Help required to convert a C++ Code to Ms Access VBA

Is it possible to get assistance on converting the CRC Code below which was done in C++ to MS Access VBA

unsigned short int cal_crc(unsigned char *ptr, unsigned int len)
{
unsigned char i;
unsigned int crc=0;
while(len--!=0)
{
for(i=0x80; i!=0; i/=2)
{
if((crc&0x8000)!=0)
{
crc*=2;
crc^=0x18005;
}
else
{
crc*=2;
}
if((*ptr&i)!=0)
crc^=0x18005;
}
ptr++;
}
return(crc);

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C++Microsoft AccessVBA

Last Comment

Hankwembo Christopher,FCCA,FZICA,CIA,MAAT,B.A.Sc

8/22/2022 - Mon

Bill Prew

1/30/2020

Can you provide some test data and the desired CRC results to be calculated from that input?

»bp

Scott McDaniel (EE MVE )

1/30/2020

If your goal is to calculate the CRC for a given string or file, perhaps this would work:

http://www.freevbcode.com/ShowCode.asp?ID=655

Also, FMS Total Visual Sourcebook has functions that do this. TVS is a purchased product, but it has a LOT of code and can save you tons of time:

https://www.fmsinc.com/MicrosoftAccess/modules/index.asp

Hankwembo Christopher,FCCA,FZICA,CIA,MAAT,B.A.Sc

1/30/2020

ASKER

Dear Bill Prew;

Kindly see below the information provided from the INSPUR ESD Device below:

The contents of the interface protocol include three commands (request/response), such as Get Status, Invoice signing and error message. All the data will be organized in JSON format starting with package header and ending with checksum. It consists of Header, Command ID, Length of data, Content and Verification Code (CRC):

Detailed description of the device:

Field
Header1 = 1 Length Byte (The first byte of package header 0x1A
Header2 = 1 Length Byte (The first byte of package header 0x5D
CmdID = 1 Command IDs : (0x01 acquire the status of the device, 0x02 invoice signing, 0x03 Error code)
Length = 4 The length of the content, big-endian
Content = ? Data to be sent
CRC = 2 (Two-Byte verification (CRC), it will be generated by bytes start from Header to Content)

Regards

Your help has saved me hundreds of hours of internet surfing.

fblack61

Bill Prew

1/30/2020

Kindly see below the information provided from the INSPUR ESD Device below:

That didn't answer my question, I am looking for some test data to know if the converted VBA routine is working properly, that is what I wanted you to provide.

For example "0123456789" seems to generate a crc value of 64788, is that correct, and what you seek?

»bp

Hankwembo Christopher,FCCA,FZICA,CIA,MAAT,B.A.Sc

1/30/2020

ASKER

Yes Bill Prew that is very correct I have asked the provider of the gadget.

Regards

Chris

Hankwembo Christopher,FCCA,FZICA,CIA,MAAT,B.A.Sc

1/30/2020

ASKER

Dear Bill Prew;

Kindly note that the CRC will be changing according to the information sent as per given parameters below:

Field
Header1 = 1 Length Byte (The first byte of package header 0x1A
Header2 = 1 Length Byte (The first byte of package header 0x5D
CmdID = 1 Command IDs : (0x01 acquire the status of the device, 0x02 invoice signing, 0x03 Error code)
Length = 4 The length of the content, big-endian
Content = ? Data to be sent
CRC = 2 (Two-Byte verification (CRC), it will be generated by bytes start from Header to Content)

For example the Content = ? Data to be sent

May have a length of 864 bytes or more depending to the invoice lines created or even less

Sorry for that.

Regards

Chris

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Hankwembo Christopher,FCCA,FZICA,CIA,MAAT,B.A.Sc

1/30/2020

ASKER

Dear Bill Prew;

Any lucky there!

Regards

Chris

Bill Prew

1/30/2020

This will take time to work up, there are several critical differences between C++ and VBA that need to be accounted and adjusted for, and it will take time to work out. A couple that have already come to mind include: