Difference between revisions of "Z80 Routines:Security:CRC32"
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These routines use RAM that is also used by the built-in MD5 routines. | These routines use RAM that is also used by the built-in MD5 routines. | ||
− | The code takes | + | The code takes 147 bytes in your program. |
== The code == | == The code == |
Latest revision as of 08:31, 29 May 2006
Contents
Notes from the author
I (84plusfreak) made this routine on-calc. If you find an error, please tell me (serninpc at gmail dot com).
Memory Usage
These routines use RAM that is also used by the built-in MD5 routines.
The code takes 147 bytes in your program.
The code
CRC32Init
CRC32Init: ;Inputs: ; A=0 -> Use 'default' Polynomial (the one used in the ZIP Format) ; A=1 -> Use custom Polynomial ; -> DEHL=Polynomial ;Outputs: ; ($8292)=Polynomial ; ($8296)=Current CRC (~($8296)=CRC32) ;Destroys: ; AF,DE,HL or a jr nz,$+08 ld de,$EDB8 ld hl,$8320 ld a,d ld d,e ld e,a ld a,h ld h,l ld l,a ld ($8292),de ld ($8294),hl ld hl,$FFFF ld ($8296),hl ld ($8298),hl ret
CRC32Update
CRC32Update: ;Inputs: ; HL -> Points to data ; BC -> Number of bytes ;Outputs: ; ($8296) = Updated ;Destroys: ; AF,BC,DE,HL ld a,b or c ret z push hl push bc ld b,(hl) call CRC32Update_Routine pop bc pop hl inc hl dec bc jr CRC32Update CRC32Update_OneByte: ;Inputs: ; A = Byte to add to CRC ;Destroys: ; AF,BC,DE,HL ld b,a CRC32Update_Routine: ld a,($8296) xor b call CRC32TableLookup ld a,($8297) xor l ld ($8296),a ld a,($8298) xor h ld ($8297),a ld a,($8299) xor e ld ($8298),a ld a,d ld ($8299),a ret CRC32TableLookup: ld de,$0000 ld h,d ld l,a ld b,8 CRC32TableLookupLoop: push bc or a rr d rr e rr h rr l jr nc,CRC32TableLookupLoopEnd push hl pop bc ld hl,$8292 ld a,d xor (hl) inc hl ld d,a ld a,e xor (hl) inc hl ld e,a ld a,b xor (hl) inc hl ld b,a ld a,c xor (hl) ld c,a push bc pop hl CRC32TableLookupLoopEnd: pop bc djnz CRC32TableLookupLoop ret
CRC32Finalize
CRC32Finalize: ;Inputs: ; None ;Outputs: ; DEHL = CRC32 ;Destroys: ; AF,BC,DE,HL ld de,($8298) ld bc,($8296) ld hl,$FFFF push hl or a sbc hl,bc ex (sp),hl sbc hl,de ex de,hl pop hl ret