hodor7

hodor7.go

// Processor implements an io.Reader
type Processor struct {
	Src       io.Reader
	Old, New  []byte
	ChunkSize int
	buf, rbuf bytes.Buffer
}

// Reset the processor
func (m *Processor) Reset(src io.Reader) {
	m.Src = src
	m.buf.Reset()
}

func (m *Processor) Read(p []byte) (int, error) {
	if m.ChunkSize == 0 {
		m.ChunkSize = DefaultChunkSize
	}

	// first flush any buffered data to p
	n, err := m.buf.Read(p)
	if n == len(p) || (err != nil && err != io.EOF) {
		return n, err
	}

	// m.buf must be empty now
	_, err = io.CopyN(&m.buf, m.Src, int64(m.ChunkSize))
	if err != nil && err != io.EOF {
		return n, err
	}

	rerr := Replace(m.buf.Bytes(), m.Old, m.New, -1, &m.rbuf)
	m.buf.Reset()

	if rerr != nil {
		return n, rerr
	}

	copied, rerr := m.rbuf.Read(p[n:])
	n += copied
	if rerr != nil && rerr != io.EOF {
		return n, rerr
	}

	// copy anything not put in p, back to the buffer
	if _, rerr := m.buf.ReadFrom(&m.rbuf); rerr != nil {
		return n, rerr
	}

	return n, err
}