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// file : libbutl/uuid-windows.cxx -*- C++ -*-
// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
// license : MIT; see accompanying LICENSE file
#ifndef BUILD2_BOOTSTRAP
#include <libbutl/uuid.hxx>
#include <rpc.h> // UuidCreate*()
#include <errno.h>
#include <cassert>
#include <system_error>
using namespace std;
namespace butl
{
void uuid::
assign (const _GUID& d)
{
time_low = d.Data1;
time_mid = d.Data2;
time_hiv = d.Data3;
clock_seq_hir = d.Data4[0];
clock_seq_low = d.Data4[1];
memcpy (node, &d.Data4[2], 6);
}
template<>
LIBBUTL_SYMEXPORT _GUID uuid::
guid<_GUID> () const
{
_GUID r;
r.Data1 = time_low;
r.Data2 = time_mid;
r.Data3 = time_hiv;
r.Data4[0] = clock_seq_hir;
r.Data4[1] = clock_seq_low;
memcpy (&r.Data4[2], node, 6);
return r;
}
void
uuid_throw_weak (); // uuid.cxx
uuid uuid_system_generator::
generate (bool strong)
{
// The common way to generate a UUID on Windows is with the CoCreateGuid()
// function which, according to the documentation, calls UuidCreate().
// There is some talk of it somehow generating stronger UUIDs but it is
// probably bogus (it most likely simply returns an error if UuidCreate()
// returns a "weak" UUID).
//
// UuidCreate(), on the other hand, has various interesting return codes
// as well as the UuidCreateSequential() variant which always generates a
// MAC/time-based UUID (according to the documentation, since Windows 2000
// UuidCreate() always generates a random UUID). So let's use that.
//
// While the documentation doesn't explicitly state this, presumably
// UuidCreate() uses a "decent" source of randomness. See this post for
// some background:
//
// https://stackoverflow.com/questions/35366368/does-uuidcreate-use-a-csprng
//
// So we assume a random UUID returned by UuidCreate() is strong. What to
// do if it's not is a tricky question (is it even possible?): we can call
// UuidCreateSequential() to generate a MAC/time-based UUID but it's
// possible the time was not obtained in a collision-safe manner (see the
// Linux implementation for background). However, the documentation
// suggests that it is safe ("... guaranteed to be unique among all UUIDs
// generated on the computer"). And so we assume it is.
//
auto rpcfail = [strong] (RPC_STATUS s)
{
if (s != RPC_S_UUID_LOCAL_ONLY)
{
char m [DCE_C_ERROR_STRING_LEN];
throw system_error (
ENOSYS,
system_category (),
(DceErrorInqTextA (s, reinterpret_cast<RPC_CSTR> (m)) == RPC_S_OK
? m
: "unknown RPC error"));
}
else if (strong)
uuid_throw_weak ();
};
UUID d;
RPC_STATUS s (UuidCreate (&d));
if (s != RPC_S_OK)
rpcfail (s);
uuid r (d);
assert (r.variant () == uuid_variant::dce); // Sanity check.
if (strong && r.version () != uuid_version::random)
{
s = UuidCreateSequential (&d);
if (s != RPC_S_OK)
rpcfail (s);
r.assign (d);
// UuidCreateSequential() on Wine returns the Microsoft variant.
//
if (r.variant () != uuid_variant::dce ||
r.version () != uuid_version::time)
rpcfail (RPC_S_UUID_LOCAL_ONLY);
}
return r;
}
void uuid_system_generator::
initialize ()
{
}
void uuid_system_generator::
terminate ()
{
}
}
#endif // BUILD2_BOOTSTRAP
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