CRC32

10 REM > CRC32

20 REM CRC32 test code

30 :

40 DIM mem% &FFF:OSCLI"LOAD CRCs/htm "+STR$~mem%:num%=&A6D

50 REM mem%=PAGE:num%=TOP-PAGE

60 :

70 @%=&90A

80 PRINT"BASIC CRC-32: ";:S%=-1:T%=TIME:PROCcrc:T%=TIME-T%:S%=NOT S%

90 PRINT"&";~S%;" in ";T%/100;"s"'

100 :

110 @%=&2040A

120 PROCAsm1

130 PRINTA$;" CRC-32: ";:T%=TIME:FOR L%=1 TO N%:S%=-1:PROCcrcAsm:NEXT:T%=TIME-T%:S%=NOT S%

140 PRINTSPC(7-LENA$)"&";~S%;" in ";T%/100/N%;"s"'

150 :

160 PROCAsm2

170 PRINTA$;" CRC-32: ";:T%=TIME:FOR L%=1 TO N%:S%=-1:PROCcrcAsm:NEXT:T%=TIME-T%:S%=NOT S%

180 PRINTSPC(7-LENA$)"&";~S%;" in ";T%/100/N%;"s"'

190 END

200 :

210 DEFPROCcopy

220 S%=-1 :REM CRC starts as &FFFFFFFF

230 REPEAT

240 num%=EXT#in%-PTR#in% :REM Number of bytes to transfer

250 IF num%>max% THEN num%=max%

260 PROCgbpb(rd%,in%,mem%,num%,0) :REM Read block of data

270 PROCcrc :REM Update CRC

280 PROCgbpb(wr%,out%,mem%,num%,0) :REM Write block of data

290 UNTIL num%<max% :REM Loop until all done

300 crc%=NOT S% :REM Final CRC is inverted

310 ENDPROC

320 :

330 REM BASIC:

340 DEFPROCcrc:FORA%=mem%TOmem%+num%-1:S%=S%EOR?A%:FORB%=1TO8:O%=S%:S%=(((S%+(S%<0))DIV2)AND&7FFFFFFF):IFO%AND1:S%=S%EOR&EDB88320

350 NEXT:NEXT:ENDPROC

360 :

370 REM Assembler:

380 DEFPROCcrcAsm:!addr=mem%:!num=num%:!crc=S%:CALL Calc:S%=!crc:ENDPROC

390 :

400 REM With CRC-32 code previously assembled with:

410 DEFPROCAsm1

420 IFPAGE>&8000:IFINKEY-256=ASC"W":PROCcrc86:A$="80x86":N%=100:ENDPROC

430 IFPAGE>&8000:PROCcrcARM:A$="ARM":N%=10:ENDPROC

440 IF?&FFF7=&6C:PROCcrc65v1:A$="6502 v1":N%=1:ENDPROC

450 IF?&FFF7=&C3:PROCcrc80:A$="Z80":N%=1:ENDPROC

460 ENDPROC

470 :

480 DEFPROCAsm2

490 IFPAGE>&8000:END

500 IF?&FFF7=&6C:PROCcrc65v2:A$="6502 v2":N%=1:ENDPROC

510 END

520 ENDPROC

530 :

540 DEFPROCcrc65v2:DIM Calcv2 63:addr=&70:num=&72:crc=&74:FORP=0TO1

550 P%=Calc:[OPT P*2

560 .bytelp

570 LDX #8 :\ Prepare to rotate CRC 8 bits

580 LDA (addr-8 AND &FF,X) :\ Fetch byte from memory

590 :

600 \ The following code updates the CRC with the byte in A ---------+

610 \ If used in isolation, requires LDX #8 here |

620 EOR crc+0 :\ EOR byte into CRC bottom byte |

630 .rotlp :\ |

640 LSR crc+3:ROR crc+2 :\ Rotate CRC clearing bit 31 |

650 ROR crc+1:ROR A :\ |

660 BCC clear :\ b0 was zero |

670 TAY :\ Hold CRC low byte in Y |

680 LDA crc+3:EOR #&ED:STA crc+3 :\ CRC=CRC EOR &EDB88320, ZIP polynomic

690 LDA crc+2:EOR #&B8:STA crc+2 :\ |

700 LDA crc+1:EOR #&83:STA crc+1 :\ |

710 TYA:EOR #&20 :\ Get CRC low byte back from Y |

720 .clear :\ |

730 DEX:BNE rotlp :\ Loop for 8 bits |

740 \ If used in isolation, requires STA crc+0 here |

750 \ ---------------------------------------------------------------+

760 :

770 INC addr:BNE next:INC addr+1 :\ Step to next byte

780 .next

790 STA crc+0 :\ Store CRC bottom byte

800 :

810 \ Now do a 16-bit decrement

820 LDA num+0:BNE skip :\ num.lo<>0, not wrapping from 00 to FF

830 DEC num+1 :\ Wrapping from 00 to FF, dec. high byte

840 .skip

850 DEC num+0:BNE bytelp :\ Dec. low byte, loop until num.lo=0

860 LDA num+1:BNE bytelp :\ Loop until num=0

870 RTS

880 ]:NEXT:ENDPROC

890 :

900 DEFPROCcrc65v1:DIM Calc 79:addr=&70:num=&72:crc=&74:FORP=0TO1

910 P%=Calc:[OPT P*2

920 LDY #0 :\ Point to first byte

930 .bytelp

940 LDA (addr),Y:EOR crc:STA crc :\ EOR byte into CRC bottom byte

950 LDX #8 :\ Prepare to rotate CRC 8 bits

960 .rotlp

970 LSR crc+3:ROR crc+2 :\ Rotate CRC

980 ROR crc+1:ROR crc+0

990 BCC clear :\ b0 was zero

1000 LDA crc+3:EOR #&ED:STA crc+3 :\ CRC=CRC EOR &EDB88320, ZIP polynomic

1010 LDA crc+2:EOR #&B8:STA crc+2

1020 LDA crc+1:EOR #&83:STA crc+1

1030 LDA crc+0:EOR #&20:STA crc+0

1040 .clear

1050 DEX:BNE rotlp :\ Loop for 8 bits

1060 INY:BNE next:INC addr+1 :\ Step to next byte

1070 .next

1080 SEC

1090 LDA num+0:SBC #1:STA num+0 :\ num=num-1

1100 LDA num+1:SBC #0:STA num+1

1110 ORA num:BNE bytelp :\ Loop until num=0

1120 RTS

1130 ]:NEXT:ENDPROC

1140 :

1150 DEFPROCcrc80:DIM Calc 79:addr=&70:num=&72:crc=&74:FORP=0TO1

1160 P%=Calc:[OPT P*2

1170 LD IX,(addr):LD BC,(num) :\ Address, Count

1180 LD DE,(crc):LD HL,(crc+2) :\ Incoming CRC

1190 :

1200 \ Enter here with IX=>data, BC=count, HLDE=incoming CRC

1210 .bytelp

1220 PUSH BC :\ Save count

1230 LD A,(IX) :\ Fetch byte from memory

1240 :

1250 \ The following code updates the CRC with the byte in A ---------+

1260 XOR E :\ XOR byte into CRC bottom byte |

1270 LD B,8 :\ Prepare to rotate 8 bits |

1280 .rotlp :\ |

1290 SRL H:RR L:RR D:RRA :\ Rotate CRC |

1300 JP NC,clear :\ b0 was zero |

1310 LD E,A :\ Put CRC low byte back into E |

1320 LD A,H:XOR &ED:LD H,A :\ CRC=CRC XOR &EDB88320, ZIP polynomic|

1330 LD A,L:XOR &B8:LD L,A :\ |

1340 LD A,D:XOR &83:LD D,A :\ |

1350 LD A,E:XOR &20 :\ And get CRC low byte back into A |

1360 .clear :\ |

1370 DEC B:JP NZ,rotlp :\ Loop for 8 bits |

1380 LD E,A :\ Put CRC low byte back into E |

1390 \ ---------------------------------------------------------------+

1400 :

1410 INC IX :\ Step to next byte

1420 POP BC:DEC BC :\ num=num-1

1430 LD A,B:OR C:JP NZ,bytelp :\ Loop until num=0

1440 LD (crc),DE:LD (crc+2),HL :\ Store outgoing CRC

1450 RET

1460 ]:NEXT:PRINTP%-Calc:ENDPROC

1470 :

1480 DEFPROCcrcARM:DIM Calc 79:FORP=0TO1

1490 P%=Calc:[OPT P*2

1500 LDR R0,addr:LDR R1,num :\ Address, Count

1510 LDR R2,crc :\ Incoming CRC

1520 \

1530 \ Enter here with R0=addr, R1=num, R2=crc

1540 \

1550 .crc32reg

1560 LDR R3,xor :\ ZIP polynomic

1570 .bytelp

1580 LDRB R4,[R0],#1 :\ Get byte, inc address

1590 :

1600 \ The following code updates the CRC with the byte in R4 --------+

1610 \ If used in isolation, requires LDR R3,xor here |

1620 EOR R2,R2,R4 :\ EOR byte into CRC bottom byte |

1630 MOV R4,#8 :\ Prepare to rotate 8 bits |

1640 .rotlp :\ |

1650 MOVS R2,R2,LSR #1 :\ Rotate CRC |

1660 EORCS R2,R2,R3 :\ If b0 was set, EOR with ZIP polynomic

1670 SUBS R4,R4,#1:BNE rotlp :\ Loop for 8 bits |

1680 \ ---------------------------------------------------------------+

1690 :

1700 SUBS R1,R1,#1:BNE bytelp :\ Loop until num=0

1710 STR R2,crc:MOV R15,R14 :\ Store outgoing CRC and return

1720 .xor:EQUD &EDB88320 :\ ZIP polynomic

1730 .addr:EQUD 0:.num:EQUD 0

1740 .crc:EQUD 0

1750 ]:NEXT:ENDPROC

1760 :

1770 DEFPROCcrc86:DIM Calc 63:FORP=0TO1

1780 P%=Calc:[OPT P*2

1790 .crc32

1800 MOV ESI,[addr] ; ESI=>start of data

1810 MOV EBX,[num] ; EBX= length of data

1820 MOV ECX,[crc] ; ECX= incoming CRC

1830 ;

1840 .bytelp

1850 MOV AL,[ESI] ; Fetch byte from memory

1860 ;

1870 ; The following code updates the CRC with the byte in AL -----+

1880 XOR CL,AL ; XOR byte into bottom of CRC |

1890 MOV AL,8 ; Prepare to rotate 8 bits |

1900 .rotlp ; |

1910 SHR ECX,1 ; Rotate CRC |

1920 JNC clear ; b0 was zero |

1930 XOR ECX,&EDB88320 ; If b0 was set, XOR with ZIP polymonic |

1940 .clear ; |

1950 DEC AL:JNZ rotlp ; Loop for 8 bits |

1960 ; ------------------------------------------------------------+

1970 ;

1980 INC SI ; Point to next byte

1990 DEC EBX:JNE bytelp ; num=num-1, loop until num=0

2000 MOV [crc],ECX ; Store outgoing CRC

2010 RETF

2020 .addr:DD 0

2030 .num:DD 0

2040 .crc:DD 0

2050 ]:NEXT:ENDPROC

2060 :