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If using std::random_device fails, fall back to just time(nullptr)

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For instance, if using LibreOfficeKit in a chroot jail, there might
not be a /dev/urandom, which causes the std::random_device ctor to
throw a std::runtime_error exception, at least in the libstdc++ I
have.

Change-Id: Icc91a4ddf92ce66c66b6ffb8b4d1a02ab5f29ee9
This commit is contained in:
Tor Lillqvist
2015-05-06 12:34:17 +03:00
parent 7bd6f298b4
commit 776d74bb55
1 changed files with 17 additions and 7 deletions
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24
comphelper/source/misc/random.cxx
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@@ -12,9 +12,11 @@
#include <comphelper/random.hxx> #include <comphelper/random.hxx>
#include <rtl/instance.hxx> #include <rtl/instance.hxx>
#include <rtl/ustring.hxx>
#include <assert.h> #include <assert.h>
#include <time.h> #include <time.h>
#include <random> #include <random>
#include <stdexcept>
// this is nothing but a simple wrapper around // this is nothing but a simple wrapper around
// the std::random generators // the std::random generators
@@ -37,13 +39,21 @@ struct RandomNumberGenerator
STD_RNG_ALGO global_rng; STD_RNG_ALGO global_rng;
RandomNumberGenerator() RandomNumberGenerator()
{ {
std::random_device rd; try
// initialises the state of the global random number generator {
// should only be called once. std::random_device rd;
// (note, a few std::variate_generator<> (like normal) have their // initialises the state of the global random number generator
// own state which would need a reset as well to guarantee identical // should only be called once.
// sequence of numbers, e.g. via myrand.distribution().reset()) // (note, a few std::variate_generator<> (like normal) have their
global_rng.seed(rd() ^ time(nullptr)); // own state which would need a reset as well to guarantee identical
// sequence of numbers, e.g. via myrand.distribution().reset())
global_rng.seed(rd() ^ time(nullptr));
}
catch (std::runtime_error& e)
{
SAL_WARN("comphelper.random", OUString("Using std::random_device failed: ") << e.what());
global_rng.seed(time(nullptr));
}
} }
}; };