Add a comment about forwardCopy semantics.
diff --git a/decode.go b/decode.go
index 8a1eca0..d4bb615 100644
--- a/decode.go
+++ b/decode.go
@@ -127,6 +127,11 @@
if offset <= 0 || d < offset || length > len(dst)-d {
return nil, ErrCorrupt
}
+ // Copy from an earlier sub-slice of dst to a later sub-slice. Unlike
+ // the built-in copy function, this byte-by-byte copy always runs
+ // forwards, even if the slices overlap. Conceptually, this is:
+ //
+ // d += forwardCopy(dst[d:d+length], dst[d-offset:])
for end := d + length; d != end; d++ {
dst[d] = dst[d-offset]
}
