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authorEric Andersen <andersen@codepoet.org>2002-04-06 00:07:58 +0000
committerEric Andersen <andersen@codepoet.org>2002-04-06 00:07:58 +0000
commitf19b4d2f61aeafa443e45cee1229c9463e62fc8d (patch)
tree8466d7cb03612cfa90a19005f8d5c8092fdf7fd0
parentcb64288cfed3d370f144dcfd2bc76094268019d9 (diff)
Faster implementation from Miles Bader
-rw-r--r--libc/unistd/swab.c26
1 files changed, 13 insertions, 13 deletions
diff --git a/libc/unistd/swab.c b/libc/unistd/swab.c
index c63ca7284..41845d4cb 100644
--- a/libc/unistd/swab.c
+++ b/libc/unistd/swab.c
@@ -1,18 +1,18 @@
#include <unistd.h>
#include <sys/types.h>
+#include <byteswap.h>
-/* swab() swaps the position of two adjacent bytes, every two bytes.
- * Contributed by Kensuke Otake <kensuke@phreaker.net> */
+/* Updated implementation based on byteswap.h from Miles Bader
+ * <miles@gnu.org>. This should be much faster on arches with machine
+ * specific, optimized definitions in include/bits/byteswap.h (i.e. on
+ * x86, use the bswap instruction on i486 and better boxes). For
+ * platforms that lack such support, this should be no slower than it
+ * was before... */
+void swab (const void *source, void *dest, ssize_t count)
+{
+ const unsigned short *from = source, *from_end = from + (count >> 1);
+ unsigned short *to = dest;
-void swab(const void *source, void *dest, ssize_t count) {
- const char *from = (const char *)source;
- char *to = (char *)dest;
-
- count &= ~((ssize_t)1);
-
- while (count > 1) {
- const char b0 = from[--count], b1 = from[--count];
- to[count] = b0;
- to[count + 1] = b1;
- }
+ while (from < from_end)
+ *to++ = bswap_16 (*from++);
}