nemora-postd: import from gBMC

This is the POST code portion of nemorad.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Google-Bug-Id: 179618653
Change-Id: Icf68fe8adf62c646238cf8235918a13effa857f8
diff --git a/subprojects/nemora-postd/src/host_manager.hpp b/subprojects/nemora-postd/src/host_manager.hpp
new file mode 100644
index 0000000..6ed2a33
--- /dev/null
+++ b/subprojects/nemora-postd/src/host_manager.hpp
@@ -0,0 +1,78 @@
+// Copyright 2021 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+#include "nemora_types.hpp"
+
+#include <sdbusplus/bus.hpp>
+#include <sdbusplus/message.hpp>
+#include <sdbusplus/server.hpp>
+
+#include <mutex>
+#include <queue>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#define POSTCODE_OBJECTPATH "/xyz/openbmc_project/state/boot/raw0"
+#define POSTCODE_BUSNAME "xyz.openbmc_project.State.Boot.Raw"
+
+class HostManager
+{
+  public:
+    HostManager();
+    ~HostManager() = default;
+
+    /**
+     * Callback for POST code DBus listener
+     * - msg: out-parameter for message received over DBus from callback
+     *
+     * - returns: error code or 0 for success
+     */
+    int DbusHandleSignal(sdbusplus::message::message& msg);
+
+    /**
+     * Helper to construct match string for callback registration for POST
+     * listener
+     * - returns: match string for use in registering callback
+     */
+    static std::string GetMatch();
+
+    /**
+     * Copies contents of POSTcode vector away to allow for sending via UDP
+     * - returns: vector filled with current state of postcodes_
+     */
+    std::vector<uint64_t> DrainPostcodes();
+
+    /**
+     * Add POST code to vector, thread-safely
+     * - postcode: POST code to add, typically only 8 or 16 bits wide
+     */
+    void PushPostcode(uint64_t postcode);
+
+  private:
+    /**
+     * Business logic of thread listening to DBus for POST codes
+     */
+    void PostPollerThread();
+
+    // It's important that postcodes_ be initialized before post_poller_!
+    std::vector<uint64_t> postcodes_;
+    std::mutex postcodes_lock_;
+
+    sdbusplus::bus::bus bus_;
+    sdbusplus::server::match::match signal_;
+    std::unique_ptr<std::thread> post_poller_;
+    bool post_poller_enabled_;
+};