Switched from sync transcoder to async transcoder

src/libs/utils/impl/ChildProcess.cpp

@@ -0,0 +1,201 @@
+#include "ChildProcess.hpp"
+
+#include <cstring>
+#include <cerrno>
+#include <fcntl.h>
+#include <stdexcept>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include <algorithm>
+#include <iostream>
+#include <mutex>
+
+#include <boost/asio/read.hpp>
+#include <boost/asio/buffer.hpp>
+
+#include "utils/Exception.hpp"
+#include "utils/Logger.hpp"
+
+namespace
+{
+	class SystemException : public ChildProcessException
+	{
+		public:
+			SystemException(int err, const std::string& errMsg)
+				: ChildProcessException {errMsg + ": " + strerror(err)}
+			{}
+	};
+}
+
+ChildProcess::ChildProcess(boost::asio::io_context& ioContext, const std::filesystem::path& path, const Args& args)
+: _ioContext {ioContext}
+, _childStdout {_ioContext}
+
+{
+	// make sure only one thread is executing this part of code
+	static std::mutex mutex;
+	std::unique_lock<std::mutex> lock {mutex};
+
+	int pipe[2];
+
+	int res {pipe2(pipe, O_NONBLOCK | O_CLOEXEC)};
+	if (res < 0)
+		throw SystemException {errno, "pipe2 failed!"};
+
+	{
+		const std::size_t pipeSize {65536*8};
+
+		if (fcntl(pipe[0], F_SETPIPE_SZ, pipeSize) == -1)
+			throw SystemException {errno, "fcntl failed!"};
+
+		if (fcntl(pipe[1], F_SETPIPE_SZ, pipeSize) == -1)
+			throw SystemException {errno, "fcntl failed!"};
+	}
+
+	res = fork();
+	if (res == -1)
+		throw SystemException {errno, "fork failed!"};
+
+	if (res == 0) // CHILD
+	{
+		close(pipe[0]);
+		close(STDIN_FILENO);
+		close(STDERR_FILENO);
+
+		// Replace stdout with pipe write
+		if (dup2(pipe[1], STDOUT_FILENO) == -1)
+			exit(-1);
+
+		std::vector<const char*> execArgs;
+		std::transform(std::cbegin(args), std::cend(args), std::back_inserter(execArgs), [](const std::string& arg) { return arg.c_str(); });
+		execArgs.push_back(nullptr);
+
+		res = execv(path.string().c_str(), (char *const*)&execArgs[0]);
+		if (res == -1)
+			exit(-1);
+	}
+	else // PARENT
+	{
+		close(pipe[1]);
+		_childStdout.assign(pipe[0]);
+		_childPID = res;
+	}
+}
+
+ChildProcess::~ChildProcess()
+{
+	if (!_waited)
+	{
+		close(_childStdout.native_handle());
+		kill();
+		wait(true);
+	}
+}
+
+void
+ChildProcess::drain()
+{
+	char buf[128];
+
+	while (boost::asio::read(_childStdout, boost::asio::buffer(buf)) > 0)
+		LMS_LOG(CHILDPROCESS, DEBUG) << "drained some bytes" << std::endl;
+}
+
+void
+ChildProcess::kill()
+{
+	::kill(_childPID, SIGKILL);
+}
+
+bool
+ChildProcess::wait(bool block)
+{
+	int wstatus {};
+
+	pid_t pid {waitpid(_childPID, &wstatus, block ? 0 : WNOHANG)};
+
+	if (pid == -1)
+		throw SystemException {errno, "waitpid failed!"};
+	else if (pid == 0)
+		return false;
+
+	if (WIFEXITED(wstatus))
+		_exitCode = WEXITSTATUS(wstatus);
+
+	_waited = true;
+	return true;
+}
+
+
+void
+ChildProcess::asyncRead(std::byte* data, std::size_t bufferSize, ReadCallback callback) 
+{
+	LMS_LOG(CHILDPROCESS, DEBUG) << "ASYNC READ";
+
+	boost::asio::async_read(_childStdout, boost::asio::buffer(data, bufferSize),
+		[this, callback {std::move(callback)}](const boost::system::error_code& error, std::size_t bytesTransferred)
+		{
+			LMS_LOG(CHILDPROCESS, DEBUG) << "ASYNC READ CB - error = '" << error.message() << "', bytesTransferred = " << bytesTransferred;
+
+			if (error)
+			{
+				{
+					boost::system::error_code closeError;
+					_childStdout.close(closeError);
+				}
+
+				if (error == boost::asio::error::operation_aborted)
+				{
+					return;
+				}
+				if (error == boost::asio::error::eof)
+				{
+					callback(ReadResult::EndOfFile, bytesTransferred);
+					return;
+				}
+				else
+				{
+					callback(ReadResult::Error, bytesTransferred);
+					return;
+				}
+			}
+
+			callback(ReadResult::Success, bytesTransferred);
+		});
+}
+
+void
+ChildProcess::asyncWaitForData(WaitCallback cb)
+{
+	LMS_LOG(CHILDPROCESS, DEBUG) << "Async wait requested";
+
+	_childStdout.async_wait(boost::asio::posix::stream_descriptor::wait_read,
+			[cb {std::move(cb)}](const boost::system::error_code& ec)
+	{
+		LMS_LOG(CHILDPROCESS, DEBUG) << "Wait CB, error = " << ec.message();
+		if (!ec)
+			cb();
+	});
+}
+
+std::size_t
+ChildProcess::readSome(std::byte* data, std::size_t bufferSize)
+{
+	boost::system::error_code ec;
+	const std::size_t res {_childStdout.read_some(boost::asio::buffer(data, bufferSize), ec)};
+	LMS_LOG(CHILDPROCESS, DEBUG) << "read some " << res << " bytes, ec = " << ec.message();
+	if (ec)
+		_childStdout.close(ec);
+
+	return res;
+}
+
+bool
+ChildProcess::finished()
+{
+	return !_childStdout.is_open();
+}
+