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-rw-r--r--src/string/stpncpy.c32
1 files changed, 32 insertions, 0 deletions
diff --git a/src/string/stpncpy.c b/src/string/stpncpy.c
new file mode 100644
index 00000000..a877f5fe
--- /dev/null
+++ b/src/string/stpncpy.c
@@ -0,0 +1,32 @@
+#include <string.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <limits.h>
+#include "libc.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)
+
+char *__stpncpy(char *d, const char *s, size_t n)
+{
+ size_t *wd;
+ const size_t *ws;
+
+ if (((uintptr_t)s & ALIGN) != ((uintptr_t)d & ALIGN)) {
+ for (; ((uintptr_t)s & ALIGN) && n && (*d=*s); n--, s++, d++);
+ if (!n || !*s) goto tail;
+ wd=(void *)d; ws=(const void *)s;
+ for (; n>=sizeof(size_t) && !HASZERO(*ws);
+ n-=sizeof(size_t), ws++, *wd++) *wd = *ws;
+ d=(void *)wd; s=(const void *)ws;
+ }
+ for (; n && (*d=*s); n--, s++, d++);
+tail:
+ memset(d, 0, n);
+ return d;
+}
+
+weak_alias(__stpncpy, stpncpy);
+