New code layout - breaking change in cpu_features_macros.h (#194)

This commit helps with platform code separation (fixes #3). It should also help with the build as we can simply include all `impl_*.c` files regardless of OS / arch.

Note: this patch contains breaking changes in `include/cpu_features_macros.h`
 - `CPU_FEATURES_OS_LINUX_OR_ANDROID` does not exist anymore
 - `CPU_FEATURES_OS_FREEBSD`, `CPU_FEATURES_OS_ANDROID` and `CPU_FEATURES_OS_LINUX` are now mutually exclusive (i.e. `CPU_FEATURES_OS_ANDROID` does not imply `CPU_FEATURES_OS_LINUX`)
 - `CPU_FEATURES_OS_DARWIN` has been renamed into `CPU_FEATURES_OS_MACOS` to be able to target non-Mac Apple products (IOS, TV, WATCH). They are now targetable with `CPU_FEATURES_OS_IPHONE`. This matches Apple naming convention described in [this stackoverflow](https://stackoverflow.com/a/49560690).

src/impl_mips_linux_or_android.c

@@ -0,0 +1,88 @@
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "cpu_features_macros.h"
+
+#ifdef CPU_FEATURES_ARCH_MIPS
+#if defined(CPU_FEATURES_OS_LINUX) || defined(CPU_FEATURES_OS_ANDROID)
+
+#include "cpuinfo_mips.h"
+
+////////////////////////////////////////////////////////////////////////////////
+// Definitions for introspection.
+////////////////////////////////////////////////////////////////////////////////
+#define INTROSPECTION_TABLE                     \
+  LINE(MIPS_MSA, msa, "msa", MIPS_HWCAP_MSA, 0) \
+  LINE(MIPS_EVA, eva, "eva", 0, 0)              \
+  LINE(MIPS_R6, r6, "r6", MIPS_HWCAP_R6, 0)
+#define INTROSPECTION_PREFIX Mips
+#define INTROSPECTION_ENUM_PREFIX MIPS
+#include "define_introspection_and_hwcaps.inl"
+
+////////////////////////////////////////////////////////////////////////////////
+// Implementation.
+////////////////////////////////////////////////////////////////////////////////
+
+#include "internal/filesystem.h"
+#include "internal/hwcaps.h"
+#include "internal/stack_line_reader.h"
+#include "internal/string_view.h"
+
+static bool HandleMipsLine(const LineResult result,
+                           MipsFeatures* const features) {
+  StringView key, value;
+  // See tests for an example.
+  if (CpuFeatures_StringView_GetAttributeKeyValue(result.line, &key, &value)) {
+    if (CpuFeatures_StringView_IsEquals(key, str("ASEs implemented"))) {
+      for (size_t i = 0; i < MIPS_LAST_; ++i) {
+        kSetters[i](features, CpuFeatures_StringView_HasWord(
+                                  value, kCpuInfoFlags[i], ' '));
+      }
+    }
+  }
+  return !result.eof;
+}
+
+static void FillProcCpuInfoData(MipsFeatures* const features) {
+  const int fd = CpuFeatures_OpenFile("/proc/cpuinfo");
+  if (fd >= 0) {
+    StackLineReader reader;
+    StackLineReader_Initialize(&reader, fd);
+    for (;;) {
+      if (!HandleMipsLine(StackLineReader_NextLine(&reader), features)) {
+        break;
+      }
+    }
+    CpuFeatures_CloseFile(fd);
+  }
+}
+
+static const MipsInfo kEmptyMipsInfo;
+
+MipsInfo GetMipsInfo(void) {
+  // capabilities are fetched from both getauxval and /proc/cpuinfo so we can
+  // have some information if the executable is sandboxed (aka no access to
+  // /proc/cpuinfo).
+  MipsInfo info = kEmptyMipsInfo;
+
+  FillProcCpuInfoData(&info.features);
+  const HardwareCapabilities hwcaps = CpuFeatures_GetHardwareCapabilities();
+  for (size_t i = 0; i < MIPS_LAST_; ++i) {
+    if (CpuFeatures_IsHwCapsSet(kHardwareCapabilities[i], hwcaps)) {
+      kSetters[i](&info.features, true);
+    }
+  }
+  return info;
+}
+
+#endif  //  defined(CPU_FEATURES_OS_LINUX) || defined(CPU_FEATURES_OS_ANDROID)
+#endif  // CPU_FEATURES_ARCH_MIPS