bool BlockNotStale(const std::shared_ptr<Block>& block)
      ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_);

  /// Look up a Key in the block cache.
  std::shared_ptr<Block> Lookup(const Key& key) ABSL_LOCKS_EXCLUDED(mu_);

  void MaybeFetch(const Key& key, const std::shared_ptr<Block>& block,
                  TF_Status* status) ABSL_LOCKS_EXCLUDED(mu_);

  /// Trim the block cache to make room for another entry.

        block->data.resize(block_size_, 0);
        int64_t bytes_transferred;
        bytes_transferred = block_fetcher_(key.first, key.second, block_size_,
                                           block->data.data(), status);
        block->mu.Lock();  // Reacquire the lock immediately afterwards
        if (TF_GetCode(status) == TF_OK) {
          block->data.resize(bytes_transferred, 0);

    }
    TF_SetStatus(status, TF_OK, "");
    return bytes_transferred;
  };
  for (size_t block_size = 2; block_size <= 4; block_size++) {
    // Make a cache of N-byte block size (1 block) and verify that reads of
    // varying offsets and lengths return correct data.
    tf_gcs_filesystem::RamFileBlockCache cache(block_size, block_size, 0,
                                               fetcher);

	timeout.LogSuccess(UTCNow().Sub(start))
	return LockContext{ctx: newCtx, cancel: cancel}, nil
}

// Unlock - block until write lock is released.
func (di *distLockInstance) Unlock(lc LockContext) {
	if lc.cancel != nil {
		lc.cancel()
	}
	di.rwMutex.Unlock(lc.ctx)
}

// RLock - block until read lock is taken or timeout has occurred.

     *    <p>
     *    Transforms context based on 512 bits from input block starting
     *    from the offset'th byte.
     *
     *    @param    block    input sub-array.
     *    @param    offset    starting position of sub-array.
     */
    private void transform (byte[] block, int offset) {

        // encodes 64 bytes from input block into an array of 16 32-bit
        // entities. Use A as a temp var.

        length -= remainder;
        int block;
        int i = 0;
        while (i < length) {
            block = ((bytes[i++] & 0xff) << 16) | ((bytes[i++] & 0xff) << 8) |
                    (bytes[i++] & 0xff);
            buffer.append(ALPHABET.charAt(block >>> 18));
            buffer.append(ALPHABET.charAt((block >>> 12) & 0x3f));
            buffer.append(ALPHABET.charAt((block >>> 6) & 0x3f));

	var totalWritten int64

	// Write all data blocks to dst.
	for _, block := range enBlocks[:dataBlocks] {
		// Skip blocks until we have reached our offset.
		if offset >= int64(len(block)) {
			// Decrement offset.
			offset -= int64(len(block))
			continue
		}

		// Skip until offset.
		block = block[offset:]

		// Reset the offset for next iteration to read everything
		// from subsequent blocks.

typedef struct GCSFile {
  google::cloud::storage::Client gcs_client;  // owned
  bool compose;
  absl::Mutex block_cache_lock;
  std::shared_ptr<RamFileBlockCache> file_block_cache
      ABSL_GUARDED_BY(block_cache_lock);
  uint64_t block_size;  // Reads smaller than block_size will trigger a read
                        // of block_size.
  std::unique_ptr<ExpiringLRUCache<GcsFileStat>> stat_cache;

            block()
        }

    internal
    fun checkBinaryCompatibleJava(v1: String = "", v2: String, block: CheckResult.() -> Unit = {}): CheckResult =
        runJavaBinaryCompatibilityCheck(v1, v2) {
            assertBinaryCompatible()
            block()
        }

    internal
    fun checkNotBinaryCompatibleJava(v1: String = "", v2: String, block: CheckResult.() -> Unit = {}): CheckResult =

// nearest block edge where 0 <= n < blockSize.
func blockPadding(offset int64) (n int64) {
	return -offset & (blockSize - 1)
}

var zeroBlock block

type block [blockSize]byte

// Convert block to any number of formats.
func (b *block) toV7() *headerV7       { return (*headerV7)(b) }
func (b *block) toGNU() *headerGNU     { return (*headerGNU)(b) }