On 1/15/07, Arnaud Nicolet <[EMAIL PROTECTED]> wrote:
Le 16 janv. 07 à 01:48 Matin, Dennis Birch a écrit: > On 1/15/07, Louis G5 Batayte <[EMAIL PROTECTED]> wrote: >> >> MacOS X 10.4.8 RB 2007R1 >> >> I let the user select a folder, then I search through the items in >> that folder looking for jpeg files. Right now I am looking at the >> extension to determine if it is a jpeg or not. But I am trying to >> determine if a file without an extension is a jpeg file. If I take a >> jpeg file with an extension, and use the MacOS System "Get Info" to >> delete the extension, the System "Get Info" still displays the "Kind" >> as a jpeg file. But I cannot figure how to determine this from >> within RealBasic. When I look at the contents of the folderitem, for >> the file without the jpeg extension, in debug mode, there is >> nothing there to indicate the file type/kind. Any suggestions? > > >> From looking at a handful of JPEG files in a hex editor, it >> appears that the > first 10 bytes of every JPEG file is identical: ff d8 ff e0 00 10 > 4a 46 49 > 46. So you might consider opening each file, or each questionable file > perhaps, and reading the first 10 bytes of its binarystream to see > if it > matches that pattern. What about if I create an application which writes files with the same pattern? I mean: is reading bytes of a file a reliable way to determine it's contents?
I suspect that those 10 bytes (and possibly more) are a standard file header for JPEG files. I also suspect it should be possible to confirm or disprove that pretty easily with a simple Web search. If that is a standard file header, then it seems to me it would be a safe method of determining a file's type. On the other hand, you raise a good point in that there's nothing to prevent somebody from writing a non-JPEG file with those 10 bytes at the beginning. _______________________________________________ Unsubscribe or switch delivery mode: <http://www.realsoftware.com/support/listmanager/> Search the archives of this list here: <http://support.realsoftware.com/listarchives/lists.html>
