**************************************************************** * * LISTING ONE: PACK.ASM * * A fully compatible replacement for Electronic Arts' PACKER.C * routine. Converts data according to cmpByteRun1 compression * protocol: * * control bytes: * * n = 0.. 127: followed by n+1 bytes of data * n = -1..-127: followed by byte to be repeated -n+1 times * n = -128: NOOP; don't do no nada. * * calling format: * * long PackRow(from, too, amt) * char **from, /* pointer to source data pointer */ * **too; /* pointer to destination data pointer */ * long amt; /* number of bytes to compress */ * * returns: * * the number of bytes written to the destination; * *from = *from + amt, and *too = *too + return; * return is "smart," that is, not greater than * MaxPackedSize = amt + ((amt+127) >> 7). * * By commenting out CHECK (below) you disable checking for runs * exceeding 128 bytes. That CHECK is not needed if you are sure * the amt to be compressed is always 128 or less. * * !!! DISCLAIMER !!! You use this code entirely at your own * risk. I don't warrantee its fitness for any purpose. I * can't even guarantee the accuracy of anything I've said * about it, though I've tried my damndest to get things right. * I may, in fact, be completely out of my tiny little mind :-). * * That being said, I can be reached for questions, comments, * or concerns at: * * Dr. Gerald Hull * CREATIVE FOCUS * 12 White Street * Binghamton, N.Y. 13901 * (607) 648-4082 * * bix: ghull * PLink: DRJERRY * *************************************************************** xdef _PackRow PT equr a0 -> beginning of replicate run (if any) IX equr a1 -> end+1 of input line IP equr a2 -> beginning of literal run (if any) IQ equr a3 -> end+1 of lit and/or rep run OP equr a4 -> end+1 of output line current pos FP equr a6 frame pointer SP equr a7 stack pointer RT equr d0 return value MX equr d1 check for maximum run = MAX AM equr d2 amount CH equr d3 character REGS reg AM/CH/IP/IQ/OP FRM equ 8 input line address TOO equ 12 output line address AMT equ 16 length of input line MAX equ 128 maximum encodable output run * CHECK equ 1 turns on maximum row checking _PackRow *************** CASE 0: GRAB PARAMS & INITIALIZE CAS0 link FP,#0 movem.l REGS,-(SP) movea.l FRM(FP),IP movea.l (IP),IP IP = *from movea.l IP,IQ IQ = IP movea.l IQ,IX adda.l AMT(FP),IX IX = IP + amt movea.l TOO(FP),OP movea.l (OP),OP OP = *too *************** CASE 1: LITERAL RUN CAS1 movea.l IQ,PT adjust PT (no replicates yet!) move.b (IQ)+,CH grab character cmpa.l IQ,IX if input is finished beq.s CAS5 branch to case 5 ifd CHECK move.l IQ,MX sub.l IP,MX cmpi #MAX,MX if run has reached MAX beq.s CAS6 branch to case 6 endc cmp.b (IQ),CH if next character != CH bne.s CAS1 stay in case 1 * else fall into case 2 *************** CASE 2: AT LEAST 2 BYTE REPEAT CAS2 move.b (IQ)+,CH grab character cmpa.l IQ,IX if input is finished beq.s CAS7 branch to case 7 ifd CHECK move.l IQ,MX sub.l IP,MX cmpi #MAX,MX if run has reached MAX beq.s CAS6 branch to case 6 endc cmp.b (IQ),CH if next character != CH bne.s CAS1 branch to case 1 * else fall into case 3 *************** CASE 3: REPLICATE RUN CAS3 move.b (IQ)+,CH grab character cmpa.l IQ,IX if input is finished beq.s CAS7 branch to case 7 ifd CHECK move.l IQ,MX sub.l PT,MX cmpi #MAX,MX if run has reached MAX beq.s CAS4 branch to case 4 endc cmp.b (IQ),CH if next character = CH beq.s CAS3 stay in case 3 * else fall into case 4 *************** CASE 4: LIT AND/OR REP DUMP & CONTINUE CAS4 move.l PT,AM sub.l IP,AM AM = PT - IP * if no literal run beq.s C41 branch to replicate run subq #1,AM AM = AM - 1 move.b AM,(OP)+ output literal control byte C40 move.b (IP)+,(OP)+ output literal run dbra AM,C40 C41 move.l PT,AM sub.l IQ,AM AM = PT - IQ (negative result!) addq #1,AM AM = AM + 1 move.b AM,(OP)+ output replicate control byte move.b CH,(OP)+ output repeated character movea.l IQ,IP reset IP bra.s CAS1 branch to case 1 (not done) *************** CASE 5: LITERAL DUMP & QUIT CAS5 move.l IQ,AM sub.l IP,AM AM = IQ - IP (positive result > 0) subq #1,AM AM = AM - 1 move.b AM,(OP)+ output literal control byte C50 move.b (IP)+,(OP)+ output literal run dbra AM,C50 bra.s CAS8 branch to case 8 (done) ifd CHECK *************** CASE 6: LITERAL DUMP & CONTINUE CAS6 move.l IQ,AM sub.l IP,AM AM = IQ - IP (positive result > 0) subq #1,AM AM = AM - 1 move.b AM,(OP)+ output literal control byte C60 move.b (IP)+,(OP)+ output literal run dbra AM,C60 bra CAS1 branch to case 1 (not done) endc *************** CASE 7: LIT AND/OR REP DUMP & FINISH CAS7 move.l PT,AM sub.l IP,AM AM = PT - IP (positive result > 0) * if no literal run beq.s C71 branch to replicate run subq #1,AM AM = AM - 1 move.b AM,(OP)+ output literal control byte C70 move.b (IP)+,(OP)+ output literal run dbra AM,C70 C71 move.l PT,AM sub.l IQ,AM AM = PT - IQ (negative result) addq #1,AM AM = AM + 1 move.b AM,(OP)+ output replicate control byte move.b CH,(OP)+ output repeated character * fall into case 8 *************** CASE 8: ADJUST PARAMS & RETURN VALUE CAS8 movea.l FRM(FP),PT PT = **from move.l IQ,(PT) *from = *from + amt movea.l TOO(FP),PT PT = **too move.l OP,RT sub.l (PT),RT return = OP - *too move.l OP,(PT) *too = *too + return movem.l (SP)+,REGS UNLK FP rts end