out, err := ctxt.Out.View(sect.Reloff)
			if err != nil {
				panic(err)
			}
			go func() {
				relocSect(ctxt, out, sect, syms)
				wg.Done()
				<-sem
			}()
		}
	} else {
		// We cannot Mmap. Write sequentially.
		fn = func(ctxt *Link, sect *sym.Section, syms []loader.Sym) {
			relocSect(ctxt, ctxt.Out, sect, syms)
		}
	}
	return fn, &wg

type RelocKind int32

// An Index represents a bitstream element index within a particular
// section.
type Index int32

// A relocEnt (relocation entry) is an entry in an element's local
// reference table.
//
// TODO(mdempsky): Rename this too.
type RelocEnt struct {
	Kind RelocKind
	Idx  Index
}

// Reserved indices within the meta relocation section.
const (
	PublicRootIdx  Index = 0

		p:   pw,
		k:   k,
		Idx: idx,
	}
}

// An Encoder provides methods for encoding an individual element's
// bitstream data.
type Encoder struct {
	p *PkgEncoder

	Relocs   []RelocEnt
	RelocMap map[RelocEnt]uint32
	Data     bytes.Buffer // accumulated element bitstream data

	encodingRelocHeader bool

	k   RelocKind
	Idx Index // index within relocation section
}