  We report a comprehensive catalog of emission episodes within long gamma-ray
bursts (GRBs) that are separated by a quiescent period during which gamma-ray
emission falls below the background level. We use a fully automated
identification method for an unbiased, large scale and expandable search. We
examine a comprehensive sample of long GRBs from the BATSE, Swift and Fermi
missions, assembling a total searched set of 2710 GRBs, the largest catalog of
isolated emission episodes so far. Our search extends out to [-1000s,750s]
around the burst trigger, expanding the covered time interval beyond previous
studies and far beyond the nominal durations (T90) of most bursts. We compare
our results to previous works by identifying pre-peak emission (or precursors),
defined as isolated emission periods prior to the episode with the highest peak
luminosity of the burst. We also systematically search for similarly defined
periods after the burst's peak emission. We find that the pre-peak and
post-peak emission periods are statistically similar, possibly indicating a
common origin. For the analyzed GRBs, we identify 24% to have more than one
isolated emission episode, with 11% having at least one pre-peak event and 15%
having at least one post-peak event. We identify GRB activity significantly
beyond their T90, which can be important for understanding the central engine
activity as well as, e.g., gravitational-wave searches.
