Method CalculateRanges

src/CacheBase.cpp:36–97

Calculate ranges of frames

// Calculate ranges of frames
void CacheBase::CalculateRanges() {
	// Only calculate when something has changed
	if (needs_range_processing) {

		// Create a scoped lock, to protect the cache from multiple threads
		const std::lock_guard<std::recursive_mutex> lock(*cacheMutex);

		// Sort ordered frame #s, and calculate JSON ranges
		std::sort(ordered_frame_numbers.begin(), ordered_frame_numbers.end());

		// Clear existing JSON variable
		Json::Value ranges = Json::Value(Json::arrayValue);

		// Increment range version
		range_version++;

		std::vector<int64_t>::iterator itr_ordered;

        int64_t starting_frame = 0;
        int64_t ending_frame = 0;
        if (ordered_frame_numbers.size() > 0) {
            starting_frame = *ordered_frame_numbers.begin();
            ending_frame = *ordered_frame_numbers.begin();

            // Loop through all known frames (in sequential order)
            for (itr_ordered = ordered_frame_numbers.begin(); itr_ordered != ordered_frame_numbers.end(); ++itr_ordered) {
                int64_t frame_number = *itr_ordered;
                if (frame_number - ending_frame > 1) {
                    // End of range detected
                    Json::Value range;

                    // Add JSON object with start/end attributes
                    // Use strings, since int64_ts are supported in JSON
                    range["start"] = std::to_string(starting_frame);
                    range["end"] = std::to_string(ending_frame);
                    ranges.append(range);

                    // Set new starting range
                    starting_frame = frame_number;
                }

                // Set current frame as end of range, and keep looping
                ending_frame = frame_number;
            }
        }

        // APPEND FINAL VALUE
        Json::Value range;

        // Add JSON object with start/end attributes
        // Use strings, since int64_ts are not supported in JSON
        range["start"] = std::to_string(starting_frame);
        range["end"] = std::to_string(ending_frame);
        ranges.append(range);

        // Cache range JSON as string
        json_ranges = ranges.toStyledString();