From f1cb2402734567b84e2b55129f98f9764167e13e Mon Sep 17 00:00:00 2001
From: Garrett D'Amore <garrett@damore.org>
Date: Sun, 8 Sep 2024 09:37:50 -0700
Subject: Endianness improvements.

This adds endian awareness at compile time, and defines some little
endian versions of some macros. We antiicpate making more use of
little endian in new protocols to reduce the "endian tax", as nearly
every modern system is little endian these days.
---
 CMakeLists.txt  | 18 +++++++++++++++++
 src/core/defs.h | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1dca028c..f859a7d0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -207,6 +207,24 @@ if (NOT WIN32 AND NOT CYGWIN)
     endif ()
 endif ()
 
+# Detect endianness -- this only handles little and big endian.
+# PDP users, sorry, but you're out of luck.'
+if (DEFINED CMAKE_LANG_C_BYTE_ORDER)
+    if (CMAKE_LANG_BYTE_ORDER EQUAL BIG_ENDIAN)
+        add_definitions(-DNNG_BIG_ENDIAN=1)
+    else()
+        add_definitions(-DNNG_LITTLE_ENDIAN=1)
+    endif()
+else()
+    include(TestBigEndian)
+    test_big_endian(NNG_BIG_ENDIAN)
+    if (NNG_BIG_ENDIAN)
+        add_definitions(-DNNG_BIG_EDNDIAN=1)
+    else()
+        add_definitions(-DNNG_LITTLE_ENDIAN=1)
+    endif()
+endif()
+
 if (CMAKE_SYSTEM_NAME MATCHES "Linux")
     add_definitions(-DNNG_PLATFORM_POSIX)
     add_definitions(-DNNG_PLATFORM_LINUX)
diff --git a/src/core/defs.h b/src/core/defs.h
index f1947fe9..6050782b 100644
--- a/src/core/defs.h
+++ b/src/core/defs.h
@@ -121,6 +121,54 @@ typedef void (*nni_cb)(void *);
 	    (((uint64_t) ((uint8_t) (ptr)[6])) << 8u) +  \
 	    (((uint64_t) (uint8_t) (ptr)[7]))
 
+// Modern CPUs are all little endian.  Let's stop paying the endian tax.
+
+#define NNI_PUT16LE(ptr, u)                                    \
+	do {                                                   \
+		(ptr)[1] = (uint8_t) (((uint16_t) (u)) >> 8u); \
+		(ptr)[0] = (uint8_t) ((uint16_t) (u));         \
+	} while (0)
+
+#define NNI_PUT32LE(ptr, u)                                     \
+	do {                                                    \
+		(ptr)[3] = (uint8_t) (((uint32_t) (u)) >> 24u); \
+		(ptr)[2] = (uint8_t) (((uint32_t) (u)) >> 16u); \
+		(ptr)[1] = (uint8_t) (((uint32_t) (u)) >> 8u);  \
+		(ptr)[0] = (uint8_t) ((uint32_t) (u));          \
+	} while (0)
+
+#define NNI_PUT64LE(ptr, u)                                     \
+	do {                                                    \
+		(ptr)[7] = (uint8_t) (((uint64_t) (u)) >> 56u); \
+		(ptr)[6] = (uint8_t) (((uint64_t) (u)) >> 48u); \
+		(ptr)[5] = (uint8_t) (((uint64_t) (u)) >> 40u); \
+		(ptr)[4] = (uint8_t) (((uint64_t) (u)) >> 32u); \
+		(ptr)[3] = (uint8_t) (((uint64_t) (u)) >> 24u); \
+		(ptr)[2] = (uint8_t) (((uint64_t) (u)) >> 16u); \
+		(ptr)[1] = (uint8_t) (((uint64_t) (u)) >> 8u);  \
+		(ptr)[0] = (uint8_t) ((uint64_t) (u));          \
+	} while (0)
+
+#define NNI_GET16LE(ptr, v)                             \
+	v = (((uint16_t) ((uint8_t) (ptr)[1])) << 8u) + \
+	    (((uint16_t) (uint8_t) (ptr)[0]))
+
+#define NNI_GET32LE(ptr, v)                              \
+	v = (((uint32_t) ((uint8_t) (ptr)[3])) << 24u) + \
+	    (((uint32_t) ((uint8_t) (ptr)[2])) << 16u) + \
+	    (((uint32_t) ((uint8_t) (ptr)[1])) << 8u) +  \
+	    (((uint32_t) (uint8_t) (ptr)[0]))
+
+#define NNI_GET64LE(ptr, v)                              \
+	v = (((uint64_t) ((uint8_t) (ptr)[7])) << 56u) + \
+	    (((uint64_t) ((uint8_t) (ptr)[6])) << 48u) + \
+	    (((uint64_t) ((uint8_t) (ptr)[5])) << 40u) + \
+	    (((uint64_t) ((uint8_t) (ptr)[4])) << 32u) + \
+	    (((uint64_t) ((uint8_t) (ptr)[3])) << 24u) + \
+	    (((uint64_t) ((uint8_t) (ptr)[2])) << 16u) + \
+	    (((uint64_t) ((uint8_t) (ptr)[1])) << 8u) +  \
+	    (((uint64_t) (uint8_t) (ptr)[0]))
+
 // This increments a pointer a fixed number of byte cells.
 #define NNI_INCPTR(ptr, n) ((ptr) = (void *) ((char *) (ptr) + (n)))
 
@@ -178,4 +226,19 @@ typedef nni_type nni_opt_type;
 	(__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)
 #endif
 
+#if !defined(NNG_BIG_ENDIAN) && !defined(NNG_LITTLE_ENDIAN)
+#if defined(__BYTE_ORDER__)
+#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#define NNG_BIG_ENDIAN 1
+#elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define NNG_LITTLE_ENDIAN 1
+#else // middle-endian? (aka PDP-11)
+#error "Unsupported or unknown endian"
+#endif // __BYTE_ORDER__
+#else  // defined(__BYTE_ORDER__)
+#define NNG_LITTLE_ENDIAN 1
+#error "Unknown endian: specify -DNNG_BIG_ENDIAN=1 or -DNNG_LITTLE_ENDIAN=1"
+#endif // defined(__BYTE_ORDER)
+#endif // defined() endianness
+
 #endif // CORE_DEFS_H
-- 
cgit v1.2.3-70-g09d2