
 create mode 100644 VirtualFileSystem/RandomDevice.cpp
 create mode 100644 VirtualFileSystem/RandomDevice.h

diff --git a/VirtualFileSystem/Makefile b/VirtualFileSystem/Makefile
index 28994083b2..d6114a4ba2 100644
--- a/VirtualFileSystem/Makefile
+++ b/VirtualFileSystem/Makefile
@@ -22,6 +22,7 @@ VFS_OBJS = \
     ZeroDevice.o \
     NullDevice.o \
     FullDevice.o \
+    RandomDevice.o \
     test.o
 
 OBJS = $(AK_OBJS) $(VFS_OBJS)
diff --git a/VirtualFileSystem/RandomDevice.cpp b/VirtualFileSystem/RandomDevice.cpp
new file mode 100644
index 0000000000..a47dc246dc
--- /dev/null
+++ b/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);
+}
+
diff --git a/VirtualFileSystem/RandomDevice.h b/VirtualFileSystem/RandomDevice.h
new file mode 100644
index 0000000000..4a30c259fc
--- /dev/null
+++ b/VirtualFileSystem/RandomDevice.h
@@ -0,0 +1,13 @@
+#pragma once
+
+#include "CharacterDevice.h"
+
+class RandomDevice final : public CharacterDevice {
+public:
+    RandomDevice();
+    virtual ~RandomDevice();
+
+    Unix::ssize_t read(byte* buffer, Unix::size_t bufferSize) override;
+    Unix::ssize_t write(const byte* buffer, Unix::size_t bufferSize) override;
+};
+
diff --git a/VirtualFileSystem/small.fs b/VirtualFileSystem/small.fs
index 0eb8186ea16e243f596bf391fa166eaa34319f0e..f336606ddbb6c623d98fc619528aa35e65435ba3 100644
GIT binary patch
delta 246
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zyC2;wWc!YBk`0FvgbNZn9L)d*j9?N*a4=3}v|>?WnVGs-k>kGnW&@53a6(dW(*~0S
zF&+jM=CsnB9C-!?h9k^u%teWLDfzh@8MiUFi7>W_Ftv#=w~4T{iLkbbu(gS>w~27H
ziEy@waJ7kWw~6qyiSV|G@U@BXw}}X}i3qld2(^g_w~2_fiHNp|h_#7`w~0u!iAc7I
WNVSPbw~5HKiO9Bz$So6**8u<yzCt7b

delta 186
zcmZo@sBLJd-5|ii_-L{qi#)4@%He3H&893jnHe8#=I8jL%xFK6QD(D(&Km(XVU@$t
z!YZ4EY~L|%HsH7*k3vik+_b?Yf#U)*3v*g&PR>TgBg}0gjBO%JZ6eHVA}nnptZgD}
zZ6fS#A{=cZoNXdpZ6e%lB0Oy(ylo<UZ6f?_A_8q9f^8x~Z6d;LA|h=fqHQ8#Z6e}r
cA`)#Pl5HYVZ6eZbA~J0vvTY)A%S7aL0KBX-!T<mO

diff --git a/VirtualFileSystem/test.cpp b/VirtualFileSystem/test.cpp
index 3977541f5d..7b07a6fc39 100644
--- a/VirtualFileSystem/test.cpp
+++ b/VirtualFileSystem/test.cpp
@@ -6,6 +6,7 @@
 #include "ZeroDevice.h"
 #include "NullDevice.h"
 #include "FullDevice.h"
+#include "RandomDevice.h"
 #include <cstring>
 #include <AK/SimpleMalloc.h>
 #include <AK/kmalloc.h>
@@ -29,6 +30,9 @@ int main(int c, char** v)
     auto full = make<FullDevice>();
     vfs.registerCharacterDevice(1, 7, *full);
 
+    auto random = make<RandomDevice>();
+    vfs.registerCharacterDevice(1, 8, *random);
+
     if (!vfs.mountRoot(makeFileSystem(filename))) {
         printf("Failed to mount root :(\n");
         return 1;
@@ -187,7 +191,6 @@ int main(int c, char** v)
             byte buffer[512];
             for (;;) {
                 nread = handle->read(buffer, sizeof(buffer));
-                printf("read() returned %d\n", nread);
                 if (nread <= 0)
                     break;
                 fwrite(buffer, 1, nread, stdout);