add ToHumanReadableSize, which formats data sizes into MiB, GiB, etc.

this is needed in order to display data sizes in upcoming changes
related to tracking statistics about the server's performance

src/Common.cpp

@@ -427,3 +427,17 @@ std::string GetPlatformAgnosticErrorString() {
     return "(no human-readable errors on this platform)";
 #endif
 }
+
+std::string ToHumanReadableSize(size_t Size) {
+    if (Size > TB) {
+        return fmt::format("{:.2f} TiB", double(Size) / TB);
+    } else if (Size > GB) {
+        return fmt::format("{:.2f} GiB", double(Size) / GB);
+    } else if (Size > MB) {
+        return fmt::format("{:.2f} MiB", double(Size) / MB);
+    } else if (Size > KB) {
+        return fmt::format("{:.2f} KiB", double(Size) / KB);
+    } else {
+        return fmt::format("{} B", Size);
+    }
+}