Support the full set of XHTML character entities

1 files changed, 59 insertions, 0 deletions

diff --git a/src/utf8.sml b/src/utf8.sml
new file mode 100644
index 00000000..cbd2fa5c
--- /dev/null
+++ b/src/utf8.sml
@@ -0,0 +1,59 @@
+(* Copyright (c) 2011, Adam Chlipala
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ * - The names of contributors may not be used to endorse or promote products
+ *   derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *)
+
+(* UTF-8 conversion *)
+
+structure Utf8 :> UTF8 = struct
+
+fun byte n = str (chr (Word.toInt n))
+
+fun encode n =
+    if n <= 0 then
+        raise Fail "Invalid character to UTF-8-encode"
+    else if n <= 0x7F then
+        str (chr n)
+    else if n <= 0x7FF then
+        let
+            val w = Word.fromInt n
+            val b1 = Word.orb (Word.fromInt (128 + 64), Word.>> (w, Word.fromInt 6))
+            val b2 = Word.orb (Word.fromInt 128, Word.andb (w, Word.fromInt 63))
+        in
+            byte b1 ^ byte b2
+        end
+    else if n <= 0xFFFF then
+        let
+            val w = Word.fromInt n
+            val b1 = Word.orb (Word.fromInt (128 + 64 + 32), Word.>> (w, Word.fromInt 12))
+            val b2 = Word.orb (Word.fromInt 128, Word.andb (Word.>> (w, Word.fromInt 6), Word.fromInt 63))
+            val b3 = Word.orb (Word.fromInt 128, Word.andb (w, Word.fromInt 63))
+        in
+            byte b1 ^ byte b2 ^ byte b3
+        end
+    else
+        raise Fail "Exceeded supported range for UTF-8 characters"
+
+end