Fry3DX 0.4: an easy 3D modeller

Shapes with live settings, shape editing, knife and hole tools, drawing
shapes onto other objects, combining objects (add / subtract / overlap),
copies, thickness, painting with stickers and layers, a Layout tab, a
Print tab with checks, packed .fry files with autosave, export to GLB,
glTF, FBX, OBJ, 3MF, STL and PLY, folders in Layers, its own crash
screen, and a website for GitHub Pages in docs/.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NMSrd5oe1GpUD7E6d825KP

engine/fs/ymp.h

@@ -0,0 +1,57 @@
+#pragma once
+// YMP ("Your Mom's Package") = a tar archive compressed with zstd's seekable
+// format. It is a normal .tar.zst (`tar --zstd -xf pak0.ymp` works), and the
+// engine can still read any file without decompressing the rest:
+//   - frames end at file boundaries, so a small file decompresses on its own
+//   - the first tar member, ".ymp-index", lists every file's offset and size
+// Plain .tar.zst files (no index, not seekable) also load: they are fully
+// decompressed into memory once.
+#include <cstdint>
+#include <map>
+#include <memory>
+#include <string>
+#include <string_view>
+#include <vector>
+
+struct ZSTD_seekable_s;
+
+namespace keel {
+
+struct PackInput {
+    std::string archivePath; // path inside the pack, forward slashes
+    std::string diskPath;
+};
+
+// Writes a pack. Level 19 is slow to build and fast to load; 3 is quick for iteration.
+bool writeYmp(const std::string& outPath, const std::vector<PackInput>& files, int level = 19);
+// Builds an uncompressed tar (with the YMP index as first member).
+std::vector<uint8_t> buildTar(const std::vector<std::pair<std::string, std::vector<uint8_t>>>& files);
+
+class YmpArchive {
+public:
+    YmpArchive();
+    ~YmpArchive();
+    YmpArchive(const YmpArchive&) = delete;
+    YmpArchive& operator=(const YmpArchive&) = delete;
+
+    bool open(const std::string& path);
+    bool read(std::string_view path, std::vector<uint8_t>& out);
+    bool contains(std::string_view path) const { return entries_.count(std::string(path)) != 0; }
+    std::vector<std::string> files() const;
+
+private:
+    struct Entry {
+        uint64_t offset; // in the uncompressed tar
+        uint64_t size;
+    };
+    bool readRange(uint64_t offset, size_t size, void* out);
+    bool parseTar(uint64_t totalSize);
+
+    std::string path_;
+    FILE* file_ = nullptr;
+    ::ZSTD_seekable_s* seekable_ = nullptr;
+    std::vector<uint8_t> memory_; // whole tar, when the archive isn't seekable
+    std::map<std::string, Entry, std::less<>> entries_;
+};
+
+} // namespace keel