Add a simple version of std::async as std_async in async.h and use it

in the RSA and DSA ops.

3 files changed, 42 insertions, 39 deletions

diff --git a/src/pubkey/dsa/dsa_op.cpp b/src/pubkey/dsa/dsa_op.cpp
index 4c84667eb..03eaebfb0 100644
--- a/src/pubkey/dsa/dsa_op.cpp
+++ b/src/pubkey/dsa/dsa_op.cpp
@@ -1,13 +1,12 @@
 /*
 * DSA Operations
-* (C) 1999-2007 Jack Lloyd
+* (C) 1999-2009 Jack Lloyd
 *
 * Distributed under the terms of the Botan license
 */
 
 #include <botan/dsa_op.h>
-#include <thread>
-#include <future>
+#include <botan/async.h>
 
 namespace Botan {
 
@@ -43,21 +42,12 @@ bool Default_DSA_Op::verify(const byte msg[], u32bit msg_len,
 
    s = inverse_mod(s, q);
 
-   // Todo: use async()
-
-   std::packaged_task<BigInt ()> task_s_i(
+   auto future_s_i = std_async(
       [&]() { return powermod_g_p(mod_q.multiply(s, i)); });
 
-   auto future_s_i = task_s_i.get_future();
-
-   std::thread thr_s_i(std::move(task_s_i));
-
    BigInt s_r = powermod_y_p(mod_q.multiply(s, r));
-
    BigInt s_i = future_s_i.get();
 
-   thr_s_i.join();
-
    s = mod_p.multiply(s_i, s_r);
 
    return (mod_q.reduce(s) == r);
@@ -72,20 +62,13 @@ SecureVector<byte> Default_DSA_Op::sign(const byte in[], u32bit length,
    if(x == 0)
       throw Internal_Error("Default_DSA_Op::sign: No private key");
 
+   auto future_r = std_async([&]() { return mod_q.reduce(powermod_g_p(k)); });
+
    const BigInt& q = group.get_q();
    BigInt i(in, length);
 
-   std::packaged_task<BigInt ()> task_r(
-      [&]() { return mod_q.reduce(powermod_g_p(k)); });
-
-   auto future_r = task_r.get_future();
-
-   std::thread thr_r(std::move(task_r));
-
    BigInt s = inverse_mod(k, q);
-
    BigInt r = future_r.get();
-   thr_r.join();
 
    s = mod_q.multiply(s, mul_add(x, r, i));
 
diff --git a/src/pubkey/if_algo/if_op.cpp b/src/pubkey/if_algo/if_op.cpp
index a59c7d5f9..7974bf4f0 100644
--- a/src/pubkey/if_algo/if_op.cpp
+++ b/src/pubkey/if_algo/if_op.cpp
@@ -1,14 +1,13 @@
 /*
-* IF (RSA/RW) Operation
-* (C) 1999-2007 Jack Lloyd
+* Integer Factorization Scheme (RSA/RW) Operation
+* (C) 1999-2009 Jack Lloyd
 *
 * Distributed under the terms of the Botan license
 */
 
 #include <botan/if_op.h>
 #include <botan/numthry.h>
-#include <future>
-#include <thread>
+#include <botan/async.h>
 
 namespace Botan {
 
@@ -44,23 +43,11 @@ BigInt Default_IF_Op::private_op(const BigInt& i) const
    * A simple std::bind(powermod_d1_p, i) would work instead of a
    * lambda but GCC 4.5's std::result_of doesn't use decltype and gets
    * confused
-   *
-   * Todo: use std::async() once it is in GCC
-   *    auto future_j1 = std::async(std::bind(powermod_d1_p, i));
-   *    BigInt j2 = powermod_d2_q(i);
-   *    BigInt j1 = future.get();
    */
-   std::packaged_task<BigInt ()> task_j1([&]() { return powermod_d1_p(i); });
-   auto future_j1 = task_j1.get_future();
-
-   std::thread thr_j1(std::move(task_j1));
-
+   auto future_j1 = std_async([&]() { return powermod_d1_p(i); });
    BigInt j2 = powermod_d2_q(i);
-
    BigInt j1 = future_j1.get();
 
-   thr_j1.join();
-
    j1 = reducer.reduce(sub_mul(j1, j2, c));
    return mul_add(j1, q, j2);
    }
diff --git a/src/utils/async.h b/src/utils/async.h
new file mode 100644
index 000000000..85702c114
--- /dev/null
+++ b/src/utils/async.h
@@ -0,0 +1,33 @@
+/**
+* Standin for C++0x's std::async
+* (C) 2009 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#ifndef BOTAN_ASYNC_H__
+#define BOTAN_ASYNC_H__
+
+#include <future>
+#include <thread>
+
+namespace Botan {
+
+/**
+* A simple version of std::async (as it is not in GCC 4.5)
+* Will be removed once GCC supports it natively
+*/
+template<typename F>
+auto std_async(F f) -> std::unique_future<decltype(f())>
+   {
+   typedef decltype(f()) result_type;
+   std::packaged_task<result_type ()> task(std::move(f));
+   std::unique_future<result_type> future = task.get_future();
+   std::thread thread(std::move(task));
+   thread.detach();
+   return future;
+   }
+
+}
+
+#endif