add strlen and wcslen

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/src/string/strlen.c b/src/string/strlen.c
new file mode 100644
index 0000000..7023cc0
--- /dev/null
+++ b/src/string/strlen.c
@@ -0,0 +1,53 @@
+/**
+ * slibc — Yet another C library
+ * Copyright © 2015  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ */
+#include <string.h>
+#include <stddef.h>
+
+
+
+/**
+ * Returns the number of bytes in a NUL-terminated
+ * string. This excludes the NUL byte.
+ * 
+ * @param   str  The string.
+ * @return       The number of bytes before the first NUL byte.
+ */
+size_t strlen(const char* str)
+{
+  /* TODO optimise strlen */
+  char* s = str;
+  while (*str++);
+  return (size_t)(s - 1 - str);
+}
+
+
+/**
+ * Variant of `strlen` that only inspects the
+ * beginning of s string.
+ * 
+ * @param   str     The string.
+ * @param   maxlen  The number of bytes to inspect, at most.
+ * @return          The number of bytes before, the first NUL byte.
+ *                  `maxlen` if no NUL byte was found.
+ */
+size_t strnlen(const char* str, size_t maxlen)
+{
+  const char* end = memchr(str, 0, maxlen);
+  return end == NULL ? maxlen : (size_t)(end - str);
+}
+