Line data    Source code

       1             : // Copyright (c) 2021 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_TOKENPIPE_H
       6             : #define BITCOIN_UTIL_TOKENPIPE_H
       7             : 
       8             : #ifndef WIN32
       9             : 
      10             : #include <cstdint>
      11             : #include <optional>
      12             : 
      13             : /** One end of a token pipe. */
      14             : class TokenPipeEnd
      15             : {
      16             : private:
      17             :     int m_fd = -1;
      18             : 
      19             : public:
      20             :     TokenPipeEnd(int fd = -1);
      21             :     ~TokenPipeEnd();
      22             : 
      23             :     /** Return value constants for TokenWrite and TokenRead. */
      24             :     enum Status {
      25             :         TS_ERR = -1, //!< I/O error
      26             :         TS_EOS = -2, //!< Unexpected end of stream
      27             :     };
      28             : 
      29             :     /** Write token to endpoint.
      30             :      *
      31             :      * @returns 0       If successful.
      32             :      *          <0 if error:
      33             :      *            TS_ERR  If an error happened.
      34             :      *            TS_EOS  If end of stream happened.
      35             :      */
      36             :     int TokenWrite(uint8_t token);
      37             : 
      38             :     /** Read token from endpoint.
      39             :      *
      40             :      * @returns >=0     Token value, if successful.
      41             :      *          <0 if error:
      42             :      *            TS_ERR  If an error happened.
      43             :      *            TS_EOS  If end of stream happened.
      44             :      */
      45             :     int TokenRead();
      46             : 
      47             :     /** Explicit close function.
      48             :      */
      49             :     void Close();
      50             : 
      51             :     /** Return whether endpoint is open.
      52             :      */
      53             :     bool IsOpen() { return m_fd != -1; }
      54             : 
      55             :     // Move-only class.
      56             :     TokenPipeEnd(TokenPipeEnd&& other)
      57             :     {
      58             :         m_fd = other.m_fd;
      59             :         other.m_fd = -1;
      60             :     }
      61           2 :     TokenPipeEnd& operator=(TokenPipeEnd&& other)
      62             :     {
      63           2 :         Close();
      64           2 :         m_fd = other.m_fd;
      65           2 :         other.m_fd = -1;
      66           2 :         return *this;
      67             :     }
      68             :     TokenPipeEnd(const TokenPipeEnd&) = delete;
      69             :     TokenPipeEnd& operator=(const TokenPipeEnd&) = delete;
      70             : };
      71             : 
      72             : /** An interprocess or interthread pipe for sending tokens (one-byte values)
      73             :  * over.
      74             :  */
      75             : class TokenPipe
      76             : {
      77             : private:
      78           1 :     int m_fds[2] = {-1, -1};
      79             : 
      80           1 :     TokenPipe(int fds[2]) : m_fds{fds[0], fds[1]} {}
      81             : 
      82             : public:
      83             :     ~TokenPipe();
      84             : 
      85             :     /** Create a new pipe.
      86             :      * @returns The created TokenPipe, or an empty std::nullopt in case of error.
      87             :      */
      88             :     static std::optional<TokenPipe> Make();
      89             : 
      90             :     /** Take the read end of this pipe. This can only be called once,
      91             :      * as the object will be moved out.
      92             :      */
      93             :     TokenPipeEnd TakeReadEnd();
      94             : 
      95             :     /** Take the write end of this pipe. This should only be called once,
      96             :      * as the object will be moved out.
      97             :      */
      98             :     TokenPipeEnd TakeWriteEnd();
      99             : 
     100             :     /** Close and end of the pipe that hasn't been moved out.
     101             :      */
     102             :     void Close();
     103             : 
     104             :     // Move-only class.
     105           1 :     TokenPipe(TokenPipe&& other)
     106             :     {
     107           3 :         for (int i = 0; i < 2; ++i) {
     108           2 :             m_fds[i] = other.m_fds[i];
     109           2 :             other.m_fds[i] = -1;
     110           2 :         }
     111           1 :     }
     112             :     TokenPipe& operator=(TokenPipe&& other)
     113             :     {
     114             :         Close();
     115             :         for (int i = 0; i < 2; ++i) {
     116             :             m_fds[i] = other.m_fds[i];
     117             :             other.m_fds[i] = -1;
     118             :         }
     119             :         return *this;
     120             :     }
     121             :     TokenPipe(const TokenPipe&) = delete;
     122             :     TokenPipe& operator=(const TokenPipe&) = delete;
     123             : };
     124             : 
     125             : #endif // WIN32
     126             : 
     127             : #endif // BITCOIN_UTIL_TOKENPIPE_H