add implementation of memccpy function

diff --git a/src/string/memccpy.c b/src/string/memccpy.c
new file mode 100644 (file)
index 0000000..4a875cf
--- /dev/null
+++ b/src/string/memccpy.c
@@ -0,0 +1,32 @@
+#include <string.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <limits.h>
+
+#define ALIGN (sizeof(size_t)-1)
+#define ONES ((size_t)-1/UCHAR_MAX)
+#define HIGHS (ONES * (UCHAR_MAX/2+1))
+#define HASZERO(x) ((x)-ONES & ~(x) & HIGHS)
+
+void *memccpy(void *dest, const void *src, int c, size_t n)
+{
+       unsigned char *d = dest;
+       const unsigned char *s = src;
+       size_t *wd, k;
+       const size_t *ws;
+
+       c = (unsigned char)c;
+       if (((uintptr_t)s & ALIGN) == ((uintptr_t)d & ALIGN)) {
+               for (; ((uintptr_t)s & ALIGN) && n && (*d=*s)!=c; n--, s++, d++);
+               if ((uintptr_t)s & ALIGN) goto tail;
+               k = ONES * c;
+               wd=(void *)d; ws=(const void *)s;
+               for (; n>=sizeof(size_t) && !HASZERO(*ws^k);
+                      n-=sizeof(size_t), ws++, *wd++) *wd = *ws;
+               d=(void *)wd; s=(const void *)ws;
+       }
+       for (; n && (*d=*s)!=c; n--, s++, d++);
+tail:
+       if (*s==c) return d+1;
+       return 0;
+}