src: don't use __builtin_bswap16() and friends

Said builtins are not supported by older versions of apple-gcc, breaking
the build on OS X 10.8.

Fixes: nodejs#7618
Refs: nodejs#4290
Refs: nodejs#7157

Author: bnoordhuis

src/node_buffer.cc

@@ -52,38 +52,6 @@
 #define BUFFER_MALLOC(length)                                               \
   zero_fill_all_buffers ? calloc(length, 1) : malloc(length)
 
-#if defined(__GNUC__) || defined(__clang__)
-#define BSWAP_INTRINSIC_2(x) __builtin_bswap16(x)
-#define BSWAP_INTRINSIC_4(x) __builtin_bswap32(x)
-#define BSWAP_INTRINSIC_8(x) __builtin_bswap64(x)
-#elif defined(__linux__)
-#include <byteswap.h>
-#define BSWAP_INTRINSIC_2(x) bswap_16(x)
-#define BSWAP_INTRINSIC_4(x) bswap_32(x)
-#define BSWAP_INTRINSIC_8(x) bswap_64(x)
-#elif defined(_MSC_VER)
-#include <intrin.h>
-#define BSWAP_INTRINSIC_2(x) _byteswap_ushort(x);
-#define BSWAP_INTRINSIC_4(x) _byteswap_ulong(x);
-#define BSWAP_INTRINSIC_8(x) _byteswap_uint64(x);
-#else
-#define BSWAP_INTRINSIC_2(x) ((x) << 8) | ((x) >> 8)
-#define BSWAP_INTRINSIC_4(x)                                                  \
-  (((x) & 0xFF) << 24) |                                                      \
-  (((x) & 0xFF00) << 8) |                                                     \
-  (((x) >> 8) & 0xFF00) |                                                     \
-  (((x) >> 24) & 0xFF)
-#define BSWAP_INTRINSIC_8(x)                                                  \
-  (((x) & 0xFF00000000000000ull) >> 56) |                                     \
-  (((x) & 0x00FF000000000000ull) >> 40) |                                     \
-  (((x) & 0x0000FF0000000000ull) >> 24) |                                     \
-  (((x) & 0x000000FF00000000ull) >> 8) |                                      \
-  (((x) & 0x00000000FF000000ull) << 8) |                                      \
-  (((x) & 0x0000000000FF0000ull) << 24) |                                     \
-  (((x) & 0x000000000000FF00ull) << 40) |                                     \
-  (((x) & 0x00000000000000FFull) << 56)
-#endif
-
 namespace node {
 
 // if true, all Buffer and SlowBuffer instances will automatically zero-fill
@@ -1209,18 +1177,8 @@ void Swap16(const FunctionCallbackInfo<Value>& args) {
 
   CHECK_EQ(ts_obj_length % 2, 0);
 
-  int align = reinterpret_cast<uintptr_t>(ts_obj_data) % sizeof(uint16_t);
-
-  if (align == 0) {
-    uint16_t* data16 = reinterpret_cast<uint16_t*>(ts_obj_data);
-    size_t len16 = ts_obj_length / 2;
-    for (size_t i = 0; i < len16; i++) {
-      data16[i] = BSWAP_INTRINSIC_2(data16[i]);
-    }
-  } else {
-    for (size_t i = 0; i < ts_obj_length; i += 2) {
-      std::swap(ts_obj_data[i], ts_obj_data[i + 1]);
-    }
+  for (size_t i = 0; i < ts_obj_length; i += 2) {
+    std::swap(ts_obj_data[i], ts_obj_data[i + 1]);
   }
 
   args.GetReturnValue().Set(args[0]);
@@ -1234,19 +1192,9 @@ void Swap32(const FunctionCallbackInfo<Value>& args) {
 
   CHECK_EQ(ts_obj_length % 4, 0);
 
-  int align = reinterpret_cast<uintptr_t>(ts_obj_data) % sizeof(uint32_t);
-
-  if (align == 0) {
-    uint32_t* data32 = reinterpret_cast<uint32_t*>(ts_obj_data);
-    size_t len32 = ts_obj_length / 4;
-    for (size_t i = 0; i < len32; i++) {
-      data32[i] = BSWAP_INTRINSIC_4(data32[i]);
-    }
-  } else {
-    for (size_t i = 0; i < ts_obj_length; i += 4) {
-      std::swap(ts_obj_data[i], ts_obj_data[i + 3]);
-      std::swap(ts_obj_data[i + 1], ts_obj_data[i + 2]);
-    }
+  for (size_t i = 0; i < ts_obj_length; i += 4) {
+    std::swap(ts_obj_data[i], ts_obj_data[i + 3]);
+    std::swap(ts_obj_data[i + 1], ts_obj_data[i + 2]);
   }
 
   args.GetReturnValue().Set(args[0]);
@@ -1260,21 +1208,11 @@ void Swap64(const FunctionCallbackInfo<Value>& args) {
 
   CHECK_EQ(ts_obj_length % 8, 0);
 
-  int align = reinterpret_cast<uintptr_t>(ts_obj_data) % sizeof(uint64_t);
-
-  if (align == 0) {
-    uint64_t* data64 = reinterpret_cast<uint64_t*>(ts_obj_data);
-    size_t len32 = ts_obj_length / 8;
-    for (size_t i = 0; i < len32; i++) {
-      data64[i] = BSWAP_INTRINSIC_8(data64[i]);
-    }
-  } else {
-    for (size_t i = 0; i < ts_obj_length; i += 8) {
-      std::swap(ts_obj_data[i], ts_obj_data[i + 7]);
-      std::swap(ts_obj_data[i + 1], ts_obj_data[i + 6]);
-      std::swap(ts_obj_data[i + 2], ts_obj_data[i + 5]);
-      std::swap(ts_obj_data[i + 3], ts_obj_data[i + 4]);
-    }
+  for (size_t i = 0; i < ts_obj_length; i += 8) {
+    std::swap(ts_obj_data[i], ts_obj_data[i + 7]);
+    std::swap(ts_obj_data[i + 1], ts_obj_data[i + 6]);
+    std::swap(ts_obj_data[i + 2], ts_obj_data[i + 5]);
+    std::swap(ts_obj_data[i + 3], ts_obj_data[i + 4]);
   }
 
   args.GetReturnValue().Set(args[0]);