Function get_attribute_string

rustcv-backend-msmf/src/device.rs:166–190

Extracts a string attribute from a Media Foundation device

(attr: &IMFActivate, guid: GUID)

/// Extracts a string attribute from a Media Foundation device
unsafe fn get_attribute_string(attr: &IMFActivate, guid: GUID) -> String {
    let mut value = MaybeUninit::uninit();
    let mut length = MaybeUninit::uninit();

    // Attempt to retrieve the string attribute.
    if attr
        .GetAllocatedString(&guid, value.as_mut_ptr(), length.as_mut_ptr())
        .is_err()
    {
        return String::new();
    }

    let value = value.assume_init();
    let length = length.assume_init();

    let result = {
        let slice = std::slice::from_raw_parts(value.as_ptr(), length as usize);
        String::from_utf16(slice).unwrap_or_else(|_| String::from_utf16_lossy(slice).to_owned())
    };

    // The memory was allocated by COM and must be freed with CoTaskMemFree.
    CoTaskMemFree(Some(value.as_ptr() as *const _));

    result
}

/// Opens a camera device and negotiates the video format based on configuration
///