text: /*
   *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree. An additional intellectual property rights grant can be found
   *  in the file PATENTS.  All contributing project authors may
   *  be found in the AUTHORS file in the root of the source tree.
   */
  
  #include <features.h>
  #include <stdlib.h>
  #include <string.h>
  
  #ifdef __GLIBC_PREREQ
  #define WEBRTC_GLIBC_PREREQ(a, b) __GLIBC_PREREQ(a, b)
  #else
  #define WEBRTC_GLIBC_PREREQ(a, b) 0
  #endif
  
  #if WEBRTC_GLIBC_PREREQ(2, 16)
  #include <sys/auxv.h>
  #else
  #include <errno.h>
  #include <fcntl.h>
  #include <link.h>
  #include <unistd.h>
  #endif
  
  #include "rtc_base/system/arch.h"
  #include "system_wrappers/include/cpu_features_wrapper.h"
  
  #if defined(WEBRTC_ARCH_ARM_FAMILY)
  #include <asm/hwcap.h>
  
  namespace webrtc {
  
  uint64_t GetCPUFeaturesARM(void) {
    uint64_t result = 0;
    int architecture = 0;
    uint64_t hwcap = 0;
    const char* platform = NULL;
  #if WEBRTC_GLIBC_PREREQ(2, 16)
    hwcap = getauxval(AT_HWCAP);
    platform = (const char*)getauxval(AT_PLATFORM);
  #else
    ElfW(auxv_t) auxv;
    int fd = open("/proc/self/auxv", O_RDONLY);
    if (fd >= 0) {
      while (hwcap == 0 || platform == NULL) {
        if (read(fd, &auxv, sizeof(auxv)) < (ssize_t)sizeof(auxv)) {
          if (errno == EINTR)
            continue;
          break;
        }
        switch (auxv.a_type) {
          case AT_HWCAP:
            hwcap = auxv.a_un.a_val;
            break;
          case AT_PLATFORM:
            platform = (const char*)auxv.a_un.a_val;
            break;
        }
      }
      close(fd);
    }
  #endif  // WEBRTC_GLIBC_PREREQ(2, 16)
  #if defined(__aarch64__)
    (void)platform;
    architecture = 8;
    if ((hwcap & HWCAP_FP) != 0)
      result |= kCPUFeatureVFPv3;
    if ((hwcap & HWCAP_ASIMD) != 0)
      result |= kCPUFeatureNEON;
  #else
    if (platform != NULL) {
      /* expect a string in the form "v6l" or "v7l", etc.
       */
      if (platform[0] == 'v' && '0' <= platform[1] && platform[1] <= '9' &&
          (platform[2] == 'l' || platform[2] == 'b')) {
        architecture = platform[1] - '0';
      }
    }
    if ((hwcap & HWCAP_VFPv3) != 0)
      result |= kCPUFeatureVFPv3;
    if ((hwcap & HWCAP_NEON) != 0)
      result |= kCPUFeatureNEON;
  #endif
    if (architecture >= 7)
      result |= kCPUFeatureARMv7;
    if (architecture >= 6)
      result |= kCPUFeatureLDREXSTREX;
    return result;
  }
  
  }  // namespace webrtc
  #endif  // WEBRTC_ARCH_ARM_FAMILY
  