IOS/FS: Move path validity check functions

They will be used in more places than just HostBackend/FS.cpp.

Also fix the check and make it accurate while we're at it.

Source/Core/Core/IOS/FS/FileSystem.cpp

@@ -11,6 +11,17 @@
 
 namespace IOS::HLE::FS
 {
+bool IsValidPath(std::string_view path)
+{
+  return path == "/" || IsValidNonRootPath(path);
+}
+
+bool IsValidNonRootPath(std::string_view path)
+{
+  return path.length() > 1 && path.length() <= MaxPathLength && path[0] == '/' &&
+         path.back() != '/';
+}
+
 std::unique_ptr<FileSystem> MakeFileSystem(Location location)
 {
   const std::string nand_root =

Source/Core/Core/IOS/FS/FileSystem.h

@@ -7,6 +7,7 @@
 #include <memory>
 #include <optional>
 #include <string>
+#include <string_view>
 #include <vector>
 
 #ifdef _WIN32
@@ -111,6 +112,13 @@ struct FileStatus
   u32 size;
 };
 
+/// The maximum number of characters a path can have.
+constexpr size_t MaxPathLength = 64;
+
+/// Returns whether a Wii path is valid.
+bool IsValidPath(std::string_view path);
+bool IsValidNonRootPath(std::string_view path);
+
 class FileSystem;
 class FileHandle final
 {

Source/Core/Core/IOS/FS/HostBackend/FS.cpp

@@ -15,11 +15,6 @@
 
 namespace IOS::HLE::FS
 {
-static bool IsValidWiiPath(const std::string& path)
-{
-  return path.compare(0, 1, "/") == 0;
-}
-
 std::string HostFileSystem::BuildFilename(const std::string& wii_path) const
 {
   if (wii_path.compare(0, 1, "/") == 0)
@@ -185,7 +180,7 @@ ResultCode HostFileSystem::CreateFile(Uid, Gid, const std::string& path, FileAtt
 
 ResultCode HostFileSystem::CreateDirectory(Uid, Gid, const std::string& path, FileAttribute, Modes)
 {
-  if (!IsValidWiiPath(path))
+  if (!IsValidPath(path))
     return ResultCode::Invalid;
 
   std::string name(BuildFilename(path));
@@ -199,7 +194,7 @@ ResultCode HostFileSystem::CreateDirectory(Uid, Gid, const std::string& path, Fi
 
 ResultCode HostFileSystem::Delete(Uid, Gid, const std::string& path)
 {
-  if (!IsValidWiiPath(path))
+  if (!IsValidPath(path))
     return ResultCode::Invalid;
 
   const std::string file_name = BuildFilename(path);
@@ -216,11 +211,11 @@ ResultCode HostFileSystem::Delete(Uid, Gid, const std::string& path)
 ResultCode HostFileSystem::Rename(Uid, Gid, const std::string& old_path,
                                   const std::string& new_path)
 {
-  if (!IsValidWiiPath(old_path))
+  if (!IsValidPath(old_path))
     return ResultCode::Invalid;
   const std::string old_name = BuildFilename(old_path);
 
-  if (!IsValidWiiPath(new_path))
+  if (!IsValidPath(new_path))
     return ResultCode::Invalid;
   const std::string new_name = BuildFilename(new_path);
 
@@ -252,7 +247,7 @@ ResultCode HostFileSystem::Rename(Uid, Gid, const std::string& old_path,
 
 Result<std::vector<std::string>> HostFileSystem::ReadDirectory(Uid, Gid, const std::string& path)
 {
-  if (!IsValidWiiPath(path))
+  if (!IsValidPath(path))
     return ResultCode::Invalid;
 
   // the Wii uses this function to define the type (dir or file)
@@ -301,7 +296,7 @@ Result<Metadata> HostFileSystem::GetMetadata(Uid, Gid, const std::string& path)
   metadata.gid = 0x3031;  // this is also known as makercd, 01 (0x3031) for nintendo and 08
                           // (0x3038) for MH3 etc
 
-  if (!IsValidWiiPath(path))
+  if (!IsValidPath(path))
     return ResultCode::Invalid;
 
   std::string file_name = BuildFilename(path);
@@ -330,7 +325,7 @@ Result<Metadata> HostFileSystem::GetMetadata(Uid, Gid, const std::string& path)
 ResultCode HostFileSystem::SetMetadata(Uid caller_uid, const std::string& path, Uid uid, Gid gid,
                                        FileAttribute, Modes)
 {
-  if (!IsValidWiiPath(path))
+  if (!IsValidPath(path))
     return ResultCode::Invalid;
   return ResultCode::Success;
 }
@@ -354,7 +349,7 @@ Result<NandStats> HostFileSystem::GetNandStats()
 
 Result<DirectoryStats> HostFileSystem::GetDirectoryStats(const std::string& wii_path)
 {
-  if (!IsValidWiiPath(wii_path))
+  if (!IsValidPath(wii_path))
     return ResultCode::Invalid;
 
   DirectoryStats stats{};