Method WaitFor

cpp/src/arrow/io/caching.cc:243–263

Return a Future that completes when the given ranges have been read.

  // Return a Future that completes when the given ranges have been read.
  virtual Future<> WaitFor(std::vector<ReadRange> ranges) {
    auto end = std::remove_if(ranges.begin(), ranges.end(),
                              [](const ReadRange& range) { return range.length == 0; });
    ranges.resize(end - ranges.begin());
    std::vector<Future<>> futures;
    futures.reserve(ranges.size());
    for (auto& range : ranges) {
      const auto it = std::lower_bound(
          entries.begin(), entries.end(), range,
          [](const RangeCacheEntry& entry, const ReadRange& range) {
            return entry.range.offset + entry.range.length < range.offset + range.length;
          });
      if (it != entries.end() && it->range.Contains(range)) {
        futures.push_back(Future<>(MaybeRead(&*it)));
      } else {
        return Status::Invalid("Range was not requested for caching: offset=",
                               range.offset, " length=", range.length);
      }
    }
    return AllComplete(futures);
  }
};

// Don't read ranges when they're first added. Instead, wait until they're requested