Aegisub/aegisub/src/video_provider_cache.cpp

// Copyright (c) 2008, Rodrigo Braz Monteiro
// All rights reserved.
//
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/// @file video_provider_cache.cpp
/// @brief Aggregate video provider caching previously requested frames
/// @ingroup video_input
///

#include "config.h"

#include "video_provider_cache.h"

#include "options.h"
#include "video_frame.h"

#include <algorithm>
#include <functional>

/// A video frame and its frame number
struct CachedFrame : public AegiVideoFrame {
	int frame_number;
};

VideoProviderCache::VideoProviderCache(VideoProvider *parent)
: master(parent)
, max_cache_size(OPT_GET("Provider/Video/Cache/Size")->GetInt() << 20) // convert MB to bytes
{
}

VideoProviderCache::~VideoProviderCache() {
	for_each(cache.begin(), cache.end(), std::mem_fn(&AegiVideoFrame::Clear));
}

const AegiVideoFrame VideoProviderCache::GetFrame(int n) {
	size_t total_size = 0;

	// See if frame is cached
	for (auto cur = cache.begin(); cur != cache.end(); ++cur) {
		if (cur->frame_number == n) {
			cache.push_front(*cur);
			cache.erase(cur);
			return cache.front();
		}

		total_size += cur->memSize;
	}

	// Not cached, retrieve it
	const AegiVideoFrame frame = master->GetFrame(n);

	// Cache full, use oldest frame
	if (total_size >= max_cache_size) {
		cache.push_front(cache.back());
		cache.pop_back();
	}
	// Cache not full, insert new one
	else
		cache.push_front(CachedFrame());

	// Cache
	cache.front().frame_number = n;
	cache.front().CopyFrom(frame);
	return cache.front();
}