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+/*************************************************
+* Perl-Compatible Regular Expressions *
+*************************************************/
+
+/* PCRE is a library of functions to support regular expressions whose syntax
+and semantics are as close as possible to those of the Perl 5 language.
+
+ Written by Philip Hazel
+ Copyright (c) 1997-2008 University of Cambridge
+
+-----------------------------------------------------------------------------
+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.
+
+ * Neither the name of the University of Cambridge nor the names of its
+ contributors may 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.
+-----------------------------------------------------------------------------
+*/
+
+
+/* This module contains an internal function for validating UTF-8 character
+strings. */
+
+/* %ExternalCopyright% */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "pcre_internal.h"
+
+
+/*************************************************
+* Validate a UTF-8 string *
+*************************************************/
+
+/* This function is called (optionally) at the start of compile or match, to
+validate that a supposed UTF-8 string is actually valid. The early check means
+that subsequent code can assume it is dealing with a valid string. The check
+can be turned off for maximum performance, but the consequences of supplying
+an invalid string are then undefined.
+
+Originally, this function checked according to RFC 2279, allowing for values in
+the range 0 to 0x7fffffff, up to 6 bytes long, but ensuring that they were in
+the canonical format. Once somebody had pointed out RFC 3629 to me (it
+obsoletes 2279), additional restrictions were applied. The values are now
+limited to be between 0 and 0x0010ffff, no more than 4 bytes long, and the
+subrange 0xd000 to 0xdfff is excluded.
+
+Arguments:
+ string points to the string
+ length length of string, or -1 if the string is zero-terminated
+
+Returns: < 0 if the string is a valid UTF-8 string
+ >= 0 otherwise; the value is the offset of the bad byte
+*/
+
+int
+_erts_pcre_valid_utf8(const uschar *string, int length)
+{
+#ifdef SUPPORT_UTF8
+register const uschar *p;
+
+if (length < 0)
+ {
+ for (p = string; *p != 0; p++);
+ length = p - string;
+ }
+
+for (p = string; length-- > 0; p++)
+ {
+ register int ab;
+ register int c = *p;
+ if (c < 128) continue;
+ if (c < 0xc0) return p - string;
+ ab = _erts_pcre_utf8_table4[c & 0x3f]; /* Number of additional bytes */
+ if (length < ab || ab > 3) return p - string;
+ length -= ab;
+
+ /* Check top bits in the second byte */
+ if ((*(++p) & 0xc0) != 0x80) return p - string;
+
+ /* Check for overlong sequences for each different length, and for the
+ excluded range 0xd000 to 0xdfff. */
+
+ switch (ab)
+ {
+ /* Check for xx00 000x (overlong sequence) */
+
+ case 1:
+ if ((c & 0x3e) == 0) return p - string;
+ continue; /* We know there aren't any more bytes to check */
+
+ /* Check for 1110 0000, xx0x xxxx (overlong sequence) or
+ 1110 1101, 1010 xxxx (0xd000 - 0xdfff) */
+
+ case 2:
+ if ((c == 0xe0 && (*p & 0x20) == 0) ||
+ (c == 0xed && *p >= 0xa0))
+ return p - string;
+ break;
+
+ /* Check for 1111 0000, xx00 xxxx (overlong sequence) or
+ greater than 0x0010ffff (f4 8f bf bf) */
+
+ case 3:
+ if ((c == 0xf0 && (*p & 0x30) == 0) ||
+ (c > 0xf4 ) ||
+ (c == 0xf4 && *p > 0x8f))
+ return p - string;
+ break;
+
+#if 0
+ /* These cases can no longer occur, as we restrict to a maximum of four
+ bytes nowadays. Leave the code here in case we ever want to add an option
+ for longer sequences. */
+
+ /* Check for 1111 1000, xx00 0xxx */
+ case 4:
+ if (c == 0xf8 && (*p & 0x38) == 0) return p - string;
+ break;
+
+ /* Check for leading 0xfe or 0xff, and then for 1111 1100, xx00 00xx */
+ case 5:
+ if (c == 0xfe || c == 0xff ||
+ (c == 0xfc && (*p & 0x3c) == 0)) return p - string;
+ break;
+#endif
+
+ }
+
+ /* Check for valid bytes after the 2nd, if any; all must start 10 */
+ while (--ab > 0)
+ {
+ if ((*(++p) & 0xc0) != 0x80) return p - string;
+ }
+ }
+#endif
+
+return -1;
+}
+
+/* End of pcre_valid_utf8.c */