c/cpp matrix

[nibbleNbits]

why doesn't this work, I'm missing somthing

; Playing with array's
; Creates a 4x2 matrix of ints
; array of pointer to array's
; example 4x2 matrix
;

• ->[1][2]
  ; [1]->[3][4]
  ; [2]->[5][6]
  ; [3]->[7][8]
  
  .586
  .model flat, C
  option casemap :none
  
  .data
  
  .code
  ;-------------------------------------------------------------------
  ; void matrx_ptrs(int **intmat,int rows, int cols); cpp calling function
  ;-------------------------------------------------------------------
  matrx_ptrs proc public intmat:PTR DWORD, rows:DWORD, cols:DWORD
  
      push eax
     push ebx
     push ecx
     push edx
     
     ;--------------- calc size ---------------------
     mov ebx, rows
     imul ebx,cols
     add ebx, rows
     ;------------------------------------------------------
     
     mov edx, intmat               ; matrix [rows][cols]
     mov ecx,rows               ; row counter start at end of rows
     mov eax,1                  ; integer value starting at one to add to matrix
     .while(ecx < ebx)            ; should be 4-12
        mov [edx+ecx*4],eax
        add eax,1
        add ecx,1
     .endw
     
     pop edx
     pop ecx
     pop ebx
     pop eax
  
      ret
  
  matrx_ptrs endp
  
  end
  
  

[qWord]

;-------------------------------------------------------------------
; void matrx_ptrs(int **intmat,int rows, int cols); cpp calling function
;-------------------------------------------------------------------
matrx_ptrs proc public intmat:PTR DWORD, rows:DWORD, cols:DWORD
...
   mov edx, intmat               ; matrix [rows][cols]

You must dereference the pointer a second time by:

Code Select Expand

mov edx,[edx]
Alternatively you can change the Cpp function:

; void matrx_ptrs(int *intmat,int rows, int cols); cpp calling function

   ;--------------- calc size ---------------------
   mov ebx, rows
   imul ebx,cols
   add ebx, rows  ; <- ???

You are calculating the number of cells and not the size.

[nibbleNbits]

c/cpp requires the ** notation. it works fine in c++
int val = 0;
for(int i = 0;i < rows; i++)
      for(int j = 0; j < cols; j++)
   {
      intmat[j] = val;
      val++;
   }
            
I added mov edx, [edx] but that didn't help
mov edx, [intmat]
mov edx, [edx]

I realized that about calculating rows and not the size, poor choice of words  :red

still does't work

[qWord]

c/cpp requires the ** notation.

surely not: you can simply use an two dimensional integer array.
The following code is speculative, because I don't know the data type of intmat:

Code Select Expand

mov edi,intmat  ; -> push/pop edi
; edi = pointer to array of  'row'-pointers
xor eax,eax
mov edx,1 ; skip first row
.while edx < rows
mov esi,PDWORD ptr [edi+edx*4] ; -> push/pop esi
; esi = pointer to row[edx]
xor ecx,ecx
.while ecx < cols
; loop through all elements in row
mov SDWORD ptr [esi+ecx*4],eax
lea eax,[eax+1]
lea ecx,[ecx+1]
.endw
lea edx,[edx+1]
.endw

[nibbleNbits]

qWord thanks for you input and help. If I use a int[4][2] and a slightly different masm algo I can make it work just fine, however I don't alway know the size. Hence the reason for dynamic allocation using pointers, in this case pointer to pointers,

int **intmat;
intmat = new int*[rows];
            
for(int i= 0; i < rows; i++)
    intmat = new int[cols];

anyway you algo works fine except the first row? not sure I have figured out just yet why you skipped row 1? the last (3) rows come out correct.

again thanks so much for you input

[nibbleNbits]

I changed mov edx,1 ; skip first row to mov edx,0 ; skip first row and all is well, almost orgasm time.

thanks again

[qWord]

anyway you algo works fine except the first row? not sure I have figured out just yet why you skipped row 1? the last (3) rows come out correct.

Reading your first post, I thought that you want to skip the first row.

qWord