LibC: Add endian.h

This is part of POSIX issue 2024 and some software depends on it

userspace/libraries/LibC/CMakeLists.txt

@@ -5,6 +5,7 @@ set(LIBC_SOURCES
 	ctype.cpp
 	dirent.cpp
 	dlfcn.cpp
+	endian.cpp
 	environ.cpp
 	errno.cpp
 	fcntl.cpp

userspace/libraries/LibC/endian.cpp

@@ -0,0 +1,31 @@
+#include <BAN/Endianness.h>
+
+#include <endian.h>
+
+#define BE_TO_H(size) \
+	uint##size##_t be##size##toh(uint##size##_t x) { return BAN::big_endian_to_host(x); }
+BE_TO_H(16)
+BE_TO_H(32)
+BE_TO_H(64)
+#undef BE_TO_H
+
+#define H_TO_BE(size) \
+	uint##size##_t htobe##size(uint##size##_t x) { return BAN::host_to_big_endian(x); }
+H_TO_BE(16)
+H_TO_BE(32)
+H_TO_BE(64)
+#undef H_TO_BE
+
+#define LE_TO_H(size) \
+	uint##size##_t le##size##toh(uint##size##_t x) { return BAN::little_endian_to_host(x); }
+LE_TO_H(16)
+LE_TO_H(32)
+LE_TO_H(64)
+#undef LE_TO_H
+
+#define H_TO_LE(size) \
+	uint##size##_t htole##size(uint##size##_t x) { return BAN::host_to_little_endian(x); }
+H_TO_LE(16)
+H_TO_LE(32)
+H_TO_LE(64)
+#undef H_TO_LE

userspace/libraries/LibC/include/endian.h

@@ -0,0 +1,41 @@
+#ifndef _ENDIAN_H
+#define _ENDIAN_H 1
+
+// https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/endian.h.html
+
+#include <sys/cdefs.h>
+
+#include <stdint.h>
+
+#define LITTLE_ENDIAN 0
+#define BIG_ENDIAN 1
+
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define BYTE_ORDER LITTLE_ENDIAN
+#endif
+
+#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#define BYTE_ORDER BIG_ENDIAN
+#endif
+
+__BEGIN_DECLS
+
+uint16_t be16toh(uint16_t);
+uint32_t be32toh(uint32_t);
+uint64_t be64toh(uint64_t);
+
+uint16_t htobe16(uint16_t);
+uint32_t htobe32(uint32_t);
+uint64_t htobe64(uint64_t);
+
+uint16_t htole16(uint16_t);
+uint32_t htole32(uint32_t);
+uint64_t htole64(uint64_t);
+
+uint16_t le16toh(uint16_t);
+uint32_t le32toh(uint32_t);
+uint64_t le64toh(uint64_t);
+
+__END_DECLS
+
+#endif