Problems with Kernel32 ReadFile!

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  • Chua Wen Ching
    #1

    Problems with Kernel32 ReadFile!

    Hi,

    I have doubts. From p/invoke and most site, they recommend to use this.

    Example1:
    [DllImport("kern el32.dll")]
    static extern bool ReadFile(IntPtr hFile, byte[] lpBuffer,
    uint nNumberOfBytesT oRead, out uint lpNumberOfBytes Read, IntPtr
    lpOverlapped);

    But I only want to read 1 byte at a time.

    Example2:
    [DllImport("kern el32.dll")]
    static extern bool ReadFile(IntPtr hFile, ref byte lpBuffer, uint
    nNumberOfBytesT oRead, ref uint lpNumberOfBytes Read, IntPtr lpOverlapped);

    Can i do this instead?

    If just say, no choice i have to stick to Example1, when i run that
    function, and only read lpBuffer[0], it does not return what i expected.

    But if only follow Example2, it will. But the only issue i have is,

    Sample snippet:

    for(;;)
    {
    // some processing

    bool test = ReadFile(...)..
    }

    so basically in this loop, it will read till 8 times of data...

    00 11 22 33 44 55 66 77 88 // just say this is what i expect it to give me

    but it give me instead

    00 11 22 33 44 55 66 00 01 // wrong! Sometimes i get this, and sometimes i
    get the above one.

    Why?

    I try to test on separate machine, or restart my machine. Sometimes i just
    get either the one with 88 99 or 00 01!

    I have an existing C SDK, and it is running smoothly. That is why i can
    compare whether my .NET SDK is working properly or not.

    Can anyone provide me any guideslines please?
    --
    Regards,
    Chua Wen Ching
    Visit us at http://www.necoders.com
    Tags: None
    • Ollie Riches
      #2
      Re: Problems with Kernel32 ReadFile!


      "Chua Wen Ching" <chua_wen_ching @nospam.hotmail .com> wrote in message
      news:87185FB0-0EF7-4FD8-B734-09B0B2735587@mi crosoft.com...[color=blue]
      > Hi,
      >
      > I have doubts. From p/invoke and most site, they recommend to use this.
      >
      > Example1:
      > [DllImport("kern el32.dll")]
      > static extern bool ReadFile(IntPtr hFile, byte[] lpBuffer,
      > uint nNumberOfBytesT oRead, out uint lpNumberOfBytes Read, IntPtr
      > lpOverlapped);
      >
      > But I only want to read 1 byte at a time.
      >
      > Example2:
      > [DllImport("kern el32.dll")]
      > static extern bool ReadFile(IntPtr hFile, ref byte lpBuffer, uint
      > nNumberOfBytesT oRead, ref uint lpNumberOfBytes Read, IntPtr lpOverlapped);
      >
      > Can i do this instead?
      >
      > If just say, no choice i have to stick to Example1, when i run that
      > function, and only read lpBuffer[0], it does not return what i expected.
      >
      > But if only follow Example2, it will. But the only issue i have is,
      >
      > Sample snippet:
      >
      > for(;;)
      > {
      > // some processing
      >
      > bool test = ReadFile(...)..
      > }
      >
      > so basically in this loop, it will read till 8 times of data...
      >
      > 00 11 22 33 44 55 66 77 88 // just say this is what i expect it to give me
      >
      > but it give me instead
      >
      > 00 11 22 33 44 55 66 00 01 // wrong! Sometimes i get this, and sometimes i
      > get the above one.
      >
      > Why?
      >
      > I try to test on separate machine, or restart my machine. Sometimes i just
      > get either the one with 88 99 or 00 01!
      >
      > I have an existing C SDK, and it is running smoothly. That is why i can
      > compare whether my .NET SDK is working properly or not.
      >
      > Can anyone provide me any guideslines please?
      > --
      > Regards,
      > Chua Wen Ching
      > Visit us at http://www.necoders.com[/color]


        Comment

        • Ollie Riches
          #3
          Re: Problems with Kernel32 ReadFile!

          why aren't you using the System.IO namespace ?


          --
          HTH

          Ollie Riches
          http://www.phoneanalyser.net


          Disclaimer: Opinions expressed in this forum are my own, and not
          representative of my employer.
          I do not answer questions on behalf of my employer. I'm just a programmer
          helping programmers.
          "Chua Wen Ching" <chua_wen_ching @nospam.hotmail .com> wrote in message
          news:87185FB0-0EF7-4FD8-B734-09B0B2735587@mi crosoft.com...[color=blue]
          > Hi,
          >
          > I have doubts. From p/invoke and most site, they recommend to use this.
          >
          > Example1:
          > [DllImport("kern el32.dll")]
          > static extern bool ReadFile(IntPtr hFile, byte[] lpBuffer,
          > uint nNumberOfBytesT oRead, out uint lpNumberOfBytes Read, IntPtr
          > lpOverlapped);
          >
          > But I only want to read 1 byte at a time.
          >
          > Example2:
          > [DllImport("kern el32.dll")]
          > static extern bool ReadFile(IntPtr hFile, ref byte lpBuffer, uint
          > nNumberOfBytesT oRead, ref uint lpNumberOfBytes Read, IntPtr lpOverlapped);
          >
          > Can i do this instead?
          >
          > If just say, no choice i have to stick to Example1, when i run that
          > function, and only read lpBuffer[0], it does not return what i expected.
          >
          > But if only follow Example2, it will. But the only issue i have is,
          >
          > Sample snippet:
          >
          > for(;;)
          > {
          > // some processing
          >
          > bool test = ReadFile(...)..
          > }
          >
          > so basically in this loop, it will read till 8 times of data...
          >
          > 00 11 22 33 44 55 66 77 88 // just say this is what i expect it to give me
          >
          > but it give me instead
          >
          > 00 11 22 33 44 55 66 00 01 // wrong! Sometimes i get this, and sometimes i
          > get the above one.
          >
          > Why?
          >
          > I try to test on separate machine, or restart my machine. Sometimes i just
          > get either the one with 88 99 or 00 01!
          >
          > I have an existing C SDK, and it is running smoothly. That is why i can
          > compare whether my .NET SDK is working properly or not.
          >
          > Can anyone provide me any guideslines please?
          > --
          > Regards,
          > Chua Wen Ching
          > Visit us at http://www.necoders.com[/color]


            Comment

            • Mattias Sjögren
              #4
              Re: Problems with Kernel32 ReadFile!

              [color=blue]
              > Can i do this instead?[/color]

              Yes

              [color=blue]
              >when i run that
              >function, and only read lpBuffer[0], it does not return what i expected.[/color]

              That's weird, it should work as well.



              Mattias

              --
              Mattias Sjögren [MVP] mattias @ mvps.org
              http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
              Please reply only to the newsgroup.

                Comment

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