CODEWITHSUNDEEP
c#memory-mapped-files
Sean Heiss
Sean Heiss

Reputation: 780

Why isn't this memory-mapped file read correctly?

I have a feeling I'm doing something wrong, but I'm not sure what.

Here is my code:

        long offset = 0x009694E3;
        long length = 0x02;
        byte[] bytes = new byte[length];

        // Create the memory-mapped file.
        using (var mmf =
            MemoryMappedFile.CreateFromFile(strFileName, FileMode.Open, "ISO"))
        {
            // Create a random access view, from the 256th megabyte (the offset)
            // to the 768th megabyte (the offset plus length).
            using (var accessor = mmf.CreateViewAccessor(offset, length))
            {
                // Make changes to the view.
                for (long i = 0; i < length; i++)
                {
                    bytes[i] = accessor.ReadByte(i);
                    dialogEdit.Text = bytes[i].ToString();
                }
            }
        }

When I load a file, the text at the above offset is 0x22 0x44 ("D in ASCII), yet the output to the text box is "68"...

I think I'm misunderstanding how bytes work, but I'm not entirely sure...

Any help is much appreciated!

Upvotes: 0

Views: 306

Answers (1)

spender
spender

Reputation: 120508

In the text box you overwrite the value 34 (0x22) with the value 68 (0x44) on the second loop.

Your program works as it is programmed. A lucky escape for memory-mapped files.

Upvotes: 1

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