1 files changed, 93 insertions, 0 deletions
diff --git a/src/common/fs/ryujinx_compat.cpp b/src/common/fs/ryujinx_compat.cpp
new file mode 100644
index 0000000000..610ba736a7
--- /dev/null
+++ b/src/common/fs/ryujinx_compat.cpp
@@ -0,0 +1,93 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "ryujinx_compat.h"
+#include "common/fs/path_util.h"
+#include <cstddef>
+#include <cstring>
+#include <fmt/ranges.h>
+#include <fstream>
+
+namespace Common::FS {
+
+namespace fs = std::filesystem;
+
+fs::path GetKvdbPath()
+{
+    return GetLegacyPath(EmuPath::RyujinxDir) / "bis" / "system" / "save" / "8000000000000000" / "0"
+           / "imkvdb.arc";
+}
+
+fs::path GetRyuSavePath(const u64 &save_id)
+{
+    std::string hex = fmt::format("{:016x}", save_id);
+
+    // TODO: what's the difference between 0 and 1?
+    return GetLegacyPath(EmuPath::RyujinxDir) / "bis" / "user" / "save" / hex / "0";
+}
+
+IMENReadResult ReadKvdb(const fs::path &path, std::vector<IMEN> &imens)
+{
+    std::ifstream kvdb{path, std::ios::binary | std::ios::ate};
+
+    if (!kvdb) {
+        return IMENReadResult::Nonexistent;
+    }
+
+    size_t file_size = kvdb.tellg();
+
+    // IMKV header + 8 bytes
+    if (file_size < 0xB) {
+        return IMENReadResult::NoHeader;
+    }
+
+    // magic (not the wizard kind)
+    kvdb.seekg(0, std::ios::beg);
+    char header[12];
+    kvdb.read(header, 12);
+
+    if (std::memcmp(header, IMKV_MAGIC, 4) != 0) {
+        return IMENReadResult::InvalidMagic;
+    }
+
+    // calculate num. of imens left
+    std::size_t remaining = (file_size - 12);
+    std::size_t num_imens = remaining / IMEN_SIZE;
+
+    // File is misaligned and probably corrupt (rip)
+    if (remaining % IMEN_SIZE != 0) {
+        return IMENReadResult::Misaligned;
+    }
+
+    // if there aren't any IMENs, it's empty and we can safely no-op out of here
+    if (num_imens == 0) {
+        return IMENReadResult::NoImens;
+    }
+
+    imens.reserve(num_imens);
+
+    // initially I wanted to do a struct, but imkvdb is 140 bytes
+    // while the compiler will murder you if you try to align u64 to 4 bytes
+    for (std::size_t i = 0; i < num_imens; ++i) {
+        char magic[4];
+        u64 title_id = 0;
+        u64 save_id = 0;
+
+        kvdb.read(magic, 4);
+        if (std::memcmp(magic, IMEN_MAGIC, 4) != 0) {
+            return IMENReadResult::InvalidMagic;
+        }
+
+        kvdb.ignore(0x8);
+        kvdb.read(reinterpret_cast<char *>(&title_id), 8);
+        kvdb.ignore(0x38);
+        kvdb.read(reinterpret_cast<char *>(&save_id), 8);
+        kvdb.ignore(0x38);
+
+        imens.emplace_back(IMEN{title_id, save_id});
+    }
+
+    return IMENReadResult::Success;
+}
+
+} // namespace Common::FS