core/fs: fix file path when using separated update folder for *nix (#1403)

src/core/file_sys/fs.cpp

@@ -28,16 +28,11 @@ void MntPoints::UnmountAll() {
     m_mnt_pairs.clear();
 }
 
-std::filesystem::path MntPoints::GetHostPath(std::string_view guest_directory, bool* is_read_only) {
+std::filesystem::path MntPoints::GetHostPath(std::string_view path, bool* is_read_only) {
     // Evil games like Turok2 pass double slashes e.g /app0//game.kpf
-    std::string corrected_path(guest_directory);
+    const auto normalized_path = std::filesystem::path(path).lexically_normal().string();
-    size_t pos = corrected_path.find("//");
-    while (pos != std::string::npos) {
-        corrected_path.replace(pos, 2, "/");
-        pos = corrected_path.find("//", pos + 1);
-    }
 
-    const MntPair* mount = GetMount(corrected_path);
+    const MntPair* mount = GetMount(normalized_path);
     if (!mount) {
         return "";
     }
@@ -47,26 +42,27 @@ std::filesystem::path MntPoints::GetHostPath(std::string_view guest_directory, b
     }
 
     // Nothing to do if getting the mount itself.
-    if (corrected_path == mount->mount) {
+    if (normalized_path == mount->mount) {
         return mount->host_path;
     }
 
     // Remove device (e.g /app0) from path to retrieve relative path.
-    pos = mount->mount.size() + 1;
+    const auto rel_path = std::string_view{normalized_path}.substr(mount->mount.size() + 1);
-    const auto rel_path = std::string_view(corrected_path).substr(pos);
     std::filesystem::path host_path = mount->host_path / rel_path;
-
     std::filesystem::path patch_path = mount->host_path;
     patch_path += "-UPDATE";
-    if ((corrected_path.starts_with("/app0") || corrected_path.starts_with("/hostapp")) &&
+    patch_path /= rel_path;
-        std::filesystem::exists(patch_path / rel_path)) {
+
-        host_path = patch_path / rel_path;
+    if ((normalized_path.starts_with("/app0") || normalized_path.starts_with("/hostapp")) &&
+        std::filesystem::exists(patch_path)) {
+        return patch_path;
     }
 
     if (!NeedsCaseInsensitiveSearch) {
         return host_path;
     }
 
+    const auto search = [&](const auto host_path) {
         // If the path does not exist attempt to verify this.
         // Retrieve parent path until we find one that exists.
         std::scoped_lock lk{m_mutex};
@@ -81,7 +77,6 @@ std::filesystem::path MntPoints::GetHostPath(std::string_view guest_directory, b
             path_parts.emplace_back(current_path.filename());
             current_path = current_path.parent_path();
         }
-
         // We have found an anchor. Traverse parts we recoded and see if they
         // exist in filesystem but in different case.
         auto guest_path = current_path;
@@ -93,7 +88,6 @@ std::filesystem::path MntPoints::GetHostPath(std::string_view guest_directory, b
                 path_cache[guest_path] = current_path;
                 path_parts.pop_back();
             };
-
             // Can happen when the mismatch is in upper folder.
             if (std::filesystem::exists(current_path / part)) {
                 add_match(part);
@@ -114,15 +108,23 @@ std::filesystem::path MntPoints::GetHostPath(std::string_view guest_directory, b
                 break;
             }
             if (!found_match) {
+                return std::optional<std::filesystem::path>({});
+            }
+        }
+        return std::optional<std::filesystem::path>(current_path);
+    };
+
+    if (const auto path = search(patch_path)) {
+        return *path;
+    }
+    if (const auto path = search(host_path)) {
+        return *path;
+    }
+
     // Opening the guest path will surely fail but at least gives
     // a better error message than the empty path.
     return host_path;
 }
-    }
-
-    // The path was found.
-    return current_path;
-}
 
 int HandleTable::CreateHandle() {
     std::scoped_lock lock{m_mutex};