Rough first version of the moby tool

- terrible code
- lots needs changing
- can build a Moby from a config yaml that boots

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

vendor/github.com/surma/gocpio/reader.go

@@ -0,0 +1,181 @@
+package cpio
+
+import (
+	"errors"
+	"io"
+	"strconv"
+)
+
+type Reader struct {
+	r               io.Reader
+	pos             int64
+	remaining_bytes int
+}
+
+func NewReader(r io.Reader) *Reader {
+	return &Reader{
+		r: r,
+	}
+}
+
+func disassemble(mode int64) (fmode int64, ftype int64) {
+	fmode = mode & 0xFFF
+	ftype = (mode >> 12) & 0xF
+	return
+}
+
+func getPrefix(buf *[]byte, len int) (pre []byte) {
+	pre, *buf = (*buf)[0:len], (*buf)[len:]
+	return
+}
+
+func Btoi(s string, base int) (int, error) {
+	i, e := strconv.ParseInt(s, base, 64)
+	return int(i), e
+}
+
+var (
+	ErrInvalidHeader = errors.New("Did not find valid magic number")
+)
+
+func parseHeader(buf []byte) (*Header, int64, error) {
+	magic := string(getPrefix(&buf, 6))
+	raw_inode := getPrefix(&buf, 8)
+	raw_mode := getPrefix(&buf, 8)
+	raw_uid := getPrefix(&buf, 8)
+	raw_gid := getPrefix(&buf, 8)
+	raw_nlinks := getPrefix(&buf, 8)
+	raw_mtime := getPrefix(&buf, 8)
+	raw_size := getPrefix(&buf, 8)
+	raw_major := getPrefix(&buf, 8)
+	raw_minor := getPrefix(&buf, 8)
+	raw_devmajor := getPrefix(&buf, 8)
+	raw_devminor := getPrefix(&buf, 8)
+	raw_namelen := getPrefix(&buf, 8)
+	raw_check := getPrefix(&buf, 8)
+
+	_, _, _, _, _ = raw_inode, raw_nlinks, raw_major, raw_minor, raw_check
+
+	if magic != "070701" {
+		return nil, 0, ErrInvalidHeader
+	}
+
+	hdr := &Header{}
+
+	mode, e := strconv.ParseInt(string(raw_mode), 16, 64)
+	if e != nil {
+		return nil, 0, e
+	}
+
+	hdr.Mode, hdr.Type = disassemble(mode)
+
+	hdr.Uid, e = Btoi(string(raw_uid), 16)
+	if e != nil {
+		return nil, 0, e
+	}
+
+	hdr.Gid, e = Btoi(string(raw_gid), 16)
+	if e != nil {
+		return nil, 0, e
+	}
+
+	hdr.Mtime, e = strconv.ParseInt(string(raw_mtime), 16, 64)
+	if e != nil {
+		return nil, 0, e
+	}
+
+	hdr.Size, e = strconv.ParseInt(string(raw_size), 16, 64)
+	if e != nil {
+		return nil, 0, e
+	}
+
+	hdr.Devmajor, e = strconv.ParseInt(string(raw_devmajor), 16, 64)
+	if e != nil {
+		return nil, 0, e
+	}
+
+	hdr.Devminor, e = strconv.ParseInt(string(raw_devminor), 16, 64)
+	if e != nil {
+		return nil, 0, e
+	}
+
+	namelen, e := strconv.ParseInt(string(raw_namelen), 16, 64)
+	if e != nil {
+		return nil, 0, e
+	}
+
+	return hdr, namelen, nil
+}
+
+func (r *Reader) Next() (*Header, error) {
+	e := r.skipRest()
+	if e != nil {
+		return nil, e
+	}
+	e = r.skipPadding(4)
+	if e != nil {
+		return nil, e
+	}
+
+	raw_hdr := make([]byte, 110)
+	_, e = r.countedRead(raw_hdr)
+	if e != nil {
+		return nil, e
+	}
+
+	hdr, namelen, e := parseHeader(raw_hdr)
+	if e != nil {
+		return nil, e
+	}
+
+	bname := make([]byte, namelen)
+	_, e = r.countedRead(bname)
+	if e != nil {
+		return nil, e
+	}
+
+	hdr.Name = string(bname[0 : namelen-1]) //Exclude terminating zero
+	r.remaining_bytes = int(hdr.Size)
+	return hdr, r.skipPadding(4)
+}
+
+func (r *Reader) skipRest() error {
+	buf := make([]byte, 1)
+	for ; r.remaining_bytes > 0; r.remaining_bytes-- {
+		_, e := r.countedRead(buf)
+		if e != nil {
+			return e
+		}
+	}
+	return nil
+}
+
+// Skips to the next position which is a multiple of mod.
+func (r *Reader) skipPadding(mod int64) error {
+	numBytesToRead := ((mod - (r.pos % mod)) % mod)
+	buf := make([]byte, numBytesToRead)
+	_, e := r.countedRead(buf)
+	return e
+}
+
+func (r *Reader) Read(b []byte) (n int, e error) {
+	if r.remaining_bytes == 0 {
+		return 0, io.EOF
+	}
+
+	if len(b) > r.remaining_bytes {
+		b = b[0:r.remaining_bytes]
+	}
+	n, e = r.countedRead(b)
+	r.remaining_bytes -= n
+	return
+}
+
+func (r *Reader) countedRead(b []byte) (n int, e error) {
+	if len(b) == 0 {
+		return
+	}
+	n, e = r.r.Read(b)
+	r.pos += int64(n)
+	return
+}