[MEDIUM] add definitions for Linux kernel splicing

Some older libc don't define the splice() syscall, and some even
define a wrong one. For this reason, we try our best to declare
it correctly. These definitions still work with recent glibc.

src/stream_sock.c

@@ -10,6 +10,7 @@
  *
  */
 
+#define _GNU_SOURCE
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
@@ -33,6 +34,49 @@
 #include <proto/task.h>
 
 
+/* On recent Linux kernels, the splice() syscall may be used for faster data copy.
+ * But it's not always defined on some OS versions, and it even happens that some
+ * definitions are wrong with some glibc due to an offset bug in syscall().
+ */
+
+#if defined(CONFIG_HAP_LINUX_SPLICE)
+#include <unistd.h>
+#include <sys/syscall.h>
+
+#ifndef SPLICE_F_MOVE
+#define SPLICE_F_MOVE           0x1
+#endif
+
+#ifndef SPLICE_F_NONBLOCK
+#define SPLICE_F_NONBLOCK       0x2
+#endif
+
+#ifndef SPLICE_F_MORE
+#define SPLICE_F_MORE           0x4
+#endif
+
+#ifndef __NR_splice
+#if defined(__powerpc__) || defined(__powerpc64__)
+#define __NR_splice             283
+#elif defined(__sparc__) || defined(__sparc64__)
+#define __NR_splice             232
+#elif defined(__x86_64__)
+#define __NR_splice             275
+#elif defined(__alpha__)
+#define __NR_splice             468
+#elif defined (__i386__)
+#define __NR_splice             313
+#else
+#warning unsupported architecture, guessing __NR_splice=313 like x86...
+#define __NR_splice             313
+#endif /* $arch */
+
+_syscall6(int, splice, int, fdin, loff_t *, off_in, int, fdout, loff_t *, off_out, size_t, len, unsigned long, flags)
+
+#endif /* __NR_splice */
+#endif /* CONFIG_HAP_LINUX_SPLICE */
+
+
 /*
  * this function is called on a read event from a stream socket.
  * It returns 0 if we have a high confidence that we will not be