Port yuzu-emu/yuzu#2511: "common/file_util: Minor cleanup" (#4782)

* common/file_util: Make IOFile's WriteString take a std::string_view

We don't need to force the usage of a std::string here, and can instead
use a std::string_view, which allows writing out other forms of strings
(e.g. C-style strings) without any unnecessary heap allocations.

* common/file_util: Remove unnecessary c_str() calls

The file stream open functions have supported std::string overloads
since C++11, so we don't need to use c_str() here. Same behavior, less
code.

* common/file_util: Make ReadFileToString and WriteStringToFile consistent

Makes the parameter ordering consistent, and also makes the filename
parameter a std::string. A std::string would be constructed anyways with
the previous code, as IOFile's only constructor with a filepath is one
taking a std::string.

We can also make WriteStringToFile's string parameter utilize a
std::string_view for the string, making use of our previous changes to
IOFile.

* common/file_util: Remove duplicated documentation comments

These are already present within the header, so they don't need to be
repeated in the cpp file.

* common/file_util: Make GetCurrentDir() return a std::optional

nullptr was being returned in the error case, which, at a glance may
seem perfectly OK... until you realize that std::string has the
invariant that it may not be constructed from a null pointer. This
means that if this error case was ever hit, then the application would
most likely crash from a thrown exception in std::string's constructor.

Instead, we can change the function to return an optional value,
indicating if a failure occurred.

* common/file_util: Remove unnecessary return at end of void StripTailDirSlashes()

While we're at it, also invert the conditional into a guard clause.

src/citra/config.cpp

@@ -29,12 +29,12 @@ Config::Config() {
 Config::~Config() = default;
 
 bool Config::LoadINI(const std::string& default_contents, bool retry) {
-    const char* location = this->sdl2_config_loc.c_str();
+    const std::string& location = this->sdl2_config_loc;
     if (sdl2_config->ParseError() < 0) {
         if (retry) {
             LOG_WARNING(Config, "Failed to load {}. Creating file from defaults...", location);
             FileUtil::CreateFullPath(location);
-            FileUtil::WriteStringToFile(true, default_contents, location);
+            FileUtil::WriteStringToFile(true, location, default_contents);
             sdl2_config = std::make_unique<INIReader>(location); // Reopen file
 
             return LoadINI(default_contents, false);

src/common/file_util.cpp

@@ -77,16 +77,17 @@ namespace FileUtil {
 // Remove any ending forward slashes from directory paths
 // Modifies argument.
 static void StripTailDirSlashes(std::string& fname) {
-    if (fname.length() > 1) {
-        std::size_t i = fname.length();
-        while (i > 0 && fname[i - 1] == DIR_SEP_CHR)
-            --i;
-        fname.resize(i);
-    }
+    if (fname.length() <= 1) {
         return;
     }
 
-// Returns true if file filename exists
+    std::size_t i = fname.length();
+    while (i > 0 && fname[i - 1] == DIR_SEP_CHR) {
+        --i;
+    }
+    fname.resize(i);
+}
+
 bool Exists(const std::string& filename) {
     struct stat file_info;
 
@@ -106,7 +107,6 @@ bool Exists(const std::string& filename) {
     return (result == 0);
 }
 
-// Returns true if filename is a directory
 bool IsDirectory(const std::string& filename) {
     struct stat file_info;
 
@@ -131,8 +131,6 @@ bool IsDirectory(const std::string& filename) {
     return S_ISDIR(file_info.st_mode);
 }
 
-// Deletes a given filename, return true on success
-// Doesn't supports deleting a directory
 bool Delete(const std::string& filename) {
     LOG_TRACE(Common_Filesystem, "file {}", filename);
 
@@ -164,7 +162,6 @@ bool Delete(const std::string& filename) {
     return true;
 }
 
-// Returns true if successful, or path already exists.
 bool CreateDir(const std::string& path) {
     LOG_TRACE(Common_Filesystem, "directory {}", path);
 #ifdef _WIN32
@@ -193,7 +190,6 @@ bool CreateDir(const std::string& path) {
 #endif
 }
 
-// Creates the full path of fullPath returns true on success
 bool CreateFullPath(const std::string& fullPath) {
     int panicCounter = 100;
     LOG_TRACE(Common_Filesystem, "path {}", fullPath);
@@ -229,7 +225,6 @@ bool CreateFullPath(const std::string& fullPath) {
     }
 }
 
-// Deletes a directory filename, returns true on success
 bool DeleteDir(const std::string& filename) {
     LOG_TRACE(Common_Filesystem, "directory {}", filename);
 
@@ -251,7 +246,6 @@ bool DeleteDir(const std::string& filename) {
     return false;
 }
 
-// renames file srcFilename to destFilename, returns true on success
 bool Rename(const std::string& srcFilename, const std::string& destFilename) {
     LOG_TRACE(Common_Filesystem, "{} --> {}", srcFilename, destFilename);
 #ifdef _WIN32
@@ -267,7 +261,6 @@ bool Rename(const std::string& srcFilename, const std::string& destFilename) {
     return false;
 }
 
-// copies file srcFilename to destFilename, returns true on success
 bool Copy(const std::string& srcFilename, const std::string& destFilename) {
     LOG_TRACE(Common_Filesystem, "{} --> {}", srcFilename, destFilename);
 #ifdef _WIN32
@@ -323,7 +316,6 @@ bool Copy(const std::string& srcFilename, const std::string& destFilename) {
 #endif
 }
 
-// Returns the size of filename (64bit)
 u64 GetSize(const std::string& filename) {
     if (!Exists(filename)) {
         LOG_ERROR(Common_Filesystem, "failed {}: No such file", filename);
@@ -350,7 +342,6 @@ u64 GetSize(const std::string& filename) {
     return 0;
 }
 
-// Overloaded GetSize, accepts file descriptor
 u64 GetSize(const int fd) {
     struct stat buf;
     if (fstat(fd, &buf) != 0) {
@@ -360,7 +351,6 @@ u64 GetSize(const int fd) {
     return buf.st_size;
 }
 
-// Overloaded GetSize, accepts FILE*
 u64 GetSize(FILE* f) {
     // can't use off_t here because it can be 32-bit
     u64 pos = ftello(f);
@@ -376,7 +366,6 @@ u64 GetSize(FILE* f) {
     return size;
 }
 
-// creates an empty file filename, returns true on success
 bool CreateEmptyFile(const std::string& filename) {
     LOG_TRACE(Common_Filesystem, "{}", filename);
 
@@ -501,7 +490,6 @@ bool DeleteDirRecursively(const std::string& directory, unsigned int recursion)
     return true;
 }
 
-// Create directory and copy contents (does not overwrite existing files)
 void CopyDir(const std::string& source_path, const std::string& dest_path) {
 #ifndef _WIN32
     if (source_path == dest_path)
@@ -538,8 +526,7 @@ void CopyDir(const std::string& source_path, const std::string& dest_path) {
 #endif
 }
 
-// Returns the current directory
-std::string GetCurrentDir() {
+std::optional<std::string> GetCurrentDir() {
 // Get the current working directory (getcwd uses malloc)
 #ifdef _WIN32
     wchar_t* dir;
@@ -550,7 +537,7 @@ std::string GetCurrentDir() {
 #endif
     {
         LOG_ERROR(Common_Filesystem, "GetCurrentDirectory failed: {}", GetLastErrorMsg());
-        return nullptr;
+        return {};
     }
 #ifdef _WIN32
     std::string strDir = Common::UTF16ToUTF8(dir);
@@ -561,7 +548,6 @@ std::string GetCurrentDir() {
     return strDir;
 }
 
-// Sets the current directory to the given directory
 bool SetCurrentDir(const std::string& directory) {
 #ifdef _WIN32
     return _wchdir(Common::UTF8ToUTF16W(directory).c_str()) == 0;
@@ -723,8 +709,6 @@ void SetUserPath(const std::string& path) {
     g_paths.emplace(UserPath::DLLDir, user_path + DLL_DIR DIR_SEP);
 }
 
-// Returns a string with a Citra data dir or file in the user's home
-// directory. To be used in "multi-user" mode (that is, installed).
 const std::string& GetUserPath(UserPath path) {
     // Set up all paths and files on the first run
     if (g_paths.empty())
@@ -732,11 +716,11 @@ const std::string& GetUserPath(UserPath path) {
     return g_paths[path];
 }
 
-size_t WriteStringToFile(bool text_file, const std::string& str, const char* filename) {
-    return FileUtil::IOFile(filename, text_file ? "w" : "wb").WriteBytes(str.data(), str.size());
+std::size_t WriteStringToFile(bool text_file, const std::string& filename, std::string_view str) {
+    return IOFile(filename, text_file ? "w" : "wb").WriteString(str);
 }
 
-size_t ReadFileToString(bool text_file, const char* filename, std::string& str) {
+std::size_t ReadFileToString(bool text_file, const std::string& filename, std::string& str) {
     IOFile file(filename, text_file ? "r" : "rb");
 
     if (!file)
@@ -746,13 +730,6 @@ size_t ReadFileToString(bool text_file, const char* filename, std::string& str)
     return file.ReadArray(&str[0], str.size());
 }
 
-/**
- * Splits the filename into 8.3 format
- * Loosely implemented following https://en.wikipedia.org/wiki/8.3_filename
- * @param filename The normal filename to use
- * @param short_name A 9-char array in which the short name will be written
- * @param extension A 4-char array in which the extension will be written
- */
 void SplitFilename83(const std::string& filename, std::array<char, 9>& short_name,
                      std::array<char, 4>& extension) {
     const std::string forbidden_characters = ".\"/\\[]:;=, ";

src/common/file_util.h

@@ -9,6 +9,7 @@
 #include <fstream>
 #include <functional>
 #include <limits>
+#include <optional>
 #include <string>
 #include <type_traits>
 #include <vector>
@@ -115,7 +116,7 @@ u64 ScanDirectoryTree(const std::string& directory, FSTEntry& parent_entry,
 bool DeleteDirRecursively(const std::string& directory, unsigned int recursion = 256);
 
 // Returns the current directory
-std::string GetCurrentDir();
+std::optional<std::string> GetCurrentDir();
 
 // Create directory and copy contents (does not overwrite existing files)
 void CopyDir(const std::string& source_path, const std::string& dest_path);
@@ -141,8 +142,9 @@ const std::string& GetExeDirectory();
 std::string AppDataRoamingDirectory();
 #endif
 
-size_t WriteStringToFile(bool text_file, const std::string& str, const char* filename);
-size_t ReadFileToString(bool text_file, const char* filename, std::string& str);
+std::size_t WriteStringToFile(bool text_file, const std::string& filename, std::string_view str);
+
+std::size_t ReadFileToString(bool text_file, const std::string& filename, std::string& str);
 
 /**
  * Splits the filename into 8.3 format
@@ -228,8 +230,8 @@ public:
         return WriteArray(&object, 1);
     }
 
-    std::size_t WriteString(const std::string& str) {
-        return WriteArray(str.c_str(), str.length());
+    std::size_t WriteString(std::string_view str) {
+        return WriteArray(str.data(), str.length());
     }
 
     bool IsOpen() const {
@@ -267,8 +269,8 @@ private:
 template <typename T>
 void OpenFStream(T& fstream, const std::string& filename, std::ios_base::openmode openmode) {
 #ifdef _MSC_VER
-    fstream.open(Common::UTF8ToUTF16W(filename).c_str(), openmode);
+    fstream.open(Common::UTF8ToUTF16W(filename), openmode);
 #else
-    fstream.open(filename.c_str(), openmode);
+    fstream.open(filename, openmode);
 #endif
 }