// Blocks will read this much and find the first following newline.
// 128KB appears to be a very reasonable default.
const csvSplitSize = 128 << 10

// startReaders will read the header if needed and spin up a parser
// and a number of workers based on GOMAXPROCS.
// If an error is returned no goroutines have been started and r.err will have been set.

	// fileList is a list of files sorted by ename,
	// for use by the Open method.
	fileListOnce sync.Once
	fileList     []fileListEntry
}

// A ReadCloser is a [Reader] that must be closed when no longer needed.
type ReadCloser struct {
	f *os.File
	Reader
}

// A File is a single file in a ZIP archive.
// The file information is in the embedded [FileHeader].
// The file content can be accessed by calling [File.Open].

	var (
		cntNewline int64
		buf        bytes.Buffer
		blk        block
	)

	// feedTokens copies data in blocks from r into buf until there are
	// at least cnt newlines in buf. It will not read more blocks than needed.
	feedTokens := func(n int64) error {
		for cntNewline < n {
			if _, err := mustReadFull(r, blk[:]); err != nil {
				return err
			}
			buf.Write(blk[:])
			for _, c := range blk {
				if c == '\n' {