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Stable release v32.1bitcoin/bitcoin · f0de87f04062 ↗3,020 source files · 47.5 MB stored on the server340 file guides

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bitcoin / src / cuckoocache.h

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251    }
252
253    /** invalid returns a special index that can never be inserted to
254     * @returns the special constexpr index that can never be inserted to */
255    constexpr uint32_t invalid() const
256    {
257        return ~(uint32_t)0;
258    }
259
260    /** allow_erase marks the element at index `n` as discardable. Threadsafe
261     * without any concurrent insert.
262     * @param n the index to allow erasure of
263     */
264    inline void allow_erase(uint32_t n) const
265    {
266        collection_flags.bit_set(n);
267    }
268
269    /** please_keep marks the element at index `n` as an entry that should be kept.
270     * Threadsafe without any concurrent insert.
271     * @param n the index to prioritize keeping
272     */
273    inline void please_keep(uint32_t n) const
274    {
275        collection_flags.bit_unset(n);
276    }
277
278    /** epoch_check handles the changing of epochs for elements stored in the
279     * cache. epoch_check should be run before every insert.
280     *
281     * First, epoch_check decrements and checks the cheap heuristic, and then does
282     * a more expensive scan if the cheap heuristic runs out. If the expensive
283     * scan succeeds, the epochs are aged and old elements are allow_erased. The
284     * cheap heuristic is reset to retrigger after the worst case growth of the
285     * current epoch's elements would exceed the epoch_size.
286     */
287    void epoch_check()
288    {
289        if (epoch_heuristic_counter != 0) {
290            --epoch_heuristic_counter;
291            return;
292        }
293        // count the number of elements from the latest epoch which
294        // have not been erased.
295        uint32_t epoch_unused_count = 0;
296        for (uint32_t i = 0; i < size; ++i)
297            epoch_unused_count += epoch_flags[i] &&
298                                  !collection_flags.bit_is_set(i);
299        // If there are more non-deleted entries in the current epoch than the
300        // epoch size, then allow_erase on all elements in the old epoch (marked
301        // false) and move all elements in the current epoch to the old epoch
302        // but do not call allow_erase on their indices.
303        if (epoch_unused_count >= epoch_size) {
304            for (uint32_t i = 0; i < size; ++i)
305                if (epoch_flags[i])
306                    epoch_flags[i] = false;
307                else
308                    allow_erase(i);
309            epoch_heuristic_counter = epoch_size;
310        } else
311            // reset the epoch_heuristic_counter to next do a scan when worst
312            // case behavior (no intermittent erases) would exceed epoch size,
313            // with a reasonable minimum scan size.
314            // Ordinarily, we would have to sanity check std::min(epoch_size,
315            // epoch_unused_count), but we already know that `epoch_unused_count
316            // < epoch_size` in this branch
317            epoch_heuristic_counter = std::max(1u, std::max(epoch_size / 16,
318                        epoch_size - epoch_unused_count));
319    }
320
321public:
322    /** You must always construct a cache with some elements via a subsequent
323     * call to setup or setup_bytes, otherwise operations may segfault.
324     */
325    cache() : table(), collection_flags(0), epoch_flags(), hash_function()
326    {
327    }
328
329    /** setup initializes the container to store no more than new_size
330     * elements and no less than 2 elements.
331     *
332     * setup should only be called once. TestOnlyReset() is the exception.
333     *
334     * @param new_size the desired number of elements to store
335     * @returns the maximum number of elements storable
336     */
337    uint32_t setup(uint32_t new_size)
338    {
339        // depth_limit must be at least one otherwise errors can occur.
340        size = std::max<uint32_t>(2, new_size);
341        depth_limit = static_cast<uint8_t>(std::log2(static_cast<float>(size)));
342        table.resize(size);
343        collection_flags.setup(size);
344        epoch_flags.resize(size);
345        // Set to 45% as described above
346        epoch_size = std::max(uint32_t{1}, (45 * size) / 100);
347        // Initially set to wait for a whole epoch
348        epoch_heuristic_counter = epoch_size;
349        return size;
350    }
351
352    /** setup_bytes is a convenience function which accounts for internal memory
353     * usage when deciding how many elements to store. It isn't perfect because
354     * it doesn't account for any overhead (struct size, MallocUsage, collection
355     * and epoch flags). This was done to simplify selecting a power of two
356     * size. In the expected use case, an extra two bits per entry should be
357     * negligible compared to the size of the elements.
358     *
359     * @param bytes the approximate number of bytes to use for this data
360     * structure
361     * @returns A pair of the maximum number of elements storable (see setup()
362     * documentation for more detail) and the approximate total size of these
363     * elements in bytes.
364     */
365    std::pair<uint32_t, size_t> setup_bytes(size_t bytes)
366    {
367        uint32_t requested_num_elems(std::min<size_t>(
368            bytes / sizeof(Element),
369            std::numeric_limits<uint32_t>::max()));
370
371        auto num_elems = setup(requested_num_elems);
372
373        size_t approx_size_bytes = num_elems * sizeof(Element);
374        return std::make_pair(num_elems, approx_size_bytes);
375    }
376
377    /** insert loops at most depth_limit times trying to insert a hash
378     * at various locations in the table via a variant of the Cuckoo Algorithm
379     * with eight hash locations.
380     *
381     * It drops the last tried element if it runs out of depth before
382     * encountering an open slot.
383     *
384     * Thus:
385     *
386     * ```
387     * insert(x);
388     * return contains(x, false);
389     * ```
390     *
391     * is not guaranteed to return true.
392     *
393     * @param e the element to insert
394     * @post one of the following: All previously inserted elements and e are
395     * now in the table, one previously inserted element is evicted from the
396     * table, the entry attempted to be inserted is evicted.
397     */
398    inline void insert(Element e)
399    {
400        epoch_check();
401        uint32_t last_loc = invalid();
402        bool last_epoch = true;
403        std::array<uint32_t, 8> locs = compute_hashes(e);
404        // Make sure we have not already inserted this element
405        // If we have, make sure that it does not get deleted
406        for (const uint32_t loc : locs)
407            if (table[loc] == e) {
408                please_keep(loc);
409                epoch_flags[loc] = last_epoch;
410                return;
411            }
412        for (uint8_t depth = 0; depth < depth_limit; ++depth) {
413            // First try to insert to an empty slot, if one exists
414            for (const uint32_t loc : locs) {
415                if (!collection_flags.bit_is_set(loc))
416                    continue;
417                table[loc] = std::move(e);
418                please_keep(loc);
419                epoch_flags[loc] = last_epoch;
420                return;
421            }
422            /** Swap with the element at the location that was
423            * not the last one looked at. Example:
424            *
425            * 1. On first iteration, last_loc == invalid(), find returns last, so
426            *    last_loc defaults to locs[0].
427            * 2. On further iterations, where last_loc == locs[k], last_loc will
428            *    go to locs[k+1 % 8], i.e., next of the 8 indices wrapping around
429            *    to 0 if needed.
430            *
431            * This prevents moving the element we just put in.
432            *
433            * The swap is not a move -- we must switch onto the evicted element
434            * for the next iteration.
435            */
436            last_loc = locs[(1 + (std::find(locs.begin(), locs.end(), last_loc) - locs.begin())) & 7];
437            std::swap(table[last_loc], e);
438            // Can't std::swap a std::vector<bool>::reference and a bool&.
439            bool epoch = last_epoch;
440            last_epoch = epoch_flags[last_loc];
441            epoch_flags[last_loc] = epoch;
442
443            // Recompute the locs -- unfortunately happens one too many times!
444            locs = compute_hashes(e);
445        }
446    }
447
448    /** contains iterates through the hash locations for a given element
449     * and checks to see if it is present.
450     *
451     * contains does not check garbage collected state (in other words,
452     * garbage is only collected when the space is needed), so:
453     *
454     * ```
455     * insert(x);
456     * if (contains(x, true))
457     *     return contains(x, false);
458     * else
459     *     return true;
460     * ```
461     *
462     * executed on a single thread will always return true!
463     *
464     * This is a great property for re-org performance for example.
465     *
466     * contains returns a bool set true if the element was found.
467     *
468     * @param e the element to check
469     * @param erase whether to attempt setting the garbage collect flag
470     *
471     * @post if erase is true and the element is found, then the garbage collect
472     * flag is set
473     * @returns true if the element is found, false otherwise
474     */
475    inline bool contains(const Element& e, const bool erase) const
476    {
477        std::array<uint32_t, 8> locs = compute_hashes(e);
478        for (const uint32_t loc : locs)
479            if (table[loc] == e) {
480                if (erase)
481                    allow_erase(loc);
482                return true;
483            }
484        return false;
485    }
486
487    /** Empty the cache and re-run setup(). */
488    void TestOnlyReset()
489    {
490        table.clear();
491        epoch_flags.clear();
492        setup(0);
493    }
494};
495} // namespace CuckooCache
496
497#endif // BITCOIN_CUCKOOCACHE_H
498

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340 guided files · 2,680 pending. Guides cover key sections, not every line.

cmake/bitcoin-build-config.h.in src/consensus/amount.h src/consensus/consensus.h src/primitives/block.h src/primitives/transaction.h src/crypto/sha256.h src/util/moneystr.h src/clientversion.h src/uint256.h src/script/script.h src/policy/policy.h CMakeLists.txt README.md COPYING src/consensus/tx_check.cpp src/consensus/tx_verify.cpp src/consensus/merkle.cpp src/pow.cpp src/validation.cpp src/script/interpreter.cpp src/script/solver.cpp src/script/sign.cpp src/key_io.cpp src/net.cpp src/net_processing.cpp src/netaddress.cpp src/protocol.h src/wallet/wallet.cpp src/wallet/spend.cpp

← Previous 250 linesCode page 2

src/wallet/receive.cpp

src/wallet/coinselection.cpp

src/consensus/validation.h

src/primitives/transaction.cpp

src/script/descriptor.cpp

src/bitcoin-cli.cpp

src/rpc/blockchain.cpp

src/rpc/rawtransaction.cpp

src/init.cpp

src/crypto/sha256.cpp

src/consensus/merkle.h

src/consensus/tx_check.h

src/consensus/tx_verify.h

src/policy/feerate.h

src/policy/feerate.cpp

src/primitives/transaction_identifier.h

src/chainparamsbase.h

src/chainparamsbase.cpp

src/util/moneystr.cpp

src/crypto/ripemd160.h

src/crypto/sha1.h

src/crypto/sha512.h

src/crypto/hmac_sha256.h

src/crypto/hmac_sha512.h

src/crypto/hmac_sha256.cpp

src/crypto/hmac_sha512.cpp

src/crypto/hkdf_sha256_32.h

src/crypto/hkdf_sha256_32.cpp

src/support/cleanse.h

src/support/cleanse.cpp

src/crypto/siphash.cpp

src/crypto/muhash.h

src/crypto/chacha20.h

src/crypto/poly1305.h

src/crypto/chacha20poly1305.h

src/crypto/chacha20poly1305.cpp

src/util/chaintype.cpp

src/util/obfuscation.h

src/util/byte_units.h

src/util/overflow.h

src/blockencodings.cpp

src/net_permissions.cpp

src/policy/packages.cpp

src/policy/rbf.cpp

src/policy/truc_policy.cpp

src/policy/ephemeral_policy.cpp

src/policy/settings.cpp

src/policy/policy.cpp

src/node/transaction.cpp

src/node/coin.cpp

src/rpc/client.cpp

src/rpc/external_signer.cpp

src/rpc/request.cpp

src/rpc/server_util.cpp

src/rpc/fees.cpp

src/rpc/output_script.cpp

src/rpc/rawtransaction_util.cpp

src/rpc/rawtransaction_util.h

src/rpc/register.h

src/rpc/request.h

src/rpc/server_util.h

src/rpc/protocol.h

src/rpc/server.h

src/rpc/signmessage.cpp

src/rpc/txoutproof.cpp

src/rpc/util.cpp

src/rpc/util.h

src/wallet/rpc/addresses.cpp

src/wallet/rpc/backup.cpp

src/wallet/rpc/coins.cpp

src/wallet/rpc/encrypt.cpp

src/wallet/rpc/signmessage.cpp

src/wallet/rpc/util.cpp

src/wallet/rpc/util.h

src/wallet/coincontrol.cpp

src/wallet/coincontrol.h

src/wallet/context.cpp

src/wallet/context.h

src/wallet/crypter.cpp

src/wallet/crypter.h

src/wallet/db.cpp

src/wallet/export.cpp

src/wallet/external_signer_scriptpubkeyman.cpp

src/wallet/rpc/spend.cpp

src/wallet/rpc/transactions.cpp

src/wallet/rpc/wallet.cpp

src/wallet/feebumper.cpp

src/wallet/feebumper.h

src/index/base.h

src/index/base.cpp

src/index/txindex.h

src/index/txindex.cpp

src/index/txindex_key.h

src/index/txospenderindex.h

src/index/txospenderindex.cpp

src/index/blockfilterindex.h

src/index/blockfilterindex.cpp

src/index/coinstatsindex.h

src/index/coinstatsindex.cpp

src/index/db_key.h

src/index/disktxpos.h

src/kernel/chain.cpp

src/kernel/chain.h

src/kernel/checks.cpp

src/kernel/checks.h

src/kernel/context.cpp

src/kernel/context.h

src/kernel/cs_main.cpp

src/kernel/cs_main.h

src/kernel/disconnected_transactions.cpp

src/kernel/disconnected_transactions.h

src/kernel/mempool_removal_reason.cpp

src/kernel/mempool_removal_reason.h

src/kernel/coinstats.cpp

src/kernel/coinstats.h

src/kernel/chainparams.cpp

src/kernel/chainparams.h

src/wallet/sqlite.cpp

src/wallet/sqlite.h

src/wallet/transaction.cpp

src/wallet/transaction.h

src/wallet/dump.cpp

src/wallet/dump.h

src/wallet/init.cpp

src/wallet/walletutil.cpp

src/wallet/walletutil.h

src/wallet/wallettool.cpp

src/wallet/wallettool.h

src/wallet/export.h

src/wallet/migrate.cpp

src/wallet/migrate.h

src/wallet/db.h

src/wallet/walletdb.cpp

src/wallet/interfaces.cpp

src/wallet/scriptpubkeyman.cpp

src/wallet/scriptpubkeyman.h

src/kernel/bitcoinkernel.cpp

src/kernel/bitcoinkernel.h

src/kernel/bitcoinkernel_wrapper.h

src/node/chainstate.cpp

src/node/chainstate.h

src/node/blockstorage.cpp

src/node/blockstorage.h

src/node/mempool_persist.cpp

src/node/mempool_persist.h

src/node/utxo_snapshot.cpp

src/node/utxo_snapshot.h

src/node/kernel_notifications.cpp

src/node/kernel_notifications.h

src/node/blockmanager_args.cpp

src/kernel/blockmanager_opts.h

src/util/expected.cpp

src/policy/settings.h

src/util/types.h

src/kernel/messagestartchars.h

src/kernel/warning.h

src/util/exception.h

src/common/license_info.h

src/node/coins_view_args.h

src/node/database_args.h

src/util/batchpriority.h

src/util/ui_change_type.h

src/node/coins_view_args.cpp

src/node/peerman_args.h

src/util/serfloat.h

src/node/blockmanager_args.h

src/node/database_args.cpp

src/util/overloaded.h

src/interfaces/types.h

src/node/chainstatemanager_args.h

src/node/minisketchwrapper.h

src/util/macros.h

src/util/syserror.h

src/common/run_command.h

src/util/bytevectorhash.cpp

src/node/mempool_persist_args.cpp

src/util/exec.h

src/util/rbf.h

src/crypto/hex_base.h

src/node/mempool_persist_args.h

src/interfaces/echo.h

src/util/any.h

src/util/batchpriority.cpp

src/util/threadnames.h

src/node/coin.h

src/node/mempool_args.h

src/util/asmap.h

src/util/bytevectorhash.h

src/node/context.cpp

src/util/insert.h

src/util/readwritefile.h

src/node/peerman_args.cpp

src/node/interface_ui.cpp

src/interfaces/handler.h

src/node/mining_args.h

src/util/hasher.cpp

src/common/init.h

src/kernel/mempool_limits.h

src/common/system.h

src/crypto/sha3.h

src/util/threadinterrupt.cpp

src/node/protocol_version.h

src/util/exception.cpp

src/common/messages.h

src/node/connection_types.cpp

src/util/bip32.h

src/common/license_info.cpp

src/util/stdmutex.h

src/common/run_command.cpp

src/util/check.cpp

src/util/golombrice.h

src/node/types.h

src/node/timeoffsets.h

src/util/readwritefile.cpp

src/util/fastrange.h

src/util/signalinterrupt.h

src/util/task_runner.h

src/util/syserror.cpp

src/common/interfaces.cpp

src/common/types.h

src/util/threadinterrupt.h

src/kernel/chainstatemanager_opts.h

src/node/psbt.h

src/policy/ephemeral_policy.h

src/util/trace.h

src/common/url.cpp

src/kernel/mempool_options.h

src/util/serfloat.cpp

src/kernel/notifications_interface.h

src/node/timeoffsets.cpp

src/node/warnings.cpp

src/util/hash_type.h

src/crypto/hex_base.cpp

src/node/eviction.h

src/util/tokenbucket.h

src/crypto/aes.h

src/common/pcp.h

src/util/feefrac.cpp

src/node/transaction.h

src/util/threadnames.cpp

src/common/signmessage.h

src/util/exec.cpp

src/util/signalinterrupt.cpp

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