part_reader.go

package mime

import "io"

func (pr partReader) Read(d []byte) (int, error) {
	p := pr.part
	br := p.reader.bufReader

	// Read into buffer until we identify some data to return,
	// or we find a reason to stop (boundary or read error).
	for p.n == 0 && p.err == nil {
		peek, _ := br.Peek(br.Buffered())
		p.n, p.err = scanUntilBoundary(peek, p.reader.dashBoundary, p.reader.nlDashBoundary, p.total, p.readErr)
		if p.n == 0 && p.err == nil {
			// Force buffered I/O to read more into buffer.
			_, p.readErr = br.Peek(len(peek) + 1)
			if p.readErr == io.EOF {
				p.readErr = io.ErrUnexpectedEOF
			}
		}
	}

	// Read out from "data to return" part of buffer.
	if p.n == 0 {
		return 0, p.err
	}
	n := len(d)
	if n > p.n {
		n = p.n
	}
	n, _ = br.Read(d[:n])
	p.total += int64(n)
	p.n -= n
	if p.n == 0 {
		return n, p.err
	}
	return n, nil
}