1// Copyright (c) 2021-present 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. */
14class TokenPipeEnd
15{
16private:
17    int m_fd = -1;
18
19public:
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    TokenPipeEnd& operator=(TokenPipeEnd&& other)
62    {
63        Close();
64        m_fd = other.m_fd;
65        other.m_fd = -1;
66        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 */
75class TokenPipe
76{
77private:
78    int m_fds[2] = {-1, -1};
79
80    TokenPipe(int fds[2]) : m_fds{fds[0], fds[1]} {}
81
82public:
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    TokenPipe(TokenPipe&& other)
106    {
107        for (int i = 0; i < 2; ++i) {
108            m_fds[i] = other.m_fds[i];
109            other.m_fds[i] = -1;
110        }
111    }
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
128