文件列表:

mainform.frx (1291, 2000-01-18)
mainform.frm (29228, 2000-01-18)
crctest.vbp (886, 2000-01-18)
CrcCtrl.ocx (69632, 2000-01-18)
testdata.dat (8253, 1999-11-05)
util.bas (4463, 2000-01-09)
crcocx.cnt (904, 2000-01-09)
CRCOCX.HLP (26517, 2000-01-18)
cmmtimer.cls (1528, 2000-01-05)

CRC Calculation Control ======================= Version 1.5 Date 16/01/00 Copyright (c) Chris Amos, 19***, 1999, 2000 Introduction ~~~~~~~~~~~~ This control (OCX) is really designed for VB4/5/6. It may work in other OCX containers but I haven't tried it. The reason for using an OCX written in C for fairly simple algorythms are speed. In short the OCX is about 500 times quicker even if you are only adding up bytes (it also skirts around the bug in VB where a byte becomes a short int when you compile the application, but I digress...) Since version 1.5, most of the algorithms are rewritten in ASM so they are twice as fast again. Usage ~~~~~ In VB you simply give the OCX a string and say what CRC to return, you have the option of showing a progress bar or passing the string in chunks. An example VB project is included. You can also give it a file name, an array of bytes or a whole bunch of file names to do asynchronously in the background. Installation ~~~~~~~~~~~~ This is a programmers tool, if you need to ask... Well, just in case, copy the OCX, the CNT and HLP file to a folder on your PC. Register the OCX ("regsvr32 crcocx.ocx"). When you first use the help function in VB, you will have to lead it to the correct directory, after which it should remember it. License ~~~~~~~ I have released this control as what I call 'swapware', this means you can use this control in any personal project for free (send me an email anyway for my intrest at freereg_crcocx@preface.co.uk). I would like to get something back so if you use this control to produce a shareware or comercial product, I would like a copy of that product, DO NOT email me an application, send me an email with a description, a URL to get the program and the regcode etc. If it a big app that is only distributed on CD send me details and we'll take it from there. The address for swaps is swapreg_crcocx@preface.co.uk Support ~~~~~~~ As this product is free, I will not guarantee to answer any queries, I, and a few others, have tested it and it does what I wanted. Send any queries to: freesupt_crcocx@preface.co.uk Source Code ~~~~~~~~~~~ I understand that commercial organisations must be able to guarantee continuity of support if they choose to use a component especially from a one-man-band. The best way I can ensure this is to make the source code available. If you wish to 'buy' the source code go to http://www.sw-reg.com and look up product id 201692. They will send the password to open the source code archive (http://www.sirocco.force9.co.uk/crcsrc.zip) and inform me of your purchase. This will not guarantee I will provide support and upgrades etc, it is your guarantee that YOU can support the component. Implementation ~~~~~~~~~~~~~~ I have implemented a selection of CRCs detailed below: 0: XOR 8 Bit Bitwise XOR 1: CRC32 This is the most widely used CRC, it expressed as x^32,26,23,22,16,12,11,10,8,7,5,4,2,1,0. This is used in zip archives. 2: Adler I believe this is the method used in GZIP archives. 3: CRC16 Fairly widely used CRC, it expressed as x^16,15,2,0. 4: CCITT Its a standard, but I have no idea who uses it, 16 x^16,12,5,0 5: 16 Bit Sum Simply adds up the bytes, way quicker than VB and bug free. Sometimes called a longitudinal redundancy check (LRC) in specs, but there must be more to something with a fancy name like that. 6: 32 Bit Sum As 16 bit sum, but bigger. 7: Private Custom type Please ignore this type. 8: CCITT Reflected and byte swapped (ie Motorola byte order) As use on ModBUS systems, variant on type 4, possibly explains why I found no users of type 4. 16 x^16,12,5,0 9: CCITT16 Reversed As 8 without the twist. 16 x^16,12,5,0 10:CRC8 By request CRC, it is expressed as x^8,5,4,3,0. 11:Custom By request, whatever you want 16 or 32 bit! History ~~~~~~~ 1.0 Initial release, requires a progress bar control in VB proj that uses the control. 1.1 Fixed requirement for second progress bar. 1.2 Added ModBUS crc 1.3 CCITT16 Reversed 1.4 Added DoCRCVar to CRC most things found in a variant Added DoCRCByteArray to CRC a Byte array, gets round some Unicode problems on Japanese systems 1.5 Added 8 bit CRC, by request source supplied, unsure of its use. Added custom 16 and 32 bit CRCs Added functions to retrieve crc as hex/dec string, for VB! Optimized most CRC calculations with ASM language. Added help Unsorted property page listbox and change size to please VB Added GetLastError fx, call this if the crc is 0, if it is Genuinely 0, GetLastError will return 0, else it returns Whatever error it got from the OS, could be anything but 0! Added CRCFile fx Added CRCFileAsyncStart, CRCFileAsyncStop and events!

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