PureBoard

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EnableExplicit

EnableASM
Procedure.l FastCRC32(lBuffer.l, lBufLen.l)
  Protected lResult.l = 0
  MOV esi, lBuffer   ;esi = ptr to buffer
  MOV edi, lBufLen   ;edi = length of buffer
  MOV ecx, -1        ;ecx = -1
  MOV edx, ecx       ;edx = -1
  nextbyte:          ;next byte from buffer
  XOr eax, eax       ;eax = 0
  XOr ebx, ebx       ;ebx = 0
  DB 0xAC            ;"lodsb" instruction to get next byte
  XOr al, cl         ;xor al with cl
  MOV cl, ch         ;cl = ch
  MOV ch, dl         ;ch = dl
  MOV dl, dh         ;dl = dh
  MOV dh, 8          ;dh = 8
  nextbit:           ;next bit in the byte
  SHR bx, 1          ;shift bits in bx right by 1
  RCR ax, 1          ;(rotate through carry) bits in ax by 1
  JNC l_nocarry_     ;jump to nocarry if carry flag not set ; <-- hier tritt der Fehler auf
  XOr ax, 0x08320    ;xor ax with 33568
  XOr bx, 0x0EDB8    ;xor bx with 60856
  nocarry:           ;if carry flag wasn't set
  DEC dh             ;dh = dh - 1
  JNZ l_nextbit_     ;if dh isnt zero, jump to nextbit
  XOr ecx, eax       ;xor ecx with eax
  XOr edx, ebx       ;xor edx with ebx
  DEC edi            ;finished with that byte, decrement counter
  JNZ l_nextbyte_    ;if edi counter isnt at 0, jump to nextbyte
  Not edx            ;invert edx bits - 1s complement
  Not ecx            ;invert ecx bits - 1s complement
  MOV eax, edx       ;mov edx into eax
  ROL eax, 16        ;rotate bits in eax left by 16 places
  MOV ax, cx         ;mov cx into ax
  MOV lResult, eax   ;crc32 result is in eax
  ProcedureReturn lResult
EndProcedure
DisableASM
; Checksum.l = 0
; Buffer.s = "Wayne Diamond"
; Checksum = FastCRC32(@Buffer, Len(Buffer))

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;EnableExplicit

EnableASM
Procedure.l FastCRC32(lBuffer.l, lBufLen.l)
  Protected lResult.l = 0
  MOV esi, lBuffer   ;esi = ptr to buffer
  MOV edi, lBufLen   ;edi = length of buffer
  MOV ecx, -1        ;ecx = -1
  MOV edx, ecx       ;edx = -1
  nextbyte:          ;next byte from buffer
  XOR eax, eax       ;eax = 0
  XOR ebx, ebx       ;ebx = 0
  DB 0xAC            ;"lodsb" instruction to get next byte
  XOR al, cl         ;xor al with cl
  MOV cl, ch         ;cl = ch
  MOV ch, dl         ;ch = dl
  MOV dl, dh         ;dl = dh
  MOV dh, 8          ;dh = 8
  nextbit:           ;next bit in the byte
  SHR bx, 1          ;shift bits in bx right by 1
  RCR ax, 1          ;(rotate through carry) bits in ax by 1
  JNC ll_fastcrc32_nocarry     ;jump to nocarry if carry flag not set ; <-- hier tritt der Fehler auf
  XOR ax, 0x08320    ;xor ax with 33568
  XOR bx, 0x0EDB8    ;xor bx with 60856
  nocarry:           ;if carry flag wasn't set
  DEC dh             ;dh = dh - 1
  JNZ ll_fastcrc32_nextbit     ;if dh isnt zero, jump to nextbit
  XOR ecx, eax       ;xor ecx with eax
  XOR edx, ebx       ;xor edx with ebx
  DEC edi            ;finished with that byte, decrement counter
  JNZ ll_fastcrc32_nextbyte    ;if edi counter isnt at 0, jump to nextbyte
  NOT edx            ;invert edx bits - 1s complement
  NOT ecx            ;invert ecx bits - 1s complement
  MOV eax, edx       ;mov edx into eax
  ROL eax, 16        ;rotate bits in eax left by 16 places
  MOV ax, cx         ;mov cx into ax
  MOV lResult, eax   ;crc32 result is in eax
  ProcedureReturn lResult
EndProcedure
DisableASM
Checksum.l = 0
Buffer.s = "Wayne Diamond"
Checksum = FastCRC32(@Buffer, Len(Buffer))

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ll_fastcrc32_nocarry