Function Spool

tools/iotools.go:111–148

Spool spools the contents from 'from' to 'to' by buffering the entire contents of 'from' into a temporary file created in the directory "dir". That buffer is held in memory until the file grows to larger than 'memoryBufferLimit`, then the remaining contents are spooled to disk. The temporary file i

(to io.Writer, from io.Reader, dir string)

// The number of bytes written to "to", as well as any error encountered are
// returned.
func Spool(to io.Writer, from io.Reader, dir string) (n int64, err error) {
	// First, buffer up to `memoryBufferLimit` in memory.
	buf := make([]byte, memoryBufferLimit)
	if bn, err := from.Read(buf); err != nil && err != io.EOF {
		return int64(bn), err
	} else {
		buf = buf[:bn]
	}

	var spool io.Reader = bytes.NewReader(buf)
	if err != io.EOF {
		// If we weren't at the end of the stream, create a temporary
		// file, and spool the remaining contents there.
		tmp, err := os.CreateTemp(dir, "")
		if err != nil {
			return 0, errors.Wrap(err, tr.Tr.Get("Unable to create temporary file for spooling"))
		}
		defer func() {
			tmp.Close()
			os.Remove(tmp.Name())
		}()

		if n, err = io.Copy(tmp, from); err != nil {
			return n, errors.Wrap(err, tr.Tr.Get("unable to spool"))
		}

		if _, err = tmp.Seek(0, io.SeekStart); err != nil {
			return 0, errors.Wrap(err, tr.Tr.Get("unable to seek"))
		}

		// The spooled contents will now be the concatenation of the
		// contents we stored in memory, then the remainder of the
		// contents on disk.
		spool = io.MultiReader(spool, tmp)
	}

	return io.Copy(to, spool)
}

// Split the input on the NUL character. Usable with bufio.Scanner.
func SplitOnNul(data []byte, atEOF bool) (advance int, token []byte, err error) {