Core: Simulate write-only file access with read-write access (#3360)

* Swap write access mode for read write

Opening with access mode w will erase the opened file. We do not want this.

* Create mode

Opening with write access was previously the only way to create a file through open, so add a separate FileAccessMode that uses the write access mode to create files.

* Update file_system.cpp

Remove a hack added to posix_rename to bypass the file clearing behaviors of FileAccessMode::Write

* Check access mode in read functions

Write-only files cause the EBADF return on the various read functions. Now that we're opening files differently, properly handling this is necessary.

* Separate appends into proper modes

Fixes a potential regression from one of my prior PRs, and ensures the Write | Append flag combo also behaves properly in read-related functions.

* Move IsWriteOnly check after device/socket reads

file->f is only valid for files, so checking this before checking for sockets/devices will cause access violations.

* Fix issues

Now that Write is identical to ReadWrite, internal uses of Write need to be swapped to my new Create mode

* Fix remaining uses of FileAccessMode write to create files

Missed these before.

* Fix rebase

* Add stubbed get_authinfo (#3722)

* mostly stubbed get_authinfo

* Return value observed on console if get_authinfo was called for the current thread, esrch otherwise

---------

Co-authored-by: kalaposfos13 <153381648+kalaposfos13@users.noreply.github.com>
Co-authored-by: georgemoralis <giorgosmrls@gmail.com>

src/common/io_file.h

@@ -21,9 +21,8 @@ enum class FileAccessMode {
      */
     Read = 1 << 0,
     /**
-     * If the file at path exists, the existing contents of the file are erased.
-     * The empty file is then opened for writing.
-     * If the file at path does not exist, it creates and opens a new empty file for writing.
+     * If the file at path exists, it opens the file for writing.
+     * If the file at path does not exist, it fails to open the file.
      */
     Write = 1 << 1,
     /**
@@ -42,6 +41,12 @@ enum class FileAccessMode {
      * reading and appending.
      */
     ReadAppend = Read | Append,
+    /**
+     * If the file at path exists, the existing contents of the file are erased.
+     * The empty file is then opened for writing.
+     * If the file at path does not exist, it creates and opens a new empty file for writing.
+     */
+    Create = 1 << 3,
 };
 DECLARE_ENUM_FLAG_OPERATORS(FileAccessMode);
 
@@ -102,6 +107,11 @@ public:
         return file != nullptr;
     }
 
+    bool IsWriteOnly() const {
+        return file_access_mode == FileAccessMode::Append ||
+               file_access_mode == FileAccessMode::Write;
+    }
+
     uintptr_t GetFileMapping();
 
     int Open(const std::filesystem::path& path, FileAccessMode mode,
@@ -210,7 +220,7 @@ public:
     }
 
     static size_t WriteBytes(const std::filesystem::path path, const auto& data) {
-        IOFile out(path, FileAccessMode::Write);
+        IOFile out(path, FileAccessMode::Create);
         return out.Write(data);
     }
     std::FILE* file = nullptr;