1 files changed, 82 insertions, 0 deletions
diff --git a/cpukit/libc/string/strlen.c b/cpukit/libc/string/strlen.c
new file mode 100644
index 0000000000..acffa49e14
--- /dev/null
+++ b/cpukit/libc/string/strlen.c
@@ -0,0 +1,82 @@
+/*
+FUNCTION
+	<<strlen>>---character string length
+
+INDEX
+	strlen
+
+SYNOPSIS
+	#include <string.h>
+	size_t strlen(const char *<[str]>);
+
+DESCRIPTION
+	The <<strlen>> function works out the length of the string
+	starting at <<*<[str]>>> by counting chararacters until it
+	reaches a <<NULL>> character.
+
+RETURNS
+	<<strlen>> returns the character count.
+
+PORTABILITY
+<<strlen>> is ANSI C.
+
+<<strlen>> requires no supporting OS subroutines.
+
+QUICKREF
+	strlen ansi pure
+*/
+
+#include <_ansi.h>
+#include <string.h>
+#include <limits.h>
+
+#define LBLOCKSIZE   (sizeof (long))
+#define UNALIGNED(X) ((long)X & (LBLOCKSIZE - 1))
+
+#if LONG_MAX == 2147483647L
+#define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
+#else
+#if LONG_MAX == 9223372036854775807L
+/* Nonzero if X (a long int) contains a NULL byte. */
+#define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
+#else
+#error long int is not a 32bit or 64bit type.
+#endif
+#endif
+
+#ifndef DETECTNULL
+#error long int is not a 32bit or 64bit byte
+#endif
+
+size_t
+strlen (const char *str)
+{
+  const char *start = str;
+
+#if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__)
+  unsigned long *aligned_addr;
+
+  /* Align the pointer, so we can search a word at a time.  */
+  while (UNALIGNED (str))
+    {
+      if (!*str)
+	return str - start;
+      str++;
+    }
+
+  /* If the string is word-aligned, we can check for the presence of
+     a null in each word-sized block.  */
+  aligned_addr = (unsigned long *)str;
+  while (!DETECTNULL (*aligned_addr))
+    aligned_addr++;
+
+  /* Once a null is detected, we check each byte in that block for a
+     precise position of the null.  */
+  str = (char *) aligned_addr;
+
+#endif /* not PREFER_SIZE_OVER_SPEED */
+
+  while (*str)
+    str++;
+  return str - start;
+}