Problem with ReadFile and WriteFile

[biggoron]

Code

GeSHi (asm):
        ; Create both input and output handles
        invoke  CreateFile, inputFileName, GENERIC_READ, FILE_SHARE_READ, NULL,\
                            OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL
        cmp     eax, INVALID_HANDLE_VALUE
        je      .fail
        mov     [hInput], eax
 
        invoke  CreateFile, outputFileName, GENERIC_WRITE, 0, NULL,\
                            CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL
        cmp     eax, INVALID_HANDLE_VALUE
        je      .fail
        mov     [hOutput], eax
 
        ; Do stuff
        invoke  ReadFile, hInput, line, 256, numBytesRead, NULL
        invoke  WriteFile, hOutput, line, numBytesRead, numBytesWritten, NULL
 
        invoke  CloseHandle, hInput
        invoke  CloseHandle, hOutput
Created by GeSHI 1.0.7.18

The opening of both files appears to work fine, but when reading nothing is read and ReadFile returns FALSE. The only thing I'm unsure about in that code is numBytesRead and numBytesWritten. Should I be declaring them like:

Code

GeSHi (asm):
numBytesRead dd ?
numBytesWritten dd ?
Created by GeSHI 1.0.7.18

or:

Code

GeSHi (asm):
numBytesRead: dd ?
numBytesWritten: dd ?
Created by GeSHI 1.0.7.18

So that numBytesRead/Written point to the dword?

[adeyblue]

You forgot to dereference the handles in the Read and WriteFile calls, and also the third param to WriteFile.

[biggoron]

=O that did it. Why did I have to dereference the handles... hInput and hOutput were the handles themselves, not pointers to them. *shrug*
Oh well, that did it! Thanks again, adeyblue!

[adeyblue]

The names you give global variables are pointers to where the actual dd or db etc are stored. So if you just printed hInput or hOutput you'd see the address of the space declared (for example 0x004004C8). Obviously if you just pass that to Read/WriteFile you'd mostly get error since 0x004004C8 is unlikely to be a valid handle value. It works for strings in things like printf because they use the address of the first character, so no dereference is necessary.

Everything you declare globally is just the address of an offset within the image to where the actual space is, if that makes sense. I'm sure someone will starch my pants if I'm wrong, I'm basically a beginner too.

[biggoron]

Oh, I thought that was only if I made a label like "variable: db 0". I got it now

[FrozenKnight]

You forgot to refrence hInput and hOutout as pointers in your readfile and writefile ruteens.

Code:

       invoke  ReadFile, [hInput], line, 256, numBytesRead, NULL
        invoke  WriteFile, [hOutput], line, numBytesRead, numBytesWritten, NULL

however if hInput and hOutput are handles themselves then you shouldn't need to place them in brackets when when you move eax into them.

[biggoron]

Guy, check the dates. In the time between the post before yours, the problem was solved, the project was finished, I started about five other ASM projects, then lost interest in ASM