[loader] add ZBIC (zstd variant) NSO decompression support for Switch 22.0+

src/common/zbic_compression.cpp

@@ -0,0 +1,43 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include <cstring>
+
+#include "common/zbic_compression.h"
+#include "common/zstd.h"
+
+namespace Common::Compression {
+
+bool IsZBIC(const void* src, size_t src_size) {
+    if (!src || src_size < 4) {
+        return false;
+    }
+    u32 magic = 0;
+    std::memcpy(&magic, src, sizeof(u32));
+    return magic == ZSTD_MAGICNUMBER; // 0x4349425A ("ZBIC")
+}
+
+int DecompressDataZBIC(void* dst, size_t dst_size, const void* src, size_t src_size) {
+    if (!dst || !src || dst_size == 0 || src_size == 0) {
+        return -1;
+    }
+    const size_t res = ZSTD_decompress(dst, dst_size, src, src_size);
+    if (ZSTD_isError(res)) {
+        return -1;
+    }
+    return static_cast<int>(res);
+}
+
+std::vector<u8> DecompressDataZBIC(std::span<const u8> compressed, std::size_t uncompressed_size) {
+    std::vector<u8> uncompressed(uncompressed_size);
+    const int r = DecompressDataZBIC(uncompressed.data(), uncompressed_size, compressed.data(), compressed.size());
+    if (r <= 0) {
+        return {};
+    }
+    if (static_cast<size_t>(r) < uncompressed_size) {
+        uncompressed.resize(static_cast<size_t>(r));
+    }
+    return uncompressed;
+}
+
+} // namespace Common::Compression