Differential D4834 Diff 15641 src/script/scriptcache.h

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src/script/scriptcache.h

	// Copyright (c) 2017 - The Bitcoin Developers			// Copyright (c) 2017 - The Bitcoin Developers
	// Distributed under the MIT software license, see the accompanying			// Distributed under the MIT software license, see the accompanying
	// file COPYING or http://www.opensource.org/licenses/mit-license.php.			// file COPYING or http://www.opensource.org/licenses/mit-license.php.

	#ifndef BITCOIN_SCRIPT_SCRIPTCACHE_H			#ifndef BITCOIN_SCRIPT_SCRIPTCACHE_H
	#define BITCOIN_SCRIPT_SCRIPTCACHE_H			#define BITCOIN_SCRIPT_SCRIPTCACHE_H

	#include <uint256.h>			#include <script/script_metrics.h>

				#include <array>
	#include <cstdint>			#include <cstdint>

	class CTransaction;			class CTransaction;

				/**
				* The script cache is a map using a key/value element, that caches the
				* success of executing a specific transaction's input scripts under a
				* specific set of flags, along with any associated information learned
				* during execution.
				*
				* The key is slightly shorter than a power-of-two size to make room for
				* the value.
				*/
				class ScriptCacheKey {
				std::array<uint8_t, 30> data;

				public:
				ScriptCacheKey() = default;
				ScriptCacheKey(const ScriptCacheKey &rhs) = default;
				ScriptCacheKey(const CTransaction &tx, uint32_t flags);

				bool operator==(const ScriptCacheKey &rhs) const {
				return rhs.data == data;
				}

				friend class ScriptCacheHasher;
				};

	// DoS prevention: limit cache size to 32MB (over 1000000 entries on 64-bit			// DoS prevention: limit cache size to 32MB (over 1000000 entries on 64-bit
	// systems). Due to how we count cache size, actual memory usage is slightly			// systems). Due to how we count cache size, actual memory usage is slightly
	// more (~32.25 MB)			// more (~32.25 MB)
	static const unsigned int DEFAULT_MAX_SCRIPT_CACHE_SIZE = 32;			static const unsigned int DEFAULT_MAX_SCRIPT_CACHE_SIZE = 32;
	// Maximum sig cache size allowed			// Maximum sig cache size allowed
	static const int64_t MAX_MAX_SCRIPT_CACHE_SIZE = 16384;			static const int64_t MAX_MAX_SCRIPT_CACHE_SIZE = 16384;

	/** Initializes the script-execution cache */			/** Initializes the script-execution cache */
	void InitScriptExecutionCache();			void InitScriptExecutionCache();

	/** Compute the cache key for a given transaction and flags. */			/**
	uint256 GetScriptCacheKey(const CTransaction &tx, uint32_t flags);			* Check if a given key is in the cache, and if so, return its values.
				* (if not found, metricsOut may or may not be set to an arbitrary value)
	/** Check if a given key is in the cache. */			*/
	bool IsKeyInScriptCache(uint256 key, bool erase);			bool IsKeyInScriptCache(ScriptCacheKey key, bool erase,
				ScriptExecutionMetrics &metricsOut);
	/** Add an entry in the cache. */
	void AddKeyInScriptCache(uint256 key);			constexpr int SCRIPT_CACHE_MAX_SIGCHECKS = UINT16_MAX;

				/**
				* Try to store a given key with values in the cache. Due to limited storage
				* bits, the cache can only store values in certain ranges:
				*
				* 0 <= metricsIn.nSigChecks <= SCRIPT_CACHE_MAX_SIGCHECKS
				*
				* If any value is out of range, this will return false rather than storing this
				* item into the cache. Otherwise it returns true.
				*/
				bool TryAddKeyInScriptCache(ScriptCacheKey key, ScriptExecutionMetrics metrics);

				/**
				* Add an entry in the cache.
				*/
				static inline void AddKeyInScriptCache(ScriptCacheKey key,
				ScriptExecutionMetrics metrics) {
				if (!TryAddKeyInScriptCache(key, metrics)) {
				throw std::range_error("metrics out of range");
				}
				}

	#endif // BITCOIN_SCRIPT_SCRIPTCACHE_H			#endif // BITCOIN_SCRIPT_SCRIPTCACHE_H