Since yesterday I started learning assembler and using Fasm, so please excuse if my questions are silly

I want to create a heap, read text file into it, append 0 character at the end of heap and display in a popup.

Here's my code:

invoke HeapCreate, HEAP_NO_SERIALIZE, 8, 0
mov [hHeap], eax
;now I have my 8 byte long heap

invoke ReadFile, [hFile], [hHeap], 8, lpBytesRead, 0
;here I read into the heap


mov [hHeap+2],0
;now I want to add 0 on the end of my heap; THIS DOESN'T WORK- HEAP IS NOT ALTERED

invoke MessageBox, NULL, [hHeap], addr MessageBoxCaption, MB_O
;I display my heap- works

HeapCreate will return a handle to the heap object.
To allocate memory from that heap object you must call HeapAlloc.

hi d0mek,

hHeap is a label say at address 0x401000 which holds a 32-bit value (memory pointer)
you destroy the high bits of pointer by storing a 0 dword at address 0x401002

it makes more sense like this

AsmGuru64:
Value 8 in:
invoke HeapCreate, HEAP_NO_SERIALIZE, 8, 0
means- set size to 8 bytes. Plus it works without HeapAlloc.

Picnic:
Thank you, this works. But I can do this without esi? If hHeap is a "variable" and "esi" is a variable- why do I have to copy from hHeap to esi?

MSDN says that you must use HeapAlloc to get blocks from heap created by HeapCreate.

d0mek, you simply don't understand what the "heap" actually is. It is not one block of memory, but a special memory object from where you can dynamically allocate one or many memory blocks depending of your needs. The heap has special structure and contains not only memory you use, but also memory that describes what memory is allocated and what memory is free. As long the exact structure of the heap is unknown and can be changed from version to version, the only legal way to allocate memory from the heap is to use heap functions of Windows.

BTW, there is no need to create a heap with HeapCreate. Every Windows application already have one. Get its handle with "GetProcessHeap" and then use it to allocate one or many blocks of memory with HeapAlloc. Don't forget to free these memory blocks when not needed with "HeapFree".

[hHeap+2] refers at address 0x401000+2
[esi+2] refers at memory block start address+2
Not the same thing, debug your code and trace values to see what's happening.

I too suggest to use HeapAlloc.

Suggest is a too weak word in this context. You must insist on using it.

AsmGuru62, JohnFound, Picnic, baldr: Thank you guys! I will use HeapAlloc then.

I mostly code in PHP, Javascript, Delphi and C# and I don't even need pointers there. I just specify a variable has to be passed by reference and don't need to care any more about it.

d0mek, so it is time to make some real programming then. Try some web programming in assembly. It is a big fun.

Web programming in assembly? That does sound interesting, how do you do that? Can you link any docs/forum/site or whatever?

Whole site of Fresh IDE is managed by an assembly written CMS - MiniMagAsm. Also my home site uses the same engine.

It is open source. You can read and download the sources in the repository.