File 2342-stdlib-Fix-mime_decode-1-binary-matching-performance.patch of Package erlang
From ec7353ae51cc02c7b381a5142322a2b560bd0fab Mon Sep 17 00:00:00 2001
From: Jesse Stimpson <jstimpson@bandwidth.com>
Date: Fri, 24 Feb 2017 13:03:20 -0500
Subject: [PATCH] stdlib: Fix mime_decode/1 binary matching performance
Symptom: Throughput of base64:mime_decode/1 significantly lower than
base64:decode/1.
Problem: tail_contains_more/2 prevents compiler from delaying creation
of sub binaries.
Solution: Restructure mime_decode_binary/2 to use binary matching best
practices from the Efficiency Guide.
See ERL-366
---
lib/stdlib/src/base64.erl | 67 +++++++++++++++++++++++++++--------------------
1 file changed, 39 insertions(+), 28 deletions(-)
diff --git a/lib/stdlib/src/base64.erl b/lib/stdlib/src/base64.erl
index bf259e669..0c8d81791 100644
--- a/lib/stdlib/src/base64.erl
+++ b/lib/stdlib/src/base64.erl
@@ -219,38 +219,49 @@ mime_decode_binary(Result, <<0:8,T/bits>>) ->
mime_decode_binary(Result, T);
mime_decode_binary(Result0, <<C:8,T/bits>>) ->
case element(C, ?DECODE_MAP) of
- Bits when is_integer(Bits) ->
- mime_decode_binary(<<Result0/bits,Bits:6>>, T);
- eq ->
- case tail_contains_more(T, false) of
- {<<>>, Eq} ->
- %% No more valid data.
- case bit_size(Result0) rem 8 of
- 0 ->
- %% '====' is not uncommon.
- Result0;
- 4 when Eq ->
- %% enforce at least one more '=' only ignoring illegals and spacing
- Split = byte_size(Result0) - 1,
- <<Result:Split/bytes,_:4>> = Result0,
- Result;
- 2 ->
- %% remove 2 bits
- Split = byte_size(Result0) - 1,
- <<Result:Split/bytes,_:2>> = Result0,
- Result
- end;
- {More, _} ->
- %% More valid data, skip the eq as invalid
- mime_decode_binary(Result0, More)
- end;
- _ ->
- mime_decode_binary(Result0, T)
+ Bits when is_integer(Bits) ->
+ mime_decode_binary(<<Result0/bits,Bits:6>>, T);
+ eq ->
+ mime_decode_binary_after_eq(Result0, T, false);
+ _ ->
+ mime_decode_binary(Result0, T)
end;
-mime_decode_binary(Result, <<>>) ->
+mime_decode_binary(Result, _) ->
true = is_binary(Result),
Result.
+mime_decode_binary_after_eq(Result, <<0:8,T/bits>>, Eq) ->
+ mime_decode_binary_after_eq(Result, T, Eq);
+mime_decode_binary_after_eq(Result0, <<C:8,T/bits>>, Eq) ->
+ case element(C, ?DECODE_MAP) of
+ bad ->
+ mime_decode_binary_after_eq(Result0, T, Eq);
+ ws ->
+ mime_decode_binary_after_eq(Result0, T, Eq);
+ eq ->
+ mime_decode_binary_after_eq(Result0, T, true);
+ Bits when is_integer(Bits) ->
+ %% More valid data, skip the eq as invalid
+ mime_decode_binary(<<Result0/bits,Bits:6>>, T)
+ end;
+mime_decode_binary_after_eq(Result0, <<>>, Eq) ->
+ %% No more valid data.
+ case bit_size(Result0) rem 8 of
+ 0 ->
+ %% '====' is not uncommon.
+ Result0;
+ 4 when Eq ->
+ %% enforce at least one more '=' only ignoring illegals and spacing
+ Split = byte_size(Result0) - 1,
+ <<Result:Split/bytes,_:4>> = Result0,
+ Result;
+ 2 ->
+ %% remove 2 bits
+ Split = byte_size(Result0) - 1,
+ <<Result:Split/bytes,_:2>> = Result0,
+ Result
+ end.
+
decode([], A) -> A;
decode([$=,$=,C2,C1|Cs], A) ->
Bits2x6 = (b64d(C1) bsl 18) bor (b64d(C2) bsl 12),
--
2.12.0