Memory and byte ptr

[georgek01]

Good day,

I would like to access individual bytes from a memory buffer created with GlobalAlloc, similar to:

mov al, byte ptr szBuffer[esi]

Code Select Expand



...

invoke GlobalAlloc,GMEM_FIXED,dwRead
mov hMem,eax

invoke GlobalLock,hMem
mov pMem,eax

...

invoke GlobalSize,hMem
mov ecx,eax

invoke InternetReadFile,hSession,pMem,ecx,addr dwRead

mov al, byte ptr pMem[esi] ; --- this does not work.

.if al == '<'

...



Your assistance will be greatly appreciated!

Regards,
George

[tenkey]

Load the "base" pointer into a register. All of the variable components of an address must be in registers.

mov ecx,pMem  ; GlobalAlloc gave us a pointer - load it
mov al, byte ptr[ecx+esi]

[dedndave]

Code Select Expand

...

mov eax,dwRead
mov dwAllocSize,eax                      ;save the allocation size
invoke GlobalAlloc,GMEM_FIXED,eax
mov hMem,eax

invoke GlobalLock,hMem
mov pMem,eax

...

invoke InternetReadFile,hSession,pMem,dwAllocSize,addr dwRead

mov edx,pMem
mov al,[edx]                             ;"byte ptr" not required
mov cl,[edx+5]                           ;example of a fixed index

.if al == '<'

...

[georgek01]

Thank you! Both those answered my question.