init: Introduce class InterprocessFifo
Prepare for introducing a second interprocess communication channel by
introducing the class InterprocessFifo. Stop using std::unique_ptr<> for
holding the pipe file descriptors. Handle EOF consistently.
Bug: 213617178
Change-Id: Ic0cf18d3d8ea61b8ee17e64de8a9df2736e26728
Signed-off-by: Bart Van Assche <bvanassche@google.com>
diff --git a/init/interprocess_fifo.cpp b/init/interprocess_fifo.cpp
new file mode 100644
index 0000000..6e0d031
--- /dev/null
+++ b/init/interprocess_fifo.cpp
@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "interprocess_fifo.h"
+
+#include <android-base/logging.h>
+
+#include <unistd.h>
+
+using ::android::base::ErrnoError;
+using ::android::base::Error;
+using ::android::base::Result;
+
+namespace android {
+namespace init {
+
+InterprocessFifo::InterprocessFifo() noexcept : fds_({-1, -1}) {}
+
+InterprocessFifo::InterprocessFifo(InterprocessFifo&& orig) noexcept : fds_({-1, -1}) {
+ std::swap(fds_, orig.fds_);
+}
+
+InterprocessFifo::~InterprocessFifo() noexcept {
+ Close();
+}
+
+void InterprocessFifo::CloseFd(int& fd) noexcept {
+ if (fd >= 0) {
+ close(fd);
+ fd = -1;
+ }
+}
+
+void InterprocessFifo::CloseReadFd() noexcept {
+ CloseFd(fds_[0]);
+}
+
+void InterprocessFifo::CloseWriteFd() noexcept {
+ CloseFd(fds_[1]);
+}
+
+void InterprocessFifo::Close() noexcept {
+ CloseReadFd();
+ CloseWriteFd();
+}
+
+Result<void> InterprocessFifo::Initialize() noexcept {
+ if (fds_[0] >= 0) {
+ return Error() << "already initialized";
+ }
+ if (pipe(fds_.data()) < 0) { // NOLINT(android-cloexec-pipe)
+ return ErrnoError() << "pipe()";
+ }
+ return {};
+}
+
+Result<uint8_t> InterprocessFifo::Read() noexcept {
+ uint8_t byte;
+ ssize_t count = read(fds_[0], &byte, 1);
+ if (count < 0) {
+ return ErrnoError() << "read()";
+ }
+ if (count == 0) {
+ return Error() << "read() EOF";
+ }
+ DCHECK_EQ(count, 1);
+ return byte;
+}
+
+Result<void> InterprocessFifo::Write(uint8_t byte) noexcept {
+ ssize_t written = write(fds_[1], &byte, 1);
+ if (written < 0) {
+ return ErrnoError() << "write()";
+ }
+ if (written == 0) {
+ return Error() << "write() EOF";
+ }
+ DCHECK_EQ(written, 1);
+ return {};
+}
+
+} // namespace init
+} // namespace android