Add support for cover raw images

server/image_cache.hpp

@@ -0,0 +1,93 @@
+/***
+    This file is part of snapcast
+    Copyright (C) 2014-2021  Johannes Pohl
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#ifndef IMAGE_CACHE_HPP
+#define IMAGE_CACHE_HPP
+
+#include <map>
+#include <mutex>
+#include <optional>
+#include <string>
+
+#include <boost/algorithm/hex.hpp>
+#include <boost/uuid/detail/md5.hpp>
+
+
+class ImageCache
+{
+public:
+    ImageCache() = default;
+    virtual ~ImageCache() = default;
+
+    std::string setImage(const std::string& key, std::string image, const std::string& extension)
+    {
+        if (image.empty())
+        {
+            clear(key);
+            return "";
+        }
+
+        using boost::uuids::detail::md5;
+        md5 hash;
+        md5::digest_type digest;
+        hash.process_bytes(image.data(), image.size());
+        hash.get_digest(digest);
+        std::string filename;
+        const auto intDigest = reinterpret_cast<const int*>(&digest);
+        boost::algorithm::hex_lower(intDigest, intDigest + (sizeof(md5::digest_type) / sizeof(int)), std::back_inserter(filename));
+        auto ext = extension;
+        if (ext.find('.') == 0)
+            ext = ext.substr(1);
+        filename += "." + ext;
+        key_to_url_[key] = filename;
+        url_to_data_[filename] = image;
+        return filename;
+    };
+
+    void clear(const std::string& key)
+    {
+        std::lock_guard<std::mutex> lock(mutex_);
+        auto iter = key_to_url_.find(key);
+        if (iter != key_to_url_.end())
+        {
+            auto url = *iter;
+            auto url_iter = url_to_data_.find(url.second);
+            if (url_iter != url_to_data_.end())
+                url_to_data_.erase(url_iter);
+            key_to_url_.erase(iter);
+        }
+    }
+
+    std::optional<std::string> getImage(const std::string& url)
+    {
+        std::lock_guard<std::mutex> lock(mutex_);
+        auto iter = url_to_data_.find(url);
+        if (iter == url_to_data_.end())
+            return std::nullopt;
+        else
+            return iter->second;
+    }
+
+private:
+    std::map<std::string, std::string> key_to_url_;
+    std::map<std::string, std::string> url_to_data_;
+    std::mutex mutex_;
+};
+
+
+#endif