stdlib: Optimize base64 functions

A few test cases with zeroes are added. They were not handled correctly
before.

The access of DECODE_MAP is moved into the inlined function b64d, for
symmetry.

The function b64e is also inlined. The speed-up is small, but
measurable.

Note: encode(List), decode(List) and mime_decode(List) no longer call
list_to_binary. This can break code that calls the functions with
I/O-lists as input.

1 files changed, 433 insertions, 266 deletions

diff --git a/lib/stdlib/src/base64.erl b/lib/stdlib/src/base64.erl
index c8cf6fdffe..6311f3c86b 100644
--- a/lib/stdlib/src/base64.erl
+++ b/lib/stdlib/src/base64.erl
@@ -24,89 +24,95 @@
 -export([encode/1, decode/1, mime_decode/1,
 	 encode_to_string/1, decode_to_string/1, mime_decode_to_string/1]).
 
-%%-------------------------------------------------------------------------
 %% The following type is a subtype of string() for return values
 %% of (some) functions of this module.
-%%-------------------------------------------------------------------------
-
 -type ascii_string() :: [1..255].
 -type ascii_binary() :: binary().
 
-%%-------------------------------------------------------------------------
-%% encode_to_string(ASCII) -> Base64String
-%%	ASCII - string() | binary()
-%%	Base64String - string()
-%%                                   
-%% Description: Encodes a plain ASCII string (or binary) into base64.
-%%-------------------------------------------------------------------------
-
 -spec encode_to_string(Data) -> Base64String when
       Data :: ascii_string() | ascii_binary(),
       Base64String :: ascii_string().
 
 encode_to_string(Bin) when is_binary(Bin) ->
-    encode_to_string(binary_to_list(Bin));
+    encode_binary_to_string(Bin);
 encode_to_string(List) when is_list(List) ->
-    encode_l(List).
-
-%%-------------------------------------------------------------------------
-%% encode(ASCII) -> Base64
-%%	ASCII - string() | binary()
-%%	Base64 - binary()
-%%                                   
-%% Description: Encodes a plain ASCII string (or binary) into base64.
-%%-------------------------------------------------------------------------
+    encode_list_to_string(List).
 
 -spec encode(Data) -> Base64 when
       Data :: ascii_string() | ascii_binary(),
       Base64 :: ascii_binary().
 
 encode(Bin) when is_binary(Bin) ->
-    encode_binary(Bin);
+    encode_binary(Bin, <<>>);
 encode(List) when is_list(List) ->
-    list_to_binary(encode_l(List)).
+    encode_list(List, <<>>).
 
--spec encode_l(ascii_string()) -> ascii_string().
+encode_binary_to_string(<<>>) ->
+    [];
+encode_binary_to_string(<<B1:8>>) ->
+    [b64e(B1 bsr 2),
+     b64e((B1 band 3) bsl 4), $=, $=];
+encode_binary_to_string(<<B1:8, B2:8>>) ->
+    [b64e(B1 bsr 2),
+     b64e(((B1 band 3) bsl 4) bor (B2 bsr 4)),
+     b64e((B2 band 15) bsl 2), $=];
+encode_binary_to_string(<<B1:8, B2:8, B3:8, Ls/bits>>) ->
+    BB = (B1 bsl 16) bor (B2 bsl 8) bor B3,
+    [b64e(BB bsr 18),
+     b64e((BB bsr 12) band 63),
+     b64e((BB bsr 6) band 63),
+     b64e(BB band 63) | encode_binary_to_string(Ls)].
 
-encode_l([]) ->
+encode_list_to_string([]) ->
     [];
-encode_l([A]) ->
-    [b64e(A bsr 2),
-     b64e((A band 3) bsl 4), $=, $=];
-encode_l([A,B]) ->
-    [b64e(A bsr 2),
-     b64e(((A band 3) bsl 4) bor (B bsr 4)), 
-     b64e((B band 15) bsl 2), $=];
-encode_l([A,B,C|Ls]) ->
-    BB = (A bsl 16) bor (B bsl 8) bor C,
+encode_list_to_string([B1]) ->
+    [b64e(B1 bsr 2),
+     b64e((B1 band 3) bsl 4), $=, $=];
+encode_list_to_string([B1,B2]) ->
+    [b64e(B1 bsr 2),
+     b64e(((B1 band 3) bsl 4) bor (B2 bsr 4)),
+     b64e((B2 band 15) bsl 2), $=];
+encode_list_to_string([B1,B2,B3|Ls]) ->
+    BB = (B1 bsl 16) bor (B2 bsl 8) bor B3,
     [b64e(BB bsr 18),
      b64e((BB bsr 12) band 63), 
      b64e((BB bsr 6) band 63),
-     b64e(BB band 63) | encode_l(Ls)].
-
-encode_binary(Bin) ->
-    Split = 3*(byte_size(Bin) div 3),
-    <<Main0:Split/binary,Rest/binary>> = Bin,
-    Main = << <<(b64e(C)):8>> || <<C:6>> <= Main0 >>,
-    case Rest of
-	<<A:6,B:6,C:4>> ->
-	    <<Main/binary,(b64e(A)):8,(b64e(B)):8,(b64e(C bsl 2)):8,$=:8>>;
-	<<A:6,B:2>> ->
-	    <<Main/binary,(b64e(A)):8,(b64e(B bsl 4)):8,$=:8,$=:8>>;
-	<<>> ->
-	    Main
-    end.
+     b64e(BB band 63) | encode_list_to_string(Ls)].
 
-%%-------------------------------------------------------------------------
-%% mime_decode(Base64) -> ASCII
-%% decode(Base64) -> ASCII
-%%	Base64 - string() | binary()
-%%	ASCII - binary()
-%%                                    
-%% Description: Decodes an base64 encoded string to plain ASCII.
-%% mime_decode strips away all characters not Base64 before converting,
-%% whereas decode crashes if an illegal character is found
-%%-------------------------------------------------------------------------
+encode_binary(<<>>, A) ->
+    A;
+encode_binary(<<B1:8>>, A) ->
+    <<A/binary,(b64e(B1 bsr 2)):8,(b64e((B1 band 3) bsl 4)):8,$=:8,$=:8>>;
+encode_binary(<<B1:8, B2:8>>, A) ->
+    <<A/binary,(b64e(B1 bsr 2)):8,
+      (b64e(((B1 band 3) bsl 4) bor (B2 bsr 4))):8,
+      (b64e((B2 band 15) bsl 2)):8, $=:8>>;
+encode_binary(<<B1:8, B2:8, B3:8, Ls/bits>>, A) ->
+    BB = (B1 bsl 16) bor (B2 bsl 8) bor B3,
+    encode_binary(Ls,
+                  <<A/binary,(b64e(BB bsr 18)):8,
+                    (b64e((BB bsr 12) band 63)):8,
+                    (b64e((BB bsr 6) band 63)):8,
+                    (b64e(BB band 63)):8>>).
+
+encode_list([], A) ->
+    A;
+encode_list([B1], A) ->
+    <<A/binary,(b64e(B1 bsr 2)):8,(b64e((B1 band 3) bsl 4)):8,$=:8,$=:8>>;
+encode_list([B1,B2], A) ->
+    <<A/binary,(b64e(B1 bsr 2)):8,
+      (b64e(((B1 band 3) bsl 4) bor (B2 bsr 4))):8,
+      (b64e((B2 band 15) bsl 2)):8, $=:8>>;
+encode_list([B1,B2,B3|Ls], A) ->
+    BB = (B1 bsl 16) bor (B2 bsl 8) bor B3,
+    encode_list(Ls,
+                <<A/binary,(b64e(BB bsr 18)):8,
+                  (b64e((BB bsr 12) band 63)):8,
+                  (b64e((BB bsr 6) band 63)):8,
+                  (b64e(BB band 63)):8>>).
+
+%% mime_decode strips away all characters not Base64 before
+%% converting, whereas decode crashes if an illegal character is found
 
 -spec decode(Base64) -> Data when
       Base64 :: ascii_string() | ascii_binary(),
@@ -122,158 +128,280 @@ decode(List) when is_list(List) ->
       Data :: ascii_binary().
 
 mime_decode(Bin) when is_binary(Bin) ->
-    mime_decode_binary(<<>>, Bin);
+    mime_decode_binary(Bin, <<>>);
 mime_decode(List) when is_list(List) ->
-    mime_decode(list_to_binary(List)).
+    mime_decode_list(List, <<>>).
 
--spec decode_l(ascii_string()) -> ascii_string().
-
-decode_l(List) ->
-    L = strip_spaces(List, []),
-    decode(L, []).
-
--spec mime_decode_l(ascii_string()) -> ascii_string().
-
-mime_decode_l(List) ->
-    L = strip_illegal(List, [], 0),
-    decode(L, []).
-
-%%-------------------------------------------------------------------------
-%% mime_decode_to_string(Base64) -> ASCII
-%% decode_to_string(Base64) -> ASCII
-%%	Base64 - string() | binary()
-%%	ASCII - binary()
-%%
-%% Description: Decodes an base64 encoded string to plain ASCII.
-%% mime_decode strips away all characters not Base64 before converting,
-%% whereas decode crashes if an illegal character is found
-%%-------------------------------------------------------------------------
+%% mime_decode_to_string strips away all characters not Base64 before
+%% converting, whereas decode_to_string crashes if an illegal
+%% character is found
 
 -spec decode_to_string(Base64) -> DataString when
       Base64 :: ascii_string() | ascii_binary(),
       DataString :: ascii_string().
 
 decode_to_string(Bin) when is_binary(Bin) ->
-    decode_to_string(binary_to_list(Bin));
+    decode_binary_to_string(Bin);
 decode_to_string(List) when is_list(List) ->
-    decode_l(List).
+    decode_list_to_string(List).
 
 -spec mime_decode_to_string(Base64) -> DataString when
       Base64 :: ascii_string() | ascii_binary(),
       DataString :: ascii_string().
 
 mime_decode_to_string(Bin) when is_binary(Bin) ->
-    mime_decode_to_string(binary_to_list(Bin));
+    mime_decode_binary_to_string(Bin);
 mime_decode_to_string(List) when is_list(List) ->
-    mime_decode_l(List).
-
-%% One-based decode map.
--define(DECODE_MAP,
-	{bad,bad,bad,bad,bad,bad,bad,bad,ws,ws,bad,bad,ws,bad,bad, %1-15
-	 bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad, %16-31
-	 ws,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,62,bad,bad,bad,63, %32-47
-	 52,53,54,55,56,57,58,59,60,61,bad,bad,bad,eq,bad,bad, %48-63
-	 bad,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,
-	 15,16,17,18,19,20,21,22,23,24,25,bad,bad,bad,bad,bad,
-	 bad,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,
-	 41,42,43,44,45,46,47,48,49,50,51,bad,bad,bad,bad,bad,
-	 bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
-	 bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
-	 bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
-	 bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
-	 bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
-	 bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
-	 bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
-	 bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad}).
+    mime_decode_list_to_string(List).
 
-decode_binary(<<C1:8, Cs/bits>>, A) ->
-    case element(C1, ?DECODE_MAP) of
-        ws -> decode_binary(Cs, A);
-        B1 -> decode_binary(Cs, A, B1)
+%% Skipping pad character if not at end of string. Also liberal about
+%% excess padding and skipping of other illegal (non-base64 alphabet)
+%% characters. See section 3.3 of RFC4648
+mime_decode_list([0 | Cs], A) ->
+    mime_decode_list(Cs, A);
+mime_decode_list([C1 | Cs], A) ->
+    case b64d(C1) of
+        B1 when is_integer(B1) -> mime_decode_list(Cs, A, B1);
+        _ -> mime_decode_list(Cs, A)  % eq is padding
     end;
-decode_binary(<<>>, A) ->
+mime_decode_list([], A) ->
     A.
 
-decode_binary(<<C2:8, Cs/bits>>, A, B1) ->
-    case element(C2, ?DECODE_MAP) of
-        ws -> decode_binary(Cs, A, B1);
-        B2 -> decode_binary(Cs, A, B1, B2)
+mime_decode_list([0 | Cs], A, B1) ->
+    mime_decode_list(Cs, A, B1);
+mime_decode_list([C2 | Cs], A, B1) ->
+    case b64d(C2) of
+        B2 when is_integer(B2) ->
+            mime_decode_list(Cs, A, B1, B2);
+        _ -> mime_decode_list(Cs, A, B1) % eq is padding
     end.
 
-decode_binary(<<C3:8, Cs/bits>>, A, B1, B2) ->
-    case element(C3, ?DECODE_MAP) of
-        ws -> decode_binary(Cs, A, B1, B2);
-        B3 -> decode_binary(Cs, A, B1, B2, B3)
+mime_decode_list([0 | Cs], A, B1, B2) ->
+    mime_decode_list(Cs, A, B1, B2);
+mime_decode_list([C3 | Cs], A, B1, B2) ->
+    case b64d(C3) of
+        B3 when is_integer(B3) ->
+            mime_decode_list(Cs, A, B1, B2, B3);
+        eq=B3 ->
+            mime_decode_list_after_eq(Cs, A, B1, B2, B3);
+        _ -> mime_decode_list(Cs, A, B1, B2)
     end.
 
-decode_binary(<<C4:8, Cs/bits>>, A, B1, B2, B3) ->
-    case element(C4, ?DECODE_MAP) of
-        ws                -> decode_binary(Cs, A, B1, B2, B3);
-        eq when B3 =:= eq -> only_ws_binary(Cs, <<A/binary,B1:6,(B2 bsr 4):2>>);
-        eq                -> only_ws_binary(Cs, <<A/binary,B1:6,B2:6,(B3 bsr 2):4>>);
-        B4                -> decode_binary(Cs, <<A/binary,B1:6,B2:6,B3:6,B4:6>>)
+mime_decode_list([0 | Cs], A, B1, B2, B3) ->
+    mime_decode_list(Cs, A, B1, B2, B3);
+mime_decode_list([C4 | Cs], A, B1, B2, B3) ->
+    case b64d(C4) of
+        B4 when is_integer(B4) ->
+            mime_decode_list(Cs, <<A/bits,B1:6,B2:6,B3:6,B4:6>>);
+        eq ->
+            mime_decode_list_after_eq(Cs, A, B1, B2, B3);
+        _ -> mime_decode_list(Cs, A, B1, B2, B3)
     end.
 
-only_ws_binary(<<>>, A) ->
-    A;
-only_ws_binary(<<C:8, Cs/bits>>, A) ->
-    case element(C, ?DECODE_MAP) of
-        ws -> only_ws_binary(Cs, A);
-        _ -> erlang:error(function_clause)
+mime_decode_list_after_eq([0 | Cs], A, B1, B2, B3) ->
+    mime_decode_list_after_eq(Cs, A, B1, B2, B3);
+mime_decode_list_after_eq([C | Cs], A, B1, B2, B3) ->
+    case b64d(C) of
+        B when is_integer(B) ->
+            %% More valid data, skip the eq as invalid
+            case B3 of
+                eq -> mime_decode_list(Cs, A, B1, B2, B);
+                _ -> mime_decode_list(Cs, <<A/bits,B1:6,B2:6,B3:6,B:6>>)
+            end;
+        _ -> mime_decode_list_after_eq(Cs, A, B1, B2, B3)
+    end;
+mime_decode_list_after_eq([], A, B1, B2, eq) ->
+    <<A/binary,B1:6,(B2 bsr 4):2>>;
+mime_decode_list_after_eq([], A, B1, B2, B3) ->
+    <<A/binary,B1:6,B2:6,(B3 bsr 2):4>>.
+
+mime_decode_binary(<<0:8, Cs/bits>>, A) ->
+    mime_decode_binary(Cs, A);
+mime_decode_binary(<<C1:8, Cs/bits>>, A) ->
+    case b64d(C1) of
+        B1 when is_integer(B1) -> mime_decode_binary(Cs, A, B1);
+        _ -> mime_decode_binary(Cs, A)  % eq is padding
+    end;
+mime_decode_binary(<<>>, A) ->
+    A.
+
+mime_decode_binary(<<0:8, Cs/bits>>, A, B1) ->
+    mime_decode_binary(Cs, A, B1);
+mime_decode_binary(<<C2:8, Cs/bits>>, A, B1) ->
+    case b64d(C2) of
+        B2 when is_integer(B2) ->
+            mime_decode_binary(Cs, A, B1, B2);
+        _ -> mime_decode_binary(Cs, A, B1) % eq is padding
     end.
 
-%% Skipping pad character if not at end of string. Also liberal about
-%% excess padding and skipping of other illegal (non-base64 alphabet)
-%% characters. See section 3.3 of RFC4648
-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);
+mime_decode_binary(<<0:8, Cs/bits>>, A, B1, B2) ->
+    mime_decode_binary(Cs, A, B1, B2);
+mime_decode_binary(<<C3:8, Cs/bits>>, A, B1, B2) ->
+    case b64d(C3) of
+        B3 when is_integer(B3) ->
+            mime_decode_binary(Cs, A, B1, B2, B3);
+        eq=B3 ->
+            mime_decode_binary_after_eq(Cs, A, B1, B2, B3);
+        _ -> mime_decode_binary(Cs, A, B1, B2)
+    end.
+
+mime_decode_binary(<<0:8, Cs/bits>>, A, B1, B2, B3) ->
+    mime_decode_binary(Cs, A, B1, B2, B3);
+mime_decode_binary(<<C4:8, Cs/bits>>, A, B1, B2, B3) ->
+    case b64d(C4) of
+        B4 when is_integer(B4) ->
+            mime_decode_binary(Cs, <<A/bits,B1:6,B2:6,B3:6,B4:6>>);
         eq ->
-            mime_decode_binary_after_eq(Result0, T, false);
-        _ ->
-            mime_decode_binary(Result0, T)
+            mime_decode_binary_after_eq(Cs, A, B1, B2, B3);
+        _ -> mime_decode_binary(Cs, A, B1, B2, B3)
+    end.
+
+mime_decode_binary_after_eq(<<0:8, Cs/bits>>, A, B1, B2, B3) ->
+    mime_decode_binary_after_eq(Cs, A, B1, B2, B3);
+mime_decode_binary_after_eq(<<C:8, Cs/bits>>, A, B1, B2, B3) ->
+    case b64d(C) of
+        B when is_integer(B) ->
+            %% More valid data, skip the eq as invalid
+            case B3 of
+                eq -> mime_decode_binary(Cs, A, B1, B2, B);
+                _ -> mime_decode_binary(Cs, <<A/bits,B1:6,B2:6,B3:6,B:6>>)
+            end;
+        _ -> mime_decode_binary_after_eq(Cs, A, B1, B2, B3)
     end;
-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);
+mime_decode_binary_after_eq(<<>>, A, B1, B2, eq) ->
+    <<A/binary,B1:6,(B2 bsr 4):2>>;
+mime_decode_binary_after_eq(<<>>, A, B1, B2, B3) ->
+    <<A/binary,B1:6,B2:6,(B3 bsr 2):4>>.
+
+mime_decode_list_to_string([0 | Cs]) ->
+    mime_decode_list_to_string(Cs);
+mime_decode_list_to_string([C1 | Cs]) ->
+    case b64d(C1) of
+        B1 when is_integer(B1) -> mime_decode_list_to_string(Cs, B1);
+        _ -> mime_decode_list_to_string(Cs) % eq is padding
+    end;
+mime_decode_list_to_string([]) ->
+    [].
+
+mime_decode_list_to_string([0 | Cs], B1) ->
+    mime_decode_list_to_string(Cs, B1);
+mime_decode_list_to_string([C2 | Cs], B1) ->
+    case b64d(C2) of
+        B2 when is_integer(B2) ->
+            mime_decode_list_to_string(Cs, B1, B2);
+        _ -> mime_decode_list_to_string(Cs, B1) % eq is padding
+    end.
+
+mime_decode_list_to_string([0 | Cs], B1, B2) ->
+    mime_decode_list_to_string(Cs, B1, B2);
+mime_decode_list_to_string([C3 | Cs], B1, B2) ->
+    case b64d(C3) of
+        B3 when is_integer(B3) ->
+            mime_decode_list_to_string(Cs, B1, B2, B3);
+        eq=B3 -> mime_decode_list_to_string_after_eq(Cs, B1, B2, B3);
+        _ -> mime_decode_list_to_string(Cs, B1, B2)
+    end.
+
+mime_decode_list_to_string([0 | Cs], B1, B2, B3) ->
+    mime_decode_list_to_string(Cs, B1, B2, B3);
+mime_decode_list_to_string([C4 | Cs], B1, B2, B3) ->
+    case b64d(C4) of
+        B4 when is_integer(B4) ->
+            Bits4x6 = (B1 bsl 18) bor (B2 bsl 12) bor (B3 bsl 6) bor B4,
+            Octet1 = Bits4x6 bsr 16,
+            Octet2 = (Bits4x6 bsr 8) band 16#ff,
+            Octet3 = Bits4x6 band 16#ff,
+            [Octet1, Octet2, Octet3 | mime_decode_list_to_string(Cs)];
         eq ->
-            mime_decode_binary_after_eq(Result0, T, true);
-        Bits when is_integer(Bits) ->
+            mime_decode_list_to_string_after_eq(Cs, B1, B2, B3);
+        _ -> mime_decode_list_to_string(Cs, B1, B2, B3)
+    end.
+
+mime_decode_list_to_string_after_eq([0 | Cs], B1, B2, B3) ->
+    mime_decode_list_to_string_after_eq(Cs, B1, B2, B3);
+mime_decode_list_to_string_after_eq([C | Cs], B1, B2, B3) ->
+    case b64d(C) of
+        B when is_integer(B) ->
             %% More valid data, skip the eq as invalid
-            mime_decode_binary(<<Result0/bits,Bits:6>>, T)
+            case B3 of
+                eq -> mime_decode_list_to_string(Cs, B1, B2, B);
+                _ ->
+                    Bits4x6 = (B1 bsl 18) bor (B2 bsl 12) bor (B3 bsl 6) bor B,
+                    Octet1 = Bits4x6 bsr 16,
+                    Octet2 = (Bits4x6 bsr 8) band 16#ff,
+                    Octet3 = Bits4x6 band 16#ff,
+                    [Octet1, Octet2, Octet3 | mime_decode_list_to_string(Cs)]
+            end;
+        _ -> mime_decode_list_to_string_after_eq(Cs, B1, B2, B3)
+    end;
+mime_decode_list_to_string_after_eq([], B1, B2, eq) ->
+    binary_to_list(<<B1:6,(B2 bsr 4):2>>);
+mime_decode_list_to_string_after_eq([], B1, B2, B3) ->
+    binary_to_list(<<B1:6,B2:6,(B3 bsr 2):4>>).
+
+mime_decode_binary_to_string(<<0:8, Cs/bits>>) ->
+    mime_decode_binary_to_string(Cs);
+mime_decode_binary_to_string(<<C1:8, Cs/bits>>) ->
+    case b64d(C1) of
+        B1 when is_integer(B1) -> mime_decode_binary_to_string(Cs, B1);
+        _ -> mime_decode_binary_to_string(Cs) % eq is padding
     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
+mime_decode_binary_to_string(<<>>) ->
+    [].
+
+mime_decode_binary_to_string(<<0:8, Cs/bits>>, B1) ->
+    mime_decode_binary_to_string(Cs, B1);
+mime_decode_binary_to_string(<<C2:8, Cs/bits>>, B1) ->
+    case b64d(C2) of
+        B2 when is_integer(B2) ->
+            mime_decode_binary_to_string(Cs, B1, B2);
+        _ -> mime_decode_binary_to_string(Cs, B1) % eq is padding
+    end.
+
+mime_decode_binary_to_string(<<0:8, Cs/bits>>, B1, B2) ->
+    mime_decode_binary_to_string(Cs, B1, B2);
+mime_decode_binary_to_string(<<C3:8, Cs/bits>>, B1, B2) ->
+    case b64d(C3) of
+        B3 when is_integer(B3) ->
+            mime_decode_binary_to_string(Cs, B1, B2, B3);
+        eq=B3 -> mime_decode_binary_to_string_after_eq(Cs, B1, B2, B3);
+        _ -> mime_decode_binary_to_string(Cs, B1, B2)
+    end.
+
+mime_decode_binary_to_string(<<0:8, Cs/bits>>, B1, B2, B3) ->
+    mime_decode_binary_to_string(Cs, B1, B2, B3);
+mime_decode_binary_to_string(<<C4:8, Cs/bits>>, B1, B2, B3) ->
+    case b64d(C4) of
+        B4 when is_integer(B4) ->
+            Bits4x6 = (B1 bsl 18) bor (B2 bsl 12) bor (B3 bsl 6) bor B4,
+            Octet1 = Bits4x6 bsr 16,
+            Octet2 = (Bits4x6 bsr 8) band 16#ff,
+            Octet3 = Bits4x6 band 16#ff,
+            [Octet1, Octet2, Octet3 | mime_decode_binary_to_string(Cs)];
+        eq ->
+            mime_decode_binary_to_string_after_eq(Cs, B1, B2, B3);
+        _ -> mime_decode_binary_to_string(Cs, B1, B2, B3)
     end.
 
+mime_decode_binary_to_string_after_eq(<<0:8, Cs/bits>>, B1, B2, B3) ->
+    mime_decode_binary_to_string_after_eq(Cs, B1, B2, B3);
+mime_decode_binary_to_string_after_eq(<<C:8, Cs/bits>>=Cs0, B1, B2, B3) ->
+    case b64d(C) of
+        B when is_integer(B) ->
+            %% More valid data, skip the eq as invalid
+            case B3 of
+                eq -> mime_decode_binary_to_string(Cs, B1, B2, B);
+                _ -> mime_decode_binary_to_string(Cs0, B1, B2, B3)
+            end;
+        _ -> mime_decode_binary_to_string_after_eq(Cs, B1, B2, B3)
+    end;
+mime_decode_binary_to_string_after_eq(<<>>, B1, B2, eq) ->
+    binary_to_list(<<B1:6,(B2 bsr 4):2>>);
+mime_decode_binary_to_string_after_eq(<<>>, B1, B2, B3) ->
+    binary_to_list(<<B1:6,B2:6,(B3 bsr 2):4>>).
+
 decode_list([C1 | Cs], A) ->
-    case element(C1, ?DECODE_MAP) of
+    case b64d(C1) of
         ws -> decode_list(Cs, A);
         B1 -> decode_list(Cs, A, B1)
     end;
@@ -281,122 +409,167 @@ decode_list([], A) ->
     A.
 
 decode_list([C2 | Cs], A, B1) ->
-    case element(C2, ?DECODE_MAP) of
+    case b64d(C2) of
         ws -> decode_list(Cs, A, B1);
         B2 -> decode_list(Cs, A, B1, B2)
     end.
 
 decode_list([C3 | Cs], A, B1, B2) ->
-    case element(C3, ?DECODE_MAP) of
+    case b64d(C3) of
         ws -> decode_list(Cs, A, B1, B2);
         B3 -> decode_list(Cs, A, B1, B2, B3)
     end.
 
 decode_list([C4 | Cs], A, B1, B2, B3) ->
-    case element(C4, ?DECODE_MAP) of
+    case b64d(C4) of
         ws                -> decode_list(Cs, A, B1, B2, B3);
         eq when B3 =:= eq -> only_ws(Cs, <<A/binary,B1:6,(B2 bsr 4):2>>);
         eq                -> only_ws(Cs, <<A/binary,B1:6,B2:6,(B3 bsr 2):4>>);
         B4                -> decode_list(Cs, <<A/binary,B1:6,B2:6,B3:6,B4:6>>)
     end.
 
+decode_binary(<<C1:8, Cs/bits>>, A) ->
+    case b64d(C1) of
+        ws -> decode_binary(Cs, A);
+        B1 -> decode_binary(Cs, A, B1)
+    end;
+decode_binary(<<>>, A) ->
+    A.
+
+decode_binary(<<C2:8, Cs/bits>>, A, B1) ->
+    case b64d(C2) of
+        ws -> decode_binary(Cs, A, B1);
+        B2 -> decode_binary(Cs, A, B1, B2)
+    end.
+
+decode_binary(<<C3:8, Cs/bits>>, A, B1, B2) ->
+    case b64d(C3) of
+        ws -> decode_binary(Cs, A, B1, B2);
+        B3 -> decode_binary(Cs, A, B1, B2, B3)
+    end.
+
+decode_binary(<<C4:8, Cs/bits>>, A, B1, B2, B3) ->
+    case b64d(C4) of
+        ws                -> decode_binary(Cs, A, B1, B2, B3);
+        eq when B3 =:= eq -> only_ws_binary(Cs, <<A/binary,B1:6,(B2 bsr 4):2>>);
+        eq                -> only_ws_binary(Cs, <<A/binary,B1:6,B2:6,(B3 bsr 2):4>>);
+        B4                -> decode_binary(Cs, <<A/binary,B1:6,B2:6,B3:6,B4:6>>)
+    end.
+
+decode_list_to_string([C1 | Cs]) ->
+    case b64d(C1) of
+        ws -> decode_list_to_string(Cs);
+        B1 -> decode_list_to_string(Cs, B1)
+    end;
+decode_list_to_string([]) ->
+    [].
+
+decode_list_to_string([C2 | Cs], B1) ->
+    case b64d(C2) of
+        ws -> decode_list_to_string(Cs, B1);
+        B2 -> decode_list_to_string(Cs, B1, B2)
+    end.
+
+decode_list_to_string([C3 | Cs], B1, B2) ->
+    case b64d(C3) of
+        ws -> decode_list_to_string(Cs, B1, B2);
+        B3 -> decode_list_to_string(Cs, B1, B2, B3)
+    end.
+
+decode_list_to_string([C4 | Cs], B1, B2, B3) ->
+    case b64d(C4) of
+        ws ->
+            decode_list_to_string(Cs, B1, B2, B3);
+        eq when B3 =:= eq ->
+            only_ws(Cs, binary_to_list(<<B1:6,(B2 bsr 4):2>>));
+        eq ->
+            only_ws(Cs, binary_to_list(<<B1:6,B2:6,(B3 bsr 2):4>>));
+        B4 ->
+            Bits4x6 = (B1 bsl 18) bor (B2 bsl 12) bor (B3 bsl 6) bor B4,
+            Octet1 = Bits4x6 bsr 16,
+            Octet2 = (Bits4x6 bsr 8) band 16#ff,
+            Octet3 = Bits4x6 band 16#ff,
+            [Octet1, Octet2, Octet3 | decode_list_to_string(Cs)]
+    end.
+
 only_ws([], A) ->
     A;
 only_ws([C | Cs], A) ->
-    case element(C, ?DECODE_MAP) of
+    case b64d(C) of
         ws -> only_ws(Cs, A);
         _ -> erlang:error(function_clause)
     end.
 
-decode([], A) -> A;
-decode([$=,$=,C2,C1|Cs], A) ->
-    Bits2x6 = (b64d(C1) bsl 18) bor (b64d(C2) bsl 12),
-    Octet1 = Bits2x6 bsr 16,
-    decode(Cs, [Octet1|A]);
-decode([$=,C3,C2,C1|Cs], A) ->
-    Bits3x6 = (b64d(C1) bsl 18) bor (b64d(C2) bsl 12)
-	bor (b64d(C3) bsl 6),
-    Octet1 = Bits3x6 bsr 16,
-    Octet2 = (Bits3x6 bsr 8) band 16#ff,
-    decode(Cs, [Octet1,Octet2|A]);
-decode([C4,C3,C2,C1| Cs], A) ->
-    Bits4x6 = (b64d(C1) bsl 18) bor (b64d(C2) bsl 12)
-	bor (b64d(C3) bsl 6) bor b64d(C4),
-    Octet1 = Bits4x6 bsr 16,
-    Octet2 = (Bits4x6 bsr 8) band 16#ff,
-    Octet3 = Bits4x6 band 16#ff,
-    decode(Cs, [Octet1,Octet2,Octet3|A]).
+decode_binary_to_string(<<C1:8, Cs/bits>>) ->
+    case b64d(C1) of
+        ws -> decode_binary_to_string(Cs);
+        B1 -> decode_binary_to_string(Cs, B1)
+    end;
+decode_binary_to_string(<<>>) ->
+    [].
 
-%%%========================================================================
-%%% Internal functions
-%%%========================================================================
+decode_binary_to_string(<<C2:8, Cs/bits>>, B1) ->
+    case b64d(C2) of
+        ws -> decode_binary_to_string(Cs, B1);
+        B2 -> decode_binary_to_string(Cs, B1, B2)
+    end.
 
-strip_spaces([], A) -> A;
-strip_spaces([$\s|Cs], A) -> strip_spaces(Cs, A);
-strip_spaces([$\t|Cs], A) -> strip_spaces(Cs, A);
-strip_spaces([$\r|Cs], A) -> strip_spaces(Cs, A);
-strip_spaces([$\n|Cs], A) -> strip_spaces(Cs, A);
-strip_spaces([C|Cs], A) -> strip_spaces(Cs, [C | A]).
+decode_binary_to_string(<<C3:8, Cs/bits>>, B1, B2) ->
+    case b64d(C3) of
+        ws -> decode_binary_to_string(Cs, B1, B2);
+        B3 -> decode_binary_to_string(Cs, B1, B2, B3)
+    end.
 
-%% Skipping pad character if not at end of string. Also liberal about
-%% excess padding and skipping of other illegal (non-base64 alphabet)
-%% characters. See section 3.3 of RFC4648
-strip_illegal([], A, _Cnt) ->
-    A;
-strip_illegal([0|Cs], A, Cnt) ->
-    strip_illegal(Cs, A, Cnt);
-strip_illegal([C|Cs], A, Cnt) ->
-    case element(C, ?DECODE_MAP) of
-	bad ->
-	    strip_illegal(Cs, A, Cnt);
-	ws ->
-	    strip_illegal(Cs, A, Cnt);
-	eq ->
-	    case {tail_contains_more(Cs, false), Cnt rem 4} of
-		{{[], _}, 0} ->
-		    A;            %% Ignore extra =
-		{{[], true}, 2} ->
-		    [$=|[$=|A]];  %% 'XX=='
-		{{[], _}, 3} ->
-		    [$=|A];       %% 'XXX='
-		{{[H|T], _}, _} ->
-		    %% more data, skip equals
-		    strip_illegal(T, [H|A], Cnt+1)
-	    end;
-	_ ->
-	    strip_illegal(Cs, [C|A], Cnt+1)
+decode_binary_to_string(<<C4:8, Cs/bits>>, B1, B2, B3) ->
+    case b64d(C4) of
+        ws -> decode_binary_to_string(Cs, B1, B2, B3);
+        eq when B3 =:= eq ->
+            only_ws_binary(Cs, binary_to_list(<<B1:6,(B2 bsr 4):2>>));
+        eq ->
+            only_ws_binary(Cs, binary_to_list(<<B1:6,B2:6,(B3 bsr 2):4>>));
+        B4 ->
+            Bits4x6 = (B1 bsl 18) bor (B2 bsl 12) bor (B3 bsl 6) bor B4,
+            Octet1 = Bits4x6 bsr 16,
+            Octet2 = (Bits4x6 bsr 8) band 16#ff,
+            Octet3 = Bits4x6 band 16#ff,
+            [Octet1, Octet2, Octet3 | decode_binary_to_string(Cs)]
     end.
 
-%% Search the tail for more valid data and remember if we saw
-%% another equals along the way.
-tail_contains_more([], Eq) ->
-    {[], Eq};
-tail_contains_more(<<>>, Eq) ->
-    {<<>>, Eq};
-tail_contains_more([C|T]=More, Eq) ->
-    case element(C, ?DECODE_MAP) of
-	bad ->
-	    tail_contains_more(T, Eq);
-	ws ->
-	    tail_contains_more(T, Eq);
-	eq ->
-	    tail_contains_more(T, true);
-	_ ->
-	    {More, Eq}
-    end;
-tail_contains_more(<<C:8,T/bits>> =More, Eq) ->
-    case element(C, ?DECODE_MAP) of
-	bad ->
-	    tail_contains_more(T, Eq);
-	ws ->
-	    tail_contains_more(T, Eq);
-	eq ->
-	    tail_contains_more(T, true);
-	_ ->
-	    {More, Eq}
+only_ws_binary(<<>>, A) ->
+    A;
+only_ws_binary(<<C:8, Cs/bits>>, A) ->
+    case b64d(C) of
+        ws -> only_ws_binary(Cs, A);
+        _ -> erlang:error(function_clause)
     end.
-    
+
+%%%========================================================================
+%%% Internal functions
+%%%========================================================================
+
 %% accessors 
+-compile({inline, [{b64d, 1}]}).
+%% One-based decode map.
+b64d(X) ->
+    element(X,
+            {bad,bad,bad,bad,bad,bad,bad,bad,ws,ws,bad,bad,ws,bad,bad, %1-15
+             bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad, %16-31
+             ws,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,62,bad,bad,bad,63, %32-47
+             52,53,54,55,56,57,58,59,60,61,bad,bad,bad,eq,bad,bad, %48-63
+             bad,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,
+             15,16,17,18,19,20,21,22,23,24,25,bad,bad,bad,bad,bad,
+             bad,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,
+             41,42,43,44,45,46,47,48,49,50,51,bad,bad,bad,bad,bad,
+             bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
+             bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
+             bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
+             bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
+             bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
+             bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
+             bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,
+             bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad,bad}).
+
+-compile({inline, [{b64e, 1}]}).
 b64e(X) ->
     element(X+1,
 	    {$A, $B, $C, $D, $E, $F, $G, $H, $I, $J, $K, $L, $M, $N,
@@ -404,9 +577,3 @@ b64e(X) ->
 	     $a, $b, $c, $d, $e, $f, $g, $h, $i, $j, $k, $l, $m, $n,
 	     $o, $p, $q, $r, $s, $t, $u, $v, $w, $x, $y, $z,
 	     $0, $1, $2, $3, $4, $5, $6, $7, $8, $9, $+, $/}).
-
-
-b64d(X) ->
-    b64d_ok(element(X, ?DECODE_MAP)).
-
-b64d_ok(I) when is_integer(I) -> I.