RequestContext support

[folly.git] / folly / Random.cpp

diff --git a/folly/Random.cpp b/folly/Random.cpp
index 13664ce8420bbd1c3b68dbe7ef450dd4658b0717..87da68b6b5216469591efd17ad68466fd1c00068 100644 (file)
--- a/folly/Random.cpp
+++ b/folly/Random.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012 Facebook, Inc.
+ * Copyright 2015 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,22 +14,106 @@
  * limitations under the License.
  */
 
-#include "folly/Random.h"
+#include <folly/Random.h>
 
+#include <atomic>
 #include <unistd.h>
 #include <sys/time.h>
+#include <random>
+#include <array>
+
+#include <glog/logging.h>
+#include <folly/File.h>
+#include <folly/FileUtil.h>
 
 namespace folly {
 
-uint32_t randomNumberSeed() {
-  struct timeval tv;
-  gettimeofday(&tv, NULL);
-  const uint32_t kPrime1 = 61631;
-  const uint32_t kPrime2 = 64997;
-  const uint32_t kPrime3 = 111857;
-  return kPrime1 * static_cast<uint32_t>(getpid())
-       + kPrime2 * static_cast<uint32_t>(tv.tv_sec)
-       + kPrime3 * static_cast<uint32_t>(tv.tv_usec);
+namespace {
+
+void readRandomDevice(void* data, size_t size) {
+  // 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);
+}
+
+class BufferedRandomDevice {
+ public:
+  static constexpr size_t kDefaultBufferSize = 128;
+
+  explicit BufferedRandomDevice(size_t bufferSize = kDefaultBufferSize);
+
+  void get(void* data, size_t size) {
+    if (LIKELY(size <= remaining())) {
+      memcpy(data, ptr_, size);
+      ptr_ += size;
+    } else {
+      getSlow(static_cast<unsigned char*>(data), size);
+    }
+  }
+
+ private:
+  void getSlow(unsigned char* data, size_t size);
+
+  inline size_t remaining() const {
+    return buffer_.get() + bufferSize_ - ptr_;
+  }
+
+  const size_t bufferSize_;
+  std::unique_ptr<unsigned char[]> buffer_;
+  unsigned char* ptr_;
+};
+
+BufferedRandomDevice::BufferedRandomDevice(size_t bufferSize)
+  : bufferSize_(bufferSize),
+    buffer_(new unsigned char[bufferSize]),
+    ptr_(buffer_.get() + bufferSize) {  // refill on first use
+}
+
+void BufferedRandomDevice::getSlow(unsigned char* data, size_t size) {
+  DCHECK_GT(size, remaining());
+  if (size >= bufferSize_) {
+    // Just read directly.
+    readRandomDevice(data, size);
+    return;
+  }
+
+  size_t copied = remaining();
+  memcpy(data, ptr_, copied);
+  data += copied;
+  size -= copied;
+
+  // refill
+  readRandomDevice(buffer_.get(), bufferSize_);
+  ptr_ = buffer_.get();
+
+  memcpy(data, ptr_, size);
+  ptr_ += size;
+}
+
+
+}  // namespace
+
+void Random::secureRandom(void* data, size_t size) {
+  static ThreadLocal<BufferedRandomDevice> bufferedRandomDevice;
+  bufferedRandomDevice->get(data, size);
+}
+
+ThreadLocalPRNG::ThreadLocalPRNG() {
+  static folly::ThreadLocal<ThreadLocalPRNG::LocalInstancePRNG> localInstance;
+  local_ = localInstance.get();
+}
+
+class ThreadLocalPRNG::LocalInstancePRNG {
+ public:
+  LocalInstancePRNG() : rng(Random::create()) { }
+
+  Random::DefaultGenerator rng;
+};
+
+uint32_t ThreadLocalPRNG::getImpl(LocalInstancePRNG* local) {
+  return local->rng();
 }
 
 }