Finish circuit.

Author: Bowen Fu

circuit.cpp

@@ -0,0 +1,228 @@
+#include <memory>
+#include <cstdlib>
+#include <functional>
+#include <vector>
+#include <string>
+#include <iostream>
+#include <queue>
+#include <map>
+
+class Wire
+{
+public:
+    auto getSignal() const
+    {
+        return mValue;
+    }
+    void setSignal(bool newValue)
+    {
+        if (mValue == newValue)
+        {
+            return;
+        }
+        mValue = newValue;
+        for (auto const& action : mActions)
+        {
+            action();
+        }
+    }
+    void addAction(std::function<void()> func)
+    {
+        func();
+        mActions.push_back(func);
+    }
+private:
+    bool mValue{};
+    std::vector<std::function<void()>> mActions;
+};
+
+using WirePtr = std::shared_ptr<Wire>;
+
+auto makeWire()
+{
+    return std::make_shared<Wire>();
+}
+
+auto afterDelay(int32_t delay, std::function<void()> action) -> std::function<void()>;
+
+void orGate(WirePtr in1, WirePtr in2, WirePtr out)
+{
+    auto const action = [out = std::move(out), in1, in2]{
+        auto const newValue = in1->getSignal() || in2->getSignal();
+        out->setSignal(newValue);
+    };
+    auto const orGateDelay = 5;
+    auto const delayedAction = afterDelay(orGateDelay, action);
+    in1->addAction(delayedAction);
+    in2->addAction(delayedAction);
+}
+
+void andGate(WirePtr in1, WirePtr in2, WirePtr out)
+{
+    auto const action = [out = std::move(out), in1, in2]{
+        auto const newValue = in1->getSignal() && in2->getSignal();
+        out->setSignal(newValue);
+    };
+    auto const andGateDelay = 3;
+    auto const delayedAction = afterDelay(andGateDelay, action);
+    in1->addAction(delayedAction);
+    in2->addAction(delayedAction);
+}
+
+void inverter(WirePtr in, WirePtr out)
+{
+    auto action = [in, out = std::move(out)]
+    {
+        auto newValue = !(in->getSignal());
+        out->setSignal(newValue);
+    };
+    auto const inverterDelay = 2;
+    in->addAction(afterDelay(inverterDelay, action));
+}
+
+auto halfAdder(WirePtr a, WirePtr b, WirePtr s, WirePtr c)
+{
+    auto d = makeWire();
+    auto e = makeWire();
+    orGate(a, b, d);
+    andGate(a, b, c);
+    inverter(c, e);
+    andGate(d, e, s);
+}
+
+auto fullAdder(WirePtr a, WirePtr b, WirePtr cIn, WirePtr sum, WirePtr cOut)
+{
+    auto s = makeWire();
+    auto c1 = makeWire();
+    auto c2 = makeWire();
+    halfAdder(b, cIn, s, c1);
+    halfAdder(a, s, sum, c2);
+    orGate(c1, c2, cOut);
+}
+
+auto adder(std::vector<WirePtr> A, std::vector<WirePtr> B, std::vector<WirePtr> S, WirePtr C)
+{
+    assert(A.size() == B.size());
+    assert(A.size() == S.size());
+    auto Cin = makeWire();
+    for (size_t i = 0; i < A.size() - 1; ++i)
+    {
+        auto Cout = makeWire();
+        fullAdder(A[i], B[i], Cin, S[i], Cout);
+        Cin = Cout;
+    }
+    fullAdder(A.back(), B.back(), Cin, S.back(), C);
+}
+
+class Agenda
+{
+private:
+    std::map<int32_t, std::queue<std::function<void()>>> mItems{};
+    int32_t mTime{};
+    Agenda() = default;
+public:
+    static Agenda& instance()
+    {
+        static Agenda theAgenda;
+        return theAgenda;
+    }
+    bool empty() const
+    {
+        return mItems.empty();
+    }
+    auto pop()
+    {
+        auto& first = mItems.begin()->second;
+        auto result = first.front();
+        mTime = mItems.begin()->first;
+        first.pop();
+        if (first.empty())
+        {
+            mItems.erase(mItems.begin());
+        }
+        return result;
+    }
+    auto push(int32_t time, std::function<void()> action)
+    {
+        mItems[time].push(action);
+        return action;
+    }
+    auto currentTime() const
+    {
+        return mTime;
+    }
+};
+
+auto afterDelay(int32_t delay, std::function<void()> action) -> std::function<void()>
+{
+    return [=]
+    {
+        auto &theAgenda = Agenda::instance();
+        theAgenda.push(theAgenda.currentTime() + delay, action);
+    };
+}
+
+auto propagate()
+{
+    auto& theAgenda = Agenda::instance();
+    if (theAgenda.empty())
+    {
+        return;
+    }
+    auto firstItem = theAgenda.pop();
+    firstItem();
+    propagate();
+}
+
+void probe(std::string const& name, WirePtr wire)
+{
+    auto const action = [=]
+    {
+        std::cout << name << " " 
+        << Agenda::instance().currentTime()
+        << " New-value = "
+        << wire->getSignal() << std::endl;
+    };
+    wire->addAction(action);
+}
+
+int32_t main()
+{
+    auto input1 = makeWire();
+    auto input2 = makeWire();
+    auto sum = makeWire();
+    auto carry = makeWire();
+    // probe("input1", input1);
+    // probe("input2", input2);
+    probe("sum", sum);
+    probe("carry", carry);
+    //sum 0 New-value = 0
+    // carry 0 New-value = 0
+
+    halfAdder(input1, input2, sum, carry);
+    input1->setSignal(1);
+    propagate();
+    // sum 5 New-value = 1
+    input2->setSignal(1);
+    propagate();
+    // carry 11 New-value = 1
+    // sum 16 New-value = 0
+
+    //=== 2 bit adder
+    auto a0 = makeWire();
+    auto a1 = makeWire();
+    auto b0 = makeWire();
+    auto b1 = makeWire();
+    auto s0 = makeWire();
+    auto s1 = makeWire();
+    auto c = makeWire();
+    adder({a0, a1}, {b0, b1}, {s0, s1}, c);
+    a0->setSignal(1);
+    a1->setSignal(1);
+    b1->setSignal(1);
+    propagate();
+    assert(s0->getSignal() == 1);
+    assert(s1->getSignal() == 0);
+    assert(c->getSignal() == 1);
+    return 0;
+}