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incompletely uploaded jpeg and tiff in FTP - how to detect?

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  • Jeffrey Martin
    We re trying to set up an FTP uploading system for images. The big issue so far is, how to tell if a file has been completely uploaded. For ZIP files, we ve
    Message 1 of 4 , Apr 30 1:43 AM
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      We're trying to set up an FTP uploading system for images.

      The big issue so far is, how to tell if a file has been completely uploaded.

      For ZIP files, we've solved it.

      Is there a simple way to tell if a JPEG or TIFF file is completely uploaded
      or not?


      [Non-text portions of this message have been removed]
    • Bernhard Vogl
      ... As far as i know - no. Same problem here if a jpeg file gets corrupt on the harddisk. No way to tell without looking at the image. Only solution i can
      Message 2 of 4 , Apr 30 3:59 PM
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        >
        > Is there a simple way to tell if a JPEG or TIFF file is completely uploaded
        > or not?
        >
        >

        As far as i know - no. Same problem here if a jpeg file gets corrupt on
        the harddisk. No way to tell without looking at the image.
        Only solution i can think of, is by building an MD5 checksum and
        comparing it. This however would need a small uploader app to transfer
        the file from the local computer to your webpage.

        Bernhard
      • Mihai Stanescu
        If you can run programs then make a small program to read the header of the image and see its length
        Message 3 of 4 , May 1, 2009
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          If you can run programs then make a small program to read the header
          of the image and see its length



          On Thu, Apr 30, 2009 at 11:43 AM, Jeffrey Martin <360cities@...> wrote:
          >
          >
          > We're trying to set up an FTP uploading system for images.
          >
          > The big issue so far is, how to tell if a file has been completely uploaded.
          >
          > For ZIP files, we've solved it.
          >
          > Is there a simple way to tell if a JPEG or TIFF file is completely uploaded
          > or not?
          >
          > [Non-text portions of this message have been removed]
          >
          >
        • Roger Howard
          Yeah, there are a number of ways, depending on the upload process - 1. If you control the uploader tool (probably don t) then you can calculate a checksum and
          Message 4 of 4 , May 1, 2009
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            Yeah, there are a number of ways, depending on the upload process -

            1. If you control the uploader tool (probably don't) then you can calculate
            a checksum and compare to the uploaded file's checksum... or even just a
            filesize compare
            2. Use one of a number of tools that will check the consistency of the
            formatting - this won't necessarily prove the upload was incomplete... it
            could have been damaged prior to upload - but is a good idea any time
            you're accepting media files anyway.

            Some ideas:

            exiftool - though not built for this, it's pretty good about error
            reporting
            libjpeg and libtiff both have a variety of tools which will report errors
            on parsing those formats - likewise, many tools based on these libraries
            (for instance, ImageMagick) will report errors back up to the user based on
            parsing problems encountered in the library
            jhove - a much more robust/complex tool, but designed for
            validating/profiling a wide range of file formats

            3. If you want something really simple:

            for jpeg: check that the file ends with "FFD9" (in hex) - the only time
            that sequence should appear in a JPEG is at the very end
            for tiff: check that the file ends with "0000" (in hex) - it's not an "end
            of file" marker technically, but, I believe, all TIFFs should end with it
            IIRC; of course it's quite possible for a TIFF to contain "0000" elsewhere
            in the file, so this isn't a guarantee - but if the file DOESN'T end with
            0000 you can be sure it's incomplete.
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