76 lines
1.9 KiB
Erlang
76 lines
1.9 KiB
Erlang
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%% @author Bob Ippolito <bob@mochimedia.com>
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%% @copyright 2006 Mochi Media, Inc.
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%% @doc Utilities for working with hexadecimal strings.
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-module(mochihex).
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-author('bob@mochimedia.com').
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-export([test/0, to_hex/1, to_bin/1, to_int/1, dehex/1, hexdigit/1]).
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%% @type iolist() = [char() | binary() | iolist()]
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%% @type iodata() = iolist() | binary()
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%% @spec to_hex(integer | iolist()) -> string()
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%% @doc Convert an iolist to a hexadecimal string.
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to_hex(0) ->
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"0";
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to_hex(I) when is_integer(I), I > 0 ->
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to_hex_int(I, []);
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to_hex(B) ->
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to_hex(iolist_to_binary(B), []).
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%% @spec to_bin(string()) -> binary()
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%% @doc Convert a hexadecimal string to a binary.
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to_bin(L) ->
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to_bin(L, []).
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%% @spec to_int(string()) -> integer()
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%% @doc Convert a hexadecimal string to an integer.
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to_int(L) ->
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erlang:list_to_integer(L, 16).
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%% @spec dehex(char()) -> integer()
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%% @doc Convert a hex digit to its integer value.
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dehex(C) when C >= $0, C =< $9 ->
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C - $0;
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dehex(C) when C >= $a, C =< $f ->
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C - $a + 10;
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dehex(C) when C >= $A, C =< $F ->
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C - $A + 10.
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%% @spec hexdigit(integer()) -> char()
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%% @doc Convert an integer less than 16 to a hex digit.
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hexdigit(C) when C >= 0, C =< 9 ->
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C + $0;
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hexdigit(C) when C =< 15 ->
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C + $a - 10.
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%% @spec test() -> ok
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%% @doc Test this module.
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test() ->
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"ff000ff1" = to_hex([255, 0, 15, 241]),
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<<255, 0, 15, 241>> = to_bin("ff000ff1"),
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16#ff000ff1 = to_int("ff000ff1"),
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"ff000ff1" = to_hex(16#ff000ff1),
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ok.
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%% Internal API
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to_hex(<<>>, Acc) ->
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lists:reverse(Acc);
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to_hex(<<C1:4, C2:4, Rest/binary>>, Acc) ->
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to_hex(Rest, [hexdigit(C2), hexdigit(C1) | Acc]).
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to_hex_int(0, Acc) ->
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Acc;
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to_hex_int(I, Acc) ->
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to_hex_int(I bsr 4, [hexdigit(I band 15) | Acc]).
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to_bin([], Acc) ->
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iolist_to_binary(lists:reverse(Acc));
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to_bin([C1, C2 | Rest], Acc) ->
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to_bin(Rest, [(dehex(C1) bsl 4) bor dehex(C2) | Acc]).
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