Aegisub/aegisub/src/video_provider_cache.cpp

// Copyright (c) 2008, Rodrigo Braz Monteiro
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//   * Redistributions of source code must retain the above copyright notice,
//     this list of conditions and the following disclaimer.
//   * Redistributions in binary form must reproduce the above copyright notice,
//     this list of conditions and the following disclaimer in the documentation
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//   * Neither the name of the Aegisub Group nor the names of its contributors
//     may be used to endorse or promote products derived from this software
//     without specific prior written permission.
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// Aegisub Project http://www.aegisub.org/
//
// $Id$

/// @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 "main.h"
#include "video_frame.h"

#ifndef AGI_PRE
#include <algorithm>
#include <tr1/functional>
#endif

/// 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::tr1::mem_fn(&AegiVideoFrame::Clear));
}

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

	// See if frame is cached
	for (std::list<CachedFrame>::iterator 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();
}