var wg sync.WaitGroup        // outstanding fetches
var urlq = make(chan string) // URLs to crawl

// urlFrag is a URL and its optional #fragment (without the #)
type urlFrag struct {
	url, frag string
}

var (
	mu          sync.Mutex
	crawled     = make(map[string]bool)      // URL without fragment -> true
	neededFrags = make(map[urlFrag][]string) // URL#frag -> who needs it
)

//
//	var spd sparseDatas = []sparseEntry{
//		{Offset: 2,  Length: 5},  // Data fragment for 2..6
//		{Offset: 18, Length: 3},  // Data fragment for 18..20
//	}
//	var sph sparseHoles = []sparseEntry{
//		{Offset: 0,  Length: 2},  // Hole fragment for 0..1
//		{Offset: 7,  Length: 11}, // Hole fragment for 7..17
//		{Offset: 21, Length: 4},  // Hole fragment for 21..24
//	}
//

	endPos := sw.pos + int64(len(b))
	for endPos > sw.pos && err == nil {
		var nf int // Bytes written in fragment
		dataStart, dataEnd := sw.sp[0].Offset, sw.sp[0].endOffset()
		if sw.pos < dataStart { // In a hole fragment
			bf := b[:min(int64(len(b)), dataStart-sw.pos)]
			nf, err = zeroWriter{}.Write(bf)
		} else { // In a data fragment
			bf := b[:min(int64(len(b)), dataEnd-sw.pos)]
			nf, err = sw.fw.Write(bf)
		}
		b = b[nf:]

	endPos := sr.pos + int64(len(b))
	for endPos > sr.pos && err == nil {
		var nf int // Bytes read in fragment
		holeStart, holeEnd := sr.sp[0].Offset, sr.sp[0].endOffset()
		if sr.pos < holeStart { // In a data fragment
			bf := b[:min(int64(len(b)), holeStart-sr.pos)]
			nf, err = tryReadFull(sr.fr, bf)
		} else { // In a hole fragment
			bf := b[:min(int64(len(b)), holeEnd-sr.pos)]
			nf, err = tryReadFull(zeroReader{}, bf)
		}

func (b *Reader) ReadBytes(delim byte) ([]byte, error) {
	full, frag, n, err := b.collectFragments(delim)
	// Allocate new buffer to hold the full pieces and the fragment.
	buf := make([]byte, n)
	n = 0
	// Copy full pieces and fragment in.
	for i := range full {
		n += copy(buf[n:], full[i])
	}
	copy(buf[n:], frag)
	return buf, err
}

pkg syscall (netbsd-arm64-cgo), const IPPROTO_ETHERIP = 97
pkg syscall (netbsd-arm64-cgo), const IPPROTO_ETHERIP ideal-int
pkg syscall (netbsd-arm64-cgo), const IPPROTO_FRAGMENT = 44
pkg syscall (netbsd-arm64-cgo), const IPPROTO_FRAGMENT ideal-int
pkg syscall (netbsd-arm64-cgo), const IPPROTO_GGP = 3
pkg syscall (netbsd-arm64-cgo), const IPPROTO_GGP ideal-int
pkg syscall (netbsd-arm64-cgo), const IPPROTO_GRE = 47

pkg syscall (darwin-arm64), const IPPROTO_ETHERIP = 97
pkg syscall (darwin-arm64), const IPPROTO_ETHERIP ideal-int
pkg syscall (darwin-arm64), const IPPROTO_FRAGMENT = 44
pkg syscall (darwin-arm64), const IPPROTO_FRAGMENT ideal-int
pkg syscall (darwin-arm64), const IPPROTO_GGP = 3
pkg syscall (darwin-arm64), const IPPROTO_GGP ideal-int
pkg syscall (darwin-arm64), const IPPROTO_GMTP = 100

pkg syscall (freebsd-arm64), const IPPROTO_ETHERIP = 97
pkg syscall (freebsd-arm64), const IPPROTO_ETHERIP ideal-int
pkg syscall (freebsd-arm64), const IPPROTO_FRAGMENT = 44
pkg syscall (freebsd-arm64), const IPPROTO_FRAGMENT ideal-int
pkg syscall (freebsd-arm64), const IPPROTO_GGP = 3
pkg syscall (freebsd-arm64), const IPPROTO_GGP ideal-int
pkg syscall (freebsd-arm64), const IPPROTO_GMTP = 100

pkg net/url, type Error struct, Op string
pkg net/url, type Error struct, URL string
pkg net/url, type EscapeError string
pkg net/url, type URL struct
pkg net/url, type URL struct, Fragment string
pkg net/url, type URL struct, Host string
pkg net/url, type URL struct, Opaque string
pkg net/url, type URL struct, Path string
pkg net/url, type URL struct, RawQuery string

pkg syscall (freebsd-riscv64), const IPPROTO_ETHERIP = 97 #53466
pkg syscall (freebsd-riscv64), const IPPROTO_ETHERIP ideal-int #53466
pkg syscall (freebsd-riscv64), const IPPROTO_FRAGMENT = 44 #53466
pkg syscall (freebsd-riscv64), const IPPROTO_FRAGMENT ideal-int #53466
pkg syscall (freebsd-riscv64), const IPPROTO_GGP = 3 #53466
pkg syscall (freebsd-riscv64), const IPPROTO_GGP ideal-int #53466