util: Add RAII TokenPipe

src/util/tokenpipe.cpp

@@ -0,0 +1,108 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+#include <util/tokenpipe.h>
+
+#include <config/bitcoin-config.h>
+
+#ifndef WIN32
+
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+TokenPipeEnd TokenPipe::TakeReadEnd()
+{
+    TokenPipeEnd res(m_fds[0]);
+    m_fds[0] = -1;
+    return res;
+}
+
+TokenPipeEnd TokenPipe::TakeWriteEnd()
+{
+    TokenPipeEnd res(m_fds[1]);
+    m_fds[1] = -1;
+    return res;
+}
+
+TokenPipeEnd::TokenPipeEnd(int fd) : m_fd(fd)
+{
+}
+
+TokenPipeEnd::~TokenPipeEnd()
+{
+    Close();
+}
+
+int TokenPipeEnd::TokenWrite(uint8_t token)
+{
+    while (true) {
+        ssize_t result = write(m_fd, &token, 1);
+        if (result < 0) {
+            // Failure. It's possible that the write was interrupted by a signal,
+            // in that case retry.
+            if (errno != EINTR) {
+                return TS_ERR;
+            }
+        } else if (result == 0) {
+            return TS_EOS;
+        } else { // ==1
+            return 0;
+        }
+    }
+}
+
+int TokenPipeEnd::TokenRead()
+{
+    uint8_t token;
+    while (true) {
+        ssize_t result = read(m_fd, &token, 1);
+        if (result < 0) {
+            // Failure. Check if the read was interrupted by a signal,
+            // in that case retry.
+            if (errno != EINTR) {
+                return TS_ERR;
+            }
+        } else if (result == 0) {
+            return TS_EOS;
+        } else { // ==1
+            return token;
+        }
+    }
+    return token;
+}
+
+void TokenPipeEnd::Close()
+{
+    if (m_fd != -1) close(m_fd);
+    m_fd = -1;
+}
+
+std::optional<TokenPipe> TokenPipe::Make()
+{
+    int fds[2] = {-1, -1};
+#if HAVE_O_CLOEXEC && HAVE_DECL_PIPE2
+    if (pipe2(fds, O_CLOEXEC) != 0) {
+        return std::nullopt;
+    }
+#else
+    if (pipe(fds) != 0) {
+        return std::nullopt;
+    }
+#endif
+    return TokenPipe(fds);
+}
+
+TokenPipe::~TokenPipe()
+{
+    Close();
+}
+
+void TokenPipe::Close()
+{
+    if (m_fds[0] != -1) close(m_fds[0]);
+    if (m_fds[1] != -1) close(m_fds[1]);
+    m_fds[0] = m_fds[1] = -1;
+}
+
+#endif // WIN32