Merge pull request #12290 from liamwhite/deferred-path-split

Improve path splitting speed

src/common/fs/path_util.cpp

@@ -354,18 +354,36 @@ std::string_view RemoveTrailingSlash(std::string_view path) {
     return path;
 }
 
-std::vector<std::string> SplitPathComponents(std::string_view filename) {
-    std::string copy(filename);
-    std::replace(copy.begin(), copy.end(), '\\', '/');
-    std::vector<std::string> out;
-
-    std::stringstream stream(copy);
-    std::string item;
-    while (std::getline(stream, item, '/')) {
-        out.push_back(std::move(item));
+template <typename F>
+static void ForEachPathComponent(std::string_view filename, F&& cb) {
+    const char* component_begin = filename.data();
+    const char* const end = component_begin + filename.size();
+    for (const char* it = component_begin; it != end; ++it) {
+        const char c = *it;
+        if (c == '\\' || c == '/') {
+            if (component_begin != it) {
+                cb(std::string_view{component_begin, it});
+            }
+            component_begin = it + 1;
+        }
     }
+    if (component_begin != end) {
+        cb(std::string_view{component_begin, end});
+    }
+}
+
+std::vector<std::string_view> SplitPathComponents(std::string_view filename) {
+    std::vector<std::string_view> components;
+    ForEachPathComponent(filename, [&](auto component) { components.emplace_back(component); });
+
+    return components;
+}
+
+std::vector<std::string> SplitPathComponentsCopy(std::string_view filename) {
+    std::vector<std::string> components;
+    ForEachPathComponent(filename, [&](auto component) { components.emplace_back(component); });
 
-    return out;
+    return components;
 }
 
 std::string SanitizePath(std::string_view path_, DirectorySeparator directory_separator) {

src/common/fs/path_util.h

@@ -289,7 +289,11 @@ enum class DirectorySeparator {
 
 // Splits the path on '/' or '\' and put the components into a vector
 // i.e. "C:\Users\Yuzu\Documents\save.bin" becomes {"C:", "Users", "Yuzu", "Documents", "save.bin" }
-[[nodiscard]] std::vector<std::string> SplitPathComponents(std::string_view filename);
+[[nodiscard]] std::vector<std::string_view> SplitPathComponents(std::string_view filename);
+
+// Splits the path on '/' or '\' and put the components into a vector
+// i.e. "C:\Users\Yuzu\Documents\save.bin" becomes {"C:", "Users", "Yuzu", "Documents", "save.bin" }
+[[nodiscard]] std::vector<std::string> SplitPathComponentsCopy(std::string_view filename);
 
 // Removes trailing slash, makes all '\\' into '/', and removes duplicate '/'. Makes '/' into '\\'
 // depending if directory_separator is BackwardSlash or PlatformDefault and running on windows

src/core/file_sys/vfs.cpp

@@ -201,8 +201,6 @@ std::string VfsFile::GetFullPath() const {
 
 VirtualFile VfsDirectory::GetFileRelative(std::string_view path) const {
     auto vec = Common::FS::SplitPathComponents(path);
-    vec.erase(std::remove_if(vec.begin(), vec.end(), [](const auto& str) { return str.empty(); }),
-              vec.end());
     if (vec.empty()) {
         return nullptr;
     }
@@ -237,8 +235,6 @@ VirtualFile VfsDirectory::GetFileAbsolute(std::string_view path) const {
 
 VirtualDir VfsDirectory::GetDirectoryRelative(std::string_view path) const {
     auto vec = Common::FS::SplitPathComponents(path);
-    vec.erase(std::remove_if(vec.begin(), vec.end(), [](const auto& str) { return str.empty(); }),
-              vec.end());
     if (vec.empty()) {
         // TODO(DarkLordZach): Return this directory if path is '/' or similar. Can't currently
         // because of const-ness
@@ -303,8 +299,6 @@ std::size_t VfsDirectory::GetSize() const {
 
 VirtualFile VfsDirectory::CreateFileRelative(std::string_view path) {
     auto vec = Common::FS::SplitPathComponents(path);
-    vec.erase(std::remove_if(vec.begin(), vec.end(), [](const auto& str) { return str.empty(); }),
-              vec.end());
     if (vec.empty()) {
         return nullptr;
     }
@@ -334,8 +328,6 @@ VirtualFile VfsDirectory::CreateFileAbsolute(std::string_view path) {
 
 VirtualDir VfsDirectory::CreateDirectoryRelative(std::string_view path) {
     auto vec = Common::FS::SplitPathComponents(path);
-    vec.erase(std::remove_if(vec.begin(), vec.end(), [](const auto& str) { return str.empty(); }),
-              vec.end());
     if (vec.empty()) {
         return nullptr;
     }

src/core/file_sys/vfs_real.cpp

@@ -268,7 +268,7 @@ void RealVfsFilesystem::RemoveReferenceFromListLocked(FileReference& reference)
 RealVfsFile::RealVfsFile(RealVfsFilesystem& base_, std::unique_ptr<FileReference> reference_,
                          const std::string& path_, Mode perms_, std::optional<u64> size_)
     : base(base_), reference(std::move(reference_)), path(path_),
-      parent_path(FS::GetParentPath(path_)), path_components(FS::SplitPathComponents(path_)),
+      parent_path(FS::GetParentPath(path_)), path_components(FS::SplitPathComponentsCopy(path_)),
       size(size_), perms(perms_) {}
 
 RealVfsFile::~RealVfsFile() {
@@ -276,7 +276,7 @@ RealVfsFile::~RealVfsFile() {
 }
 
 std::string RealVfsFile::GetName() const {
-    return path_components.back();
+    return path_components.empty() ? "" : std::string(path_components.back());
 }
 
 std::size_t RealVfsFile::GetSize() const {
@@ -375,7 +375,7 @@ std::vector<VirtualDir> RealVfsDirectory::IterateEntries<RealVfsDirectory, VfsDi
 
 RealVfsDirectory::RealVfsDirectory(RealVfsFilesystem& base_, const std::string& path_, Mode perms_)
     : base(base_), path(FS::RemoveTrailingSlash(path_)), parent_path(FS::GetParentPath(path)),
-      path_components(FS::SplitPathComponents(path)), perms(perms_) {
+      path_components(FS::SplitPathComponentsCopy(path)), perms(perms_) {
     if (!FS::Exists(path) && True(perms & Mode::Write)) {
         void(FS::CreateDirs(path));
     }
@@ -464,7 +464,7 @@ bool RealVfsDirectory::IsReadable() const {
 }
 
 std::string RealVfsDirectory::GetName() const {
-    return path_components.back();
+    return path_components.empty() ? "" : std::string(path_components.back());
 }
 
 VirtualDir RealVfsDirectory::GetParentDirectory() const {

src/core/hle/service/filesystem/filesystem.cpp

@@ -104,11 +104,7 @@ Result VfsDirectoryServiceWrapper::CreateDirectory(const std::string& path_) con
     const auto components = Common::FS::SplitPathComponents(path);
     std::string relative_path;
     for (const auto& component : components) {
-        // Skip empty path components
-        if (component.empty()) {
-            continue;
-        }
-        relative_path = Common::FS::SanitizePath(relative_path + '/' + component);
+        relative_path = Common::FS::SanitizePath(fmt::format("{}/{}", relative_path, component));
         auto new_dir = backing->CreateSubdirectory(relative_path);
         if (new_dir == nullptr) {
             // TODO(DarkLordZach): Find a better error code for this