annotate src/utf8.sml @ 2042:336070df8aec

Manual: Heuristic compilation warning
author Adam Chlipala <adam@chlipala.net>
date Sat, 26 Jul 2014 09:39:45 -0400
parents 1c9f8f06c1d6
children
rev   line source
adam@1592 1 (* Copyright (c) 2011, Adam Chlipala
adam@1592 2 * All rights reserved.
adam@1592 3 *
adam@1592 4 * Redistribution and use in source and binary forms, with or without
adam@1592 5 * modification, are permitted provided that the following conditions are met:
adam@1592 6 *
adam@1592 7 * - Redistributions of source code must retain the above copyright notice,
adam@1592 8 * this list of conditions and the following disclaimer.
adam@1592 9 * - Redistributions in binary form must reproduce the above copyright notice,
adam@1592 10 * this list of conditions and the following disclaimer in the documentation
adam@1592 11 * and/or other materials provided with the distribution.
adam@1592 12 * - The names of contributors may not be used to endorse or promote products
adam@1592 13 * derived from this software without specific prior written permission.
adam@1592 14 *
adam@1592 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
adam@1592 16 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
adam@1592 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
adam@1592 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
adam@1592 19 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
adam@1592 20 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
adam@1592 21 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
adam@1592 22 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
adam@1592 23 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
adam@1592 24 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
adam@1592 25 * POSSIBILITY OF SUCH DAMAGE.
adam@1592 26 *)
adam@1592 27
adam@1592 28 (* UTF-8 conversion *)
adam@1592 29
adam@1592 30 structure Utf8 :> UTF8 = struct
adam@1592 31
adam@1592 32 fun byte n = str (chr (Word.toInt n))
adam@1592 33
adam@1592 34 fun encode n =
adam@1592 35 if n <= 0 then
adam@1592 36 raise Fail "Invalid character to UTF-8-encode"
adam@1592 37 else if n <= 0x7F then
adam@1592 38 str (chr n)
adam@1592 39 else if n <= 0x7FF then
adam@1592 40 let
adam@1592 41 val w = Word.fromInt n
adam@1592 42 val b1 = Word.orb (Word.fromInt (128 + 64), Word.>> (w, Word.fromInt 6))
adam@1592 43 val b2 = Word.orb (Word.fromInt 128, Word.andb (w, Word.fromInt 63))
adam@1592 44 in
adam@1592 45 byte b1 ^ byte b2
adam@1592 46 end
adam@1592 47 else if n <= 0xFFFF then
adam@1592 48 let
adam@1592 49 val w = Word.fromInt n
adam@1592 50 val b1 = Word.orb (Word.fromInt (128 + 64 + 32), Word.>> (w, Word.fromInt 12))
adam@1592 51 val b2 = Word.orb (Word.fromInt 128, Word.andb (Word.>> (w, Word.fromInt 6), Word.fromInt 63))
adam@1592 52 val b3 = Word.orb (Word.fromInt 128, Word.andb (w, Word.fromInt 63))
adam@1592 53 in
adam@1592 54 byte b1 ^ byte b2 ^ byte b3
adam@1592 55 end
adam@1592 56 else
adam@1592 57 raise Fail "Exceeded supported range for UTF-8 characters"
adam@1592 58
adam@1592 59 end