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authorHans Bolinder <[email protected]>2017-05-15 14:16:52 +0200
committerHans Bolinder <[email protected]>2017-05-18 15:29:24 +0200
commitb57e89092409193457aa2ad026c895d5559d428d (patch)
treea408601f6bedacfb69052a7b9d4f96ccb2590549 /lib/stdlib/src
parent05dce0f330c83278cb134c7235a5353ce4116307 (diff)
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stdlib: Add io_lib:limit_term/2
The term returned by io_lib:limit_term(Term, Depth) should return the same string if substituted for Term in io_lib:format("~P", [Term, Depth]) or io_lib:format("~W", [Term, Depth]).
Diffstat (limited to 'lib/stdlib/src')
-rw-r--r--lib/stdlib/src/io_lib.erl115
1 files changed, 115 insertions, 0 deletions
diff --git a/lib/stdlib/src/io_lib.erl b/lib/stdlib/src/io_lib.erl
index 5ed2f4d888..9d447418f8 100644
--- a/lib/stdlib/src/io_lib.erl
+++ b/lib/stdlib/src/io_lib.erl
@@ -84,6 +84,8 @@
-export([write_unicode_string/1, write_unicode_char/1,
deep_unicode_char_list/1]).
+-export([limit_term/2]).
+
-export_type([chars/0, latin1_string/0, continuation/0,
fread_error/0, fread_item/0, format_spec/0]).
@@ -911,3 +913,116 @@ binrev(L) ->
binrev(L, T) ->
list_to_binary(lists:reverse(L, T)).
+
+-spec limit_term(term(), non_neg_integer()) -> term().
+
+%% The intention is to mimic the depth limitation of io_lib:write()
+%% and io_lib_pretty:print(). The leaves ('...') should never be
+%% seen when printed with the same depth. Bitstrings are never
+%% truncated, which is OK as long as they are not sent to other nodes.
+limit_term(Term, Depth) ->
+ try test_limit(Term, Depth) of
+ ok -> Term
+ catch
+ throw:limit ->
+ limit(Term, Depth)
+ end.
+
+limit(_, 0) -> '...';
+limit([H|T]=L, D) ->
+ if
+ D =:= 1 -> '...';
+ true ->
+ case printable_list(L) of
+ true -> L;
+ false ->
+ [limit(H, D-1)|limit_tail(T, D-1)]
+ end
+ end;
+limit(Term, D) when is_map(Term) ->
+ limit_map(Term, D);
+limit({}=T, _D) -> T;
+limit(T, D) when is_tuple(T) ->
+ if
+ D =:= 1 -> '...';
+ true ->
+ list_to_tuple([limit(element(1, T), D-1)|
+ limit_tail(tl(tuple_to_list(T)), D-1)])
+ end;
+limit(<<_/bitstring>>=Term, D) -> limit_bitstring(Term, D);
+limit(Term, _D) -> Term.
+
+limit_tail([], _D) -> [];
+limit_tail(_, 1) -> ['...'];
+limit_tail([H|T], D) ->
+ [limit(H, D-1)|limit_tail(T, D-1)];
+limit_tail(Other, D) ->
+ limit(Other, D-1).
+
+%% Cannot limit maps properly since there is no guarantee that
+%% maps:from_list() creates a map with the same internal ordering of
+%% the selected associations as in Map.
+limit_map(Map, D) ->
+ maps:from_list(erts_internal:maps_to_list(Map, D)).
+%% maps:from_list(limit_map_body(erts_internal:maps_to_list(Map, D), D)).
+
+%% limit_map_body(_, 0) -> [{'...', '...'}];
+%% limit_map_body([], _) -> [];
+%% limit_map_body([{K,V}], D) -> [limit_map_assoc(K, V, D)];
+%% limit_map_body([{K,V}|KVs], D) ->
+%% [limit_map_assoc(K, V, D) | limit_map_body(KVs, D-1)].
+
+%% limit_map_assoc(K, V, D) ->
+%% {limit(K, D-1), limit(V, D-1)}.
+
+limit_bitstring(B, _D) -> B. %% Keeps all printable binaries.
+
+test_limit(_, 0) -> throw(limit);
+test_limit([H|T]=L, D) when is_integer(D) ->
+ if
+ D =:= 1 -> throw(limit);
+ true ->
+ case printable_list(L) of
+ true -> ok;
+ false ->
+ test_limit(H, D-1),
+ test_limit_tail(T, D-1)
+ end
+ end;
+test_limit(Term, D) when is_map(Term) ->
+ test_limit_map(Term, D);
+test_limit({}, _D) -> ok;
+test_limit(T, D) when is_tuple(T) ->
+ test_limit_tuple(T, 1, tuple_size(T), D);
+test_limit(<<_/bitstring>>=Term, D) -> test_limit_bitstring(Term, D);
+test_limit(_Term, _D) -> ok.
+
+test_limit_tail([], _D) -> ok;
+test_limit_tail(_, 1) -> throw(limit);
+test_limit_tail([H|T], D) ->
+ test_limit(H, D-1),
+ test_limit_tail(T, D-1);
+test_limit_tail(Other, D) ->
+ test_limit(Other, D-1).
+
+test_limit_tuple(_T, I, Sz, _D) when I > Sz -> ok;
+test_limit_tuple(_, _, _, 1) -> throw(limit);
+test_limit_tuple(T, I, Sz, D) ->
+ test_limit(element(I, T), D-1),
+ test_limit_tuple(T, I+1, Sz, D-1).
+
+test_limit_map(_Map, _D) -> ok.
+%% test_limit_map_body(erts_internal:maps_to_list(Map, D), D).
+
+%% test_limit_map_body(_, 0) -> throw(limit);
+%% test_limit_map_body([], _) -> ok;
+%% test_limit_map_body([{K,V}], D) -> test_limit_map_assoc(K, V, D);
+%% test_limit_map_body([{K,V}|KVs], D) ->
+%% test_limit_map_assoc(K, V, D),
+%% test_limit_map_body(KVs, D-1).
+
+%% test_limit_map_assoc(K, V, D) ->
+%% test_limit(K, D-1),
+%% test_limit(V, D-1).
+
+test_limit_bitstring(_, _) -> ok.