===================================================================
RCS file: /cvs/mandoc/preconv.c,v
retrieving revision 1.12
retrieving revision 1.13
diff -u -p -r1.12 -r1.13
--- mandoc/preconv.c	2014/11/14 04:24:04	1.12
+++ mandoc/preconv.c	2014/12/19 04:58:35	1.13
@@ -1,4 +1,4 @@
-/*	$Id: preconv.c,v 1.12 2014/11/14 04:24:04 schwarze Exp $ */
+/*	$Id: preconv.c,v 1.13 2014/12/19 04:58:35 schwarze Exp $ */
 /*
  * Copyright (c) 2011 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2014 Ingo Schwarze <schwarze@openbsd.org>
@@ -19,6 +19,7 @@
 
 #include <sys/types.h>
 
+#include <assert.h>
 #include <stdio.h>
 #include <string.h>
 #include "mandoc.h"
@@ -28,88 +29,70 @@ int
 preconv_encode(struct buf *ib, size_t *ii, struct buf *ob, size_t *oi,
     int *filenc)
 {
-	size_t		 i;
-	int		 state;
+	unsigned char	*cu;
+	int		 nby;
 	unsigned int	 accum;
-	unsigned char	 cu;
 
+	cu = ib->buf + *ii;
+	assert(*cu & 0x80);
+
 	if ( ! (*filenc & MPARSE_UTF8))
 		goto latin;
 
-	state = 0;
-	accum = 0U;
+	nby = 1;
+	while (nby < 5 && *cu & (1 << (7 - nby)))
+		nby++;
 
-	for (i = *ii; i < ib->sz; i++) {
-		cu = ib->buf[i];
-		if (state) {
-			if ( ! (cu & 128) || (cu & 64)) {
-				/* Bad sequence header. */
-				break;
-			}
+	switch (nby) {
+	case 2:
+		accum = *cu & 0x1f;
+		if (accum < 0x02)  /* Obfuscated ASCII. */
+			goto latin;
+		break;
+	case 3:
+		accum = *cu & 0x0f;
+		break;
+	case 4:
+		accum = *cu & 0x07;
+		if (accum > 0x04) /* Beyond Unicode. */
+			goto latin;
+		break;
+	default:  /* Bad sequence header. */
+		goto latin;
+	}
 
-			/* Accept only legitimate bit patterns. */
+	cu++;
+	switch (nby) {
+	case 3:
+		if ((accum == 0x00 && ! (*cu & 0x20)) ||  /* Use 2-byte. */
+		    (accum == 0x0d && *cu & 0x20))  /* Surrogates. */
+			goto latin;
+		break;
+	case 4:
+		if ((accum == 0x00 && ! (*cu & 0x30)) ||  /* Use 3-byte. */
+		    (accum == 0x04 && *cu & 0x30))  /* Beyond Unicode. */
+			goto latin;
+		break;
+	default:
+		break;
+	}
 
-			if (cu > 191 || cu < 128) {
-				/* Bad in-sequence bits. */
-				break;
-			}
-
-			accum |= (cu & 63) << --state * 6;
-
-			if (state)
-				continue;
-
-			if (accum < 0x80)
-				ob->buf[(*oi)++] = accum;
-			else
-				*oi += snprintf(ob->buf + *oi,
-				    11, "\\[u%.4X]", accum);
-			*ii = i + 1;
-			*filenc &= ~MPARSE_LATIN1;
-			return(1);
-		} else {
-			/*
-			 * Entering a UTF-8 state:  if we encounter a
-			 * UTF-8 bitmask, calculate the expected UTF-8
-			 * state from it.
-			 */
-			for (state = 0; state < 7; state++)
-				if ( ! (cu & (1 << (7 - state))))
-					break;
-
-			/* Accept only legitimate bit patterns. */
-
-			switch (state--) {
-			case (4):
-				if (cu <= 244 && cu >= 240) {
-					accum = (cu & 7) << 18;
-					continue;
-				}
-				/* Bad 4-sequence start bits. */
-				break;
-			case (3):
-				if (cu <= 239 && cu >= 224) {
-					accum = (cu & 15) << 12;
-					continue;
-				}
-				/* Bad 3-sequence start bits. */
-				break;
-			case (2):
-				if (cu <= 223 && cu >= 194) {
-					accum = (cu & 31) << 6;
-					continue;
-				}
-				/* Bad 2-sequence start bits. */
-				break;
-			default:
-				/* Bad sequence bit mask. */
-				break;
-			}
-			break;
-		}
+	while (--nby) {
+		if ((*cu & 0xc0) != 0x80)  /* Invalid continuation. */
+			goto latin;
+		accum <<= 6;
+		accum += *cu & 0x3f;
+		cu++;
 	}
 
-	/* FALLTHROUGH: Invalid or incomplete UTF-8 sequence. */
+	assert(accum > 0x7f);
+	assert(accum < 0x110000);
+	assert(accum < 0xd800 || accum > 0xdfff);
+
+	*oi += snprintf(ob->buf + *oi, 11, "\\[u%.4X]", accum);
+	*ii = (char *)cu - ib->buf;
+	*filenc &= ~MPARSE_LATIN1;
+	return(1);
 
 latin:
 	if ( ! (*filenc & MPARSE_LATIN1))