added memcmp function to make rockbox compilable with latest gcc versions without using libc
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@2304 a1c6a512-1295-4272-9138-f99709370657
diff --git a/firmware/common/memcmp.c b/firmware/common/memcmp.c
new file mode 100644
index 0000000..ac7a194
--- /dev/null
+++ b/firmware/common/memcmp.c
@@ -0,0 +1,113 @@
+/*
+FUNCTION
+ <<memcmp>>---compare two memory areas
+
+INDEX
+ memcmp
+
+ANSI_SYNOPSIS
+ #include <string.h>
+ int memcmp(const void *<[s1]>, const void *<[s2]>, size_t <[n]>);
+
+TRAD_SYNOPSIS
+ #include <string.h>
+ int memcmp(<[s1]>, <[s2]>, <[n]>)
+ void *<[s1]>;
+ void *<[s2]>;
+ size_t <[n]>;
+
+DESCRIPTION
+ This function compares not more than <[n]> characters of the
+ object pointed to by <[s1]> with the object pointed to by <[s2]>.
+
+
+RETURNS
+ The function returns an integer greater than, equal to or
+ less than zero according to whether the object pointed to by
+ <[s1]> is greater than, equal to or less than the object
+ pointed to by <[s2]>.
+
+PORTABILITY
+<<memcmp>> is ANSI C.
+
+<<memcmp>> requires no supporting OS subroutines.
+
+QUICKREF
+ memcmp ansi pure
+*/
+
+#include <string.h>
+
+
+/* Nonzero if either X or Y is not aligned on a "long" boundary. */
+#define UNALIGNED(X, Y) \
+ (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
+
+/* How many bytes are copied each iteration of the word copy loop. */
+#define LBLOCKSIZE (sizeof (long))
+
+/* Threshhold for punting to the byte copier. */
+#define TOO_SMALL(LEN) ((LEN) < LBLOCKSIZE)
+
+int
+_DEFUN (memcmp, (m1, m2, n),
+ _CONST _PTR m1 _AND
+ _CONST _PTR m2 _AND
+ size_t n)
+{
+#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
+ unsigned char *s1 = (unsigned char *) m1;
+ unsigned char *s2 = (unsigned char *) m2;
+
+ while (n--)
+ {
+ if (*s1 != *s2)
+ {
+ return *s1 - *s2;
+ }
+ s1++;
+ s2++;
+ }
+ return 0;
+#else
+ unsigned char *s1 = (unsigned char *) m1;
+ unsigned char *s2 = (unsigned char *) m2;
+ unsigned long *a1;
+ unsigned long *a2;
+
+ /* If the size is too small, or either pointer is unaligned,
+ then we punt to the byte compare loop. Hopefully this will
+ not turn up in inner loops. */
+ if (!TOO_SMALL(n) && !UNALIGNED(s1,s2))
+ {
+ /* Otherwise, load and compare the blocks of memory one
+ word at a time. */
+ a1 = (unsigned long*) s1;
+ a2 = (unsigned long*) s2;
+ while (n >= LBLOCKSIZE)
+ {
+ if (*a1 != *a2)
+ break;
+ a1++;
+ a2++;
+ n -= LBLOCKSIZE;
+ }
+
+ /* check m mod LBLOCKSIZE remaining characters */
+
+ s1 = (char*)a1;
+ s2 = (char*)a2;
+ }
+
+ while (n--)
+ {
+ if (*s1 != *s2)
+ return *s1 - *s2;
+ s1++;
+ s2++;
+ }
+
+ return 0;
+#endif /* not PREFER_SIZE_OVER_SPEED */
+}
+