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Diffstat (limited to 'src/couch_inets/http_base_64.erl')
| -rw-r--r-- | src/couch_inets/http_base_64.erl | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/src/couch_inets/http_base_64.erl b/src/couch_inets/http_base_64.erl new file mode 100644 index 00000000..00cd966b --- /dev/null +++ b/src/couch_inets/http_base_64.erl @@ -0,0 +1,126 @@ +%% ``The contents of this file are subject to the Erlang Public License, +%% Version 1.1, (the "License"); you may not use this file except in +%% compliance with the License. You should have received a copy of the +%% Erlang Public License along with this software. If not, it can be +%% retrieved via the world wide web at http://www.erlang.org/. +%% +%% Software distributed under the License is distributed on an "AS IS" +%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See +%% the License for the specific language governing rights and limitations +%% under the License. +%% +%% The Initial Developer of the Original Code is Ericsson Utvecklings AB. +%% Portions created by Ericsson are Copyright 1999, Ericsson Utvecklings +%% AB. All Rights Reserved.'' +%% +%% $Id$ +%% +%% Description: Implements base 64 encode and decode, see RFC2045. +-module(http_base_64). + +-export([encode/1, decode/1]). + +-deprecated({'_', '_', next_major_release}). + +%%%========================================================================= +%%% API +%%%========================================================================= + +%%------------------------------------------------------------------------- +%% encode(ASCII) -> Base64 +%% ASCII - string() +%% Base64 - string() +%% +%% Description: Encodes a plain ASCII string into base64. +%%------------------------------------------------------------------------- +encode(ASCII) when is_list(ASCII) -> + encode_base64_list(ASCII). + + +%%------------------------------------------------------------------------- +%% decode(Base64) -> ASCII +%% Base64 - string() +%% ASCII - string() +%% +%% Description: Decodes an base64 encoded string to plain ASCII. +%%------------------------------------------------------------------------- +decode(Base64) when is_list(Base64) -> + decode_base64_list(sixtets(Base64), []). + +%%%======================================================================== +%%% Internal functions +%%%======================================================================== + +%% Base-64 encoding: take 6 bits at a time from the head of the binary +%% and emit it as 8 bit characters. +encode_base64_list([]) -> + []; +encode_base64_list([A]) -> + [int_to_b64(A bsr 2), int_to_b64((A band 3) bsl 4), $=, $=]; +encode_base64_list([A,B]) -> + [int_to_b64(A bsr 2), int_to_b64(((A band 3) bsl 4) bor (B bsr 4)), + int_to_b64((B band 15) bsl 2), $=]; +encode_base64_list([A,B,C|Ls]) -> + encode_base64_list_do(A,B,C, Ls). + +encode_base64_list_do(A,B,C, Rest) -> + BB = (A bsl 16) bor (B bsl 8) bor C, + [int_to_b64(BB bsr 18), int_to_b64((BB bsr 12) band 63), + int_to_b64((BB bsr 6) band 63), int_to_b64(BB band 63) | + encode_base64_list(Rest)]. + +int_to_b64(X) when X >= 0, X =< 25 -> X + $A; +int_to_b64(X) when X >= 26, X =< 51 -> X - 26 + $a; +int_to_b64(X) when X >= 52, X =< 61 -> X - 52 + $0; +int_to_b64(62) -> $+; +int_to_b64(63) -> $/. + +%% This version works by consuming groups of 4 input characters to create +%% a group of 3 output characters, with the three special-cases for +%% end-of-input first: + +decode_base64_list({[],[]}, Acc) -> + lists:reverse(Acc); +decode_base64_list({[Sixtet1,Sixtet2,pad,pad], []}, Acc) -> + Bits2x6 = (Sixtet1 bsl 18) bor (Sixtet2 bsl 12), + Octet1 = Bits2x6 bsr 16, + lists:reverse([Octet1 | Acc]); +decode_base64_list({[Sixtet1,Sixtet2,Sixtet3,pad], []}, Acc) -> + Bits3x6 = (Sixtet1 bsl 18) bor (Sixtet2 bsl 12) bor (Sixtet3 bsl 6), + Octet1 = Bits3x6 bsr 16, + Octet2 = (Bits3x6 bsr 8) band 16#ff, + lists:reverse([Octet2, Octet1 | Acc]); +decode_base64_list({[Sixtet1,Sixtet2,Sixtet3,Sixtet4],Rest}, Acc) when + Sixtet1 =/= pad, + Sixtet2 =/= pad, + Sixtet3 =/= pad, + Sixtet4 =/= pad -> + Bits4x6 = + (Sixtet1 bsl 18) bor (Sixtet2 bsl 12) bor (Sixtet3 bsl 6) bor Sixtet4, + Octet1 = Bits4x6 bsr 16, + Octet2 = (Bits4x6 bsr 8) band 16#ff, + Octet3 = Bits4x6 band 16#ff, + decode_base64_list(sixtets(Rest), [Octet3, Octet2, Octet1 | Acc]). + +b64_to_int(X) when X >= $A, X =< $Z -> X - $A; +b64_to_int(X) when X >= $a, X =< $z -> X - $a + 26; +b64_to_int(X) when X >= $0, X =< $9 -> X - $0 + 52; +b64_to_int($+) -> 62; +b64_to_int($/) -> 63; +b64_to_int($=) -> pad; % Padding will be removed by decode_base64_list/2 +b64_to_int(_) -> ignore. % Not in base 64 should be ignored + +sixtets(Str) -> + sixtets(Str, []). + +sixtets([], Sixtets) -> + {lists:reverse(Sixtets), []}; +sixtets(Rest, Sixtets) when length(Sixtets) == 4 -> + {lists:reverse(Sixtets), Rest}; +sixtets([Base64 | Tail], Sixtets) when length(Sixtets) < 4 -> + case b64_to_int(Base64) of + ignore -> + sixtets(Tail, Sixtets); + Int -> + sixtets(Tail, [Int | Sixtets]) + end. |