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authorRich Felker <dalias@aerifal.cx>2011-02-24 12:35:42 -0500
committerRich Felker <dalias@aerifal.cx>2011-02-24 12:35:42 -0500
commitb8ff2aaabb55521686179464593553fe1c91b2e2 (patch)
tree827d17f8d0dba9f0694946a5fbe62eed89428db8
parent9f19b3ec8dec1e9402e31172a74b72cd46d3da36 (diff)
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add implementation of memccpy function
-rw-r--r--src/string/memccpy.c32
1 files changed, 32 insertions, 0 deletions
diff --git a/src/string/memccpy.c b/src/string/memccpy.c
new file mode 100644
index 00000000..4a875cf5
--- /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;
+}