The preamble may contain any C code, including function and variable
declarations and definitions. These may then be referred to from Go
code as though they were defined in the package "C". All names
declared in the preamble may be used, even if they start with a
lower-case letter. Exception: static variables in the preamble may
not be referenced from Go code; static functions are permitted.

}

// alignSparseEntries mutates src and returns dst where each fragment's
// starting offset is aligned up to the nearest block edge, and each
// ending offset is aligned down to the nearest block edge.
//
// Even though the Go tar Reader and the BSD tar utility can handle entries
// with arbitrary offsets and lengths, the GNU tar utility can only handle
// offsets and lengths that are multiples of blockSize.

		// Set the compression method to Store to ensure data length is truly zero,
		// which the writeHeader method always encodes for the size fields.
		// This is necessary as most compression formats have non-zero lengths
		// even when compressing an empty string.
		fh.Method = Store
		fh.Flags &^= 0x8 // we will not write a data descriptor

		// Explicitly clear sizes as they have no meaning for directories.
		fh.CompressedSize = 0

	for {
		for i := 0; i < s.maxEntries(); i++ {
			// This termination condition is identical to GNU and BSD tar.
			if s.entry(i).offset()[0] == 0x00 {
				break // Don't return, need to process extended headers (even if empty)
			}
			offset := p.parseNumeric(s.entry(i).offset())
			length := p.parseNumeric(s.entry(i).length())
			if p.err != nil {
				return nil, p.err
			}