Source: readwriter.go in package golang.org/x/text/unicode/norm


package norm

import "io"

type normWriter struct {
	rb  reorderBuffer
	w   io.Writer
	buf []byte
}

Write implements the standard write interface. If the last characters are not at a normalization boundary, the bytes will be buffered for the next write. The remaining bytes will be written on close.

Process data in pieces to keep w.buf size bounded.

	const chunk = 4000

Normalize into w.buf.

		m := len(data)
		if m > chunk {
			m = chunk
		}
		w.rb.src = inputBytes(data[:m])
		w.rb.nsrc = m
		w.buf = doAppend(&w.rb, w.buf, 0)
		data = data[m:]
		n += m

Write out complete prefix, save remainder. Note that lastBoundary looks back at most 31 runes.

		i := lastBoundary(&w.rb.f, w.buf)
		if i == -1 {
			i = 0
		}
		if i > 0 {
			if _, err = w.w.Write(w.buf[:i]); err != nil {
				break
			}
			bn := copy(w.buf, w.buf[i:])
			w.buf = w.buf[:bn]
		}
	}
	return n, err
}

Close forces data that remains in the buffer to be written.

func (w *normWriter) Close() error {
	if len(w.buf) > 0 {
		_, err := w.w.Write(w.buf)
		if err != nil {
			return err
		}
	}
	return nil
}

Writer returns a new writer that implements Write(b) by writing f(b) to w. The returned writer may use an internal buffer to maintain state across Write calls. Calling its Close method writes any buffered data to w.

func (f Form) Writer(w io.Writer) io.WriteCloser {
	wr := &normWriter{rb: reorderBuffer{}, w: w}
	wr.rb.init(f, nil)
	return wr
}

type normReader struct {
	rb           reorderBuffer
	r            io.Reader
	inbuf        []byte
	outbuf       []byte
	bufStart     int
	lastBoundary int
	err          error
}

Read implements the standard read interface.

func (r *normReader) Read(p []byte) (int, error) {
	for {
		if r.lastBoundary-r.bufStart > 0 {
			n := copy(p, r.outbuf[r.bufStart:r.lastBoundary])
			r.bufStart += n
			if r.lastBoundary-r.bufStart > 0 {
				return n, nil
			}
			return n, r.err
		}
		if r.err != nil {
			return 0, r.err
		}
		outn := copy(r.outbuf, r.outbuf[r.lastBoundary:])
		r.outbuf = r.outbuf[0:outn]
		r.bufStart = 0

		n, err := r.r.Read(r.inbuf)
		r.rb.src = inputBytes(r.inbuf[0:n])
		r.rb.nsrc, r.err = n, err
		if n > 0 {
			r.outbuf = doAppend(&r.rb, r.outbuf, 0)
		}
		if err == io.EOF {
			r.lastBoundary = len(r.outbuf)
		} else {
			r.lastBoundary = lastBoundary(&r.rb.f, r.outbuf)
			if r.lastBoundary == -1 {
				r.lastBoundary = 0
			}
		}
	}
}

Reader returns a new reader that implements Read by reading data from r and returning f(data).

func (f Form) Reader(r io.Reader) io.Reader {
	const chunk = 4000
	buf := make([]byte, chunk)
	rr := &normReader{rb: reorderBuffer{}, r: r, inbuf: buf}
	rr.rb.init(f, buf)
	return rr