Create byteorder header for host_to_le functions

include/Makefile.am

@@ -1,6 +1,7 @@
 noinst_HEADERS =  \
 bios_disk.h \
 bios.h \
+byteorder.h \
 callback.h \
 compiler.h \
 control.h \

include/byteorder.h

@@ -0,0 +1,121 @@
+/*
+ *  SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ *  Copyright (C) 2020-2020  The dosbox-staging team
+ *
+ *  This program 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 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program 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, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#ifndef DOSBOX_BYTEORDER_H
+#define DOSBOX_BYTEORDER_H
+
+/* Usual way of handling endianess and byteswapping is via endian.h
+ * (for e.g. htole* functions) or byteswap.h (e.g. bswap_16 macro).
+ *
+ * However, these headers are non-standard and almost every OS has their own
+ * variations. It's easier to use compiler-provided intrinsics and builtins than
+ * to rely on OS libraries.
+ *
+ * This header provides functions deliberately named differently
+ * than popular variations on these implementations (e.g. bswap_u16 instead of
+ * bswap_16), to avoid conflicts.
+ */
+
+#include "config.h"
+
+#include <cstdint>
+#include <cstdlib>
+
+#if !defined(_MSC_VER)
+
+/* Aside of MSVC, every C++11-capable compiler provides __builtin_bswap*
+ * as compiler intrinsics or builtin functions.
+ */
+
+#define bswap_u16(x) __builtin_bswap16(x)
+#define bswap_u32(x) __builtin_bswap32(x)
+#define bswap_u64(x) __builtin_bswap64(x)
+
+#else
+
+/* MSVCS does not provide __builtin_bswap* functions, but has its own
+ * byteswap builtin's.  MSDN lists these as library functions, but MSVC makes
+ * good job of inlinig them when compiling with /O2.
+ *
+ * https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/byteswap-uint64-byteswap-ulong-byteswap-ushort
+ */
+
+#define bswap_u16(x) _byteswap_ushort(x)
+#define bswap_u32(x) _byteswap_ulong(x)
+#define bswap_u64(x) _byteswap_uint64(x)
+
+#endif // MSC_VER
+
+#ifdef WORDS_BIGENDIAN
+
+#define host_to_le16(x) bswap_u16(static_cast<uint16_t>(x))
+#define host_to_le32(x) bswap_u32(static_cast<uint32_t>(x))
+#define host_to_le64(x) bswap_u64(static_cast<uint64_t>(x))
+                                                           
+#define le16_to_host(x) bswap_u16(static_cast<uint16_t>(x))
+#define le32_to_host(x) bswap_u32(static_cast<uint32_t>(x))
+#define le64_to_host(x) bswap_u64(static_cast<uint64_t>(x))
+
+#else
+
+#define host_to_le16(x) static_cast<uint16_t>(x)
+#define host_to_le32(x) static_cast<uint32_t>(x)
+#define host_to_le64(x) static_cast<uint64_t>(x)
+
+#define le16_to_host(x) static_cast<uint16_t>(x)
+#define le32_to_host(x) static_cast<uint32_t>(x)
+#define le64_to_host(x) static_cast<uint64_t>(x)
+
+#endif
+
+/* 'host_to_le' functions allow for byte order conversion on big endian
+ * architectures while respecting memory alignment on low endian.
+ *
+ * We overload these functions to let compiler pick the correct byteswapping
+ * function if user is ok with that.
+ *
+ * The only caveat in here is: MSVC bswap implementations are not constexpr,
+ * so these functions won't compile using MSVC for big endian
+ * architecture, but it's unlikely to ever be a real problem.
+ */
+
+constexpr uint8_t host_to_le(uint8_t x) noexcept { return x; }
+
+#ifdef WORDS_BIGENDIAN
+
+constexpr uint16_t host_to_le(uint16_t x) noexcept { return bswap_u16(x); }
+constexpr uint32_t host_to_le(uint32_t x) noexcept { return bswap_u32(x); }
+constexpr uint64_t host_to_le(uint64_t x) noexcept { return bswap_u64(x); }
+
+#else
+
+constexpr uint16_t host_to_le(uint16_t x) noexcept { return x; }
+constexpr uint32_t host_to_le(uint32_t x) noexcept { return x; }
+constexpr uint64_t host_to_le(uint64_t x) noexcept { return x; }
+
+#endif
+
+/* Functions 'le_to_host' and 'host_to_le' are the same function, only the user
+ * intent might be different.
+ */
+
+#define le_to_host(x) host_to_le(x)
+
+#endif

include/mem.h

@@ -23,6 +23,8 @@
 #include "dosbox.h"
 #endif
 
+#include "byteorder.h"
+
 typedef Bit32u PhysPt;
 typedef Bit8u * HostPt;
 typedef Bit32u RealPt;
@@ -118,49 +120,6 @@ static INLINE void host_writed(HostPt off,Bit32u val) {
 
 #endif
 
-// host_to_le functions allow for byte order conversion on big endian
-// architectures while respecting memory alignment on low endian.
-//
-// It is extremely unlikely that we'll ever try to compile on big endian arch
-// with a compiler missing __builtin_bswap*, so let's not overcomplicate
-// things.
-//
-// __builtin_bswap* is supported since GCC 4.3 and Clang 3.4
-
-constexpr static INLINE uint8_t host_to_le(uint8_t val) {
-	return val;
-}
-
-#if defined(WORDS_BIGENDIAN)
-
-constexpr static INLINE int16_t host_to_le(int16_t val) {
-	return __builtin_bswap16(val);
-}
-
-constexpr static INLINE uint16_t host_to_le(uint16_t val) {
-	return __builtin_bswap16(val);
-}
-
-constexpr static INLINE uint32_t host_to_le(uint32_t val) {
-	return __builtin_bswap32(val);
-}
-
-#else
-
-constexpr static INLINE int16_t host_to_le(int16_t val) {
-	return val;
-}
-
-constexpr static INLINE uint16_t host_to_le(uint16_t val) {
-	return val;
-}
-
-constexpr static INLINE uint32_t host_to_le(uint32_t val) {
-	return val;
-}
-
-#endif
-
 static INLINE void var_write(Bit8u * var, Bit8u val) {
 	host_writeb(var, val);
 }

src/hardware/mixer.cpp

@@ -503,8 +503,10 @@ static void MIXER_MixData(Bitu needed) {
 		for (size_t i = 0; i < added; i++) {
 			const int32_t sample_1 = mixer.work[readpos][0] >> MIXER_VOLSHIFT;
 			const int32_t sample_2 = mixer.work[readpos][1] >> MIXER_VOLSHIFT;
-			convert[i][0] = host_to_le(MIXER_CLIP(sample_1));
-			convert[i][1] = host_to_le(MIXER_CLIP(sample_2));
+			const int16_t s1 = MIXER_CLIP(sample_1);
+			const int16_t s2 = MIXER_CLIP(sample_2);
+			convert[i][0] = host_to_le(static_cast<uint16_t>(s1));
+			convert[i][1] = host_to_le(static_cast<uint16_t>(s2));
 			readpos = (readpos + 1) & MIXER_BUFMASK;
 		}
 		CAPTURE_AddWave(mixer.freq, added, reinterpret_cast<int16_t*>(convert));

vs/dosbox.vcxproj

@@ -272,6 +272,7 @@
   <ItemGroup>
     <ClInclude Include="..\include\bios.h" />
     <ClInclude Include="..\include\bios_disk.h" />
+    <ClInclude Include="..\include\byteorder.h" />
     <ClInclude Include="..\include\callback.h" />
     <ClInclude Include="..\include\control.h" />
     <ClInclude Include="..\include\cpu.h" />
@@ -390,4 +391,4 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
-</Project>
+</Project>

vs/dosbox.vcxproj.filters

@@ -390,6 +390,9 @@
     <ClInclude Include="..\include\bios_disk.h" >
       <Filter>include</Filter>
     </ClInclude>
+    <ClInclude Include="..\include\byteorder.h" >
+      <Filter>include</Filter>
+    </ClInclude>
     <ClInclude Include="..\include\callback.h" >
       <Filter>include</Filter>
     </ClInclude>