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pdp10_extint: rewrite in Erlang

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Mikael Pettersson 2019-08-19 22:14:55 +02:00
parent 07d88d7697
commit 54cb1c0a94
1 changed files with 54 additions and 0 deletions
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54
erlang/apps/lib/src/pdp10_extint.erl Normal file
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%%% -*- erlang-indent-level: 2 -*-
%%%
%%% converts between 18 and 36-bit integers and sequences of nonets
%%% Copyright (C) 2013-2019 Mikael Pettersson
%%%
%%% This file is part of pdp10-tools.
%%%
%%% pdp10-tools is free software: you can redistribute it and/or modify
%%% it under the terms of the GNU General Public License as published by
%%% the Free Software Foundation, either version 3 of the License, or
%%% (at your option) any later version.
%%%
%%% pdp10-tools is distributed in the hope that it will be useful,
%%% but WITHOUT ANY WARRANTY; without even the implied warranty of
%%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
%%% GNU General Public License for more details.
%%%
%%% You should have received a copy of the GNU General Public License
%%% along with pdp10-tools. If not, see <http://www.gnu.org/licenses/>.
-module(pdp10_extint).
-export([ uint18_to_ext/1
, uint18_from_ext/1
, uint36_to_ext/1
, uint36_from_ext/1
]).
-include_lib("lib/include/pdp10_stdint.hrl").
%% The PDP10 is big-endian, so the conversions here are big-endian.
%% The bytes (nonets) are numbered in storage order.
-spec uint18_to_ext(uint18_t()) -> [uint9_t()].
uint18_to_ext(U18) ->
[_B0 = (U18 bsr 9) band ?PDP10_UINT9_MAX, _B1 = U18 band ?PDP10_UINT9_MAX].
-spec uint18_from_ext([uint9_t()]) -> uint18_t().
uint18_from_ext([B0, B1]) ->
((B0 band ?PDP10_UINT9_MAX) bsl 9) bor (B1 band ?PDP10_UINT9_MAX).
-spec uint36_to_ext(uint36_t()) -> [uint9_t()].
uint36_to_ext(U36) ->
[_B0 = (U36 bsr 27) band ?PDP10_UINT9_MAX,
_B1 = (U36 bsr 18) band ?PDP10_UINT9_MAX,
_B2 = (U36 bsr 9) band ?PDP10_UINT9_MAX,
_B3 = U36 band ?PDP10_UINT9_MAX].
-spec uint36_from_ext([uint9_t()]) -> uint36_t().
uint36_from_ext([B0, B1, B2, B3]) ->
((B0 band ?PDP10_UINT9_MAX) bsl 27) bor
((B1 band ?PDP10_UINT9_MAX) bsl 18) bor
((B2 band ?PDP10_UINT9_MAX) bsl 9) bor
(B3 band ?PDP10_UINT9_MAX).