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「CRC」(2010/02/18 (木) 11:58:39) の最新版変更点

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#asciiart(blockquote){
/***********************************************************
	crc32t.c -- CRC
***********************************************************/

Const CRCPOLY1 = &h04C11DB7
	/* xXor{32}+xXor{26}+xXor{23}+xXor{22}+xXor{16}+xXor{12}+xXor{11]+
	   xXor{10}+xXor8+xXor7+xXor5+xXor4+xXor2+xXor1+1 */
Const CRCPOLY2 = &hEDB88320  /* 左右逆転 */

Const UCHAR_MAX = 255
Const CHAR_BIT  = 8
Dim crctable[UCHAR_MAX] As DWord

Sub makecrctable1()
	Dim i As DWord, j As DWord
	Dim r As DWord

	For i=0 To UCHAR_MAX
		r = i << (32 - CHAR_BIT)
		For j=0 To  CHAR_BIT-1
			If (r And &h80000000) Then
				r = (r << 1) Xor CRCPOLY1
			Else
			 r = r << 1
			End If
		Next
		crctable[i] = r And &hFFFFFFFF
	Next
End Sub

Function crc1(n As Long, c As *Byte) As DWord
	Dim r As DWord

	r = &hFFFFFFFF
	n=n-1
	while (n >= 0)
		r = (r << CHAR_BIT) Xor crctable[(r >> (32 - CHAR_BIT)) As Byte Xor GetByte(c)]
		c++
		n=n-1
	Wend
	crc1= Not r And &hFFFFFFFF
End Function

Sub makecrctable2()
	Dim i As DWord, j As DWord
	Dim r As DWord

	For i=0 To UCHAR_MAX
		r = i
		For j=0 To  CHAR_BIT-1
			If (r And 1) Then
				r = (r >> 1) Xor CRCPOLY2
			Else
			 r = r >> 1
			End If
		Next
		crctable[i] = r
	Next
End Sub

Function crc2(n As Long, c As *Byte) As DWord
	Dim r As DWord
	Dim t As Byte
	r = &hFFFFFFFF
	n=n-1
	while (n >= 0)
		t = (r As Byte) Xor GetByte(c)
		r = (r >> CHAR_BIT) Xor crctable[t]
		c++
		n=n-1
	Wend
	crc2= r Xor &hFFFFFFFF
End Function


#N88BASIC
Dim s As *Byte
Dim out[100] As Byte
s = "Hello, world!"
makecrctable1()
wsprintf(out, Ex"crc1(%s) = %08lX", s, crc1(13, s))
Print MakeStr(out)
makecrctable2()
wsprintf(out, Ex"crc2(%s) = %08lX", s, crc2(13, s))
Print MakeStr(out)
}