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How to read from a binary file using VBScript

I'm very new to VBScript, correct me at any point, if I'm wrong.

I'm facing issue while reading from a binary file.

My need is to read the last four bytes from a binary file and compare the same with a local variable.

But the issue is I'm getting value of 0x3F while converting the ASCII characters (of last 4 bytes) to Hex equivalent. But I'm able to see valid data in the files created by this script by opening, where the same binary stream is used to write to file.

I'm not sure if I'm missing something

Below is the code for reference

Const adTypeBinary = 1 
Const adSaveCreateOverWrite = 2 
Const CRC = 4
Dim BinaryStream, OutStream, StartPos, Bytes
'debug
Dim fso, MyFile
Const ForReading = 1, ForWriting = 2, ForAppending = 8
Const TristateUseDefault = -2, TristateTrue = -1, TristateFalse = 0
'debug
Dim bootstrapIOPCRC, bootIOPCRC, appIOPCRC, bootDSPCRC, codeDSPCRC, dataDSPCRC
Dim a(1)
bootstrapIOP = "C:\Bins\1.bin"
bootIOP = "C:\Bins\2.bin"
appIOP = "C:\Bins\3.bin"
bootDSP = "C:\Bins\4.bin"
codeDSP = "C:\Bins\5.bin"
dataDSP = "C:\Bins\6.bin"
'Create the BinaryStream object 
Set BinaryStream = CreateObject("ADODB.Stream") 
'Set it up and load in the source file 
BinaryStream.Type = adTypeBinary 
BinaryStream.Open 
' *** For bootstrapIOP
Bytes = 0
StartPos = 0
BinaryStream.LoadFromFile bootstrapIOP
'Create OutStream 
Set OutStream = CreateObject("ADODB.Stream") 
OutStream.Type = adTypeBinary 
OutStream.Open 
SET objFSO = CREATEOBJECT("Scripting.FileSystemObject")
SET objFile = objFSO.GetFile(bootstrapIOP)
Bytes = CLng(objFile.Size)
StartPos = Bytes-CRC
'selecting the required data
BinaryStream.Position = StartPos 
BinaryStream.CopyTo OutStream, CRC
OutStream.SaveToFile "C:\bootstrapIOP.txt", adSaveCreateOverWrite 
bootstrapIOPCRC = 0
bootstrapIOPCRC = OutStream.Read ( CRC)
strHex =""
MsgBox((Asc(Mid(bootstrapIOPCRC,1,1))))
MsgBox(Mid(bootstrapIOPCRC,2,1))
MsgBox(bootstrapIOPCRC)
For i=1 To Len(bootstrapIOPCRC)
    strHex = strHex + Hex(Asc(Mid(bootstrapIOPCRC,i,1)))
Next
If (strHex = "") Then 
    MsgBox "Yippy"
Else 
    MsgBox(strHex)
End If
MsgBox(Len(bootstrapIOPCRC))
Set objFSO1=CreateObject("Scripting.FileSystemObject")
' How to write file
outFile="c:\test.txt"
Set objFile = objFSO1.CreateTextFile(outFile,True)
objFile.Write a(0)
objFile.Write a(1)
objFile.Close
' *** For bootIOP
Bytes = 0
StartPos = 0
BinaryStream.LoadFromFile bootIOP
SET objFile = objFSO.GetFile(bootIOP)
Bytes = CLng(objFile.Size)
StartPos = Bytes-CRC
'selecting the required data
BinaryStream.Position = StartPos 
BinaryStream.CopyTo OutStream, CRC
OutStream.SaveToFile "C:\bootIOP.txt", adSaveCreateOverWrite 
bootIOPCRC = 0
bootIOPCRC = OutStream.Read ( CRC)
' *** For appIOP
Bytes = 0
StartPos = 0
BinaryStream.LoadFromFile appIOP
SET objFile = objFSO.GetFile(appIOP)
Bytes = CLng(objFile.Size)
StartPos = Bytes-CRC
'selecting the required data
BinaryStream.Position = StartPos 
BinaryStream.CopyTo OutStream, CRC
OutStream.SaveToFile "C:\appIOP.txt", adSaveCreateOverWrite 
appIOPCRC = 0
appIOPCRC = OutStream.Read ( CRC)
' *** For bootDSP
Bytes = 0
StartPos = 0
BinaryStream.LoadFromFile bootDSP
SET objFile = objFSO.GetFile(bootDSP)
Bytes = CLng(objFile.Size)
StartPos = Bytes-CRC
'selecting the required data
BinaryStream.Position = StartPos 
BinaryStream.CopyTo OutStream, CRC
OutStream.SaveToFile "C:\bootDSP.txt", adSaveCreateOverWrite 
bootDSPCRC = 0
bootDSPCRC = OutStream.Read ( CRC)
' *** For codeDSP
Bytes = 0
StartPos = 0
BinaryStream.LoadFromFile codeDSP
SET objFile = objFSO.GetFile(codeDSP)
Bytes = CLng(objFile.Size)
StartPos = Bytes-CRC
'selecting the required data
BinaryStream.Position = StartPos 
BinaryStream.CopyTo OutStream, CRC
OutStream.SaveToFile "C:\codeDSP.txt", adSaveCreateOverWrite 
codeDSPCRC = 0
codeDSPCRC = OutStream.Read ( CRC)
' *** For dataDSP
Bytes = 0
StartPos = 0
BinaryStream.LoadFromFile dataDSP
SET objFile = objFSO.GetFile(dataDSP)
Bytes = CLng(objFile.Size)
StartPos = Bytes-CRC
'selecting the required data
BinaryStream.Position = StartPos 
BinaryStream.CopyTo OutStream, CRC
OutStream.SaveToFile "C:\dataDSP.txt", adSaveCreateOverWrite 
dataDSPCRC = 0
dataDSPCRC = OutStream.Read ( CRC)
Solution

  • When working with binary data instead of string data you need to use the correct Function variations.

    • LenB() - Returns the length of binary data in bytes.
    • MidB() - Returns a specified number of bytes from binary data.
    • AscB() - Returns a character code for a byte.
    'Using the following pseudo code should help
hexstring = Hex(AscB(MidB(binarydata, start, numofbytes)))

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