/// <summary>
/// Executes a new gPhoto2 process and retrieves its output.
/// </summary>
/// <param name="commandLineParameters">The command line paramters, which are passed to the process.</param>
/// <returns>Returns what the process wrote to the standard output.</returns>
public Task <string> ExecuteAsync(string commandLineParameters)
{
// Creates a gPhoto2 command, which is scheduled to run on the camera, it contains a task completion source, which resolves when the
// command has been executed
GPhoto2Command gPhoto2Command = new GPhoto2Command
{
Command = () => Task <string> .Run(() =>
{
// Creates the start information that are needed to run the process
ProcessStartInfo processStartInfo = new ProcessStartInfo
{
Arguments = string.IsNullOrWhiteSpace(this.StandardCommandLineParameters) ?
commandLineParameters : string.Concat(this.StandardCommandLineParameters, " ", commandLineParameters),
FileName = "gphoto2",
UseShellExecute = false,
CreateNoWindow = true,
RedirectStandardOutput = true,
RedirectStandardError = true,
RedirectStandardInput = true,
StandardOutputEncoding = Encoding.UTF8,
};
// Sets the language in which the application is to be started (the languages is set to american english in order to make it
// easier to parse the output regardless of the system language)
if (processStartInfo.EnvironmentVariables.ContainsKey("LANG"))
{
processStartInfo.EnvironmentVariables["LANG"] = "en_US.UTF-8";
}
else
{
processStartInfo.EnvironmentVariables.Add("LANG", "en_US.UTF-8");
}
// Starts the process
Process process = new Process();
process.StartInfo = processStartInfo;
process.Start();
// Reads the output that the process wrote to the standard output
string output = process.StandardOutput.ReadToEnd();
// Waits till the process has finished
process.WaitForExit();
// Checks if the output of gPhoto2 contains any errors, if so a camera exception is thrown
CameraException.DetectCameraErrors(output);
// Returns the output of the process, so that the user is able to parse it
return(output);
})
};
// Schedules the camera command, so that it can run on the camera (it must be scheduled to ensure that only one command is executed at
// a time)
this.cameraActionBlock.Post(gPhoto2Command);
// Awaits the execution of the scheduled camera command
return(gPhoto2Command.TaskCompletionSource.Task);
}
/// <summary>
/// Executes the specified command line parameters in the gPhoto2 interactive shell process. This method of executing a command has better
/// performace, because the shell mode process has only to be spawned once and can then be reused.
/// </summary>
/// <param name="commandLineParameters">The command line paramters, which are passed to the process.</param>
public Task <string> ExecuteInteractiveAsync(string commandLineParameters)
{
// Creates a gPhoto2 command, which is scheduled to run on the camera, it contains a task completion source, which resolves when the
// command has been executed
GPhoto2Command gPhoto2Command = new GPhoto2Command
{
Command = () => Task <string> .Run(() =>
{
// Checks whether the gPhoto2 interactive shell process has been started, yet, if not then a new one is spawned
if (this.gPhoto2InteractiveShellProcess == null)
{
// Creates the start information that are needed to run the gPhoto2 process in the interactive shell mode
ProcessStartInfo processStartInfo = new ProcessStartInfo
{
Arguments = string.Concat("--shell ", this.StandardCommandLineParameters),
FileName = "gphoto2",
UseShellExecute = false,
CreateNoWindow = true,
RedirectStandardOutput = true,
RedirectStandardError = true,
RedirectStandardInput = true,
StandardOutputEncoding = Encoding.UTF8,
};
// Sets the language in which the application is to be started (the languages is set to american english in order to make
// it easier to parse the output regardless of the system language)
if (processStartInfo.EnvironmentVariables.ContainsKey("LANG"))
{
processStartInfo.EnvironmentVariables["LANG"] = "en_US.UTF-8";
}
else
{
processStartInfo.EnvironmentVariables.Add("LANG", "en_US.UTF-8");
}
// Starts the process gPhoto2 process in the interactive shell mode
this.gPhoto2InteractiveShellProcess = new Process();
this.gPhoto2InteractiveShellProcess.StartInfo = processStartInfo;
this.gPhoto2InteractiveShellProcess.Start();
}
// Executes the specified command by writing it to the standard input of the gPhoto2 interactive shell process
this.gPhoto2InteractiveShellProcess.StandardInput.WriteLine(commandLineParameters);
// Reads the output of the process line by line and returns it, the end of the output is detected by checking if the read
// output line starts with "gphoto2:" (in the interactive shell mode of gPhoto2 prints out the prompt "gphoto2:" followed
// by the current path)
int outputCharacterCode;
int currentLineNumber = 1;
string currentOutputLine = string.Empty;
List <string> outputLines = new List <string>();
while ((outputCharacterCode = this.gPhoto2InteractiveShellProcess.StandardOutput.Read()) != -1)
{
// Converts the current character code to a character
char outputCharacter = Convert.ToChar(outputCharacterCode);
// Checks what kind of character was read
if (outputCharacter == '\r')
{
// When a carriage return is read, then nothing is done (since the look-ahead is only one character and some systems
// need two characters for a new line, it is much safer to only watch for line feed and ignore the carriage return
// alltogether)
continue;
}
else if (outputCharacter == '\n')
{
// When the read character is a line feed, then the current line is added to the result (but empty lines and the
// first two lines, which just contain the shell prompt and a repitition of the command that is to be executed, are
// not added, because their are not needed)
if (currentLineNumber > 2 && !string.IsNullOrWhiteSpace(currentOutputLine))
{
outputLines.Add(currentOutputLine);
}
// After the current line has been added to the result or discarded, the current line is reset to empty
currentOutputLine = string.Empty;
// Counts up the current line number, because the algorithm has to know in what line it currently is
currentLineNumber += 1;
}
else
{
// All other characters are added to the content of the current line
currentOutputLine += outputCharacter;
}
// Finally it is checked whether the output has reached its end (which is when the line contains the shell prompt
// "ghoto2:" and when it is not the first line, because the first line contains a shell prompt as well), if so then the
// reading of the output of gPhoto2 is finished
if (currentOutputLine.ToUpperInvariant().StartsWith("GPHOTO2:") && currentLineNumber > 1)
{
break;
}
}
// Joins all the lines written to the output together, so that they can be returned as a single string
string output = string.Join(Environment.NewLine, outputLines);
// Checks if the output of gPhoto2 contains any errors, if so a camera exception is thrown
CameraException.DetectCameraErrors(output);
// Returns the output of the process, so that the user is able to parse it
return(output);
})
};
// Schedules the camera command, so that it can run on the camera (it must be scheduled to ensure that only one command is executed at
// a time)
this.cameraActionBlock.Post(gPhoto2Command);
// Awaits the execution of the scheduled camera command
return(gPhoto2Command.TaskCompletionSource.Task);
}
