fsp_srv: Use std::string_view's copy() function instead of strncpy()

Given elements inserted into a vector are zeroed out, we can just copy
MAX_LEN - 1 elements and the data will already be properly null
terminated.

src/core/file_sys/directory.h

@@ -4,8 +4,9 @@
 
 #pragma once
 
-#include <array>
 #include <cstddef>
+#include <iterator>
+#include <string_view>
 #include "common/common_funcs.h"
 #include "common/common_types.h"
 
@@ -21,9 +22,14 @@ enum EntryType : u8 {
 
 // Structure of a directory entry, from
 // http://switchbrew.org/index.php?title=Filesystem_services#DirectoryEntry
-const size_t FILENAME_LENGTH = 0x300;
 struct Entry {
-    char filename[FILENAME_LENGTH];
+    Entry(std::string_view view, EntryType entry_type, u64 entry_size)
+        : type{entry_type}, file_size{entry_size} {
+        const size_t copy_size = view.copy(filename, std::size(filename) - 1);
+        filename[copy_size] = '\0';
+    }
+
+    char filename[0x300];
     INSERT_PADDING_BYTES(4);
     EntryType type;
     INSERT_PADDING_BYTES(3);

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

@@ -196,11 +196,7 @@ static void BuildEntryIndex(std::vector<FileSys::Entry>& entries, const std::vec
     entries.reserve(entries.size() + new_data.size());
 
     for (const auto& new_entry : new_data) {
-        auto& entry = entries.emplace_back();
-        entry.filename[0] = '\0';
-        std::strncat(entry.filename, new_entry->GetName().c_str(), FileSys::FILENAME_LENGTH - 1);
-        entry.type = type;
-        entry.file_size = new_entry->GetSize();
+        entries.emplace_back(new_entry->GetName(), type, new_entry->GetSize());
     }
 }