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Stable release v32.1bitcoin/bitcoin · f0de87f04062 ↗3,020 source files · 47.5 MB stored on the server440 file guides

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1// Copyright (c) The Bitcoin Core developers
2// Distributed under the MIT software license, see the accompanying
3// file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5#ifndef BITCOIN_UTIL_BTCSIGNALS_H
6#define BITCOIN_UTIL_BTCSIGNALS_H
7
8#include <sync.h>
9
10#include <algorithm>
11#include <atomic>
12#include <functional>
13#include <memory>
14#include <optional>
15#include <type_traits>
16#include <utility>
17#include <vector>
18
19/**
20 * btcsignals is a simple mechanism for signaling events to multiple subscribers.
21 * It is api-compatible with a minimal subset of boost::signals2.
22 *
23 * Rather than using a custom slot type, and the features/complexity that they
24 * imply, std::function is used to store the callbacks. Lifetime management of
25 * the callbacks is left up to the user.
26 *
27 * All usage is thread-safe except for interacting with a connection while
28 * copying/moving it on another thread.
29 */
30
31namespace btcsignals {
32
33/// The default combiner, which only returns void.
34class null_value
35{
36public:
37    using result_type = void;
38};
39
40/// A combiner, which checks if at least one callback returned true.
41class any_of
42{
43public:
44    // This is the only supported combiner with a non-void return type. As
45    // such, its behavior is embedded into the signal functor.
46    using result_type = bool;
47};
48
49template <typename Signature, typename Combiner = null_value>
50class signal;
51
52/*
53 * State object representing the liveness of a registered callback.
54 * signal::connect() returns an enabled connection which can be held and
55 * disabled in the future.
56 */
57class connection
58{
59    template <typename Signature, typename Combiner>
60    friend class signal;
61    /**
62     * Track liveness. Also serves as a tag for the constructor used by signal.
63     */
64    class liveness
65    {
66        friend class connection;
67        std::atomic_bool m_connected{true};
68
69        void disconnect() { m_connected.store(false); }
70    public:
71        bool connected() const { return m_connected.load(); }
72    };
73
74    /**
75     * connections have shared_ptr-like copy and move semantics.
76     */
77    std::shared_ptr<liveness> m_state{};
78
79    /**
80     * Only a signal can create an enabled connection.
81     */
82    explicit connection(std::shared_ptr<liveness>&& state) : m_state{std::move(state)}{}
83
84public:
85    /**
86     * The default constructor creates a connection with no associated signal
87     */
88    constexpr connection() noexcept = default;
89
90    /**
91     * If a callback is associated with this connection, prevent it from being
92     * called in the future.
93     *
94     * If a connection is disabled as part of a signal's callback function, it
95     * will _not_ be executed in the current signal invocation.
96     *
97     * Note that disconnected callbacks are not removed from their owning
98     * signals here. They are garbage collected in signal::connect().
99     */
100    void disconnect()
101    {
102        if (m_state) {
103            m_state->disconnect();
104        }
105    }
106
107    /**
108     * Returns true if this connection was created by a signal and has not been
109     * disabled.
110     */
111    bool connected() const
112    {
113        return m_state && m_state->connected();
114    }
115};
116
117/*
118 * RAII-style connection management
119 */
120class scoped_connection
121{
122    connection m_conn;
123
124public:
125    explicit scoped_connection(connection rhs) noexcept : m_conn{std::move(rhs)} {}
126
127    scoped_connection(scoped_connection&&) noexcept = default;
128
129    /**
130     * For simplicity, disable copy construction and copy/move assignment.
131     */
132    scoped_connection& operator=(scoped_connection&&) = delete;
133    scoped_connection& operator=(const scoped_connection&) = delete;
134    scoped_connection(const scoped_connection&) = delete;
135
136    void disconnect()
137    {
138        m_conn.disconnect();
139    }
140
141    ~scoped_connection()
142    {
143        disconnect();
144    }
145};
146
147/*
148 * Functor for calling zero or more connected callbacks
149 */
150template <typename Signature, typename Combiner>
151class signal
152{
153    using function_type = std::function<Signature>;
154
155    /*
156     * Helper struct for maintaining a callback and its associated connection liveness
157     */
158    struct connection_holder : connection::liveness {
159        template <typename Callable>
160        connection_holder(Callable&& callback) : m_callback{std::forward<Callable>(callback)}
161        {
162        }
163
164        const function_type m_callback;
165    };
166
167    mutable Mutex m_mutex;
168
169    std::vector<std::shared_ptr<connection_holder>> m_connections GUARDED_BY(m_mutex){};
170
171public:
172    using result_type = Combiner::result_type;
173
174    constexpr signal() noexcept = default;
175    ~signal() = default;
176
177    /*
178     * For simplicity, disable all moving/copying/assigning.
179     */
180    signal(const signal&) = delete;
181    signal(signal&&) = delete;
182    signal& operator=(const signal&) = delete;
183    signal& operator=(signal&&) = delete;
184
185    /*
186     * Execute all enabled callbacks for the signal. Rather than allowing for
187     * custom combiners, the behavior of any_of is hard-coded here.
188     *
189     * Callbacks which return void require special handling.
190     *
191     * In order to avoid locking during the callbacks, the list of callbacks is
192     * cached before they are called. This allows a callback to call connect(),
193     * but the newly connected callback will not be run during the current
194     * signal invocation.
195     *
196     * Note that the parameters are accepted as universal references, though
197     * they are not perfectly forwarded as that could cause a use-after-move if
198     * more than one callback is enabled.
199     */
200    template <typename... Args>
201    [[nodiscard]] result_type operator()(Args&&... args) const EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
202    {
203        std::vector<std::shared_ptr<connection_holder>> connections;
204        {
205            LOCK(m_mutex);
206            connections = m_connections;
207        }
208        if constexpr (std::is_void_v<result_type>) {
209            static_assert(std::is_same_v<result_type, typename function_type::result_type>,
210                          "Callback result type must be equal to the combiner result type (void).");
211            for (const auto& connection : connections) {
212                if (connection->connected()) {
213                    connection->m_callback(args...);
214                }
215            }
216        } else {
217            static_assert(std::is_same_v<Combiner, any_of>,
218                          "only the any_of combiner is supported and hard-coded into this functor.");
219            static_assert(std::is_same_v<result_type, typename function_type::result_type>,
220                          "Callback result type must be equal to the combiner result type (bool).");
221            result_type ret{false};
222            for (const auto& connection : connections) {
223                if (connection->connected()) {
224                    ret |= connection->m_callback(args...);
225                }
226            }
227            return ret;
228        }
229    }
230
231    /*
232     * Connect a new callback to the signal. A forwarding callable accepts
233     * anything that can be stored in a std::function.
234     */
235    template <typename Callable>
236    connection connect(Callable&& func) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
237    {
238        LOCK(m_mutex);
239
240        // Garbage-collect disconnected connections to prevent unbounded growth
241        std::erase_if(m_connections, [](const auto& holder) { return !holder->connected(); });
242
243        const auto& entry = m_connections.emplace_back(std::make_shared<connection_holder>(std::forward<Callable>(func)));
244        return connection(entry);
245    }
246
247    /*
248     * Returns true if there are no enabled callbacks
249     */
250    [[nodiscard]] bool empty() const EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

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

src/clientversion.cpp

src/common/signmessage.cpp

src/compat/assumptions.h

src/compat/byteswap.h

src/deploymentinfo.cpp

src/deploymentinfo.h

src/deploymentstatus.cpp

src/deploymentstatus.h

src/dummywallet.cpp

src/external_signer.h

src/init/bitcoin-gui.cpp

src/init/bitcoin-node.cpp

src/init/bitcoin-qt.cpp

src/init/bitcoin-wallet.cpp

src/init/bitcoind.cpp

src/init/common.h

src/interfaces/init.h

src/interfaces/ipc.h

src/key_io.h

src/logging/categories.h

src/logging/timer.h

src/mapport.h

src/musig.h

src/net_permissions.h

src/netgroup.h

src/netmessagemaker.h

src/node/chainstatemanager_args.cpp

src/node/connection_types.h

src/node/context.h

src/node/interface_ui.h

src/node/mempool_args.cpp

src/node/mining_args.cpp

src/node/minisketchwrapper.cpp

src/node/txreconciliation.h

src/policy/fees/estimator_args.cpp

src/policy/fees/estimator_args.h

src/policy/fees/estimator_man.cpp

src/policy/fees/estimator_man.h

src/policy/packages.h

src/policy/rbf.h

src/policy/truc_policy.h

src/pow.h

src/primitives/block.cpp

src/randomenv.h

src/rest.h

src/script/keyorigin.h

src/script/parsing.cpp

src/script/parsing.h

src/script/script_error.h

src/script/sigcache.cpp

src/script/sigcache.h

src/script/solver.h

src/script/verify_flags.h

src/semaphore_grant.h

src/signet.h

src/span.h

src/support/allocators/secure.h

src/support/allocators/zeroafterfree.h

src/util/tokenpipe.cpp

src/util/translation.h

src/util/vector.h

src/versionbits.h

src/versionbits_impl.h

src/wallet/external_signer_scriptpubkeyman.h

src/wallet/fees.h

src/wallet/load.h

src/wallet/receive.h

src/wallet/rpc/wallet.h

src/wallet/types.h

src/walletinitinterface.h

src/zmq/zmqabstractnotifier.cpp

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