1 files changed, 93 insertions, 0 deletions

diff --git a/firmware/libc/strlen.c b/firmware/libc/strlen.c
new file mode 100644
index 0000000000..4d33eafce6
--- /dev/null
+++ b/firmware/libc/strlen.c
@@ -0,0 +1,93 @@
+/*
+FUNCTION
+        <<strlen>>---character string length
+        
+INDEX
+        strlen
+
+ANSI_SYNOPSIS
+        #include <string.h>
+        size_t strlen(const char *<[str]>);
+
+TRAD_SYNOPSIS
+        #include <string.h>
+        size_t strlen(<[str]>)
+        char *<[src]>;
+
+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 "config.h"
+#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
+_DEFUN (strlen, (str),
+        _CONST char *str) ICODE_ATTR;
+
+size_t
+_DEFUN (strlen, (str),
+        _CONST char *str)
+{
+#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
+  _CONST char *start = str;
+
+  while (*str)
+    str++;
+
+  return str - start;
+#else
+  _CONST char *start = str;
+  unsigned long *aligned_addr;
+
+  if (!UNALIGNED (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;
+    }
+ 
+  while (*str)
+    str++;
+  return str - start;
+#endif /* not PREFER_SIZE_OVER_SPEED */
+}