Function profile_write_pprof_file

lib/cpp/src/thrift/VirtualProfiling.cpp:351–389

* Write a BacktraceMap as Google CPU profiler binary data. */

 * Write a BacktraceMap as Google CPU profiler binary data.
 */
static void profile_write_pprof_file(FILE* f, BacktraceMap const& map) {
  // Write the header
  uintptr_t header[5] = {0, 3, 0, 0, 0};
  fwrite(&header, sizeof(header), 1, f);

  // Write the profile records
  for (BacktraceMap::const_iterator it = map.begin(); it != map.end(); ++it) {
    uintptr_t count = it->second;
    fwrite(&count, sizeof(count), 1, f);

    Backtrace const* bt = it->first.getBacktrace();
    uintptr_t num_pcs = bt->getDepth();
    fwrite(&num_pcs, sizeof(num_pcs), 1, f);

    for (uintptr_t n = 0; n < num_pcs; ++n) {
      void* pc = bt->getFrame(n);
      fwrite(&pc, sizeof(pc), 1, f);
    }
  }

  // Write the trailer
  uintptr_t trailer[3] = {0, 1, 0};
  fwrite(&trailer, sizeof(trailer), 1, f);

  // Write /proc/self/maps
  // TODO(simpkins): This only works on linux
  FILE* proc_maps = fopen("/proc/self/maps", "r");
  if (proc_maps) {
    uint8_t buf[4096];
    while (true) {
      size_t bytes_read = fread(buf, 1, sizeof(buf), proc_maps);
      if (bytes_read == 0) {
        break;
      }
      fwrite(buf, 1, bytes_read, f);
    }
    fclose(proc_maps);
  }
}

/**
 * Write the recorded profiling information as pprof files.