import newlib-2000-02-17 snapshot

1 files changed, 143 insertions, 0 deletions

diff --git a/newlib/libc/string/memchr.c b/newlib/libc/string/memchr.c
new file mode 100644
index 000000000..2fd3c861d
--- /dev/null
+++ b/newlib/libc/string/memchr.c
@@ -0,0 +1,143 @@
+/*
+FUNCTION
+	<<memchr>>---find character in memory
+
+INDEX
+	memchr
+
+ANSI_SYNOPSIS
+	#include <string.h>
+	void *memchr(const void *<[src]>, int <[c]>, size_t <[length]>);
+
+TRAD_SYNOPSIS
+	#include <string.h>
+	void *memchr(<[src]>, <[c]>, <[length]>)
+	void *<[src]>;
+	void *<[c]>;
+	size_t <[length]>;
+
+DESCRIPTION
+	This function searches memory starting at <<*<[src]>>> for the
+	character <[c]>.  The search only ends with the first
+	occurrence of <[c]>, or after <[length]> characters; in
+	particular, <<NULL>> 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
+<<memchr>>> is ANSI C.
+
+<<memchr>>  requires no supporting OS subroutines.
+
+QUICKREF
+	memchr ansi pure
+*/
+
+#include <_ansi.h>
+#include <string.h>
+#include <limits.h>
+
+/* Nonzero if either X or Y is not aligned on a "long" boundary.  */
+#define UNALIGNED(X) ((long)X & (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
+
+
+_PTR
+_DEFUN (memchr, (src_void, c, length),
+	_CONST _PTR src_void _AND
+	int c _AND
+	size_t length)
+{
+#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
+  _CONST unsigned char *src = (_CONST unsigned char *) src_void;
+
+  c &= 0xff;
+  
+  while (length--)
+    {
+      if (*src == c)
+	return (char *) src;
+      src++;
+    }
+  return NULL;
+#else
+  _CONST unsigned char *src = (_CONST unsigned char *) src_void;
+  unsigned long *asrc;
+  unsigned long  buffer;
+  unsigned long  mask;
+  int i, j;
+
+  c &= 0xff;
+  
+  /* If the size is small, or src is unaligned, then 
+     use the bytewise loop.  We can hope this is rare.  */
+  if (!TOO_SMALL (length) && !UNALIGNED (src)) 
+    {
+      /* The fast code reads the ASCII 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 NULL in the
+         result.  */
+      asrc = (unsigned long*) src;
+      mask = 0;
+      for (i = 0; i < LBLOCKSIZE; i++)
+        mask = (mask << 8) + c;
+
+      while (length >= LBLOCKSIZE)
+        {
+          buffer = *asrc;
+          buffer ^=  mask;
+          if (DETECTNULL (buffer))
+	    {
+              src = (unsigned char*) asrc;
+  	      for ( j = 0; j < LBLOCKSIZE; j++ )
+	        {
+                  if (*src == c)
+                    return (char*) src;
+                  src++;
+	        }
+   	    }
+          length -= LBLOCKSIZE;
+          asrc++;
+        }
+  
+      /* If there are fewer than LBLOCKSIZE characters left,
+         then we resort to the bytewise loop.  */
+
+      src = (unsigned char*) asrc;
+    }
+
+  while (length--)
+    { 
+      if (*src == c)
+        return (char*) src;
+      src++;
+    } 
+
+  return NULL;
+#endif /* not PREFER_SIZE_OVER_SPEED */
+}