Remove leading and trailing whitespaces #247
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from field-values to be RFC 7230 compliant.
| @@ -215,6 +215,9 @@ tokenize_header_value(undefined) -> | |||
| tokenize_header_value(V) -> | |||
| reversed_tokens(trim_and_reverse(V, false), [], []). | |||
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| trim_leading_and_trailing_ws(S) -> | |||
| re:replace(S, "^[ \\t]*|[ \\t]*$", "", [global, {return, list}]). | |||
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suggest string:trim(String, both, [9,32]). for performance;
RE input: ' hello there ', output: 'hello there', speed: 6.276318
TRIM input: ' hello there ', output: 'hello there', speed: 1.377677
Count = 1_000_000,
{Time, _} = timer:tc(fun() -> lists:foreach(fun(_) -> F() end, lists:seq(1, Count)) end),
Time / Count.```
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I had the same idea too but then noticed mochiweb supports Erlang 18+ versions and string:trim/1 is an Erlang 20+ function.
string:strip/3 can be used but it would have to be called twice once for space and once for the tab character.
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suggest
string:trim(String, both, [9,32]).for performance;RE input: ' hello there ', output: 'hello there', speed: 6.276318 TRIM input: ' hello there ', output: 'hello there', speed: 1.377677
Thats significant. Can we make a runtime distinction and differentiate between the Erlang versions? So if Erlang > 20 use trim/3 else use strip/3?
I had the same idea too but then noticed mochiweb supports Erlang 18+ versions and
string:trim/1is an Erlang 20+ function.
If we want to be RFC compliant, we can't usetrim/1because that would remove more chars thanspaceandtab.
OWS = *( SP / HTAB )
; optional whitespace
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On closer read the -define(IS_WHITESPACE(C),
(C =:= $\s orelse C =:= $\t orelse C =:= $\r orelse C =:= $\n)).
is_whitespace(C) ->
?IS_WHITESPACE(C).
trim_leading_and_trailing_ws(S) ->
trim_trailing_ws(lists:dropwhile(fun is_whitespace/1, S), [], 0).
trim_trailing_ws([C | Rest], Acc, N) when ?IS_WHITESPACE(C) ->
trim_trailing_ws(Rest, [C | Acc], 1 + N);
trim_trailing_ws([C | Rest], Acc, N) ->
trim_trailing_ws(Rest, [C | Acc], 0);
trim_trailing_ws([], Acc, N) ->
lists:reverse(lists:nthtail(Acc, N)). |
But 2 times 1> mochiweb_headers_playground:test().
T1 (trim_leading_and_trailing_ws) : 13.43003
T2 (trim_and_reverse) : 0.404285
T3 (trim_leading_and_trailing_ws_2): 0.609125I made a small playground file which can be used to test this (with all your work and ideas)! So, let us use the following? trim_and_reverse(S) ->
trim_and_reverse(trim_and_reverse(S, false), false). |
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I'll merge this and apply the suggestions (a test and more performant implementation) in a follow-up |
from field-values to be RFC 7230 compliant.
Fix #246