From b4b7224dd05acc1188f2ce764530e5d5324e65e1 Mon Sep 17 00:00:00 2001
From: q66 <daniel@octaforge.org>
Date: Sat, 18 Mar 2017 01:05:10 +0100
Subject: [PATCH] initial skeleton for concurrency module

---
 build.sh                |  4 +--
 examples/concurrency.cc | 47 +++++++++++++++++++++++++
 ostd/concurrency.hh     | 78 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 127 insertions(+), 2 deletions(-)
 create mode 100644 examples/concurrency.cc
 create mode 100644 ostd/concurrency.hh

diff --git a/build.sh b/build.sh
index 1c6a9e2..8778e56 100755
--- a/build.sh
+++ b/build.sh
@@ -5,7 +5,7 @@ set -e
 
 # example sources
 EXAMPLES="format listdir range range_pipe signal"
-EXAMPLES="${EXAMPLES} stream1 stream2 coroutine1 coroutine2"
+EXAMPLES="${EXAMPLES} stream1 stream2 coroutine1 coroutine2 concurrency"
 
 # assembly sources
 ASM_SOURCE_DIR="src/asm"
@@ -136,7 +136,7 @@ if [ ! -z "$CPPFLAGS" ]; then
 fi
 
 # linker flags
-OSTD_LDFLAGS=""
+OSTD_LDFLAGS="-pthread"
 
 # custom linker flags
 if [ ! -z "$LDFLAGS" ]; then
diff --git a/examples/concurrency.cc b/examples/concurrency.cc
new file mode 100644
index 0000000..f70bd33
--- /dev/null
+++ b/examples/concurrency.cc
@@ -0,0 +1,47 @@
+#include <ostd/io.hh>
+#include <ostd/concurrency.hh>
+
+using namespace ostd;
+
+thread_scheduler sched;
+
+void foo() {
+    auto arr = ostd::iter({ 150, 38, 76, 25, 67, 18, -15, -38, 25, -10 });
+
+    auto h1 = arr.slice(0, arr.size() / 2);
+    auto h2 = arr.slice(arr.size() / 2, arr.size());
+
+    auto c = sched.make_channel<int>();
+    auto f = [&c](auto half) {
+        int ret = 0;
+        for (int i: half) {
+            ret += i;
+        }
+        c.put(ret);
+    };
+    sched.spawn(f, h1);
+    sched.spawn(f, h2);
+
+    int a, b;
+    c.get(a);
+    c.get(b);
+    writefln("first half: %s", a);
+    writefln("second half: %s", b);
+    writefln("total: %s", a + b);
+}
+
+int main() {
+    sched.start([]() {
+        writeln("starting...");
+        foo();
+        writeln("finishing...");
+    });
+}
+
+/*
+starting...
+first half: 356
+second half: -20
+total: 336
+finishing...
+*/
diff --git a/ostd/concurrency.hh b/ostd/concurrency.hh
new file mode 100644
index 0000000..e706211
--- /dev/null
+++ b/ostd/concurrency.hh
@@ -0,0 +1,78 @@
+/* Concurrency module with custom scheduler support.
+ *
+ * This file is part of OctaSTD. See COPYING.md for futher information.
+ */
+
+#ifndef OSTD_CONCURRENCY_HH
+#define OSTD_CONCURRENCY_HH
+
+#include <stdio.h>
+#include <thread>
+#include <utility>
+
+#include "ostd/channel.hh"
+
+namespace ostd {
+
+struct thread_scheduler {
+    ~thread_scheduler() {
+        join_all();
+    }
+
+    template<typename F, typename ...A>
+    void start(F &&func, A &&...args) {
+        func(std::forward<A>(args)...);
+    }
+
+    template<typename F, typename ...A>
+    void spawn(F &&func, A &&...args) {
+        std::unique_lock<std::mutex> l{p_lock};
+        p_threads.emplace_front();
+        auto it = p_threads.begin();
+        *it = std::thread{
+            [this, it](auto func, auto ...args) {
+                func(std::move(args)...);
+                this->remove_thread(it);
+            },
+            std::forward<F>(func), std::forward<A>(args)...
+        };
+    }
+
+    void yield() {
+        std::this_thread::yield();
+    }
+
+    template<typename T>
+    channel<T> make_channel() {
+        return channel<T>{};
+    }
+
+private:
+    void remove_thread(typename std::list<std::thread>::iterator it) {
+        std::unique_lock<std::mutex> l{p_lock};
+        std::thread t{std::exchange(p_dead, std::move(*it))};
+        if (t.joinable()) {
+            t.join();
+        }
+        p_threads.erase(it);
+    }
+
+    void join_all() {
+        /* wait for all threads to finish */
+        std::unique_lock<std::mutex> l{p_lock};
+        if (p_dead.joinable()) {
+            p_dead.join();
+        }
+        for (auto &t: p_threads) {
+            t.join();
+        }
+    }
+
+    std::list<std::thread> p_threads;
+    std::thread p_dead;
+    std::mutex p_lock;
+};
+
+} /* namespace ostd */
+
+#endif