--- /dev/null
+/* Test of <endian.h> substitute.
+ Copyright (C) 2024 Free Software Foundation, Inc.
+
+ This file is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published
+ by the Free Software Foundation, either version 3 of the License,
+ or (at your option) any later version.
+
+ This file is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>. */
+
+/* Written by Collin Funk <collin.funk1@gmail.com>, 2024. */
+
+#include <config.h>
+
+/* Specification. */
+#include <endian.h>
+
+/* Check for uint16_t and uint32_t. */
+uint16_t t1;
+uint32_t t2;
+
+/* The next POSIX revision requires 64-bit types. Gnulib doesn't. */
+#if 0
+uint64_t t3;
+#endif
+
+static_assert (LITTLE_ENDIAN != BIG_ENDIAN);
+static_assert (BYTE_ORDER == LITTLE_ENDIAN || BYTE_ORDER == BIG_ENDIAN);
+
+#include <stdint.h>
+
+#include "macros.h"
+
+/* Test byte order conversion functions with constant values. */
+static void
+test_convert_constant (void)
+{
+#if BYTE_ORDER == BIG_ENDIAN
+ /* 16-bit. */
+ ASSERT (be16toh (UINT16_C (0x1234)) == UINT16_C (0x1234));
+ ASSERT (htobe16 (UINT16_C (0x1234)) == UINT16_C (0x1234));
+ ASSERT (le16toh (UINT16_C (0x1234)) == UINT16_C (0x3412));
+ ASSERT (htole16 (UINT16_C (0x1234)) == UINT16_C (0x3412));
+
+ /* 32-bit. */
+ ASSERT (be32toh (UINT32_C (0x12345678)) == UINT32_C (0x12345678));
+ ASSERT (htobe32 (UINT32_C (0x12345678)) == UINT32_C (0x12345678));
+ ASSERT (le32toh (UINT32_C (0x12345678)) == UINT32_C (0x78563412));
+ ASSERT (htole32 (UINT32_C (0x12345678)) == UINT32_C (0x78563412));
+
+ /* 64-bit. */
+# ifdef UINT64_MAX
+ ASSERT (be64toh (UINT64_C (0x1234567890ABCDEF))
+ == UINT64_C (0x1234567890ABCDEF));
+ ASSERT (htobe64 (UINT64_C (0x1234567890ABCDEF))
+ == UINT64_C (0x1234567890ABCDEF));
+ ASSERT (le64toh (UINT64_C (0x1234567890ABCDEF))
+ == UINT64_C (0xEFCDAB9078563412));
+ ASSERT (htole64 (UINT64_C (0x1234567890ABCDEF))
+ == UINT64_C (0xEFCDAB9078563412));
+# endif
+#else
+ /* 16-bit. */
+ ASSERT (be16toh (UINT16_C (0x1234)) == UINT16_C (0x3412));
+ ASSERT (htobe16 (UINT16_C (0x1234)) == UINT16_C (0x3412));
+ ASSERT (le16toh (UINT16_C (0x1234)) == UINT16_C (0x1234));
+ ASSERT (htole16 (UINT16_C (0x1234)) == UINT16_C (0x1234));
+
+ /* 32-bit. */
+ ASSERT (be32toh (UINT32_C (0x12345678)) == UINT32_C (0x78563412));
+ ASSERT (htobe32 (UINT32_C (0x12345678)) == UINT32_C (0x78563412));
+ ASSERT (le32toh (UINT32_C (0x12345678)) == UINT32_C (0x12345678));
+ ASSERT (htole32 (UINT32_C (0x12345678)) == UINT32_C (0x12345678));
+
+ /* 64-bit. */
+# ifdef UINT64_MAX
+ ASSERT (be64toh (UINT64_C (0x1234567890ABCDEF))
+ == UINT64_C (0xEFCDAB9078563412));
+ ASSERT (htobe64 (UINT64_C (0x1234567890ABCDEF))
+ == UINT64_C (0xEFCDAB9078563412));
+ ASSERT (le64toh (UINT64_C (0x1234567890ABCDEF))
+ == UINT64_C (0x1234567890ABCDEF));
+ ASSERT (htole64 (UINT64_C (0x1234567890ABCDEF))
+ == UINT64_C (0x1234567890ABCDEF));
+# endif
+#endif
+}
+
+/* Test that the byte order conversion functions evaluate their
+ arguments once. */
+static void
+test_convert_eval_once (void)
+{
+ /* 16-bit. */
+ {
+ uint16_t value = 0;
+ ASSERT (be16toh (value++) == 0);
+ ASSERT (value == 1);
+ }
+ {
+ uint16_t value = 0;
+ ASSERT (htobe16 (value++) == 0);
+ ASSERT (value == 1);
+ }
+ {
+ uint16_t value = 0;
+ ASSERT (le16toh (value++) == 0);
+ ASSERT (value == 1);
+ }
+ {
+ uint16_t value = 0;
+ ASSERT (htole16 (value++) == 0);
+ ASSERT (value == 1);
+ }
+
+ /* 32-bit. */
+ {
+ uint32_t value = 0;
+ ASSERT (be32toh (value++) == 0);
+ ASSERT (value == 1);
+ }
+ {
+ uint32_t value = 0;
+ ASSERT (htobe32 (value++) == 0);
+ ASSERT (value == 1);
+ }
+ {
+ uint32_t value = 0;
+ ASSERT (le32toh (value++) == 0);
+ ASSERT (value == 1);
+ }
+ {
+ uint32_t value = 0;
+ ASSERT (htole32 (value++) == 0);
+ ASSERT (value == 1);
+ }
+
+ /* 64-bit. */
+#ifdef UINT64_MAX
+ {
+ uint64_t value = 0;
+ ASSERT (be64toh (value++) == 0);
+ ASSERT (value == 1);
+ }
+ {
+ uint64_t value = 0;
+ ASSERT (htobe64 (value++) == 0);
+ ASSERT (value == 1);
+ }
+ {
+ uint64_t value = 0;
+ ASSERT (le64toh (value++) == 0);
+ ASSERT (value == 1);
+ }
+ {
+ uint64_t value = 0;
+ ASSERT (htole64 (value++) == 0);
+ ASSERT (value == 1);
+ }
+#endif
+}
+
+/* Test that the byte order conversion functions accept floating-point
+ arguments. */
+static void
+test_convert_double (void)
+{
+ /* 16-bit. */
+ ASSERT (be16toh (0.0) == 0);
+ ASSERT (htobe16 (0.0) == 0);
+ ASSERT (le16toh (0.0) == 0);
+ ASSERT (htole16 (0.0) == 0);
+
+ /* 32-bit. */
+ ASSERT (be32toh (0.0) == 0);
+ ASSERT (htobe32 (0.0) == 0);
+ ASSERT (le32toh (0.0) == 0);
+ ASSERT (htole32 (0.0) == 0);
+
+ /* 64-bit. */
+#ifdef UINT64_MAX
+ ASSERT (be64toh (0.0) == 0);
+ ASSERT (htobe64 (0.0) == 0);
+ ASSERT (le64toh (0.0) == 0);
+ ASSERT (htole64 (0.0) == 0);
+#endif
+}
+
+int
+main (void)
+{
+ test_convert_constant ();
+ test_convert_eval_once ();
+ test_convert_double ();
+
+ return 0;
+}