reading floats in a struct

[Jon Hulatt]

Hi all, I have a struct a bit like this, which is the header to a file on disk:-

struct Header
{
short a;
short b;
short c;
float floatvalue;
}

I read the header from the disk like this:-

ReadFile(hFile,&header,sizeof(Header),&bytesRead,NULL);

Once I'd done that, the values in a,b,c are as expected, but the floatvalue is not. However, if I adjust the struct so that instead of float, I have BYTE[4] as follows:-

struct Header
{
short a;
short b;
short c;
BYTE floatvalue[4];
}

And then after reading the header as before, I do:-

float f;
memcpy(&f,header.floatvalue,sizeof(float));

Then f contains the value expected. I don't understand why the first version didn't work. Can anyone enlighten me please? Thanks Jon

using System.Beer;

[Code o mat]

Maybe take a look at this[^], i hope it explains what you need explained. :)

> The problem with computers is that they do what you tell them to do and not what you want them to do. < > Life: great graphics, but the gameplay sux. <

[Jon Hulatt]

Thank for that, it's clear now. Looks like a can get around the issue with #pragma pack (2)

using System.Beer;

[RomTibi]

I think that a

#pragma pack (1)

or

#pragma pack (2)

declaration before the structure's definition would help. Think so?

36. When you surround an army, leave an outlet free. ... Do not press a desperate foe too hard. SUN-TZU - Art of War