Subversion Repositories Kolibri OS

align 4

proc user_alloc_at stdcall, address:dword, alloc_size:dword

           push ebx

           push esi

           push edi

           mov ebx, [current_slot]

           mov edx, [address]

           and edx, not 0xFFF

           mov [address], edx

           sub edx, 0x1000

           jb  .error

           mov esi, [ebx+APPDATA.heap_base]

           mov edi, [ebx+APPDATA.heap_top]

           cmp edx, esi

           jb  .error

.scan:

           cmp esi, edi

           jae .error

           mov ebx, esi

           shr ebx, 12

           mov eax, [page_tabs+ebx*4]

           mov ecx, eax

           and ecx, 0xFFFFF000

           add ecx, esi

           cmp edx, ecx

           jb  .found

           mov esi, ecx

           jmp .scan

.error:

           xor eax, eax

           pop edi

           pop esi

           pop ebx

           ret

.found:

           test al, FREE_BLOCK

           jz  .error

           mov eax, ecx

           sub eax, edx

           sub eax, 0x1000

           cmp eax, [alloc_size]

           jb  .error

; Here we have 1 big free block which includes requested area.

; In general, 3 other blocks must be created instead:

; free at [esi, edx);

; busy at [edx, edx+0x1000+ALIGN_UP(alloc_size,0x1000));

; free at [edx+0x1000+ALIGN_UP(alloc_size,0x1000), ecx)

; First or third block (or both) may be absent.

           mov eax, edx

           sub eax, esi

           jz  .nofirst

           or  al, FREE_BLOCK

           mov [page_tabs+ebx*4], eax

.nofirst:

           mov eax, [alloc_size]

           add eax, 0x1FFF

           and eax, not 0xFFF

           mov ebx, edx

           add edx, eax

           shr ebx, 12

           or  al, USED_BLOCK

           mov [page_tabs+ebx*4], eax

           shr eax, 12

           dec eax

           jz  .second_nofill

           inc ebx

.fill:

           mov dword [page_tabs+ebx*4], 2

           inc ebx

           dec eax

           jnz .fill

.second_nofill:

           sub ecx, edx

           jz  .nothird

           or  cl, FREE_BLOCK

           mov [page_tabs+ebx*4], ecx

.nothird:

           mov     edx, [current_slot]

           mov     ebx, [alloc_size]

           add     ebx, 0xFFF

           and     ebx, not 0xFFF

           add     ebx, [edx+APPDATA.mem_size]

           call    update_mem_size

           mov eax, [address]

           pop edi

           pop esi

           pop ebx

           ret

endp