Mercurial > hg > Members > kono > nitros9-code
diff level2/modules/kernel/fallbit.asm @ 1145:ca83286ded5b
Start of new OS-9 L2 Kernel
| author | boisy |
|---|---|
| date | Tue, 22 Apr 2003 19:35:48 +0000 |
| parents | |
| children | 90bad6d8388c |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/level2/modules/kernel/fallbit.asm Tue Apr 22 19:35:48 2003 +0000 @@ -0,0 +1,313 @@ +************************************************** +* System Call: F$AllBit +* +* Function: Sets bits in an allocation bitmap +* +* Input: X = Address of allocation bitmap +* D = Number of first bit to set +* Y = Bit count (number of bits to set) +* +* Output: None +* +* Error: CC = C bit set; B = error code +* +FAllBit ldd R$D,u get bit # to start with + ldx R$X,u get address of allocation bit map + bsr CalcBit calculate byte & position & get first bit mask + ldy <D.Proc get current task # + ldb P$Task,y get task number + bra SetBit go do it + +* F$AllBit (System State) +FSAllBit ldd R$D,u get bit # to start with + ldx R$X,u get address of allocation bit map + bsr CalcBit calculate byte & pos & get first bit mask + ldb <D.SysTsk Get system task # + +* Main bit setting loop +SetBit equ * + IFNE H6309 + ldw R$Y,u get # bits to set + ELSE + ldy R$Y,u get # bits to set + ENDC + beq BitEx nothing to set, return + sta ,-s preserve current mask + bmi SkpBit If high bit set, skip ahead + os9 F$LDABX Go get original value from bit map +NxtBitLp ora ,s OR it with the current mask + IFNE H6309 + decw Dec the bit counter + ELSE + leay -1,y + ENDC + beq BitStEx Done, go put the byte back into the task's map + lsr ,s Shift out the lowest bit of original + bcc NxtBitLp If it is a 0, do next bit + os9 F$STABX If it was a 1 (which means whole byte done), + leax 1,x Store finished byte and bump ptr +SkpBit lda #$FF Preload a finished byte + bra SkpBit2 Skip ahead + +StFulByt os9 F$STABX Store full byte + leax 1,x Bump ptr up 1 + IFNE H6309 + subw #8 Bump counter down by 8 +SkpBit2 cmpw #8 Is there at least 8 more (a full byte) to do? + ELSE + leay -8,y +SkpBit2 cmpy #$0008 + ENDC + bhi StFulByt More than 1, go do current + beq BitStEx Exactly 1 byte left, do final store & exit + +* Last byte: Not a full byte left loop +L085A lsra Bump out least sig. bit + IFNE H6309 + decw Dec the bit counter + ELSE + leay -1,y + ENDC + bne L085A Keep going until last one is shifted out + coma Invert byte to get proper result + sta ,s Preserve a sec + os9 F$LDABX Get byte for original map + ora ,s Merge with new mask +BitStEx os9 F$STABX Store finished byte into task + leas 1,s Eat the working copy of the mask +BitEx clrb No error & return + rts + +* Calculate address of first byte we want, and which bit in that byte, from +* a bit allocation map given the address of the map & the bit # we want to +* point to +* Entry: D=Bit # +* X=Ptr to bit mask table +* Exit: A=Mask to point to bit # within byte we are starting on +* X=Ptr in allocation map to first byte we are starting on +CalcBit pshs b,y preserve registers + IFNE H6309 + lsrd divide bit # by 8 to calculate byte # to start + lsrd allocating at + lsrd + addr d,x Offset that far into the map + ELSE + lsra + rorb + lsra + rorb + lsra + rorb + leax d,x + ENDC + puls b restore bit position LSB + leay <L0883,pc point to mask table + andb #7 round it down to nearest bit + lda b,y get bit mask + puls y,pc restore & return + +* Bit position table (NOTE that bit #'s are done by left to right) +L0883 fcb $80,$40,$20,$10,$08,$04,$02,$01 + + +************************************************** +* System Call: F$DelBit +* +* Function: Clears bits in an allocation bitmap +* +* Input: X = Address of allocation bitmap +* D = Number of first bit to clear +* Y = Bit count (number of bits to clear) +* +* Output: None +* +* Error: CC = C bit set; B = error code +* +FDelBit ldd R$D,u Get bit # to start with + ldx R$X,u Get addr. of bit allocation map + bsr CalcBit Point to starting bit + ldy <D.Proc Get current Task # + ldb P$Task,y get task # + bra L08A0 Do rest of 0 bits + +* F$DelBit entry point for system state +FSDelBit ldd R$D,u Get bit # to start with + ldx R$X,u Get addr. of bit allocation map + bsr CalcBit Point to starting bit + ldb <D.SysTsk Get system task # + +L08A0 equ * + IFNE H6309 + ldw R$Y,u Get # bits to clear + ELSE + ldy R$Y,u Get # bits to clear + ENDC + beq L08E0 None, return + coma Invert current bit mask + sta ,-s Preserve on stack + bpl L08BC If high bit clear, skip ahead + os9 F$LDABX Go get byte from user's map +L08AD anda ,s AND it with current mask + IFNE H6309 + decw Dec the bits left counter + ELSE + leay -1,y + ENDC + beq BitDone Done, store finished byte back in task's map + asr ,s Shift out lowest bit, leaving highest alone + bcs L08AD If it is a 1, do next bit + os9 F$STABX If it was a 0 (which means whole byte done), + leax 1,x store finished byte & inc. ptr +L08BC clra Preload a cleared byte + bra ChkFull skip ahead +L08BF os9 F$STABX Store full byte + leax 1,x Bump ptr up by 1 + IFNE H6309 + subw #8 Dec bits left counter by 8 +ChkFull cmpw #8 At least 1 full byte left? + ELSE + leay -8,y +ChkFull cmpy #8 + ENDC + bhi L08BF Yes, do a whole byte in 1 shot + beq BitDone Exactly 1, store byte & exit + coma < full byte left, invert bits +L08CF lsra Shift out rightmost bit + IFNE H6309 + decw Dec bits left counter + ELSE + leay -1,y + ENDC + bne L08CF Keep doing till done + sta ,s Save finished mask + os9 F$LDABX Get original byte from task + anda ,s Merge cleared bits with it +BitDone os9 F$STABX Store finished byte into task + leas 1,s Eat working copy of mask +L08E0 clrb Eat error & return + rts + + +************************************************** +* System Call: F$SchBit +* +* Function: Search bitmap for a free area +* +* Input: X = Address of allocation bitmap +* D = Starting bit number +* Y = Bit count (free bit block size) +* U = Address of end of allocation bitmap +* +* Output: D = Beginning bit number +* Y = Bit count +* +* Error: CC = C bit set; B = error code +* +FSchBit ldd R$D,u Get start bit # + ldx R$X,u Get addr. of allocation bit map + bsr CalcBit Point to starting bit + ldy <D.Proc Get task # + ldb P$Task,y + bra L08F8 skip ahead + +* F$SchBit entry point for system +FSSchBit ldd R$D,u Get start bit # + ldx R$X,u Get addr. of allocation bit map + lbsr CalcBit Point to starting bit + ldb <D.SysTsk Get task # +* Stack: 0,s : byte we are working on (from original map) +* 1,s : Mask of which bit in current byte to start on +* 2,s : Task number the allocation bit map is in +* 3,s : Largest block found so far +* 5,s : Starting bit # of requested (or closest) size found +* 7,s : Starting bit # of current block being checked (2 bytes) (NOW IN Y) + IFNE H6309 +L08F8 pshs cc,d,x,y Preserve task # & bit mask & reserve stack space + clrd Faster than 2 memory clears + ELSE +L08F8 pshs cc,d,x,y,u Preserve task # & bit mask & reserve stack space + clra + clrb + ENDC + std 3,s Preserve it + IFNE H6309 + ldw R$D,u get start bit # + tfr w,y save as current block starting bit # + ELSE + ldy R$D,u + sty 7,s + ENDC + bra Skipper skip ahead + +* New start point for search at current location +RstSrch equ * + IFNE H6309 + tfr w,y Preserve current block bit # start + ELSE + sty 7,s + ENDC +* Move to next bit position, and to next byte if current byte is done +MoveBit lsr 1,s Move to next bit position + bcc CheckBit If not the last one, check it + ror 1,s Move bit position marker to 1st bit again + leax 1,x Move byte ptr (in map) to next byte + +* Check if we are finished allocation map +Skipper cmpx R$U,u done entire map? + bhs BadNews yes, couldn't fit in 1 block, notify caller + ldb 2,s Get task number + os9 F$LDABX Get byte from bit allocation map + sta ,s Preserve in scratch area + +* Main checking +CheckBit equ * + IFNE H6309 + incw Increment current bit # + ELSE + leay 1,y + ENDC + lda ,s Get current byte + anda 1,s Mask out all but current bit position + bne RstSrch If bit not free, restart search from next bit + IFNE H6309 + tfr w,d Dupe current bit # into D + subr y,d Calculate size we have free so far + cmpd R$Y,u As big as user requested? + ELSE + tfr y,d + subd 7,s + cmpd R$Y,u + ENDC + bhs WereDone Yes, we are done + cmpd $03,s As big as the largest one we have found so far? + bls MoveBit No, move to next bit and keep going + std $03,s It is the largest, save current size + IFNE H6309 + sty $05,s Save as start bit # of largest block found so far + ELSE + ldd 7,s + std 5,s + ENDC + bra MoveBit Move to next bit and keep going + +* Couldn't find requested size block; tell user where the closest was found +* and how big it was +BadNews ldd $03,s Get size of largest block we found + std R$Y,u Put into callers Y register + comb Set carry to indicate we couldn't get full size + ldd 5,s Get starting bit # of largest block we found + bra BadSkip skip ahead +* Found one, tell user where it is +WereDone equ * + IFNE H6309 + tfr y,d Get start bit # of the block we found + ELSE + ldd 7,s + ENDC +BadSkip std R$D,u Put starting bit # of block into callers D register + IFNE H6309 + leas $07,s Eat our temporary stack area & return + ELSE + leas $09,s + ENDC + rts