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|
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
}
|
