From c8804cbe8eeee88d94ce6f16de3cf3f7df21cdae Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 21 Jun 2011 23:36:51 +1000
Subject: [PATCH] Added generic hton and ntoh functions

---
 configure.ac     |  4 +++
 test/.gitignore  |  1 +
 test/Makefile.am |  5 ++-
 test/hton.cpp    | 26 ++++++++++++++++
 types.cpp        | 79 ++++++++++++++++++++++++++++++++++++++++++++++++
 types.hpp        |  8 +++++
 6 files changed, 122 insertions(+), 1 deletion(-)
 create mode 100644 test/hton.cpp

diff --git a/configure.ac b/configure.ac
index 7975ff30..94533c33 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,10 @@ AC_C_CONST
 AC_C_RESTRICT
 AC_C_INLINE
 
+##
+## Architecture features
+AC_C_BIGENDIAN
+
 ##
 ## stdlib features
 AC_FUNC_MMAP
diff --git a/test/.gitignore b/test/.gitignore
index 5a6e99aa..5407c90c 100644
--- a/test/.gitignore
+++ b/test/.gitignore
@@ -1,5 +1,6 @@
 /backtrace
 /float
+/hton
 /ip
 /json-check
 /maths
diff --git a/test/Makefile.am b/test/Makefile.am
index f641d486..d3887ac0 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -7,7 +7,7 @@ AM_CPPFLAGS =                   \
 
 AM_LDFLAGS  = $(COMMON_LDFLAGS)
 
-TEST_BIN = backtrace float range maths matrix version ip
+TEST_BIN = backtrace float range maths matrix version ip hton
 TESTS = $(TEST_BIN) json.pl
 check_PROGRAMS = $(TEST_BIN) json-check
 EXTRA_DIST = json.pl
@@ -34,5 +34,8 @@ version_LDADD      = $(builddir)/../libutil.la $(BOOST_SYSTEM_LIB)
 ip_SOURCES         = ip.cpp
 ip_LDADD      	   = $(builddir)/../libutil.la $(BOOST_SYSTEM_LIB)
 
+hton_SOURCES	   = hton.cpp
+hton_LDADD	   = $(builddir)/../libutil.la $(BOOST_SYSTEM_LIB)
+
 json_check_SOURCES = json-check.cpp
 json_check_LDADD   = $(builddir)/../libutil.la $(BOOST_FILESYSTEM_LIB)
diff --git a/test/hton.cpp b/test/hton.cpp
new file mode 100644
index 00000000..4bbe6183
--- /dev/null
+++ b/test/hton.cpp
@@ -0,0 +1,26 @@
+
+#include "../types.hpp"
+
+#include "../debug.hpp"
+
+#include <cstdlib>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+
+using namespace std;
+
+
+int 
+main (int argc, char **argv) {
+
+    uint16_t u16 = 0x1358;
+    uint32_t u32 = 0x12345678;
+
+    check_eq (htons (u16), hton (u16));
+    check_eq (htonl (u32), hton (u32));
+
+    check_eq (ntohs (u16), hton (u16));
+    check_eq (ntohl (u32), hton (u32));
+
+    return EXIT_SUCCESS;
+}
diff --git a/types.cpp b/types.cpp
index 82b72f61..e9c91c8f 100644
--- a/types.cpp
+++ b/types.cpp
@@ -1,5 +1,7 @@
 #include "types.hpp"
 
+#include <type_traits>
+
 using namespace std;
 
 
@@ -10,3 +12,80 @@ template <> std::string type_to_string <const T> (void) { return "const " #T; }
 do_type_to_string (float)
 do_type_to_string (double)
 
+#ifdef WORDS_BIGENDIAN
+/* Big endian doesn't need swapping */
+template <typename T>
+T hton (T val) {
+    static_assert (is_fundamental <T>(), "hton implementation assumes fundamental types");
+    static_assert (is_unsigned    <T>(), "hton implementation does not handle signed");
+    return val;
+}
+
+template <typename T>
+T ntoh (T val) {
+    static_assert (is_fundamental <T>(), "ntoh implementation assumes fundamental types");
+    static_assert (is_unsigned    <T>(), "ntoh implementation does not handle signed");
+    return val;
+}
+
+template <>  uint8_t hton ( uint8_t);
+template <> uint16_t hton (uint16_t);
+template <> uint32_t hton (uint32_t);
+template <> uint64_t hton (uint64_t);
+
+template <>  uint8_t ntoh ( uint8_t);
+template <> uint16_t ntoh (uint16_t);
+template <> uint32_t ntoh (uint32_t);
+template <> uint64_t ntoh (uint64_t);
+
+#else
+
+static void
+byte_swap (uint8_t *restrict dst, uint8_t *restrict src, size_t len) {
+    for (unsigned int i = 0; i < len; ++i)
+        dst[len - i - 1] = src[i];
+}
+
+
+template <typename T>
+T
+hton (T i) {
+    // Unsure if this will really be sensible for non-intrinsic types, or types larger than 8 bytes.
+    static_assert (is_fundamental <T>::value, "hton implementation assumes fundamental types");
+    static_assert (is_unsigned    <T>::value, "hton implementation does not handle signed");
+
+    T swapped;
+    byte_swap (reinterpret_cast <uint8_t*>(&swapped),
+               reinterpret_cast <uint8_t*>(&i),
+               sizeof (T));
+    return swapped;
+}
+
+
+template <typename T>
+T
+ntoh (T i) {
+    // Unsure if this will really be sensible for non-intrinsic types, or types larger than 8 bytes.
+    static_assert (is_fundamental <T>::value, "ntoh implementation assumes fundamental types");
+    static_assert (is_unsigned    <T>::value, "ntoh implementation does not handle signed");
+
+    T swapped;
+    byte_swap (reinterpret_cast <uint8_t*>(&swapped),
+               reinterpret_cast <uint8_t*>(&i),
+               sizeof (T));
+    return swapped;
+}
+
+template <> uint8_t hton (uint8_t i) { return i; }
+template <> uint8_t ntoh (uint8_t i) { return i; }
+
+template uint16_t ntoh<uint16_t> (uint16_t);
+template uint32_t ntoh<uint32_t> (uint32_t);
+template uint64_t ntoh<uint64_t> (uint64_t);
+
+template uint16_t hton<uint16_t> (uint16_t);
+template uint32_t hton<uint32_t> (uint32_t);
+template uint64_t hton<uint64_t> (uint64_t);
+
+#endif
+
diff --git a/types.hpp b/types.hpp
index dbbd9922..e9c5691a 100644
--- a/types.hpp
+++ b/types.hpp
@@ -97,4 +97,12 @@ template <typename T, size_t N>
 size_t elems(T (&)[N])
     { return N; }
 
+
+template <typename T>
+T hton (T);
+
+
+template <typename T>
+T ntoh (T);
+
 #endif // __TYPES_HPP