for i := 0; i < 5<<10; i++ {
		b.Write(buf)
		b.Read(buf)
		if i == 0 {
			cap0 = b.Cap()
		}
	}
	cap1 := b.Cap()
	// (*Buffer).grow allows for 2x capacity slop before sliding,
	// so set our error threshold at 3x.
	if cap1 > cap0*3 {
		t.Errorf("buffer cap = %d; too big (grew from %d)", cap1, cap0)
	}
}

func BenchmarkWriteByte(b *testing.B) {
	const n = 4 << 10
	b.SetBytes(n)

	}
	c := cap(b.buf)
	if n <= c/2-m {
		// We can slide things down instead of allocating a new
		// slice. We only need m+n <= c to slide, but
		// we instead let capacity get twice as large so we
		// don't spend all our time copying.
		copy(b.buf, b.buf[b.off:])
	} else if c > maxInt-c-n {
		panic(ErrTooLarge)
	} else {
		// Add b.off to account for b.buf[:b.off] being sliced off the front.
		b.buf = growSlice(b.buf[b.off:], b.off+n)

		return nil, 0, ErrFormat
	}

	baseOffset = directoryEndOffset - int64(d.directorySize) - int64(d.directoryOffset)

	// Make sure directoryOffset points to somewhere in our file.
	if o := baseOffset + int64(d.directoryOffset); o < 0 || o >= size {
		return nil, 0, ErrFormat
	}

	// If the directory end data tells us to use a non-zero baseOffset,

			85, 84, 5, 0, 3, 154, 144, 195, 77, // tag 21589 size 5
			85, 120, 0, 0, // tag 30805 size 0
		},
	}
	testValidHeader(&h, t)
}

// Just benchmarking how fast the Zip64 test above is. Not related to
// our zip performance, since the test above disabled CRC32 and flate.
func BenchmarkZip64Test(b *testing.B) {
	for i := 0; i < b.N; i++ {
		testZip64(b, 1<<26)
	}
}

func BenchmarkZip64TestSizes(b *testing.B) {

	// still broken on our builders in 2023. Instead, append the exitcode to
	// the output and parse it from there.
	filter, exitStr := newExitCodeFilter(os.Stdout)
	args += "; echo -n " + exitStr + "$?"

	cmd := adbCmd("exec-out", args)
	cmd.Stdout = filter
	// If the adb subprocess somehow hangs, go test will kill this wrapper
	// and wait for our os.Stderr (and os.Stdout) to close as a result.

			// - Package "unsafe" contains special signatures requiring
			//   extra care when printing them - ignore since it is not
			//   going to change w/o a language change.
			// - Internal and vendored packages do not contribute to our
			//   API surface. (If we are running within the "std" module,
			//   vendored dependencies appear as themselves instead of
			//   their "vendor/" standard-library copies.)