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gen-base64-tbl
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gen-base64-tbl
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#!/usr/bin/ruby
#############################################################################
## Generates the base64-decoding table for mapping an encoded 'digit' into
## the 6-bit value it represents.
##
## --------------------------------------------------------------------------
## Copyright (C) 2009 Young Hyun
##
## This program 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 2 of the License, or
## (at your option) any later version.
##
## This program 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 this program; if not, write to the Free Software
## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
##
#############################################################################
require 'enumerator'
encode_tbl = []
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".each_byte do
|c|
encode_tbl << c
end
decode_tbl = [ 64 ] * 256
encode_tbl.each_with_index do |c, i|
decode_tbl[c] = i
end
#p decode_tbl
puts <<EOF
/*
** A base64-decoding table for mapping an encoded 'digit' into the 6-bit
** value it represents. A non-base64 character maps to 64 (this works for
** the full unsigned 8-bit range, including NUL).
*/
EOF
puts "static const unsigned char decode_tbl[256] =\n{"
decode_tbl.each_slice(16) do |values|
puts " " + values.map { |x| sprintf "%2d", (x || 255) }.join(", ") + ","
end
puts "};"