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// Copyright (c) 2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/rand_util.h"
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include "base/file_util.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
namespace {
// We keep the file descriptor for /dev/urandom around so we don't need to
// reopen it (which is expensive), and since we may not even be able to reopen
// it if we are later put in a sandbox. This class wraps the file descriptor so
// we can use LazyInstance to handle opening it on the first access.
class URandomFd {
public:
URandomFd() {
fd_ = open("/dev/urandom", O_RDONLY);
CHECK(fd_ >= 0) << "Cannot open /dev/urandom: " << errno;
}
~URandomFd() {
close(fd_);
}
int fd() const { return fd_; }
private:
int fd_;
};
base::LazyInstance<URandomFd> g_urandom_fd(base::LINKER_INITIALIZED);
} // namespace
namespace base {
uint64 RandUint64() {
uint64 number;
int urandom_fd = g_urandom_fd.Pointer()->fd();
bool success = file_util::ReadFromFD(urandom_fd,
reinterpret_cast<char*>(&number),
sizeof(number));
CHECK(success);
return number;
}
} // namespace base
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