asset compression

interfaces/Crafter.Asset-Compression.cppm

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+/*
+Crafter®.Asset
+Copyright (C) 2026 Catcrafts®
+catcrafts.net
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License version 3.0 as published by the Free Software Foundation;
+
+This library 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
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
+*/
+
+export module Crafter.Asset:Compression;
+import std;
+
+export namespace Crafter::Compression {
+    // One independently-decompressable GDeflate stream inside CompressedBlob::bytes.
+    // Layout matches what VK_EXT_memory_decompression's VkDecompressMemoryRegionEXT
+    // expects, minus the device addresses (which the consumer fills in).
+    struct RegionMeta {
+        std::uint64_t srcOffset;
+        std::uint64_t compressedSize;
+        std::uint64_t decompressedSize;
+    };
+
+    struct CompressedBlob {
+        std::vector<std::byte> bytes;
+        std::vector<RegionMeta> regions;
+
+        std::uint64_t TotalDecompressedSize() const noexcept {
+            std::uint64_t sum = 0;
+            for (const RegionMeta& r : regions) sum += r.decompressedSize;
+            return sum;
+        }
+    };
+
+    // Compresses each input span as its own GDeflate tile-stream; concatenates
+    // them into one byte buffer with a parallel region table. Streams are
+    // independent and can be addressed individually by VkDecompressMemoryRegionEXT
+    // entries on the GPU path.
+    CompressedBlob CompressStreams(std::span<const std::span<const std::byte>> streams);
+
+    // CPU fallback decoder. outputs.size() must equal blob.regions.size();
+    // outputs[i].size() must equal blob.regions[i].decompressedSize.
+    void DecompressCPU(const CompressedBlob& blob, std::span<const std::span<std::byte>> outputs);
+
+    // Length-prefixed serialization of a CompressedBlob. Used by per-asset
+    // SaveCompressed/LoadCompressed implementations after they've written
+    // their own type-specific header.
+    void WriteBlob(std::ostream& file, const CompressedBlob& blob);
+    CompressedBlob ReadBlob(std::istream& file);
+}