MINOR: standard: provide htonll() and ntohll()
These are the 64-bit equivalent of htonl() and ntohl(). They're a bit
tricky in order to avoid expensive operations.
The principle consists in letting the compiler detect we're playing
with a union and simplify most or all operations. The asm-optimized
htonl() version involving bswap (x86) / rev (arm) / other is a single
operation on little endian, or a NOP on big-endian. In both cases,
this lets the compiler "see" that we're rebuilding a 64-bit word from
two 32-bit quantities that fit into a 32-bit register. In big endian,
the whole code is optimized out. In little endian, with a decent compiler,
a few bswap and 2 shifts are left, which is the minimum acceptable.
diff --git a/include/common/standard.h b/include/common/standard.h
index 085ec79..fc044fb 100644
--- a/include/common/standard.h
+++ b/include/common/standard.h
@@ -30,6 +30,7 @@
#include <sys/socket.h>
#include <sys/un.h>
#include <netinet/in.h>
+#include <arpa/inet.h>
#include <common/chunk.h>
#include <common/config.h>
#include <eb32tree.h>
@@ -992,6 +993,34 @@
return code & 0x0f;
}
+/* Turns 64-bit value <a> from host byte order to network byte order.
+ * The principle consists in letting the compiler detect we're playing
+ * with a union and simplify most or all operations. The asm-optimized
+ * htonl() version involving bswap (x86) / rev (arm) / other is a single
+ * operation on little endian, or a NOP on big-endian. In both cases,
+ * this lets the compiler "see" that we're rebuilding a 64-bit word from
+ * two 32-bit quantities that fit into a 32-bit register. In big endian,
+ * the whole code is optimized out. In little endian, with a decent compiler,
+ * a few bswap and 2 shifts are left, which is the minimum acceptable.
+ */
+static inline unsigned long long htonll(unsigned long long a)
+{
+ union {
+ struct {
+ unsigned int w1;
+ unsigned int w2;
+ } by32;
+ unsigned long long by64;
+ } w = { .by64 = a };
+ return ((unsigned long long)htonl(w.by32.w1) << 32) | htonl(w.by32.w2);
+}
+
+/* Turns 64-bit value <a> from network byte order to host byte order. */
+static inline unsigned long long ntohll(unsigned long long a)
+{
+ return htonll(a);
+}
+
/* returns a 64-bit a timestamp with the finest resolution available. The
* unit is intentionally not specified. It's mostly used to compare dates.
*/