refactor chunk compression

Author: moritz-h

libsave/src/GameTypes/Save/Blueprint.cpp

@@ -60,23 +60,5 @@ void SatisfactorySave::Blueprint::save(const std::filesystem::path& filepath) {
 
     fileAr << header;
 
-    // Split blob into chunks
-    uint64_t blob_pos = 0;
-    const std::byte* blob_buffer = ar.buffer_view().data();
-
-    while (blob_size > 0) {
-        // Compress chunk
-        int64_t chunk_size = std::min(static_cast<int64_t>(blob_size), ChunkHeader::COMPRESSION_CHUNK_SIZE);
-        std::vector<std::byte> chunk_uncompressed{blob_buffer + blob_pos, blob_buffer + blob_pos + chunk_size};
-        std::vector<std::byte> chunk_compressed = zlibCompress(chunk_uncompressed);
-
-        blob_pos += chunk_size;
-        blob_size -= chunk_size;
-
-        // Chunk header
-        ChunkHeader chunkHeader(static_cast<int64_t>(chunk_compressed.size()), chunk_size);
-        fileAr << chunkHeader;
-
-        fileAr.write_buffer(chunk_compressed);
-    }
+    compressChunks(fileAr, ar.buffer_view());
 }

libsave/src/GameTypes/Save/ChunkHelper.cpp

@@ -28,3 +28,20 @@ std::vector<std::byte> SatisfactorySave::decompressChunks(IStreamArchive& inAr)
 
     return file_data_blob;
 }
+
+void SatisfactorySave::compressChunks(OStreamArchive& outAr, std::span<const std::byte> blob) {
+    // Split blob into chunks
+    while (!blob.empty()) {
+        // Compress chunk
+        int64_t chunk_size = std::min(static_cast<int64_t>(blob.size()), ChunkHeader::COMPRESSION_CHUNK_SIZE);
+        std::vector<std::byte> chunk_compressed = zlibCompress(blob.first(chunk_size));
+
+        blob = blob.subspan(chunk_size);
+
+        // Chunk header
+        ChunkHeader chunkHeader(static_cast<int64_t>(chunk_compressed.size()), chunk_size);
+        outAr << chunkHeader;
+
+        outAr.write_buffer(chunk_compressed);
+    }
+}

libsave/src/GameTypes/Save/ChunkHelper.h

@@ -2,10 +2,12 @@
 
 #include <cstddef>
 #include <memory>
+#include <span>
 #include <vector>
 
 #include "ChunkHeader.h"
 #include "IO/Archive/IStreamArchive.h"
+#include "IO/Archive/OStreamArchive.h"
 
 namespace SatisfactorySave {
 
@@ -20,4 +22,6 @@ namespace SatisfactorySave {
     };
 
     std::vector<std::byte> decompressChunks(IStreamArchive& inAr);
+
+    void compressChunks(OStreamArchive& outAr, std::span<const std::byte> blob);
 } // namespace SatisfactorySave

libsave/src/GameTypes/Save/SaveGame.cpp

@@ -150,25 +150,8 @@ void SatisfactorySave::SaveGame::save(const std::filesystem::path& filepath) {
     // Write header
     fileAr << mSaveHeader;
 
-    // Split blob into chunks
-    uint64_t blob_pos = 0;
-    const std::byte* blob_buffer = ar.buffer_view().data();
-
-    while (blob_size > 0) {
-        // Compress chunk
-        int64_t chunk_size = std::min(static_cast<int64_t>(blob_size), ChunkHeader::COMPRESSION_CHUNK_SIZE);
-        std::vector<std::byte> chunk_uncompressed{blob_buffer + blob_pos, blob_buffer + blob_pos + chunk_size};
-        std::vector<std::byte> chunk_compressed = zlibCompress(chunk_uncompressed);
-
-        blob_pos += chunk_size;
-        blob_size -= chunk_size;
-
-        // Chunk header
-        ChunkHeader chunkHeader(static_cast<int64_t>(chunk_compressed.size()), chunk_size);
-        fileAr << chunkHeader;
-
-        fileAr.write_buffer(chunk_compressed);
-    }
+    // Write blob
+    compressChunks(fileAr, ar.buffer_view());
 }
 
 void SatisfactorySave::SaveGame::initAccessStructures() {