Patch #1232549 by Ryan Jackson, adds seeking and comments to Vorbis playback

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@7025 a1c6a512-1295-4272-9138-f99709370657

firmware/common/memchr.c

@@ -0,0 +1,116 @@
+/*
+FUNCTION
+	<<memchr>>---search for character in memory
+
+INDEX
+	memchr
+
+ANSI_SYNOPSIS
+	#include <string.h>
+	void * memchr(const void *<[s1]>, int <[c]>, size_t <[n]>);
+
+TRAD_SYNOPSIS
+	#include <string.h>
+	void * memchr(<[s1]>, <[c]>, <[n]>);
+	void *<[string]>;
+	int *<[c]>;
+	size_t *<[n]>;
+
+DESCRIPTION
+	This function scans the first <[n]> bytes of the memory pointed
+	to by <[s1]> for the character <[c]> (converted to a char).
+
+RETURNS
+	Returns a pointer to the matching byte, or a null pointer if
+	<[c]> does not occur in <[s1]>.
+
+PORTABILITY
+<<memchr>> is ANSI C.
+
+<<memchr>> requires no supporting OS subroutines.
+
+QUICKREF
+	memchr ansi pure
+*/
+
+#include <string.h>
+#include <limits.h>
+
+/* Nonzero if X 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))
+
+#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
+
+/* DETECTCHAR returns nonzero if (long)X contains the byte used 
+   to fill (long)MASK. */
+#define DETECTCHAR(X,MASK) (DETECTNULL(X ^ MASK))
+
+void *
+_DEFUN (memchr, (s1, i, n),
+	_CONST void *s1 _AND
+	int i _AND size_t n)
+{
+  _CONST unsigned char *s = (_CONST unsigned char *)s1;
+#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
+  unsigned char c = (unsigned char)i;
+
+  while (n-- > 0)
+    {
+      if (*s == c)
+	{
+          return (void *)s;
+	}
+      s++;
+    }
+
+  return NULL;
+#else
+  unsigned char c = (unsigned char)i;
+  unsigned long mask,j;
+  unsigned long *aligned_addr;
+
+  if (!UNALIGNED (s))
+    {
+      mask = 0;
+      for (j = 0; j < LBLOCKSIZE; j++)
+        mask = (mask << 8) | c;
+
+      aligned_addr = (unsigned long*)s;
+      while ((!DETECTCHAR (*aligned_addr, mask)) && (n>LBLOCKSIZE))
+	{
+          aligned_addr++;
+	  n -= LBLOCKSIZE;
+	}
+
+      /* The block of bytes currently pointed to by aligned_addr
+         may contain the target character or there may be less than
+	 LBLOCKSIZE bytes left to search. We check the last few
+	 bytes using the bytewise search.  */
+
+      s = (unsigned char*)aligned_addr;
+    }
+
+  while (n-- > 0)
+    {
+      if (*s == c)
+	{
+          return (void *)s;
+	}
+      s++;
+    }
+
+  return NULL;
+#endif /* not PREFER_SIZE_OVER_SPEED */
+}