您应致电

You should call Seek:seek with a relative offset of 0. This has no side effect and returns the information you are looking for.

Seek用于多种类型，包括:

Seek is implemented for a number of types, including:

• impl Seek for File
• impl<'_> Seek for &'_ File
• impl<'_, S: Seek + ?Sized> Seek for &'_ mut S
• impl<R: Seek> Seek for BufReader<R>
• impl<S: Seek + ?Sized> Seek for Box<S>
• impl<T> Seek for Cursor<T> where
• impl<W: Write + Seek> Seek for BufWriter<W>

• impl Seek for File
• impl<'_> Seek for &'_ File
• impl<'_, S: Seek + ?Sized> Seek for &'_ mut S
• impl<R: Seek> Seek for BufReader<R>
• impl<S: Seek + ?Sized> Seek for Box<S>
• impl<T> Seek for Cursor<T> where
• impl<W: Write + Seek> Seek for BufWriter<W>

使用 Cursor 类 可能会更有效，因为您可以避免进行额外的系统调用.

Using the Cursor class mentioned by Aaronepower might be more efficient though, since you could avoid having to make an extra system call.