Add the xopen swab() function, contributed by Kensuke Otake <kensuke@phreaker.net>

1 files changed, 18 insertions, 0 deletions

diff --git a/libc/unistd/swab.c b/libc/unistd/swab.c
new file mode 100644
index 000000000..c63ca7284
--- /dev/null
+++ b/libc/unistd/swab.c
@@ -0,0 +1,18 @@
+#include <unistd.h>
+#include <sys/types.h>
+
+/* swab() swaps the position of two adjacent bytes, every two bytes.
+ * Contributed by Kensuke Otake <kensuke@phreaker.net> */
+
+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;
+  }
+}