Reading a DXF File

The following example is a simple Visual Basic 6 program that reads a DXF file and extracts specific codes and values from a given object in a given section.

' ReadDXF extracts specified code/value pairs from a DXF file.
' This function requires four string parameters, a valid DXF
' file name, a DXF section name, the name of an object in that
' section, and a comma delimited list of codes.
Function ReadDXF( _
		ByVal dxfFile As String, ByVal strSection As String, _
		ByVal strObject As String, ByVal strCodeList As String)
	Dim tmpCode, lastObj As String
	Open dxfFile For Input As #1
	' Get the first code/value pair
	codes = ReadCodes
	' Loop through the whole file until the "EOF" line
	While codes(1) <> "EOF"
		' If the group code is '0' and the value is 'SECTION' ..
		If codes(0) = "0" And codes(1) = "SECTION" Then
			' This must be a new section, so get the next
			' code/value pair.
			codes = ReadCodes()
			' If this section is the right one ..
			If codes(1) = strSection Then
				' Get the next code/value pair and ..
				codes = ReadCodes
				' Loop through this section until the 'ENDSEC'
				While codes(1) <> "ENDSEC"
					' While in a section, all '0' codes indicate
					' an object. If you find a '0' store the
					' object name for future use.
					If codes(0) = "0" Then lastObj = codes(1)
					' If this object is one you're interested in
					If lastObj = strObject Then
						' Surround the code with commas
						tmpCode = "," & codes(0) & ","
						' If this code is in the list of codes ..
						If InStr(strCodeList, tmpCode) Then
							' Append the return value.
							ReadDXF = ReadDXF & _
								codes(0) & "=" & codes(1) & vbCrLf
						End If
					End If
					' Read another code/value pair
					codes = ReadCodes
			End If
			codes = ReadCodes
		End If
	Close #1
End Function

' ReadCodes reads two lines from an open file and returns a two item
' array, a group code and its value. As long as a DXF file is read 
' two lines at a time, all should be fine. However, to make your 
' code more reliable, you should add some additional error and
' other checking.
Function ReadCodes() As Variant
	Dim codeStr, valStr As String
	Line Input #1, codeStr
	Line Input #1, valStr
	' Trim the leading and trailing space from the code
	ReadCodes = Array(Trim(codeStr), valStr)
End Function