-// "allow_fast_path" is a parameter that says if there is at least 16
-// readable bytes in "ip". It is currently only used by SnappyArrayWriter.
+// // The difference between TryFastAppend and Append is that TryFastAppend
+// // is allowed to read up to <available> bytes from the input buffer,
+// // whereas Append is allowed to read <length>.
+// //
+// // Also, TryFastAppend is allowed to return false, declining the append,
+// // without it being a fatal error -- just "return false" would be
+// // a perfectly legal implementation of TryFastAppend. The intention
+// // is for TryFastAppend to allow a fast path in the common case of
+// // a small append.
+// //
+// // NOTE(user): TryFastAppend must always return decline (return false)
+// // if <length> is 61 or more, as in this case the literal length is not
+// // decoded fully. In practice, this should not be a big problem,
+// // as it is unlikely that one would implement a fast path accepting
+// // this much data.
+// bool TryFastAppend(const char* ip, size_t available, size_t length);
+// };