--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/General/utf8.scala Wed Dec 21 11:21:46 2016 +0100
@@ -0,0 +1,99 @@
+/* Title: Pure/General/utf8.scala
+ Author: Makarius
+
+Variations on UTF-8.
+*/
+
+package isabelle
+
+
+import java.nio.charset.Charset
+import scala.io.Codec
+
+
+object UTF8
+{
+ /* charset */
+
+ val charset_name: String = "UTF-8"
+ val charset: Charset = Charset.forName(charset_name)
+ def codec(): Codec = Codec(charset)
+
+ def bytes(s: String): Array[Byte] = s.getBytes(charset)
+
+ object Length extends Codepoint.Length
+ {
+ override def codepoint_length(c: Int): Int =
+ if (c < 0x80) 1
+ else if (c < 0x800) 2
+ else if (c < 0x10000) 3
+ else 4
+ }
+
+
+ /* permissive UTF-8 decoding */
+
+ // see also http://en.wikipedia.org/wiki/UTF-8#Description
+ // overlong encodings enable byte-stuffing of low-ASCII
+
+ def decode_permissive(text: CharSequence): String =
+ {
+ val buf = new java.lang.StringBuilder(text.length)
+ var code = -1
+ var rest = 0
+ def flush()
+ {
+ if (code != -1) {
+ if (rest == 0 && Character.isValidCodePoint(code))
+ buf.appendCodePoint(code)
+ else buf.append('\uFFFD')
+ code = -1
+ rest = 0
+ }
+ }
+ def init(x: Int, n: Int)
+ {
+ flush()
+ code = x
+ rest = n
+ }
+ def push(x: Int)
+ {
+ if (rest <= 0) init(x, -1)
+ else {
+ code <<= 6
+ code += x
+ rest -= 1
+ }
+ }
+ for (i <- 0 until text.length) {
+ val c = text.charAt(i)
+ if (c < 128) { flush(); buf.append(c) }
+ else if ((c & 0xC0) == 0x80) push(c & 0x3F)
+ else if ((c & 0xE0) == 0xC0) init(c & 0x1F, 1)
+ else if ((c & 0xF0) == 0xE0) init(c & 0x0F, 2)
+ else if ((c & 0xF8) == 0xF0) init(c & 0x07, 3)
+ }
+ flush()
+ buf.toString
+ }
+
+ private class Decode_Chars(decode: String => String,
+ buffer: Array[Byte], start: Int, end: Int) extends CharSequence
+ {
+ def length: Int = end - start
+ def charAt(i: Int): Char = (buffer(start + i).asInstanceOf[Int] & 0xFF).asInstanceOf[Char]
+ def subSequence(i: Int, j: Int): CharSequence =
+ new Decode_Chars(decode, buffer, start + i, start + j)
+
+ // toString with adhoc decoding: abuse of CharSequence interface
+ override def toString: String = decode(decode_permissive(this))
+ }
+
+ def decode_chars(decode: String => String,
+ buffer: Array[Byte], start: Int, end: Int): CharSequence =
+ {
+ require(0 <= start && start <= end && end <= buffer.length)
+ new Decode_Chars(decode, buffer, start, end)
+ }
+}