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errors.md

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Error Handling

This SDK uses std::error_code for all errors. Internally these codes are used to populate and throw std::system_error. All exceptions are caught at the library boundry to prevent exceptions from crossing that boundry. The exception's code and message are stored in the library object and accessible through the getLastError and getLastErrorString methods.

#include <rsdio.h>
#include <rserrors.h>
...
std::shared_ptr<rs::RsDio> dio(rs::createRsDio(), std::mem_fn(&rs::RsDio::destroy));
if (!dio->setXmlFile('ecs9000.xml'))
{
    if (dio->getLastError() == std::errc::operation_not_permitted)
        std::cerr << "Program must be run as root" << std::endl;
    else if (dio->getLastError() == RsErrorCode::XmlParseError)
        std::cerr << "Failed to parse XML file" << std::endl;
    else
        std::cerr << dio->getLastErrorString() << std::endl;

    return 1;
}

In the above example the error code is being compared directly to another error code. A better approach is to compare the error code to an error condition. Error condtions group multiple codes into a single condition to help create separate execution paths. For example, say you are running the same program on multiple devices with different hardware. You may want to handle or ignore errors when the hardware doesn't support a specific function and log the error if it is more serious.

if (!dio->setOutputMode(rs::OutputMode::Source))
{
    // Fatal unrecoverable error occured. Log it and terminate.
    if (dio->getLastError() == RsErrorCondition::HardwareError)
    {
        logError(dio->getLastErrorString());
        exit(1);
    }
    // This computer doesn't have that feature.
    else if (dio->getLastError() == RsErrorCondition::UnsupportedFunction)
    {
        ...
    }
}

RsErrorCode

enum class RsErrorCode
Constant Description
NotInitialized setXmlFile was never successfully called
XmlParseError There was an error parsing the XML file
UnknownError An exception occurred that the library doesn't know how to handle. Hopefully this never happens...

RsErrorCondition

enum class RsErrorCondition
Constant Description
HardwareError A low level error occured while communicating with the hardware
UnsupportedFunction This unit doesn't support this functionality
PermissionErrror Permission was denied trying to communicate with the hardware Linux only