73 lines
1.6 KiB
Go
73 lines
1.6 KiB
Go
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package cpio
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import (
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"io"
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"io/ioutil"
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)
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// A Reader provides sequential access to the contents of a CPIO archive. A CPIO
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// archive consists of a sequence of files. The Next method advances to the next
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// file in the archive (including the first), and then it can be treated as an
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// io.Reader to access the file's data.
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type Reader struct {
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r io.Reader // underlying file reader
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hdr *Header // current Header
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eof int64 // bytes until the end of the current file
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}
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// NewReader creates a new Reader reading from r.
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func NewReader(r io.Reader) *Reader {
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return &Reader{
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r: r,
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}
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}
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// Read reads from the current entry in the CPIO archive. It returns 0, io.EOF
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// when it reaches the end of that entry, until Next is called to advance to the
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// next entry.
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func (r *Reader) Read(p []byte) (n int, err error) {
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if r.hdr == nil || r.eof == 0 {
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return 0, io.EOF
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}
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rn := len(p)
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if r.eof < int64(rn) {
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rn = int(r.eof)
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}
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n, err = r.r.Read(p[0:rn])
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r.eof -= int64(n)
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return
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}
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// Next advances to the next entry in the CPIO archive.
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// io.EOF is returned at the end of the input.
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func (r *Reader) Next() (*Header, error) {
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if r.hdr == nil {
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return r.next()
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}
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skp := r.eof + r.hdr.pad
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if skp > 0 {
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_, err := io.CopyN(ioutil.Discard, r.r, skp)
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if err != nil {
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return nil, err
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}
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}
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return r.next()
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}
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func (r *Reader) next() (*Header, error) {
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r.eof = 0
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hdr, err := readHeader(r.r)
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if err != nil {
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return nil, err
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}
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r.hdr = hdr
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r.eof = hdr.Size
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return hdr, nil
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}
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// ReadHeader creates a new Header, reading from r.
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func readHeader(r io.Reader) (*Header, error) {
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// currently only SVR4 format is supported
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return readSVR4Header(r)
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}
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