is1x0 = true
	case major != "" || minor != "":
		return nil, nil // Unknown GNU sparse PAX version
	case hdr.PAXRecords[paxGNUSparseMap] != "":
		is1x0 = false // 0.0 and 0.1 did not have explicit version records, so guess
	default:
		return nil, nil // Not a PAX format GNU sparse file.
	}
	hdr.Format.mayOnlyBe(FormatPAX)

	// Update hdr from GNU sparse PAX headers.
	if name := hdr.PAXRecords[paxGNUSparseName]; name != "" {

		{"22 GNU.sparse.size=10\n26 GNU.sparse.numblocks=2\n" +
			"23 GNU.sparse.offset=1\n25 GNU.sparse.numbytes=2\n" +
			"23 GNU.sparse.offset=3\n25 GNU.sparse.numbytes=4\n",
			map[string]string{paxGNUSparseSize: "10", paxGNUSparseNumBlocks: "2", paxGNUSparseMap: "1,2,3,4"}, true},
		{"22 GNU.sparse.size=10\n26 GNU.sparse.numblocks=1\n" +
			"25 GNU.sparse.numbytes=2\n23 GNU.sparse.offset=1\n",
			nil, false},

	paxSchilyXattr = "SCHILY.xattr."

	// Keywords for GNU sparse files in a PAX extended header.
	paxGNUSparse          = "GNU.sparse."
	paxGNUSparseNumBlocks = "GNU.sparse.numblocks"
	paxGNUSparseOffset    = "GNU.sparse.offset"
	paxGNUSparseNumBytes  = "GNU.sparse.numbytes"
	paxGNUSparseMap       = "GNU.sparse.map"
	paxGNUSparseName      = "GNU.sparse.name"
	paxGNUSparseMajor     = "GNU.sparse.major"
	paxGNUSparseMinor     = "GNU.sparse.minor"

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

	// defined by the GNU manual (e.g., "GNU.sparse.map").
	//
	// Reference:
	//	http://pubs.opengroup.org/onlinepubs/009695399/utilities/pax.html
	FormatPAX

	// FormatGNU represents the GNU header format.
	//
	// The GNU header format is older than the USTAR and PAX standards and
	// is not compatible with them. The GNU format supports

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//