mirror of
https://github.com/wader/fq.git
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114 lines
2.8 KiB
Go
114 lines
2.8 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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"fmt"
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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.Format
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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}, Formats: &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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str := func(nBytes int) string {
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s := d.UTF8(nBytes)
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ts := strings.Trim(s, " \x00")
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return ts
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}
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fieldStr := func(d *decode.D, name string, nBytes int) string {
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return d.FieldStrFn(name, func() (string, string) {
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return str(nBytes), ""
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})
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}
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fieldNumStr := func(d *decode.D, name string, nBytes int) uint64 {
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return d.FieldUFn(name, func() (uint64, decode.DisplayFormat, string) {
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ts := strings.TrimLeft(str(nBytes), "0 \x00")
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if ts == "" {
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return 0, decode.NumberDecimal, ts
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}
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n, err := strconv.ParseUint(ts, 8, 64)
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if err != nil {
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d.Invalid(fmt.Sprintf("failed to parse %s number %s: %s", name, ts, err))
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}
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return n, decode.NumberDecimal, ts
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})
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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.FieldValidateZeroPadding(name, int(blockPadding))
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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.FieldArrayFn("files", func(d *decode.D) {
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for !d.End() {
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d.FieldStructFn("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.Invalid(fmt.Sprintf("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.FieldTryFormatLen("data", int64(size)*8, probeFormat)
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if dv == nil {
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d.FieldBitBufLen("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.FieldBitBufLen("end_marker", 512*2*8)
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if !foundEndMarker {
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d.Invalid("no files found")
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}
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return nil
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}
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