1 files changed, 56 insertions, 0 deletions
diff --git a/lib/libc/string/memchr.c b/lib/libc/string/memchr.c
new file mode 100644
index 000000000000..367eac5108c1
--- /dev/null
+++ b/lib/libc/string/memchr.c
@@ -0,0 +1,56 @@
+/*-
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright (c) 2005-2014 Rich Felker, et al.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include <limits.h>
+#include <stdint.h>
+#include <string.h>
+
+#define SS (sizeof(size_t))
+#define ALIGN (sizeof(size_t) - 1)
+#define ONES ((size_t)-1 / UCHAR_MAX)
+#define HIGHS (ONES * (UCHAR_MAX / 2 + 1))
+#define HASZERO(x) (((x)-ONES) & ~(x)&HIGHS)
+
+void *
+memchr(const void *src, int c, size_t n)
+{
+	const unsigned char *s = src;
+	c = (unsigned char)c;
+#ifdef __GNUC__
+	for (; ((uintptr_t)s & ALIGN) && n && *s != c; s++, n--)
+		;
+	if (n && *s != c) {
+		typedef size_t __attribute__((__may_alias__)) word;
+		const word *w;
+		size_t k = ONES * c;
+		for (w = (const void *)s; n >= SS && !HASZERO(*w ^ k);
+		     w++, n -= SS)
+			;
+		s = (const void *)w;
+	}
+#endif
+	for (; n && *s != c; s++, n--)
+		;
+	return n ? (void *)s : 0;
+}