From 03d656652776e0e292f1d890ffdff2898df6adc5 Mon Sep 17 00:00:00 2001
From: Walter Doekes <walter+github@wjd.nu>
Date: Fri, 29 Apr 2016 11:50:14 +0200
Subject: [PATCH] build: Fix compile error on CentOS5 and other old Linuxen
 lacking le16toh.

Reported by: @mscdex
(closes #211)
---
 configure.ac         | 12 +++++++++++-
 include/config.h.in  | 10 ++++++++++
 include/endianshim.h | 41 ++++++++++++++++++++++++++++++-----------
 3 files changed, 51 insertions(+), 12 deletions(-)

diff --git a/configure.ac b/configure.ac
index 1ecf0aee..daf51d03 100644
--- a/configure.ac
+++ b/configure.ac
@@ -207,7 +207,7 @@ AM_CONDITIONAL(HAVE_EPOLL, test "$epoll" = "yes")
 # ==================== checks for header files ==========================
 
 AC_FUNC_ALLOCA
-AC_CHECK_HEADERS([arpa/inet.h fcntl.h limits.h netdb.h netinet/in.h stdlib.h string.h sys/socket.h sys/time.h unistd.h])
+AC_CHECK_HEADERS([arpa/inet.h endian.h fcntl.h limits.h netdb.h netinet/in.h stdlib.h string.h sys/endian.h sys/socket.h sys/time.h unistd.h])
 
 # ===== checks for typedefs, structures and compiler characteristics ====
 
@@ -229,6 +229,16 @@ AC_FUNC_FORK
 #AC_FUNC_STRTOD
 AC_CHECK_FUNCS([alarm dup2 floor gethostname gettimeofday inet_ntoa memmove memset pow regcomp socket sqrt strcasecmp strchr strcspn strdup strerror strncasecmp strrchr strstr strtol strtoul strtoull])
 
+# Check for le16toh in both endian.h and sys/endian.h (for BSD).
+AC_CHECK_DECLS([le16toh], [], [],
+[#ifdef HAVE_ENDIAN_H
+# include <endian.h>
+#endif
+#ifdef HAVE_SYS_ENDIAN_H
+# include <sys/endian.h>
+#endif])
+
+
 # ==================== check for clang/gmock workaround =================
 
 # clang++ falls over the use of is_default_constructible, suggesting
diff --git a/include/config.h.in b/include/config.h.in
index 4ca8d406..7e26471a 100644
--- a/include/config.h.in
+++ b/include/config.h.in
@@ -24,9 +24,16 @@
 /* define if the compiler supports basic C++11 syntax */
 #undef HAVE_CXX11
 
+/* Define to 1 if you have the declaration of `le16toh', and to 0 if you
+   don't. */
+#undef HAVE_DECL_LE16TOH
+
 /* Define to 1 if you have the `dup2' function. */
 #undef HAVE_DUP2
 
+/* Define to 1 if you have the <endian.h> header file. */
+#undef HAVE_ENDIAN_H
+
 /* This platform supports epoll(7). */
 #undef HAVE_EPOLL
 
@@ -180,6 +187,9 @@
 /* Define to 1 if you have the `strtoull' function. */
 #undef HAVE_STRTOULL
 
+/* Define to 1 if you have the <sys/endian.h> header file. */
+#undef HAVE_SYS_ENDIAN_H
+
 /* Define to 1 if you have the <sys/socket.h> header file. */
 #undef HAVE_SYS_SOCKET_H
 
diff --git a/include/endianshim.h b/include/endianshim.h
index 5867a3a6..ad3f51ab 100644
--- a/include/endianshim.h
+++ b/include/endianshim.h
@@ -1,25 +1,44 @@
 #ifndef ENDIANSHIM_H
 #define ENDIANSHIM_H 1
 
-#if defined(__CYGWIN) || defined(__LINUX)
-#include <endian.h>
-#elif defined(__FreeBSD__)
-#include <sys/endian.h>
-#elif defined(__DARWIN)
+/* Fetch HAVE_ENDIAN_H, HAVE_SYS_ENDIAN_H, HAVE_DECL_LE16TOH */
+#include "config.h"
+
+#ifdef HAVE_ENDIAN_H
+/* Linux and friends. */
+# include <endian.h>
+#endif
+#ifdef HAVE_SYS_ENDIAN_H
+/* BSDs */
+# include <sys/endian.h>
+#endif
+#if defined(__DARWIN)
+/* Darwin does something else. */
 #include <libkern/OSByteOrder.h>
 #endif
 
-#ifdef __DARWIN
+
+#if defined(__DARWIN)
 #define le16toh(x) OSSwapLittleToHostInt16(x)
-#endif
 
-/* HP-UX 11 is missing byteswap.h, so we provide our own bswap_16() */
-#ifdef __HPUX
-#define bswap_16(x) ((uint16_t)( \
+#elif defined(__HPUX)
+/* HPUX is big endian (apparently..) */
+#define le16toh(x) ((uint16_t)( \
     (((uint16_t)(x)) << 8) | \
     (((uint16_t)(x)) >> 8)))
 
-#define le16toh(x) bswap_16(x)
+#elif !defined(HAVE_DECL_LE16TOH) || HAVE_DECL_LE16TOH == 0
+/* le16toh() is missing in glibc before 2.9 */
+#if BYTE_ORDER == BIG_ENDIAN
+#   define le16toh(x) ((uint16_t)( \
+        (((uint16_t)(x)) << 8) | \
+        (((uint16_t)(x)) >> 8)))
+#elif BYTE_ORDER == LITTLE_ENDIAN
+#   define le16toh(x) (x)
+#else /* BYTE_ORDER == <undefined> */
+#   error Unknown endianness
 #endif
 
+#endif /* !HAVE_DECL_LE16TOH */
+
 #endif /* ENDIANSHIM_H */