actual := LastIndexByte([]byte(test.a), test.b[0])
		if actual != test.i {
			t.Errorf("LastIndexByte(%q,%c) = %v; want %v", test.a, test.b[0], actual, test.i)
		}
	}
}

// test a larger buffer with different sizes and alignments
func TestIndexByteBig(t *testing.T) {
	var n = 1024
	if testing.Short() {
		n = 128
	}
	b := make([]byte, n)
	for i := 0; i < n; i++ {

	n := len(b) * count

	if len(b) == 0 {
		return []byte{}
	}

	// Past a certain chunk size it is counterproductive to use
	// larger chunks as the source of the write, as when the source
	// is too large we are basically just thrashing the CPU D-cache.
	// So if the result length is larger than an empirically-found
	// limit (8KB), we stop growing the source string once the limit

If both <code>n</code> and <code>m</code> are provided and are constant, then
<code>n</code> must be no larger than <code>m</code>.
For slices and channels, if <code>n</code> is negative or larger than <code>m</code> at run time,
a <a href="#Run_time_panics">run-time panic</a> occurs.
</p>

<pre>

	// difference that for some j, a[j]>b[j] and a[j+1]<b[j+1]. If the implementation
	// compares large chunks with wrong endianness, it gets wrong result.
	// no vector register is larger than 512 bytes for now
	const maxLength = 512
	a := make([]byte, maxLength)
	b := make([]byte, maxLength)
	// randomish but deterministic data. No 0 or 255.
	for i := 0; i < maxLength; i++ {

</p>

<p>
Reads of memory locations larger than a single machine word
are encouraged but not required to meet the same semantics
as word-sized memory locations,
observing a single allowed write <i>w</i>.
For performance reasons,
implementations may instead treat larger operations
as a set of individual machine-word-sized operations
in an unspecified order.

			break
		}
	}
	if got, want := scanner.Err(), ErrBadReadCount; got != want {
		t.Errorf("scanner.Err: got %v, want %v", got, want)
	}
}

// largeReader returns an invalid count that is larger than the number
// of bytes requested.
type largeReader struct{}

func (largeReader) Read(p []byte) (int, error) {
	return len(p) + 1, nil
}

// being valid at the next read call. If Peek returns fewer than n bytes, it
// also returns an error explaining why the read is short. The error is
// [ErrBufferFull] if n is larger than b's buffer size.
//
// Calling Peek prevents a [Reader.UnreadByte] or [Reader.UnreadRune] call from succeeding
// until the next read operation.
func (b *Reader) Peek(n int) ([]byte, error) {
	if n < 0 {

		}
	}
	return hdr, &tr.blk, p.err
}

// readOldGNUSparseMap reads the sparse map from the old GNU sparse format.
// The sparse map is stored in the tar header if it's small enough.
// If it's larger than four entries, then one or more extension headers are used
// to store the rest of the sparse map.
//
// The Header.Size does not reflect the size of any extended headers used.