;------------------------------------------------------------------------------
align 4
sys_clipboard:
xor eax, eax
dec eax
; check availability of main list
cmp [clipboard_main_list], eax
je .exit_1 ; main list area not found
test ebx, ebx ; 0 - Get the number of slots in the clipboard
jnz .1
; get the number of slots
mov eax, [clipboard_slots]
jmp .exit_1
;------------------------------------------------------------------------------
align 4
.1:
dec ebx ; 1 - Read the data from the clipboard
jnz .2
; verify the existence of slot
cmp ecx, [clipboard_slots]
jae .exit_2
; get a pointer to the data of slot
shl ecx, 2
add ecx, [clipboard_main_list]
mov esi, [ecx]
mov ecx, [esi]
; allocate memory for application for copy the data of slots
push ecx
stdcall user_alloc, ecx
pop ecx
; copying data of slots
mov edi, eax
cld
rep movsb
jmp .exit_1
;------------------------------------------------------------------------------
align 4
.2:
dec ebx ; 2 - Write the data to the clipboard
jnz .3
; check the lock
mov ebx, clipboard_write_lock
xor eax, eax
cmp [ebx], eax
jne .exit_2
; lock last slot
inc eax
mov [ebx], eax
; check the overflow pointer of slots
cmp [clipboard_slots], 1024
jae .exit_3
; get memory for new slot
push ebx ecx edx
stdcall kernel_alloc, ecx
pop edx ecx ebx
test eax, eax
jz .exit_3
; create a new slot
mov edi, eax
mov eax, [clipboard_slots]
shl eax, 2
add eax, [clipboard_main_list]
mov [eax], edi
; copy the data into the slot
mov esi, edx
mov eax, ecx
cld
stosd ; store size of slot
sub ecx, 4
add esi, 4
rep movsb ; store slot data
; increase the counter of slots
inc [clipboard_slots]
; unlock last slot
xor eax, eax
mov [ebx], eax
jmp .exit_1
;------------------------------------------------------------------------------
align 4
.3:
dec ebx ; 3 - Delete the last slot in the clipboard
jnz .4
; check the availability of slots
mov eax, [clipboard_slots]
test eax, eax
jz .exit_2
; check the lock
mov ebx, clipboard_write_lock
xor eax, eax
cmp [ebx], eax
jne .exit_2
; lock last slot
inc eax
mov [ebx], eax
; decrease the counter of slots
mov eax, clipboard_slots
dec dword [eax]
; free of kernel memory allocated for the slot
mov eax, [eax]
shl eax, 2
add eax, [clipboard_main_list]
mov eax, [eax]
push ebx
stdcall kernel_free, eax
pop ebx
; unlock last slot
xor eax, eax
mov [ebx], eax
jmp .exit_1
;------------------------------------------------------------------------------
align 4
.4:
dec ebx ; 4 - Emergency discharge of clipboard
jnz .exit
; check the lock
mov ebx, clipboard_write_lock
xor eax, eax
cmp [ebx], eax
je .exit_2
; there should be a procedure for checking the integrity of the slots
; and I will do so in the future
; unlock last slot
mov [ebx], eax
jmp .exit
;------------------------------------------------------------------------------
align 4
.exit_3:
; unlock last slot
xor eax, eax
mov [ebx], eax
.exit_2:
xor eax, eax
inc eax ; error
.exit_1:
mov [esp + 32], eax
.exit:
ret
;------------------------------------------------------------------------------
uglobal
align 4
clipboard_slots dd ?
clipboard_main_list dd ?
clipboard_write_lock dd ?
endg
;------------------------------------------------------------------------------