Re: Binary Reading

wahid <>
Thu, 06 Nov 2008 18:41:14 +0100
struct Header
    DWORD base_version;
    DWORD current_version;
    DWORD vfs_count;

struct VFSinfo
    DWORD Filecount;
    DWORD unk1;
    DWORD unk2;

struct FileData
    WORD nameLen;
    char name[100];
    DWORD data_offset;
    DWORD offset;
    DWORD enc_length;
    DWORD dec_length;
    WORD unk3;
    char unk4;
    DWORD version;
    DWORD checksum;

struct Lists
    CList<DWORD> Dataoffset;
    CList<CString> Name;

These are the structures a SSTR is a WORD which gives the name Lenght
and then using that WORD you read the name. My code is correct for as
far as I know.
I use CList for this because in C# I used them to store data I don't
know if MFC has something better for that. I also want to know if its
possible to give the char array it size after reading the WORD(name
length) btw name length can never be higher then 100.

*Sorry for my bad english and the lack of information.

See below...
On Thu, 06 Nov 2008 13:04:48 +0100, wahid <> wrote:


Im new to MFC i used to program in C# im trying to read a binary file
with this format:

DWORD base_version
DWORD current_version
DWORD vfs_count

:FOREACH( vfs_count )
SSTR vfs_path
DWORD data_offset

:FOREACH( vfs_count )
// Seek to <( data_offset )>
DWORD file_count
DWORD unk1
DWORD unk2
:FOREACH file_count
SSTR file_path
DWORD offset
DWORD enc_length
DWORD dec_length
WORD unk3
BYTE unk4
DWORD version
DWORD checksum

this is the code i use to read it i wanna know if this is the best way
to read it or there is a better way to do it?

if(file.Open(_T(filename), CFile::modeRead, &e))
        file.Read(&h, sizeof(Header));

        for(DWORD i = 0; i < h.vfs_count; i++)
            file.Read(&VFS.nameLen, sizeof(WORD));
            file.Read(&, VFS.nameLen);
            file.Read(&VFS.data_offset, sizeof(DWORD));
THis suggests several things: that the size is a WORD value (16 bits), that the string is
NOT NUL-terminated (otherwise you would need to read VFS.nameLen +1) and there is no
padding added to make the next DWORD lie on a DWORD boundary.

Also, you have not shown us the declaration of VFS, so it is hard to tell what you are
reading into here.

You have not given the declaration of lists, nor justified why a list is the best
representation here.


        POSITION pos = lists.Dataoffset.GetHeadPosition();

        for(DWORD i = 0; i < h.vfs_count; i++)
The above code does assume that GetNext returns a valid value...

             file.Read(&Vinfo, sizeof(VFSinfo));

            for(DWORD x = 0; x < Vinfo.Filecount; x++)
                file.Read(&VFS.nameLen, sizeof(WORD));
                file.Read(&, VFS.nameLen);
                file.Read(&VFS.offset, sizeof(DWORD));
                file.Read(&VFS.unk3, sizeof(WORD));
                file.Read(&VFS.unk4, sizeof(char));
                file.Read(&VFS.version, sizeof(DWORD));
                file.Read(&VFS.checksum, sizeof(DWORD));
Same caveats as previously; you're sure an SSTR uses a WORD for the length, is not
NUL-terminated, and there is no padding to ensure DWORD-alignment of the next object...
and you have not shown the structure, so it is hard to tell if this code is correct. Note
also that if is a character array of fixed size that you have not verified that
the name length is smaller than the array size; alternatively, you have a lot of 64K
strings, which might not be a good idea if there are lots of these structures around.

In asking such a question, it is ESSENTIAL to give ALL the critical information!

Joseph M. Newcomer [MVP]
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