* libc/include/string.h (memrchr): Declare.

	* libc/string/Makefile.am (ELIX_4_SOURCES): Add memrchr.c.
	(CHEWOUT_FILES): Add memrchr.def.
	* libc/string/Makefile.in: Regenerate.
	* libc/string/memrchr.c: New file.

1 files changed, 134 insertions, 0 deletions

diff --git a/newlib/libc/string/memrchr.c b/newlib/libc/string/memrchr.c
new file mode 100644
index 000000000..42d9d147b
--- /dev/null
+++ b/newlib/libc/string/memrchr.c
@@ -0,0 +1,134 @@
+/*
+FUNCTION
+	<<memrchr>>---reverse search for character in memory
+
+INDEX
+	memrchr
+
+ANSI_SYNOPSIS
+	#include <string.h>
+	void *memrchr(const void *<[src]>, int <[c]>, size_t <[length]>);
+
+TRAD_SYNOPSIS
+	#include <string.h>
+	void *memrchr(<[src]>, <[c]>, <[length]>)
+	void *<[src]>;
+	void *<[c]>;
+	size_t <[length]>;
+
+DESCRIPTION
+	This function searches memory starting at <[length]> bytes
+	beyond <<*<[src]>>> backwards for the character <[c]>.
+	The search only ends with the first occurrence of <[c]>; in
+	particular, <<NUL>> does not terminate the search.
+
+RETURNS
+	If the character <[c]> is found within <[length]> characters
+	of <<*<[src]>>>, a pointer to the character is returned. If
+	<[c]> is not found, then <<NULL>> is returned.
+
+PORTABILITY
+<<memrchr>> is a GNU extension.
+
+<<memrchr>> requires no supporting OS subroutines.
+
+QUICKREF
+	memrchr
+*/
+
+#include <_ansi.h>
+#include <string.h>
+#include <limits.h>
+
+/* Nonzero if X is not aligned on a "long" boundary.  */
+#define UNALIGNED(X) ((long)(X + 1) & (sizeof (long) - 1))
+
+/* How many bytes are loaded each iteration of the word copy loop.  */
+#define LBLOCKSIZE (sizeof (long))
+
+/* Threshhold for punting to the bytewise iterator.  */
+#define TOO_SMALL(LEN)  ((LEN) < LBLOCKSIZE)
+
+#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
+
+/* DETECTCHAR returns nonzero if (long)X contains the byte used
+   to fill (long)MASK. */
+#define DETECTCHAR(X,MASK) (DETECTNULL(X ^ MASK))
+
+_PTR
+_DEFUN (memrchr, (src_void, c, length),
+	_CONST _PTR src_void _AND
+	int c _AND
+	size_t length)
+{
+  _CONST unsigned char *src = (_CONST unsigned char *) src_void + length - 1;
+  unsigned char d = c;
+
+#if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__)
+  unsigned long *asrc;
+  unsigned long  mask;
+  int i;
+
+  while (UNALIGNED (src))
+    {
+      if (!length--)
+        return NULL;
+      if (*src == d)
+        return (void *) src;
+      src--;
+    }
+
+  if (!TOO_SMALL (length))
+    {
+      /* If we get this far, we know that length is large and src is
+         word-aligned. */
+      /* The fast code reads the source one word at a time and only
+         performs the bytewise search on word-sized segments if they
+         contain the search character, which is detected by XORing
+         the word-sized segment with a word-sized block of the search
+         character and then detecting for the presence of NUL in the
+         result.  */
+      asrc = (unsigned long *) (src - LBLOCKSIZE + 1);
+      mask = d << 8 | d;
+      mask = mask << 16 | mask;
+      for (i = 32; i < LBLOCKSIZE * 8; i <<= 1)
+        mask = (mask << i) | mask;
+
+      while (length >= LBLOCKSIZE)
+        {
+          if (DETECTCHAR (*asrc, mask))
+            break;
+          length -= LBLOCKSIZE;
+          asrc--;
+        }
+
+      /* If there are fewer than LBLOCKSIZE characters left,
+         then we resort to the bytewise loop.  */
+
+      src = (unsigned char *) asrc + LBLOCKSIZE - 1;
+    }
+
+#endif /* not PREFER_SIZE_OVER_SPEED */
+
+  while (length--)
+    {
+      if (*src == d)
+        return (void *) src;
+      src--;
+    }
+
+  return NULL;
+}