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util: Add RAII TokenPipe
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‎src/Makefile.am‎

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@@ -249,6 +249,7 @@ BITCOIN_CORE_H = \
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util/system.h \
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util/threadnames.h \
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util/time.h \
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util/tokenpipe.h \
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util/trace.h \
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util/translation.h \
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util/ui_change_type.h \
@@ -577,6 +578,7 @@ libbitcoin_util_a_SOURCES = \
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util/strencodings.cpp \
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util/string.cpp \
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util/time.cpp \
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util/tokenpipe.cpp \
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$(BITCOIN_CORE_H)
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if USE_LIBEVENT

‎src/util/tokenpipe.cpp‎

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// Copyright (c) 2021 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#include <util/tokenpipe.h>
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#include <config/bitcoin-config.h>
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#ifndef WIN32
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#include <errno.h>
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#include <fcntl.h>
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#include <unistd.h>
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TokenPipeEnd TokenPipe::TakeReadEnd()
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{
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TokenPipeEnd res(m_fds[0]);
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m_fds[0] = -1;
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return res;
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}
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TokenPipeEnd TokenPipe::TakeWriteEnd()
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{
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TokenPipeEnd res(m_fds[1]);
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m_fds[1] = -1;
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return res;
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}
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TokenPipeEnd::TokenPipeEnd(int fd) : m_fd(fd)
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{
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}
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TokenPipeEnd::~TokenPipeEnd()
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{
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Close();
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}
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int TokenPipeEnd::TokenWrite(uint8_t token)
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{
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while (true) {
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ssize_t result = write(m_fd, &token, 1);
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if (result < 0) {
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// Failure. It's possible that the write was interrupted by a signal,
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// in that case retry.
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if (errno != EINTR) {
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return TS_ERR;
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}
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} else if (result == 0) {
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return TS_EOS;
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} else { // ==1
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return 0;
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}
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}
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}
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int TokenPipeEnd::TokenRead()
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{
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uint8_t token;
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while (true) {
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ssize_t result = read(m_fd, &token, 1);
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if (result < 0) {
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// Failure. Check if the read was interrupted by a signal,
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// in that case retry.
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if (errno != EINTR) {
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return TS_ERR;
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}
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} else if (result == 0) {
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return TS_EOS;
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} else { // ==1
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return token;
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}
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}
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return token;
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}
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void TokenPipeEnd::Close()
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{
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if (m_fd != -1) close(m_fd);
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m_fd = -1;
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}
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std::optional<TokenPipe> TokenPipe::Make()
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{
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int fds[2] = {-1, -1};
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#if HAVE_O_CLOEXEC && HAVE_DECL_PIPE2
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if (pipe2(fds, O_CLOEXEC) != 0) {
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return std::nullopt;
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}
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#else
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if (pipe(fds) != 0) {
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return std::nullopt;
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}
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#endif
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return TokenPipe(fds);
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}
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TokenPipe::~TokenPipe()
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{
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Close();
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}
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void TokenPipe::Close()
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{
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if (m_fds[0] != -1) close(m_fds[0]);
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if (m_fds[1] != -1) close(m_fds[1]);
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m_fds[0] = m_fds[1] = -1;
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}
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#endif // WIN32

‎src/util/tokenpipe.h‎

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// Copyright (c) 2021 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#ifndef BITCOIN_UTIL_TOKENPIPE_H
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#define BITCOIN_UTIL_TOKENPIPE_H
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#ifndef WIN32
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#include <cstdint>
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#include <optional>
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/** One end of a token pipe. */
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class TokenPipeEnd
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{
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private:
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int m_fd = -1;
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public:
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TokenPipeEnd(int fd = -1);
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~TokenPipeEnd();
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/** Return value constants for TokenWrite and TokenRead. */
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enum Status {
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TS_ERR = -1, //!< I/O error
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TS_EOS = -2, //!< Unexpected end of stream
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};
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/** Write token to endpoint.
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*
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* @returns 0 If successful.
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* <0 if error:
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* TS_ERR If an error happened.
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* TS_EOS If end of stream happened.
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*/
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int TokenWrite(uint8_t token);
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/** Read token from endpoint.
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*
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* @returns >=0 Token value, if successful.
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* <0 if error:
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* TS_ERR If an error happened.
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* TS_EOS If end of stream happened.
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*/
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int TokenRead();
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/** Explicit close function.
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*/
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void Close();
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/** Return whether endpoint is open.
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*/
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bool IsOpen() { return m_fd != -1; }
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// Move-only class.
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TokenPipeEnd(TokenPipeEnd&& other)
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{
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m_fd = other.m_fd;
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other.m_fd = -1;
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}
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TokenPipeEnd& operator=(TokenPipeEnd&& other)
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{
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Close();
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m_fd = other.m_fd;
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other.m_fd = -1;
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return *this;
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}
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TokenPipeEnd(const TokenPipeEnd&) = delete;
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TokenPipeEnd& operator=(const TokenPipeEnd&) = delete;
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};
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/** An interprocess or interthread pipe for sending tokens (one-byte values)
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* over.
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*/
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class TokenPipe
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{
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private:
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int m_fds[2] = {-1, -1};
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TokenPipe(int fds[2]) : m_fds{fds[0], fds[1]} {}
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public:
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~TokenPipe();
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/** Create a new pipe.
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* @returns The created TokenPipe, or an empty std::nullopt in case of error.
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*/
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static std::optional<TokenPipe> Make();
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/** Take the read end of this pipe. This can only be called once,
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* as the object will be moved out.
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*/
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TokenPipeEnd TakeReadEnd();
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/** Take the write end of this pipe. This should only be called once,
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* as the object will be moved out.
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*/
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TokenPipeEnd TakeWriteEnd();
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/** Close and end of the pipe that hasn't been moved out.
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*/
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void Close();
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// Move-only class.
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TokenPipe(TokenPipe&& other)
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{
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for (int i = 0; i < 2; ++i) {
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m_fds[i] = other.m_fds[i];
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other.m_fds[i] = -1;
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}
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}
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TokenPipe& operator=(TokenPipe&& other)
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{
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Close();
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for (int i = 0; i < 2; ++i) {
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m_fds[i] = other.m_fds[i];
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other.m_fds[i] = -1;
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}
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return *this;
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}
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TokenPipe(const TokenPipe&) = delete;
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TokenPipe& operator=(const TokenPipe&) = delete;
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};
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#endif // WIN32
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#endif // BITCOIN_UTIL_TOKENPIPE_H

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