From: Orvid King <blah38621@gmail.com>
Date: Mon, 17 Aug 2015 17:32:51 +0000 (-0700)
Subject: Implement Random.cpp for MSVC
X-Git-Tag: v0.54.0~3
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=9af380441971bc1d285c1c64cea3e3d80fe45079;p=folly.git

Implement Random.cpp for MSVC

Summary: This uses `<random>` to implement it, because there is no `/dev/urandom` on Windows.
Closes #250

Reviewed By: @yfeldblum

Differential Revision: D2282887

Pulled By: @sgolemon
---

diff --git a/folly/Random.cpp b/folly/Random.cpp
index 87da68b6..62eb8f9f 100644
--- a/folly/Random.cpp
+++ b/folly/Random.cpp
@@ -19,6 +19,7 @@
 #include <atomic>
 #include <unistd.h>
 #include <sys/time.h>
+#include <mutex>
 #include <random>
 #include <array>
 
@@ -26,16 +27,31 @@
 #include <folly/File.h>
 #include <folly/FileUtil.h>
 
+#ifdef _MSC_VER
+# include <wincrypt.h>
+#endif
+
 namespace folly {
 
 namespace {
 
 void readRandomDevice(void* data, size_t size) {
+#ifdef _MSC_VER
+  static std::once_flag flag;
+  static HCRYPTPROV cryptoProv;
+  std::call_once(flag, [&] {
+    PCHECK(CryptAcquireContext(&cryptoProv, nullptr, nullptr,
+                               PROV_RSA_FULL, 0));
+  });
+  CHECK(size <= std::numeric_limits<DWORD>::max());
+  PCHECK(CryptGenRandom(cryptoProv, (DWORD)size, (BYTE*)data));
+#else
   // Keep the random device open for the duration of the program.
   static int randomFd = ::open("/dev/urandom", O_RDONLY);
   PCHECK(randomFd >= 0);
   auto bytesRead = readFull(randomFd, data, size);
   PCHECK(bytesRead >= 0 && size_t(bytesRead) == size);
+#endif
 }
 
 class BufferedRandomDevice {