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From dav...@apache.org
Subject [16/29] twig commit: updated refs/heads/import to 2d56280
Date Mon, 03 Feb 2014 22:12:30 GMT
Add trunc_io.erl v 1.11 from Matthias Lang

http://www.corelatus.com/~matthias/trunc_io.erl


Project: http://git-wip-us.apache.org/repos/asf/couchdb-twig/repo
Commit: http://git-wip-us.apache.org/repos/asf/couchdb-twig/commit/c4d7baf1
Tree: http://git-wip-us.apache.org/repos/asf/couchdb-twig/tree/c4d7baf1
Diff: http://git-wip-us.apache.org/repos/asf/couchdb-twig/diff/c4d7baf1

Branch: refs/heads/import
Commit: c4d7baf143748a30f1b0991429d760b134065c4c
Parents: 263e017
Author: Adam Kocoloski <adam@cloudant.com>
Authored: Tue Mar 8 22:05:13 2011 -0500
Committer: Adam Kocoloski <adam@cloudant.com>
Committed: Tue Mar 8 22:05:13 2011 -0500

----------------------------------------------------------------------
 src/trunc_io.erl | 215 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 215 insertions(+)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/couchdb-twig/blob/c4d7baf1/src/trunc_io.erl
----------------------------------------------------------------------
diff --git a/src/trunc_io.erl b/src/trunc_io.erl
new file mode 100644
index 0000000..d3d5bb4
--- /dev/null
+++ b/src/trunc_io.erl
@@ -0,0 +1,215 @@
+%% ``The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with your Erlang distribution. If not, it can be
+%% retrieved via the world wide web at http://www.erlang.org/.
+%% 
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%% 
+%% The Initial Developer of the Original Code is Corelatus AB.
+%% Portions created by Corelatus are Copyright 2003, Corelatus
+%% AB. All Rights Reserved.''
+%%
+%% Module to print out terms for logging. Limits by length rather than depth.
+%%
+%% The resulting string may be slightly larger than the limit; the intention
+%% is to provide predictable CPU and memory consumption for formatting
+%% terms, not produce precise string lengths.
+%%
+%% Typical use:
+%%
+%%   trunc_io:print(Term, 500).
+%%
+-module(trunc_io).
+-author('matthias@corelatus.se').
+%% And thanks to Chris Newcombe for a bug fix 
+-export([print/2, fprint/2, safe/2]).               % interface functions
+-export([perf/0, perf/3, perf1/0, test/0, test/2]). % testing functions
+-version("$Id: trunc_io.erl,v 1.11 2009-02-23 12:01:06 matthias Exp $").
+
+
+%% Returns an flattened list containing the ASCII representation of the given
+%% term.
+fprint(T, Max) -> 
+    {L, _} = print(T, Max),
+    lists:flatten(L).
+
+%% Same as print, but never crashes. 
+%%
+%% This is a tradeoff. Print might conceivably crash if it's asked to
+%% print something it doesn't understand, for example some new data
+%% type in a future version of Erlang. If print crashes, we fall back
+%% to io_lib to format the term, but then the formatting is
+%% depth-limited instead of length limited, so you might run out
+%% memory printing it. Out of the frying pan and into the fire.
+%% 
+safe(What, Len) ->
+    case catch print(What, Len) of
+	{L, Used} when list(L) -> {L, Used};
+	_ -> {"unable to print" ++ io_lib:write(What, 99)}
+    end.	     
+
+%% Returns {List, Length}
+print(_, Max) when Max < 0 -> {"...", 3};
+print(Tuple, Max) when tuple(Tuple) -> 
+    {TC, Len} = tuple_contents(Tuple, Max-2),
+    {[${, TC, $}], Len + 2};
+
+%% We assume atoms, floats, funs, integers, PIDs, ports and refs never need 
+%% to be truncated. This isn't strictly true, someone could make an 
+%% arbitrarily long bignum. Let's assume that won't happen unless someone
+%% is being malicious.
+%%
+print(Atom, _Max) when atom(Atom) ->
+    L = atom_to_list(Atom),
+    {L, length(L)};
+
+print(<<>>, _Max) ->
+    {"<<>>", 4};
+
+print(Binary, Max) when binary(Binary) ->
+    B = binary_to_list(Binary, 1, lists:min([Max, size(Binary)])),
+    {L, Len} = alist_start(B, Max-4),
+    {["<<", L, ">>"], Len};
+
+print(Float, _Max) when float(Float) ->
+    L = float_to_list(Float),
+    {L, length(L)};
+
+print(Fun, _Max) when function(Fun) ->
+    L = erlang:fun_to_list(Fun),
+    {L, length(L)};
+
+print(Integer, _Max) when integer(Integer) ->
+    L = integer_to_list(Integer),
+    {L, length(L)};
+
+print(Pid, _Max) when pid(Pid) ->
+    L = pid_to_list(Pid),
+    {L, length(L)};
+
+print(Ref, _Max) when reference(Ref) ->
+    L = erlang:ref_to_list(Ref),
+    {L, length(L)};
+
+print(Port, _Max) when port(Port) ->
+    L = erlang:port_to_list(Port),
+    {L, length(L)};
+
+print(List, Max) when list(List) ->
+    alist_start(List, Max).
+
+%% Returns {List, Length}
+tuple_contents(Tuple, Max) ->
+    L = tuple_to_list(Tuple),
+    list_body(L, Max).
+
+%% Format the inside of a list, i.e. do not add a leading [ or trailing ].
+%% Returns {List, Length}
+list_body([], _) -> {[], 0};
+list_body(_, Max) when Max < 4 -> {"...", 3};
+list_body([H|T], Max) -> 
+    {List, Len} = print(H, Max),
+    {Final, FLen} = list_bodyc(T, Max - Len),
+    {[List|Final], FLen + Len};
+list_body(X, Max) ->  %% improper list
+    {List, Len} = print(X, Max - 1),
+    {[$|,List], Len + 1}.
+
+list_bodyc([], _) -> {[], 0};
+list_bodyc(_, Max) when Max < 4 -> {"...", 3};
+list_bodyc([H|T], Max) -> 
+    {List, Len} = print(H, Max),
+    {Final, FLen} = list_bodyc(T, Max - Len - 1),
+    {[$,, List|Final], FLen + Len + 1};
+list_bodyc(X,Max) ->  %% improper list
+    {List, Len} = print(X, Max - 1),
+    {[$|,List], Len + 1}.
+
+%% The head of a list we hope is ascii. Examples:
+%%
+%% [65,66,67] -> "ABC"
+%% [65,0,67] -> "A"[0,67]
+%% [0,65,66] -> [0,65,66]
+%% [65,b,66] -> "A"[b,66]
+%%
+alist_start([], _) -> {"[]", 2};
+alist_start(_, Max) when Max < 4 -> {"...", 3};
+alist_start([H|T], Max) when H >= 16#20, H =< 16#7e ->  % definitely printable
+    {L, Len} = alist([H|T], Max-1),
+    {[$\"|L], Len + 1};
+alist_start([H|T], Max) when H == 9; H == 10; H == 13 ->   % show as space
+    {L, Len} = alist(T, Max-1),
+    {[$ |L], Len + 1};
+alist_start(L, Max) ->
+    {R, Len} = list_body(L, Max-2),
+    {[$[, R, $]], Len + 2}.
+
+alist([], _) -> {"\"", 1};
+alist(_, Max) when Max < 5 -> {"...\"", 4};
+alist([H|T], Max) when H >= 16#20, H =< 16#7e ->     % definitely printable
+    {L, Len} = alist(T, Max-1),
+    {[H|L], Len + 1};
+alist([H|T], Max) when H == 9; H == 10; H == 13 ->   % show as space
+    {L, Len} = alist(T, Max-1),
+    {[$ |L], Len + 1};
+alist(L, Max) ->
+    {R, Len} = list_body(L, Max-3),
+    {[$\", $[, R, $]], Len + 3}.
+
+
+%%--------------------
+%% The start of a test suite. So far, it only checks for not crashing.
+test() ->
+    test(trunc_io, print).
+
+test(Mod, Func) ->
+    Simple_items = [atom, 1234, 1234.0, {tuple}, [], [list], "string", self(),
+		    <<1,2,3>>, make_ref(), fun() -> ok end],
+    F = fun(A) ->
+		Mod:Func(A, 100),
+		Mod:Func(A, 2),
+		Mod:Func(A, 20)
+	end,
+
+    G = fun(A) ->
+		case catch F(A) of
+		    {'EXIT', _} -> exit({failed, A});
+		    _ -> ok
+		end
+	end,
+    
+    lists:foreach(G, Simple_items),
+    
+    Tuples = [ {1,2,3,a,b,c}, {"abc", def, 1234},
+	       {{{{a},b,c,{d},e}},f}],
+    
+    Lists = [ [1,2,3,4,5,6,7], lists:seq(1,1000),
+	      [{a}, {a,b}, {a, [b,c]}, "def"], [a|b], [$a|$b] ],
+    
+    
+    lists:foreach(G, Tuples),
+    lists:foreach(G, Lists).
+    
+perf() ->
+    {New, _} = timer:tc(trunc_io, perf, [trunc_io, print, 1000]),
+    {Old, _} = timer:tc(trunc_io, perf, [io_lib, write, 1000]),
+    io:fwrite("New code took ~p us, old code ~p\n", [New, Old]).
+
+perf(M, F, Reps) when Reps > 0 ->
+    test(M,F),
+    perf(M,F,Reps-1);
+perf(_,_,_) ->
+    done.    
+
+%% Performance test. Needs a particularly large term I saved as a binary...
+perf1() ->
+    {ok, Bin} = file:read_file("bin"),
+    A = binary_to_term(Bin),
+    {N, _} = timer:tc(trunc_io, print, [A, 1500]),
+    {M, _} = timer:tc(io_lib, write, [A]),
+    {N, M}.
+


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