; $Id: buffer.asm,v 1.5 2000-02-21 09:24:02 bird Exp $ ; ; Simple resident buffer for use when overloading tkExecPgm. ; ; Copyright (c) 2000 knut st. osmundsen ; ; Project Odin Software License can be found in LICENSE.TXT ; .486p ; ; Defined Constants And Macros ; NBR_BUFFERS EQU 20 BUFFER_SIZE EQU 1536 ; ; Include files ; include devsegdf.inc ; ; Exported symbols ; public AcquireBuffer public ReleaseBuffer public QueryBufferSegmentOffset public QueryBufferPointerFromFilename ; ; Imported Functions ; extrn stricmp:PROC ; ; Global Variables ; DATA16 SEGMENT aachBuffer db BUFFER_SIZE*NBR_BUFFERS dup(?) ; The buffer DATA16 ENDS DATA32 SEGMENT afBuffer db NBR_BUFFERS dup(0) ; Access "semaphore" ; 0 - not in use ; 1 - in use DATA32 ENDS CODE32 segment assume CS:CODE32, DS:NOTHING, SS:NOTHING ;; ; Aquires a resident buffer. (intended use for tkExecPgm) ; @cproto assembly only for time being. ; @returns Pointer to buffer ; @uses eax ; @sketch if AfBuffer == 0 then ; ok! ; fBuffer <- 1 ; return pointer to buffer ; else ; fail ; return NULL ; endif ; @status completely implemented. ; @author knut st. osmundsen (knut.stange.osmundsen@pmsc.no) ; @remark cbBuffer holds the size of the buffer. AcquireBuffer PROC NEAR push ds push ecx push edx ; make ds flat mov ax, seg FLAT:DATA32 mov ds, ax ASSUME DS:FLAT ; loop thru all buffers and try reserve one mov ah, 1 ; afBuffer[ecx] is set to this value (if equal to al) mov ecx, NBR_BUFFERS ; interations. mov edx, offset FLAT:afBuffer add edx, ecx AcquireBuffer_loop: dec edx mov al, 0 ; afBuffer[ecx] should have this value lock cmpxchg [edx], ah je AcquireBuffer_ok loop AcquireBuffer_loop ; failure AcquireBuffer_nok: xor eax,eax jmp AcquireBuffer_ret ;success - calc buffer pointer AcquireBuffer_ok: mov eax, BUFFER_SIZE dec ecx imul eax, ecx ; ecx has the buffer number add eax, offset FLAT:aachBuffer AcquireBuffer_ret: pop edx pop ecx pop ds ret AcquireBuffer ENDP ;; ; Release the resident buffer pointed to by eax from use. ; @cproto assembly only for time being. ; @returns 0 on success, 87 on error. ; @param eax Pointer to buffer. ; @uses eax ; @equiv ; @status ; @author knut st. osmundsen (knut.stange.osmundsen@pmsc.no) ; @remark ReleaseBuffer PROC NEAR ASSUME DS:NOTHING push ds push ecx push edx ; make ds flat push eax mov ax, seg FLAT:DATA32 mov ds, ax ASSUME DS:FLAT pop eax push eax ; validate input and calc buffer number cmp eax, offset FLAT:aachBuffer jl ReleaseBuffer_nok ; if eax (buffer pointer) is less than the first buffer, then fail. sub eax, offset FLAT:aachBuffer ; eax <- offset to buffer from aachBuffer xor edx, edx mov ecx, BUFFER_SIZE div ecx ; eax <- buffer number, edx <- offset into buffer (should be NULL) or edx, edx jnz ReleaseBuffer_nok ; if offset into buffer not 0 the fail. cmp eax, NBR_BUFFERS jge ReleaseBuffer_nok ; if buffernumber >= number of buffers then fail. ; unlock buffer - if locked mov edx, eax add edx, offset FLAT:afBuffer ; ds:edx points at buffer "semaphore" mov al, 1 mov ah, 0 lock cmpxchg [edx], ah jne ReleaseBuffer_nok ; fail if buffer was not locked ReleaseBuffer_ok: ;swipe out buffer pop eax push edi push es mov edi, eax mov ax, ds mov es, ax ASSUME es:FLAT xor eax, eax ; ecx is allready BUFFER_SIZE rep stosb pop es pop edi ;return successfully jmp ReleaseBuffer_ret ReleaseBuffer_nok: ;failure pop eax mov eax, 87 ;some error ReleaseBuffer_ret: pop edx pop ecx pop ds ret ReleaseBuffer ENDP ;; ; Gets the 16-bit segment and offset for this buffer. ; @cproto assembly only for time being. ; @returns segment in es and offset in eax ; On error high word of eax is 87. ; @param eax Buffer pointer. ; @uses eax, es ; @status completely implemented. ; @author knut st. osmundsen (knut.stange.osmundsen@pmsc.no) ; @remark cbBuffer holds the size of the buffer. QueryBufferSegmentOffset PROC NEAR ASSUME DS:NOTHING push ds ; make ds FLAT push eax mov ax, seg FLAT:DATA32 mov ds, ax ASSUME DS:FLAT pop eax ; validate parameter and calc offset relative to aachBuffer cmp eax, offset FLAT:aachBuffer jl QueryBufferSegmentOffset_nok sub eax, offset FLAT:aachBuffer cmp eax, NBR_BUFFERS * BUFFER_SIZE jge QueryBufferSegmentOffset_nok QueryBufferSegmentOffset_ok: jmp far ptr CODE16:GetBufferSegmentOffset16 QueryBufferSegmentOffset_Back:: pop ds ret QueryBufferSegmentOffset_nok: mov eax, 00570000h pop ds ret QueryBufferSegmentOffset ENDP ;; ; Special function which checks all used buffers for the string passed in in eax. ; @cproto PCHAR _Optlink QueryBufferPointerFromFilename(const char *pszFilename) ; @returns Pointer to Buffer. NULL on error/notfound. ; @param ds:eax Pointer to filename. The filename will later be compared to the string at buffer start. ; Currently this parameter is not used, since there is only one buffer. ; @uses eax. ; @sketch ; @status completely implemented ; @author knut st. osmundsen (knut.stange.osmundsen@pmsc.no) ; @remark assumes ds flat on call. QueryBufferPointerFromFilename PROC NEAR ASSUME cs:CODE32, ds:FLAT push ecx push edx push ebx ; loop thru all buffers until found or non left mov ecx, NBR_BUFFERS mov edx, BUFFER_SIZE imul edx, ecx ; edx <- sizeof(aachBuffer) add edx, offset FLAT:aachBuffer ; edx points at the first byte after the buffers. mov ebx, offset FLAT:afBuffer add ebx, ecx ; edx points at the first byte after the "semaphore" array (afBuffer). QueryBufferPointerFromFilename_loop: sub edx, BUFFER_SIZE ; edx points at the buffer being concidered. dec ebx ; ebx points at the "semaphore" for the buffer being concidered. cmp byte ptr [ebx], 1 ; Is buffer in use? jne QueryBufferPointerFromFilename_next ; buffer is active - lets compare push eax push ecx push edx sub esp, 8 call stricmp add esp, 8 pop edx pop ecx or eax, eax jz QueryBufferPointerFromFilename_found pop eax QueryBufferPointerFromFilename_next: loop QueryBufferPointerFromFilename_loop ; when we exit this loop we have failed! QueryBufferPointerFromFilename_nok: ; The buffer was not found, return NULL pointer. xor eax, eax pop ebx pop edx pop ecx ret QueryBufferPointerFromFilename_found: ; The buffer was found, return the pointer to it! pop eax pop ebx mov eax, edx pop edx pop ecx ret QueryBufferPointerFromFilename ENDP CODE32 ENDS CODE16 SEGMENT ;; ; Gets the segment(->es) and offset(+ax -> ax) of the achBuffer. ; @param ax offset to buffer relative to aachBuffer ; Jumps back to GetBufferOffset32 GetBufferSegmentOffset16: ASSUME CS:CODE16, DS:NOTHING push ax mov ax, seg aachBuffer mov es, ax pop ax add ax, offset aachBuffer jmp far ptr FLAT:QueryBufferSegmentOffset_Back CODE16 ENDS END