libcamera: process: start(): Use span instead of vector

Use a span instead of a const reference to a vector, this does not
change the behaviour and allows e.g. arrays to be used to hold
arguments/file descriptors.

Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/internal/process.h

@@ -9,10 +9,10 @@
 
 #include <signal.h>
 #include <string>
-#include <vector>
 
 #include <libcamera/base/class.h>
 #include <libcamera/base/signal.h>
+#include <libcamera/base/span.h>
 #include <libcamera/base/unique_fd.h>
 
 namespace libcamera {
@@ -32,8 +32,8 @@ public:
 	~Process();
 
 	int start(const std::string &path,
-		  const std::vector<std::string> &args = std::vector<std::string>(),
-		  const std::vector<int> &fds = std::vector<int>());
+		  Span<const std::string> args = {},
+		  Span<const int> fds = {});
 
 	ExitStatus exitStatus() const { return exitStatus_; }
 	int exitCode() const { return exitCode_; }

src/libcamera/ipc_pipe_unixsocket.cpp

@@ -28,10 +28,6 @@ IPCPipeUnixSocket::IPCPipeUnixSocket(const char *ipaModulePath,
 				     const char *ipaProxyWorkerPath)
 	: IPCPipe()
 {
-	std::vector<int> fds;
-	std::vector<std::string> args;
-	args.push_back(ipaModulePath);
-
 	socket_ = std::make_unique<IPCUnixSocket>();
 	UniqueFD fd = socket_->create();
 	if (!fd.isValid()) {
@@ -39,8 +35,9 @@ IPCPipeUnixSocket::IPCPipeUnixSocket(const char *ipaModulePath,
 		return;
 	}
 	socket_->readyRead.connect(this, &IPCPipeUnixSocket::readyRead);
-	args.push_back(std::to_string(fd.get()));
-	fds.push_back(fd.get());
+
+	std::array args{ std::string(ipaModulePath), std::to_string(fd.get()) };
+	std::array fds{ fd.get() };
 
 	proc_ = std::make_unique<Process>();
 	int ret = proc_->start(ipaProxyWorkerPath, args, fds);

src/libcamera/process.cpp

@@ -235,8 +235,8 @@ Process::~Process()
  * or a negative error code otherwise
  */
 int Process::start(const std::string &path,
-		   const std::vector<std::string> &args,
-		   const std::vector<int> &fds)
+		   Span<const std::string> args,
+		   Span<const int> fds)
 {
 	int ret;
 
@@ -262,7 +262,7 @@ int Process::start(const std::string &path,
 		if (isolate())
 			_exit(EXIT_FAILURE);
 
-		std::vector<int> v(fds);
+		std::vector<int> v(fds.begin(), fds.end());
 		v.push_back(STDERR_FILENO);
 		closeAllFdsExcept(v);
 

test/process/process_test.cpp

@@ -5,9 +5,9 @@
  * Process test
  */
 
+#include <array>
 #include <iostream>
 #include <unistd.h>
-#include <vector>
 
 #include <libcamera/base/event_dispatcher.h>
 #include <libcamera/base/thread.h>
@@ -48,8 +48,7 @@ protected:
 		Timer timeout;
 
 		int exitCode = 42;
-		vector<std::string> args;
-		args.push_back(to_string(exitCode));
+		std::array args{ to_string(exitCode) };
 		proc_.finished.connect(this, &ProcessTest::procFinished);
 
 		/* Test that kill() on an unstarted process is safe. */