go-dpkg/ar/write.go

package ar

import "io"

type Writer struct {
	w             io.Writer
	size          int64
	previusHeader *Header
}

func NewWriter(w io.Writer) (wr *Writer, err error) {
	// Write ar magic header
	if _, err = w.Write([]byte(arMagic)); err == nil {
		wr = &Writer{w: w, size: 0}
	}
	return
}

func (w *Writer) WriteFile(data []byte, hdr *Header) (n int64, err error) {
	if w.size <= 0 {
		if err = w.WriteHeader(hdr); err == nil {
			n2, err2 := w.Write(data)
			n = int64(n2)
			if err2 != nil {
				err = err2
			}
		}
	}
	return
}

func (w *Writer) Write(p []byte) (n int, err error) {
	if w.size <= 0 {
		return 0, io.EOF
	} else if int64(len(p)) > w.size {
		p = p[0:w.size]
	}
	n, err = w.w.Write(p)
	w.size -= int64(n)
	if w.size == 0 && (w.previusHeader.Size&1) == 1 {
		w.w.Write([]byte{0x0A}) // Ignore the last byte if the size is odd
	}
	return
}

func (w *Writer) WriteHeader(hdr *Header) error {
	if w.size > 0 {
		return io.ErrShortWrite
	}
	w.size = hdr.Size
	w.previusHeader = hdr
	_, err := w.w.Write(hdr.gnuHeader()) // Writed gnu header
	return err
}