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/*
* Copyright (c) SAS Institute, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cpio
import (
"errors"
"fmt"
"io"
)
// TRAILER is the filename found on the last entry of a cpio archive
const TRAILER = "TRAILER!!!"
// ErrStrippedHeader indicates that a RPM-style archive was read without calling SetFileSizes()
var ErrStrippedHeader = errors.New("invalid cpio header: rpm-style stripped cpio requires supplemental size info")
// CpioEntry points to a single file within a cpio stream
type CpioEntry struct {
Header *Cpio_newc_header
payload *file_stream
}
// CpioStream reads file metadata and contents from a cpio archive
type CpioStream struct {
stream *countingReader
nextPos int64
sizes []int64
}
type countingReader struct {
stream io.Reader
curPos int64
}
// NewCpioStream starts reading files from a cpio archive
func NewCpioStream(stream io.Reader) *CpioStream {
return &CpioStream{
stream: &countingReader{
stream: stream,
curPos: 0,
},
nextPos: 0,
}
}
// SetFileSizes provides supplemental file size info so that RPMs with files > 4GiB can be read
func (cs *CpioStream) SetFileSizes(sizes []int64) {
cs.sizes = sizes
}
// ReadNextEntry returns the metadata of the next file in the archive.
//
// The final file in the archive can be detected by checking for a Filename of TRAILER.
func (cs *CpioStream) ReadNextEntry() (*CpioEntry, error) {
if cs.nextPos != cs.stream.curPos {
_, err := cs.stream.Seek(cs.nextPos-cs.stream.curPos, 1)
if err != nil {
return nil, err
}
}
// Read header
hdr, err := readHeader(cs.stream)
if err != nil {
return nil, err
} else if hdr.stripped {
return cs.readStrippedEntry(hdr)
}
// Read filename
buf := make([]byte, hdr.namesize)
if _, err = io.ReadFull(cs.stream, buf); err != nil {
return nil, err
}
filename := string(buf[:len(buf)-1])
offset := pad(newcHeaderLength+int(hdr.namesize)) - newcHeaderLength - int(hdr.namesize)
if offset > 0 {
_, err := cs.stream.Seek(int64(offset), 1)
if err != nil {
return nil, err
}
}
// Find the next entry
cs.nextPos = pad64(cs.stream.curPos + int64(hdr.filesize))
// Find the payload
payload, err := newFileStream(cs.stream, int64(hdr.filesize))
if err != nil {
return nil, err
}
// Create then entry
hdr.filename = filename
entry := CpioEntry{
Header: hdr,
payload: payload,
}
return &entry, nil
}
func (cs *CpioStream) readStrippedEntry(hdr *Cpio_newc_header) (*CpioEntry, error) {
// magic has already been read
if cs.sizes == nil {
return nil, ErrStrippedHeader
} else if hdr.index >= len(cs.sizes) {
return nil, fmt.Errorf("stripped cpio refers to invalid file index %d", hdr.index)
}
size := cs.sizes[hdr.index]
cs.nextPos = pad64(cs.stream.curPos + size)
payload, err := newFileStream(cs.stream, size)
if err != nil {
return nil, err
}
return &CpioEntry{Header: hdr, payload: payload}, nil
}
func (cr *countingReader) Read(p []byte) (n int, err error) {
n, err = cr.stream.Read(p)
cr.curPos += int64(n)
return
}
func (cr *countingReader) Seek(offset int64, whence int) (int64, error) {
if whence != 1 {
return 0, fmt.Errorf("only seeking from current location supported")
}
if offset == 0 {
return cr.curPos, nil
}
b := make([]byte, offset)
n, err := io.ReadFull(cr, b)
if err != nil && err != io.EOF {
return 0, err
}
return int64(n), nil
}
func pad(num int) int {
return num + 3 - (num+3)%4
}
func pad64(num int64) int64 {
return num + 3 - (num+3)%4
}
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