Function get_cached_file

tools/emscripten.py:300–335

Implement a file cache which lives inside the main emscripten cache directory. The defference here is that we use a per-file lock rather than a cache-wide lock. The cache is pruned (by removing the oldest files) if it grows above a certain number of files.

(filetype, filename, generator, cache_limit)

def get_cached_file(filetype, filename, generator, cache_limit):
  """Implement a file cache which lives inside the main emscripten cache directory.

  The defference here is that we use a per-file lock rather than a cache-wide lock.

  The cache is pruned (by removing the oldest files) if it grows above
  a certain number of files.
  """
  root = cache.get_path(filetype)
  utils.safe_ensure_dirs(root)

  cache_file = os.path.join(root, filename)

  with filelock.FileLock(cache_file + '.lock'):
    if os.path.exists(cache_file):
      # Cache hit, read the file
      file_content = utils.read_file(cache_file)
    else:
      # Cache miss, generate the symbol list and write the file
      file_content = generator()
      utils.write_file(cache_file, file_content)

  if len([f for f in os.listdir(root) if not f.endswith('.lock')]) > cache_limit:
    with filelock.FileLock(cache.get_path(f'{filetype}.lock')):
      files = []
      for f in os.listdir(root):
        if not f.endswith('.lock'):
          f = os.path.join(root, f)
          files.append((f, os.path.getmtime(f)))
      files.sort(key=lambda x: x[1])
      # Delete all but the newest N files
      for f, _ in files[:-cache_limit]:
        with filelock.FileLock(f + '.lock'):
          utils.delete_file(f)

  return file_content


@ToolchainProfiler.profile()