Import regex from OpenBSD

Change-Id: I7ad7d907ef65e4e345f94777d730813b1270a612
diff --git a/libc/include/regex.h b/libc/include/regex.h
new file mode 100644
index 0000000..aec38e3
--- /dev/null
+++ b/libc/include/regex.h
@@ -0,0 +1,105 @@
+/*	$OpenBSD: regex.h,v 1.6 2003/06/02 19:34:12 millert Exp $	*/
+/*	$NetBSD: regex.h,v 1.4.6.1 1996/06/10 18:57:07 explorer Exp $	*/
+
+/*-
+ * Copyright (c) 1992 Henry Spencer.
+ * Copyright (c) 1992, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Henry Spencer of the University of Toronto.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ * 3. Neither the name of the University 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 REGENTS 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 REGENTS 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.
+ *
+ *	@(#)regex.h	8.1 (Berkeley) 6/2/93
+ */
+
+#ifndef _REGEX_H_
+#define	_REGEX_H_
+
+#include <sys/cdefs.h>
+#include <sys/types.h>
+
+/* types */
+typedef off_t regoff_t;
+
+typedef struct {
+	int re_magic;
+	size_t re_nsub;		/* number of parenthesized subexpressions */
+	const char *re_endp;	/* end pointer for REG_PEND */
+	struct re_guts *re_g;	/* none of your business :-) */
+} regex_t;
+
+typedef struct {
+	regoff_t rm_so;		/* start of match */
+	regoff_t rm_eo;		/* end of match */
+} regmatch_t;
+
+/* regcomp() flags */
+#define	REG_BASIC	0000
+#define	REG_EXTENDED	0001
+#define	REG_ICASE	0002
+#define	REG_NOSUB	0004
+#define	REG_NEWLINE	0010
+#define	REG_NOSPEC	0020
+#define	REG_PEND	0040
+#define	REG_DUMP	0200
+
+/* regerror() flags */
+#define	REG_NOMATCH	 1
+#define	REG_BADPAT	 2
+#define	REG_ECOLLATE	 3
+#define	REG_ECTYPE	 4
+#define	REG_EESCAPE	 5
+#define	REG_ESUBREG	 6
+#define	REG_EBRACK	 7
+#define	REG_EPAREN	 8
+#define	REG_EBRACE	 9
+#define	REG_BADBR	10
+#define	REG_ERANGE	11
+#define	REG_ESPACE	12
+#define	REG_BADRPT	13
+#define	REG_EMPTY	14
+#define	REG_ASSERT	15
+#define	REG_INVARG	16
+#define	REG_ATOI	255	/* convert name to number (!) */
+#define	REG_ITOA	0400	/* convert number to name (!) */
+
+/* regexec() flags */
+#define	REG_NOTBOL	00001
+#define	REG_NOTEOL	00002
+#define	REG_STARTEND	00004
+#define	REG_TRACE	00400	/* tracing of execution */
+#define	REG_LARGE	01000	/* force large representation */
+#define	REG_BACKR	02000	/* force use of backref code */
+
+__BEGIN_DECLS
+int	regcomp(regex_t *, const char *, int);
+size_t	regerror(int, const regex_t *, char *, size_t);
+int	regexec(const regex_t *, const char *, size_t, regmatch_t [], int);
+void	regfree(regex_t *);
+__END_DECLS
+
+#endif /* !_REGEX_H_ */