diff options
| -rw-r--r-- | lib/stdlib/src/sys.erl | 68 |
1 files changed, 56 insertions, 12 deletions
diff --git a/lib/stdlib/src/sys.erl b/lib/stdlib/src/sys.erl index 8f654841b6..7b161460b0 100644 --- a/lib/stdlib/src/sys.erl +++ b/lib/stdlib/src/sys.erl @@ -595,9 +595,6 @@ stat({out, _Msg, _To}, {Time, Reds, In, Out}) -> {Time, Reds, In, Out+1}; stat({out, _Msg, _To, _State}, {Time, Reds, In, Out}) -> {Time, Reds, In, Out+1}; stat(_, StatData) -> StatData. -trim(N, LogData) -> - lists:sublist(LogData, 1, N-1). - %%----------------------------------------------------------------- %% Debug structure manipulating functions %%----------------------------------------------------------------- @@ -640,22 +637,69 @@ close_log_file(Debug) -> %%----------------------------------------------------------------- %% Keep the last N Log functions %%----------------------------------------------------------------- +%% +%% Streamlined Okasaki queue as base for "keep the last N" log. +%% +%% To the reverse list head we cons new items. +%% The forward list contains elements in insertion order, +%% so the head is the oldest and the one to drop off +%% when the log is full. +%% +%% Here is how we can get away with only using one cons cell +%% to wrap the forward and reverse list, and the log size: +%% +%% A full log does not need a counter; we just cons one +%% and drop one: +%% +%% [ReverseList|ForwardList] +%% +%% A non-full log is filling up to N elements; +%% use a down counter instead of a list as first element: +%% +%% [RemainingToFullCount|ReverseList] nlog_new() -> nlog_new(10). %% -nlog_new(N) when is_integer(N) -> - {N, []}; -nlog_new(NLog) -> - nlog_new(10, NLog). +nlog_new([_|_] = NLog) -> + nlog_new(10, NLog); +nlog_new(N) -> + [N]. % Empty log size N >= 1 %% -nlog_new(NewN, {_N, R}) -> - {NewN, trim(NewN, R)}. +nlog_new(N, NLog) -> + lists:foldl( + fun (Item, NL) -> nlog_put(Item, NL) end, + nlog_new(N), + nlog_get(NLog)). -nlog_put(Item, {N, R}) -> - {N, [Item | trim(N, R)]}. +%% +nlog_put(Item, NLog) -> + case NLog of + [R|FF] when is_list(R) -> + %% Full log + case FF of + [_|F] -> + %% Cons to reverse list, drop from forward list + [[Item|R]|F]; + [] -> + %% Create new forward list from reverse list, + %% create new empty reverse list + [_|F] = lists:reverse(R, [Item]), + [[]|F] + end; + [1|R] -> + %% Log now gets full + [[Item|R]]; + [J|R] -> + %% Filling up to N elements + [J - 1,Item|R] + end. -nlog_get({_N, R}) -> +nlog_get([[]|F]) -> + F; +nlog_get([[_|_] = R|F]) -> + F ++ lists:reverse(R); +nlog_get([_J|R]) -> lists:reverse(R). %%----------------------------------------------------------------- |