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+/* util.c  -- Various error checking wrappers and utilities.
+ *
+ *  Copyright (C) 2016 Tomasz Kramkowski <tk@the-tk.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Some contents of this file (indicated below) are based on work covered by
+ * the following copyright and permission notice:
+ *
+ *  Copyright (c) 2008 Otto Moerbeek <otto@drijf.net>
+ *
+ *  Permission to use, copy, modify, and distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#include <assert.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+#include "log.h"
+#include "util.h"
+
+/* szadd: checked size_t addition */
+size_t szadd(size_t a, size_t b)
+{
+	if (SIZE_MAX - a < b)
+		error(0, EMSG_SZOP);
+
+	return a + b;
+}
+
+/* szmul: checked size_t multiplication
+ * License information can be found at the top of this file */
+size_t szmul(size_t a, size_t b)
+{
+#define MUL_NO_OVERFLOW ((size_t)1 << (sizeof (size_t) * 4))
+	if ((a >= MUL_NO_OVERFLOW || b >= MUL_NO_OVERFLOW) &&
+		a > 0 && SIZE_MAX / a < b)
+		error(0, EMSG_SZOP);
+#undef MUL_NO_OVERFLOW
+
+	return a * b;
+}
+
+/* xstrmalloc: allocate for a string (+1) or exit with error */
+void *xstrmalloc(size_t size)
+{
+	size_t nsize;
+
+	nsize = size + 1;
+	if (nsize < size)
+		error(0, EMSG_ALLOC);
+
+	return xmalloc(nsize);
+}
+
+/* xstrdup: duplicae string or exit with error */
+char *xstrdup(const char *s)
+{
+	char *ret;
+
+	assert(s);
+
+	ret = xstrmalloc(strlen(s));
+	strcpy(ret, s);
+
+	return ret;
+}
+
+/* xrealloc: reallocate or exit with error */
+void *xrealloc(void *p, size_t size)
+{
+	p = realloc(p, size);
+	if (!p)
+		error(errno, EMSG_ALLOC);
+
+	return p;
+}
+
+/* xmalloc: allocate or exit with error */
+void *xmalloc(size_t size)
+{
+	return xrealloc(NULL, size);
+}
+
+/* xstrcut: cut out a bit of a string into a new string */
+char *xstrcut(const char *s, size_t offt, size_t len)
+{
+	char *ret;
+
+	ret = xstrmalloc(len);
+	strncpy(ret, s + offt, len + 1);
+
+	return ret;
+}
+
+/* xstrcasecmp: case insensitive strcmp */
+int xstrcasecmp(const char *s1, const char *s2)
+{
+	while (toupper(*s1++) == toupper(*s2++))
+		if (*s1 == '\0' || *s2 == '\0')
+			break;
+	if (*s1 == *s2)
+		return 0;
+	if (*s1 < *s2)
+		return -1;
+	return 1;
+}