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adam@1592
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1 (* Copyright (c) 2011, Adam Chlipala
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2 * All rights reserved.
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3 *
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4 * Redistribution and use in source and binary forms, with or without
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5 * modification, are permitted provided that the following conditions are met:
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6 *
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7 * - Redistributions of source code must retain the above copyright notice,
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8 * this list of conditions and the following disclaimer.
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9 * - Redistributions in binary form must reproduce the above copyright notice,
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10 * this list of conditions and the following disclaimer in the documentation
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11 * and/or other materials provided with the distribution.
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12 * - The names of contributors may not be used to endorse or promote products
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13 * derived from this software without specific prior written permission.
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14 *
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15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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16 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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18 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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19 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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20 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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21 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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22 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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23 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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24 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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25 * POSSIBILITY OF SUCH DAMAGE.
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26 *)
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27
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28 (* UTF-8 conversion *)
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29
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30 structure Utf8 :> UTF8 = struct
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31
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32 fun byte n = str (chr (Word.toInt n))
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33
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34 fun encode n =
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35 if n <= 0 then
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36 raise Fail "Invalid character to UTF-8-encode"
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37 else if n <= 0x7F then
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38 str (chr n)
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39 else if n <= 0x7FF then
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40 let
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41 val w = Word.fromInt n
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42 val b1 = Word.orb (Word.fromInt (128 + 64), Word.>> (w, Word.fromInt 6))
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43 val b2 = Word.orb (Word.fromInt 128, Word.andb (w, Word.fromInt 63))
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44 in
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45 byte b1 ^ byte b2
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46 end
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47 else if n <= 0xFFFF then
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48 let
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49 val w = Word.fromInt n
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50 val b1 = Word.orb (Word.fromInt (128 + 64 + 32), Word.>> (w, Word.fromInt 12))
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51 val b2 = Word.orb (Word.fromInt 128, Word.andb (Word.>> (w, Word.fromInt 6), Word.fromInt 63))
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52 val b3 = Word.orb (Word.fromInt 128, Word.andb (w, Word.fromInt 63))
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53 in
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54 byte b1 ^ byte b2 ^ byte b3
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55 end
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56 else
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57 raise Fail "Exceeded supported range for UTF-8 characters"
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58
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59 end
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