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authorHans Nilsson <[email protected]>2016-12-13 10:40:31 +0100
committerHans Nilsson <[email protected]>2016-12-16 15:26:51 +0100
commit767234a17378db0985ca49415ae5b9d3423ed754 (patch)
tree615fb284a57f72647a5beba16f55a210f6632534 /lib/ssh/src/ssh_bits.erl
parent2b36238bc2a2444b97a3d01fa35ab1ceecfe1c4d (diff)
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ssh: Optimze ssh_bits:mpint/1
By using binary constructors we push the hard work down into the emulator
Diffstat (limited to 'lib/ssh/src/ssh_bits.erl')
-rw-r--r--lib/ssh/src/ssh_bits.erl38
1 files changed, 18 insertions, 20 deletions
diff --git a/lib/ssh/src/ssh_bits.erl b/lib/ssh/src/ssh_bits.erl
index cc2e7e2be5..3ce7758447 100644
--- a/lib/ssh/src/ssh_bits.erl
+++ b/lib/ssh/src/ssh_bits.erl
@@ -36,27 +36,25 @@ name_list(NamesList) -> list_to_binary(lists:join($,, NamesList)).
%%% Multi Precision Integer encoding
mpint(-1) -> <<0,0,0,1,16#ff>>;
mpint(0) -> <<0,0,0,0>>;
-mpint(X) when X < 0 -> mpint_neg(X,0,[]);
-mpint(X) -> mpint_pos(X,0,[]).
-
-mpint_neg(-1,I,Ds=[MSB|_]) ->
- if MSB band 16#80 =/= 16#80 ->
- <<?UINT32((I+1)), (list_to_binary([255|Ds]))/binary>>;
- true ->
- <<?UINT32(I), (list_to_binary(Ds))/binary>>
+mpint(I) when I>0 ->
+ <<B1,V/binary>> = binary:encode_unsigned(I),
+ case B1 band 16#80 of
+ 16#80 ->
+ <<(size(V)+2):32/unsigned-big-integer, 0,B1,V/binary >>;
+ _ ->
+ <<(size(V)+1):32/unsigned-big-integer, B1,V/binary >>
end;
-mpint_neg(X,I,Ds) ->
- mpint_neg(X bsr 8,I+1,[(X band 255)|Ds]).
-
-mpint_pos(0,I,Ds=[MSB|_]) ->
- if MSB band 16#80 == 16#80 ->
- <<?UINT32((I+1)), (list_to_binary([0|Ds]))/binary>>;
- true ->
- <<?UINT32(I), (list_to_binary(Ds))/binary>>
- end;
-mpint_pos(X,I,Ds) ->
- mpint_pos(X bsr 8,I+1,[(X band 255)|Ds]).
-
+mpint(N) when N<0 ->
+ Sxn = 8*size(binary:encode_unsigned(-N)),
+ Sxn1 = Sxn+8,
+ <<W:Sxn1>> = <<1, 0:Sxn>>,
+ <<B1,V/binary>> = binary:encode_unsigned(W+N),
+ case B1 band 16#80 of
+ 16#80 ->
+ <<(size(V)+1):32/unsigned-big-integer, B1,V/binary >>;
+ _ ->
+ <<(size(V)+2):32/unsigned-big-integer, 255,B1,V/binary >>
+ end.
%%%----------------------------------------------------------------
%% random/1