Implementing the File Sniffer

This section explains how to validate a file before your sample file type plug-in processes it.

Determine the validation criteria

You can use the file extension that you defined in the File Type Component Builder to identify candidate files. However, the extension alone does not provide a reliable validation rule. A file can use the expected extension and still contain unsupported content. Different file types can also share the same extension.

Define one or more checks that clearly identify a valid file. For this simple text file type plug-in, assume that a .text file is valid when its first line starts with [Version=n].

If the file matches this rule, treat it as valid. Otherwise, report that the file type plug-in does not support the file. Implement this validation logic in a dedicated file sniffer component.

Implement the file sniffer

Add a new class, for example SimpleTextSniffer.cs, to your project. Implement the INativeFileSniffer interface in that class. The class must include the Sniff method. This method returns a SniffInfo object. Set that object to indicate whether the file matches your validation criteria.

If the file sniffer requires custom settings, use the ISettingsGroup parameter that the Sniff method receives. For more information, see The File Sniffer.

The following example shows the minimum code required to create a file sniffer component:

using Sdl.Core.Settings;
using Sdl.FileTypeSupport.Framework.NativeApi;
using Sdl.Core.Globalization;

namespace Sdk.Snippets.Native
{
    class SimpleTextSniffer1 : INativeFileSniffer
    {
        public SniffInfo Sniff(string nativeFilePath, Language language, Codepage suggestedCodepage,
           INativeTextLocationMessageReporter messageReporter, ISettingsGroup settingsGroup)
        {
            var fileInfo = new SniffInfo();
            return fileInfo;
        }
    }
}

Now add the validation logic that determines whether the file is supported. If the file is supported, set IsSupported to true. Otherwise, set it to false. The following example shows the complete file sniffer class:

using System.IO;
using Sdl.Core.Settings;
using Sdl.FileTypeSupport.Framework.NativeApi;
using Sdl.Core.Globalization;

namespace Sdk.Snippets.Native
{
    class SimpleTextSniffer : INativeFileSniffer
    {
        public SniffInfo Sniff(string nativeFilePath, Language language, Codepage suggestedCodepage, INativeTextLocationMessageReporter messageReporter, ISettingsGroup settingsGroup)
        {
            var fileInfo = new SniffInfo();

            using var reader = new StreamReader(nativeFilePath);
            fileInfo.IsSupported = reader.ReadLine().StartsWith("[Version=");

            return fileInfo;
        }
    }
}

Add the component reference to the file type definition

Reference the file sniffer component in the File Type Component Builder by implementing the BuildFileSniffer method in your implementation of IFileTypeComponentBuilder. If you skip this step, Trados Studio will not use the sniffer component, even though the assembly contains it.

Implementing the File Sniffer

Determine the validation criteria

Implement the file sniffer

Add the component reference to the file type definition

See also

Note