var fw fileWriter
		switch maker := v.maker.(type) {
		case makeReg:
			fw = &regFileWriter{w, maker.size}
			wantStr = maker.wantStr
		case makeSparse:
			if !validateSparseEntries(maker.sph, maker.size) {
				t.Fatalf("invalid sparse map: %v", maker.sph)
			}
			spd := invertSparseEntries(maker.sph, maker.size)
			fw = &regFileWriter{w, maker.makeReg.size}
			fw = &sparseFileWriter{fw, spd, 0}

		var fr fileReader
		switch maker := v.maker.(type) {
		case makeReg:
			r := testNonEmptyReader{strings.NewReader(maker.str)}
			fr = &regFileReader{r, maker.size}
		case makeSparse:
			if !validateSparseEntries(maker.spd, maker.size) {
				t.Fatalf("invalid sparse map: %v", maker.spd)
			}
			sph := invertSparseEntries(maker.spd, maker.size)
			r := testNonEmptyReader{strings.NewReader(maker.makeReg.str)}

github.com/tidwall/gjson
https://github.com/tidwall/gjson
----------------------------------------------------------------
The MIT License (MIT)

Copyright (c) 2016 Josh Baker

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in