VILLASnode/common/lib/popen.cpp

/** Bi-directional popen
 *
 * @author Steffen Vogel <post@steffenvogel.de>
 * @copyright 2014-2022, Institute for Automation of Complex Power Systems, EONERC
 * @license Apache License 2.0
 *********************************************************************************/

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <signal.h>
#include <fcntl.h>
#include <unistd.h>
#include <paths.h>
#include <dirent.h>

#include <cstring>
#include <cerrno>
#include <cstdio>
#include <cstdlib>

#include <iostream>

#include <fmt/core.h>
#include <villas/utils.hpp>
#include <villas/exceptions.hpp>
#include <villas/popen.hpp>

namespace villas {
namespace utils {

Popen::Popen(const std::string &cmd,
             const arg_list &args,
             const env_map &env,
             const std::string &wd,
             bool sh) :
	command(cmd),
	working_dir(wd),
	arguments(args),
	environment(env),
	shell(sh)
{
	open();
}

Popen::~Popen()
{
	close();
}

void Popen::kill(int signal)
{
	::kill(pid, signal);
}

void Popen::open()
{
	std::vector<char *> argv, envp;

	const int READ = 0;
	const int WRITE = 1;

	int ret;
	int inpipe[2];
	int outpipe[2];

	ret = pipe(inpipe);
	if (ret)
		goto error_out;

	ret = pipe(outpipe);
	if (ret)
		goto clean_inpipe_out;

	fd_in = outpipe[READ];
	fd_out = inpipe[WRITE];

	pid = fork();
	if (pid == -1)
		goto clean_outpipe_out;

	if (pid == 0) {
		// Prepare arguments
		if (shell) {
			argv.push_back((char *) "sh");
			argv.push_back((char *) "-c");
			argv.push_back((char *) command.c_str());
		}
		else {
			for (auto arg: arguments) {
				auto s = strdup(arg.c_str());

				argv.push_back(s);
			}
		}

		// Prepare environment
		for (char **p = environ; *p; p++)
			envp.push_back(*p);

		for (auto env: environment) {
			auto e = fmt::format("{}={}", env.first, env.second);
			auto s = strdup(e.c_str());

			envp.push_back(s);
		}

		argv.push_back(nullptr);
		envp.push_back(nullptr);

		// Redirect IO
		::close(outpipe[READ]);
		::close(inpipe[WRITE]);

		if (inpipe[READ] != STDIN_FILENO) {
			dup2(inpipe[READ], STDIN_FILENO);
			::close(inpipe[READ]);
		}

		if (outpipe[WRITE] != STDOUT_FILENO) {
			dup2(outpipe[WRITE], STDOUT_FILENO);
			::close(outpipe[WRITE]);
		}

		// Change working directory
		if (!working_dir.empty()) {
			int ret;

			ret = chdir(working_dir.c_str());
			if (ret)
				exit(127);
		}

		execvpe(shell ? _PATH_BSHELL : command.c_str(), (char * const *) argv.data(), (char * const *) envp.data());
		exit(127);
	}

	::close(outpipe[WRITE]);
	::close(inpipe[READ]);

	return;

clean_outpipe_out:
	::close(outpipe[READ]);
	::close(outpipe[WRITE]);

clean_inpipe_out:
	::close(inpipe[READ]);
	::close(inpipe[WRITE]);

error_out:
	throw SystemError("Failed to start subprocess");
}

int Popen::close()
{
	int pstat;

	if (pid != -1) {
		do {
			pid = waitpid(pid, &pstat, 0);
		} while (pid == -1 && errno == EINTR);
	}

	return pid == -1 ? -1 : pstat;
}


PopenStream::PopenStream(const std::string &cmd,
             const arg_list &args,
             const env_map &env,
             const std::string &wd,
             bool sh) :
	Popen(cmd, args, env, wd, sh)
{
	open();
}

PopenStream::~PopenStream()
{
	close();
}

void PopenStream::open()
{
	Popen::open();

	input.buffer = std::make_unique<stdio_buf>(fd_in, std::ios_base::in);
	output.buffer = std::make_unique<stdio_buf>(fd_out, std::ios_base::out);

	input.stream  = std::make_unique<std::istream>(input.buffer.get());
	output.stream = std::make_unique<std::ostream>(output.buffer.get());
}

int PopenStream::close()
{
	int ret = Popen::close();

	input.stream.reset();
	output.stream.reset();

	input.buffer.reset();
	output.buffer.reset();

	return ret;
}

} // namespace utils
} // namespace villas