Internally compress (zlib lvl.9) replay files

This effort reduces the size of replays by a factor 2 to 10 depending on
the park complexity. ZLIB is used as the compression backend.

- The replay file version is bumped to 2.
- An `sv6r` file still starts with a magic number and a version.
- If version = 1, the file stream is consumed by the ReplayRecordData
serializer.
- If version > 1, the file stream is decompressed and the resulting
stream is consumed by the ReplayRecordData serializer.
- Introduced `Compatible` that indicates whether a file with a version
mismatch is compatible. E.g.: v1 is compatible with this `ReplayManager`

src/openrct2/ReplayManager.cpp

@@ -23,6 +23,7 @@
 #include "object/ObjectRepository.h"
 #include "rct2/S6Exporter.h"
 #include "world/Park.h"
+#include "zlib.h"
 
 #include <chrono>
 #include <vector>
@@ -77,6 +78,14 @@ namespace OpenRCT2
         }
     };
 
+    struct ReplayRecordFile
+    {
+        uint32_t magic;
+        uint16_t version;
+        uint64_t uncompressedSize;
+        MemoryStream data;
+    };
+
     struct ReplayRecordData
     {
         uint32_t magic;
@@ -97,8 +106,9 @@ namespace OpenRCT2
 
     class ReplayManager final : public IReplayManager
     {
-        static constexpr uint16_t ReplayVersion = 1;
+        static constexpr uint16_t ReplayVersion = 2;
         static constexpr uint32_t ReplayMagic = 0x5243524F; // ORCR.
+        static constexpr int ReplayCompressionLevel = 9;
 
         enum class ReplayMode
         {
@@ -284,19 +294,41 @@ namespace OpenRCT2
             _currentRecording->tickEnd = gCurrentTicks;
 
             // Serialise Body.
-            DataSerialiser serialiser(true);
+            DataSerialiser recSerialiser(true);
-            Serialise(serialiser, *_currentRecording);
+            Serialise(recSerialiser, *_currentRecording);
 
-            bool result = true;
+            const auto& stream = recSerialiser.GetStream();
+            size_t streamLength = stream.GetLength();
+            size_t compressLength = compressBound(streamLength);
+
+            MemoryStream data(compressLength);
+
+            ReplayRecordFile file{ .magic = _currentRecording->magic,
+                                   .version = _currentRecording->version,
+                                   .uncompressedSize = streamLength,
+                                   .data = data };
+
+            auto compressBuf = std::make_unique<unsigned char[]>(compressLength);
+            compress2(
+                compressBuf.get(), &compressLength, (unsigned char*)stream.GetData(), stream.GetLength(),
+                ReplayCompressionLevel);
+            file.data.Write(compressBuf.get(), compressLength);
+
+            DataSerialiser fileSerialiser(true);
+            fileSerialiser << file.magic;
+            fileSerialiser << file.version;
+            fileSerialiser << file.uncompressedSize;
+            fileSerialiser << file.data;
+
+            bool result = false;
 
             const std::string& outFile = _currentRecording->filePath;
 
             FILE* fp = fopen(outFile.c_str(), "wb");
             if (fp)
             {
-                const auto& stream = serialiser.GetStream();
+                const auto& fileStream = fileSerialiser.GetStream();
-                fwrite(stream.GetData(), 1, stream.GetLength(), fp);
+                fwrite(fileStream.GetData(), 1, fileStream.GetLength(), fp);
-
                 fclose(fp);
 
                 result = true;
@@ -556,10 +588,42 @@ namespace OpenRCT2
             return true;
         }
 
+        /**
+         * Returns true if decompression was not needed or succeeded
+         * @param stream
+         * @return
+         */
+        bool TryDecompress(MemoryStream& stream)
+        {
+            ReplayRecordFile recFile;
+            stream.SetPosition(0);
+            DataSerialiser fileSerializer(false, stream);
+            fileSerializer << recFile.magic;
+            fileSerializer << recFile.version;
+
+            if (recFile.version >= 2)
+            {
+                fileSerializer << recFile.uncompressedSize;
+                fileSerializer << recFile.data;
+
+                auto buff = std::make_unique<unsigned char[]>(recFile.uncompressedSize);
+                unsigned long outSize = recFile.uncompressedSize;
+                uncompress(
+                    (unsigned char*)buff.get(), &outSize, (unsigned char*)recFile.data.GetData(), recFile.data.GetLength());
+                if (outSize != recFile.uncompressedSize)
+                {
+                    return false;
+                }
+                stream.SetPosition(0);
+                stream.Write(buff.get(), outSize);
+            }
+
+            return true;
+        }
+
         bool ReadReplayData(const std::string& file, ReplayRecordData& data)
         {
             MemoryStream stream;
-            DataSerialiser serialiser(false, stream);
 
             std::string fileName = file;
             if (fileName.size() < 5 || fileName.substr(fileName.size() - 5) != ".sv6r")
@@ -584,8 +648,11 @@ namespace OpenRCT2
             if (!loaded)
                 return false;
 
-            stream.SetPosition(0);
+            if (!TryDecompress(stream))
+                return false;
 
+            stream.SetPosition(0);
+            DataSerialiser serialiser(false, stream);
             if (!Serialise(serialiser, data))
             {
                 return false;
@@ -671,6 +738,14 @@ namespace OpenRCT2
             return true;
         }
 
+        bool Compatible(ReplayRecordData& data)
+        {
+            if (data.version == 1 && ReplayVersion == 2)
+                return true;
+
+            return false;
+        }
+
         bool Serialise(DataSerialiser& serialiser, ReplayRecordData& data)
         {
             serialiser << data.magic;
@@ -680,7 +755,7 @@ namespace OpenRCT2
                 return false;
             }
             serialiser << data.version;
-            if (data.version != ReplayVersion)
+            if (data.version != ReplayVersion && !Compatible(data))
             {
                 log_error("Invalid version detected %04X, expected: %04X", data.version, ReplayVersion);
                 return false;