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authorBjörn Gustavsson <[email protected]>2012-11-28 08:54:16 +0100
committerBjörn Gustavsson <[email protected]>2012-12-06 14:22:37 +0100
commit5af45916c69a5e3ad4027a06c56b5b620e05c283 (patch)
tree69e4faea25871cb68fd4fc8c7ff502478452ff7d
parentb38a42c5eacceee57333e26948216d199c123e84 (diff)
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Teach asn1ct_imm to optimize alignment
-rw-r--r--lib/asn1/src/asn1ct_imm.erl118
1 files changed, 110 insertions, 8 deletions
diff --git a/lib/asn1/src/asn1ct_imm.erl b/lib/asn1/src/asn1ct_imm.erl
index 1d1013b0a9..1b6a25b917 100644
--- a/lib/asn1/src/asn1ct_imm.erl
+++ b/lib/asn1/src/asn1ct_imm.erl
@@ -20,7 +20,8 @@
-module(asn1ct_imm).
-export([per_dec_boolean/0,per_dec_enumerated/2,per_dec_enumerated/3,
per_dec_integer/2,per_dec_length/3,per_dec_named_integer/3,
- per_dec_octet_string/2,
+ per_dec_octet_string/2]).
+-export([optimize_alignment/1,optimize_alignment/2,
dec_slim_cg/2,dec_code_gen/2]).
-export([effective_constraint/2]).
-import(asn1ct_gen, [emit/1]).
@@ -28,7 +29,8 @@
-record(st, {var,
base}).
-dec_slim_cg(Imm, BytesVar) ->
+dec_slim_cg(Imm0, BytesVar) ->
+ {Imm,_} = optimize_alignment(Imm0),
asn1ct_name:new(v),
[H|T] = atom_to_list(asn1ct_name:curr(v)) ++ "@",
VarBase = [H-($a-$A)|T],
@@ -45,6 +47,13 @@ dec_code_gen(Imm, BytesVar) ->
"end"]),
ok.
+optimize_alignment(Imm) ->
+ opt_al(Imm, unknown).
+
+optimize_alignment(Imm, Al) ->
+ opt_al(Imm, Al).
+
+
per_dec_boolean() ->
{map,{get_bits,1,[1]},[{0,false},{1,true}]}.
@@ -211,6 +220,91 @@ per_num_bits(N) when N =< 128 -> 7;
per_num_bits(N) when N =< 255 -> 8.
%%%
+%%% Remove unnecessary aligning to octet boundaries.
+%%%
+
+opt_al({get_bits,E0,Opts0}, A0) ->
+ {E,A1} = opt_al(E0, A0),
+ Opts = opt_al_1(A1, Opts0),
+ A = update_al(A1, E, Opts),
+ {{get_bits,E,Opts},A};
+opt_al({call,Fun,E0}, A0) ->
+ {E,A} = opt_al(E0, A0),
+ {{call,Fun,E},A};
+opt_al({convert,Op,E0}, A0) ->
+ {E,A} = opt_al(E0, A0),
+ {{convert,Op,E},A};
+opt_al({value,E0}, A0) ->
+ {E,A} = opt_al(E0, A0),
+ {{value,E},A};
+opt_al({add,E0,I}, A0) when is_integer(I) ->
+ {E,A} = opt_al(E0, A0),
+ {{add,E,I},A};
+opt_al({test,E0,V,B0}, A0) ->
+ {E,A1} = opt_al(E0, A0),
+ {B,A2} = opt_al(B0, A1),
+ {{test,E,V,B},A2};
+opt_al({'case',Cs0}, A0) ->
+ {Cs,A} = opt_al_cs(Cs0, A0),
+ {{'case',Cs},A};
+opt_al({map,E0,Cs}, A0) ->
+ {E,A} = opt_al(E0, A0),
+ {{map,E,Cs},A};
+opt_al(I, A) when is_integer(I) ->
+ {I,A}.
+
+opt_al_cs([C0|Cs0], A0) ->
+ {C,A1} = opt_al(C0, A0),
+ {Cs,A2} = opt_al_cs(Cs0, A0),
+ {[C|Cs],merge_al(A1, A2)};
+opt_al_cs([], _) -> {[],none}.
+
+merge_al(unknown, _) -> unknown;
+merge_al(Other, none) -> Other;
+merge_al(_, unknown) -> unknown;
+merge_al(I0, I1) ->
+ case {I0 rem 8,I1 rem 8} of
+ {I,I} -> I;
+ {_,_} -> unknown
+ end.
+
+opt_al_1(unknown, Opts) ->
+ Opts;
+opt_al_1(A, Opts0) ->
+ case alignment(Opts0) of
+ none ->
+ Opts0;
+ full ->
+ case A rem 8 of
+ 0 ->
+ %% Already in alignment.
+ proplists:delete(align, Opts0);
+ Bits ->
+ %% Cheaper alignment with a constant padding.
+ Opts1 = proplists:delete(align, Opts0),
+ [{align,8-Bits }|Opts1]
+ end;
+ A -> %Assertion.
+ Opts0
+ end.
+
+update_al(A0, E, Opts) ->
+ A = case alignment(Opts) of
+ none -> A0;
+ full -> 0;
+ Bits when is_integer(A0) ->
+ 0 = (A0 + Bits) rem 8; %Assertion.
+ _ ->
+ 0
+ end,
+ [U] = [U || U <- Opts, is_integer(U)],
+ if
+ U rem 8 =:= 0 -> A;
+ is_integer(A), is_integer(E) -> A + U*E;
+ true -> unknown
+ end.
+
+%%%
%%% Flatten the intermediate format and assign temporaries.
%%%
@@ -288,16 +382,21 @@ flatten_hoist_align_1([], Ab, Acc) ->
{[Ab],lists:reverse(Acc)}.
flatten_align({get_bits,{SrcBits,SrcBuf},U,Dst}=Gb0, Pre, St0) ->
- case is_aligned(U) of
- false ->
+ case alignment(U) of
+ none ->
flatten_align_1(U, Dst, Pre++[Gb0], St0);
- true ->
+ full ->
{PadBits,St1} = new_var("Pad", St0),
{DstBuf,St2} = new_var("Buf", St1),
Ab = {align_bits,SrcBuf,PadBits},
Agb = {get_bits,{PadBits,SrcBuf},[1],{'_',DstBuf}},
Gb = {get_bits,{SrcBits,DstBuf},U,Dst},
- flatten_align_1(U, Dst, Pre++[Ab,Agb,Gb], St2)
+ flatten_align_1(U, Dst, Pre++[Ab,Agb,Gb], St2);
+ PadBits when is_integer(PadBits), PadBits > 0 ->
+ {DstBuf,St1} = new_var("Buf", St0),
+ Agb = {get_bits,{PadBits,SrcBuf},[1],{'_',DstBuf}},
+ Gb = {get_bits,{SrcBits,DstBuf},U,Dst},
+ flatten_align_1(U, Dst, Pre++[Agb,Gb], St1)
end.
flatten_align_1(U, {D,_}=Dst, Pre, St) ->
@@ -316,8 +415,11 @@ new_var_pair(St0) ->
new_var(Tag, #st{base=VarBase,var=N}=St) ->
{VarBase++Tag++integer_to_list(N),St#st{var=N+1}}.
-is_aligned(Fl) ->
- proplists:get_bool(align, Fl).
+alignment([{align,false}|_]) -> none;
+alignment([{align,true}|_]) -> full;
+alignment([{align,Bits}|_]) -> Bits;
+alignment([_|T]) -> alignment(T);
+alignment([]) -> none.
is_non_zero(Fl) ->
lists:member(non_zero, Fl).