7ae9561610
Rather than going through writeHeader, which attempts to handle all formats, implement writePAXHeader, which only has an understanding of the PAX format. In PAX, the USTAR header is filled out in a best-effort manner. Thus, we change logic of formatString and formatOctal to try their best to output something (possibly truncated) in the event of an error. The new implementation of PAX headers causes several tests to fail. An investigation into the new output reveals that the new behavior is correct, while the tests had actually locked in incorrect behavior before. A dump of the differences is listed below (-before, +after): << writer-big.tar >> This change is due to fact that we changed the Header.Devminor to force the tar.Writer to choose the GNU format over the PAX one. The ability to control the output is an open issue (see #18710). - 00000150 00 30 30 30 30 30 30 30 00 00 00 00 00 00 00 00 |.0000000........| + 00000150 00 ff ff ff ff ff ff ff ff 00 00 00 00 00 00 00 |................| << writer-big-long.tar>> The previous logic generated the GNU magic values for a PAX file. The new logic correctly uses the USTAR magic values. - 00000100 00 75 73 74 61 72 20 20 00 00 00 00 00 00 00 00 |.ustar ........| - 00000500 00 75 73 74 61 72 20 20 00 67 75 69 6c 6c 61 75 |.ustar .guillau| + 00000100 00 75 73 74 61 72 00 30 30 00 00 00 00 00 00 00 |.ustar.00.......| + 00000500 00 75 73 74 61 72 00 30 30 67 75 69 6c 6c 61 75 |.ustar.00guillau| The previous logic tried to use the specified timestmap in the PAX headers file, but this is problematic as this timestamp can overflow, defeating the point of using PAX, which is intended to extend tar. The new logic uses the zero timestamp similar to what GNU and BSD tar do. - 00000080 30 30 30 30 32 33 32 00 31 32 33 33 32 37 37 30 |0000232.12332770| + 00000080 30 30 30 30 32 35 36 00 30 30 30 30 30 30 30 30 |0000256.00000000| The previous logic populated the devminor and devmajor fields. The new logic leaves them zeroed just like what GNU and BSD tar do. - 00000140 00 00 00 00 00 00 00 00 00 30 30 30 30 30 30 30 |.........0000000| - 00000150 00 30 30 30 30 30 30 30 00 00 00 00 00 00 00 00 |.0000000........| + 00000140 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| + 00000150 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| The previous logic uses PAX headers, but fails to add a record for the size. The new logic does properly add a record for the size. - 00000290 31 36 67 69 67 2e 74 78 74 0a 00 00 00 00 00 00 |16gig.txt.......| - 000002a0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| + 00000290 31 36 67 69 67 2e 74 78 74 0a 32 30 20 73 69 7a |16gig.txt.20 siz| + 000002a0 65 3d 31 37 31 37 39 38 36 39 31 38 34 0a 00 00 |e=17179869184...| The previous logic encoded the size as a base-256 field, which is only valid in GNU, but the previous PAX headers implies this should be a PAX file. This result in a strange hybrid that is neither GNU nor PAX. The new logic uses PAX headers to store the size. - 00000470 37 35 30 00 30 30 30 31 37 35 30 00 80 00 00 00 |750.0001750.....| - 00000480 00 00 00 04 00 00 00 00 31 32 33 33 32 37 37 30 |........12332770| + 00000470 37 35 30 00 30 30 30 31 37 35 30 00 30 30 30 30 |750.0001750.0000| + 00000480 30 30 30 30 30 30 30 00 31 32 33 33 32 37 37 30 |0000000.12332770| << ustar.issue12594.tar >> The previous logic used the specified timestamp for the PAX headers file. The new logic just uses the zero timestmap. - 00000080 30 30 30 30 32 33 31 00 31 32 31 30 34 34 30 32 |0000231.12104402| + 00000080 30 30 30 30 32 33 31 00 30 30 30 30 30 30 30 30 |0000231.00000000| The previous logic populated the devminor and devmajor fields. The new logic leaves them zeroed just like what GNU and BSD tar do. - 00000140 00 00 00 00 00 00 00 00 00 30 30 30 30 30 30 30 |.........0000000| - 00000150 00 30 30 30 30 30 30 30 00 00 00 00 00 00 00 00 |.0000000........| + 00000140 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| + 00000150 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| Change-Id: I33419eb1124951968e9d5a10d50027e03133c811 Reviewed-on: https://go-review.googlesource.com/55231 Reviewed-by: Ian Lance Taylor <iant@golang.org> Run-TryBot: Ian Lance Taylor <iant@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> |
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