mirror of
https://github.com/wader/fq.git
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111 lines
2.7 KiB
Go
111 lines
2.7 KiB
Go
package tar
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// https://www.gnu.org/software/tar/manual/html_node/Standard.html
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// TODO: extensions?
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import (
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"bytes"
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"strconv"
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"strings"
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"github.com/wader/fq/format"
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"github.com/wader/fq/format/registry"
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"github.com/wader/fq/pkg/decode"
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)
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var probeFormat decode.Group
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func init() {
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registry.MustRegister(decode.Format{
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Name: format.TAR,
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Description: "Tar archive",
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Groups: []string{format.PROBE},
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DecodeFn: tarDecode,
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Dependencies: []decode.Dependency{
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{Names: []string{format.PROBE}, Group: &probeFormat},
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},
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})
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}
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func tarDecode(d *decode.D, in interface{}) interface{} {
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fieldStr := func(d *decode.D, name string, nBytes int) string {
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return d.FieldUTF8(name, nBytes, d.Trim(" \x00"))
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}
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fieldNumStr := func(d *decode.D, name string, nBytes int) uint64 {
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// TODO: some kind of FieldUScalarFn func that returns sym value?
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var n uint64
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d.FieldScalar(name, func(_ decode.Scalar) (decode.Scalar, error) {
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a := d.UTF8NullFixedLen(nBytes)
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ts := strings.Trim(a, " ")
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n = uint64(0)
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if ts != "" {
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var err error
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n, err = strconv.ParseUint(ts, 8, 64)
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if err != nil {
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d.Errorf("failed to parse %s number %s: %s", name, ts, err)
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}
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}
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return decode.Scalar{Actual: a, Sym: n}, nil
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})
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return n
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}
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fieldBlockPadding := func(d *decode.D, name string) {
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const blockBits = 512 * 8
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blockPadding := (blockBits - (d.Pos() % blockBits)) % blockBits
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if blockPadding > 0 {
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d.FieldRawLen(name, blockPadding, d.BitBufIsZero)
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}
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}
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// 512*2 zero bytes
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endMarker := [512 * 2]byte{}
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foundEndMarker := false
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d.FieldArray("files", func(d *decode.D) {
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for !d.End() {
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d.FieldStruct("file", func(d *decode.D) {
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fieldStr(d, "name", 100)
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fieldNumStr(d, "mode", 8)
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fieldNumStr(d, "uid", 8)
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fieldNumStr(d, "gid", 8)
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size := fieldNumStr(d, "size", 12)
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fieldNumStr(d, "mtime", 12)
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fieldNumStr(d, "chksum", 8)
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fieldStr(d, "typeflag", 1)
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fieldStr(d, "linkname", 100)
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magic := fieldStr(d, "magic", 6)
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if magic != "ustar" {
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d.Errorf("invalid magic %s", magic)
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}
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fieldNumStr(d, "version", 2)
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fieldStr(d, "uname", 32)
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fieldStr(d, "gname", 32)
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fieldNumStr(d, "devmajor", 8)
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fieldNumStr(d, "devminor", 8)
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fieldStr(d, "prefix", 155)
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fieldBlockPadding(d, "header_block_padding")
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if size > 0 {
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dv, _, _ := d.TryFieldFormatLen("data", int64(size)*8, probeFormat, nil)
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if dv == nil {
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d.FieldRawLen("data", int64(size)*8)
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}
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}
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fieldBlockPadding(d, "data_block_padding")
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})
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bs := d.PeekBytes(512 * 2)
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if bytes.Equal(bs, endMarker[:]) {
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foundEndMarker = true
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break
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}
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}
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})
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d.FieldRawLen("end_marker", 512*2*8)
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if !foundEndMarker {
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d.Errorf("no files found")
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}
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return nil
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}
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