XMLParse (Read and Parse an XML File)

The following CR6 example program shows the use of the XMLParse function to parse an XML file that is downloaded from a remote datalogger (a program for other datalogger models would be similar).

'Declare variables
Dim fields_counter 'counts the number of fields in our xml file
Public file_handle 'file pointer used by FileOpen
Public file_read_bytes 'number of bytes given by FileRead when reading XML_FILE_NAME
'Const HTTP_CODE = "HTTP/1.1 200 OK" 'used to determine if we receved the file sucessfully over http.  Will need to be updated if HTTP/1.1 changes.
Public http_header As String * 100
Const HTTP_SERVER = "192.168.7.154" 'ip address or name of web server
Const MAX_BYTES_READ = 1300 'max number of bytes to read from file.  Compare file_read_bytes and bump this number up if getting close.
Public record_counter 'counts the number of records in our xml file
Public remote_model As String * 10
Public remote_os_version As String * 19
Public remote_station_name As String * 15
Public state 'Tells us where are we at in the Campbell Scientific XML file
Dim xml_attribute_name As String * 50
Dim xml_attribute_namespace As String * 100
Public xml_content As String * 5000   'RETURN TO DIM after debugging test program
Public xml_data_value_1(10)
Public xml_data_value_2(10)
Dim xml_element_namespace As String * 30
Dim xml_element_name As String * 30
Public xml_fields(2) As String * 64 'Dim after testing
Const XML_FILE_NAME = "cpu:test_data.xml" 'where the xml is stored we retrieved
Public xml_record_number(10)
Public xml_record_time(10) As String * 20
Public xml_response_code 'used to see what XMLParse is returning
Public xml_types(2) As String * 6
Dim xml_value As String * 30

'Return values
Const XML_TOO_MANY_NAMESPACES = -3 ' Too many name space declarations encountered while parsing an element
Const XML_NESTED_TOO_DEEP = -2 ' Too many nested XML elements
Const XML_SYNTAX_ERROR_OR_FAILED = -1 ' XML syntax error or XMLParse failed
Const XML_UNRECOGNIZED_ERROR_CONDITION = 0 'Unrecognized error condition
Const XML_START = 1 'Start of XML element
Const XML_ATTRIBUTE_READ = 2 ' XML attribute read.
Const XML_END_OF_ELEMENT = 3 ' End of XML element
Const XML_END_OF_DOCUMENT = 4 ' END of XML document encountered.  The document has been read/parsed successfully.

'XMLParse max settings
Const XML_MAX_DEPTH = 5 ' Campbell Scientific's XML format has a maximum nexting depth of 4 elements. So give it one more than is needed in memory.
Const XML_MAX_NAMESPACES = 1 ' SOAP standard usually has two name spaces minimum. The ones we are looking at only have one (the default namespace).

'State codes we can use to tell use where we are at in the Campbell Scientific XML file
Const STATE_BEFORE_ROOT = 1
Const STATE_IN_ROOT = 2
Const STATE_IN_HEAD = 3
Const STATE_IN_ENVIRONMENT = 4
Const STATE_IN_FIELDS = 5
Const STATE_IN_DATA = 6
Const STATE_IN_RECORD = 7
Const STATE_COMPLETE = 8

'Main Program
BeginProg
  http_header = "" 'make sure we don't send anything in the header to the web server

  'initialize some variables that we use in arrays
  fields_counter = 1
  record_counter = 1

  'program only runs once
  Scan (1,sec,0,1)
    ' get XML from another datalogger (or webserver) with the xml we want to parse using the WebServerAPI (Campbell Scientific datalogger/webserver)
    HTTPGet("http://" + HTTP_SERVER + "/?command=DataQuery&uri=dl:Test&format=xml&mode=most-recent&p1=10", XML_FILE_NAME, http_header)    

    'copy the the content of the xml file to a string variable we can use to parse against (can also read file directly)
    file_handle = FileOpen (XML_FILE_NAME, "r", 0) 'open file for reading
    file_read_bytes = FileRead( file_handle, xml_content, MAX_BYTES_READ) ' read the file into our string
    FileClose (file_handle)  'close the filehandle to the file we just read   

    'now parse some data from the xml file and put it in our table for use   
    xml_response_code = XML_START
    xml_element_namespace = "Initialize" 'has to be included to get XMLParse to do its thing 
    state = STATE_BEFORE_ROOT

    While xml_response_code > XML_UNRECOGNIZED_ERROR_CONDITION AND xml_response_code <> XML_END_OF_DOCUMENT
      xml_response_code = XMLParse( xml_content, xml_value, xml_attribute_name, xml_attribute_namespace, _
        xml_element_name, xml_element_namespace, XML_MAX_DEPTH, XML_MAX_NAMESPACES)

      'check to see if the XMLParse worked
      If xml_response_code = XML_SYNTAX_ERROR_OR_FAILED OR xml_response_code = XML_UNRECOGNIZED_ERROR_CONDITION
        'return some error message
      EndIf

      If xml_response_code = XML_START AND xml_element_name = "csixml"
         state = STATE_IN_ROOT
      EndIf

      If xml_response_code = XML_START AND xml_element_name = "head"
         state = STATE_IN_HEAD
      EndIf

      If xml_response_code = XML_START AND xml_element_name = "environment"
         state = STATE_IN_ENVIRONMENT
      EndIf

      If xml_response_code = XML_START AND xml_element_name = "fields"
         state = STATE_IN_FIELDS
      EndIf

      If xml_response_code = XML_START AND xml_element_name = "data"
         state = STATE_IN_DATA
      EndIf

      If xml_response_code = XML_START AND xml_element_name = "r"
         state = STATE_IN_RECORD
      EndIf

      If xml_response_code = XML_END_OF_ELEMENT AND xml_element_name = "csixml" AND state = STATE_IN_ENVIRONMENT
         state = STATE_COMPLETE
      EndIf

      'get remote station name from XML file     
      If xml_response_code = XML_END_OF_ELEMENT AND xml_element_name = "station-name" AND state = STATE_IN_ENVIRONMENT
        remote_station_name = xml_value
      EndIf

           'get remote model
      If xml_response_code = XML_END_OF_ELEMENT AND xml_element_name = "model" AND state = STATE_IN_ENVIRONMENT
        remote_model = xml_value
      EndIf     

      'get remote OS version
      If xml_response_code = XML_END_OF_ELEMENT AND xml_element_name = "os-version" AND state = STATE_IN_ENVIRONMENT
        remote_os_version = xml_value
      EndIf

      'get all the field names and data types (there should be 3)
      If xml_response_code = XML_ATTRIBUTE_READ AND xml_element_name = "field" AND xml_attribute_name = "name" AND state = STATE_IN_FIELDS
        xml_fields(fields_counter) = xml_value
      EndIf     

      If xml_response_code = XML_ATTRIBUTE_READ AND xml_element_name = "field" AND xml_attribute_name = "type" AND state = STATE_IN_FIELDS
        xml_types(fields_counter) = xml_value
      EndIf     

      If (xml_fields(fields_counter) <> "") AND (xml_types(fields_counter) <> "") AND (fields_counter <> 2) Then
        fields_counter = fields_counter + 1
      EndIf

      'get the data and timestamps
      If xml_response_code = XML_ATTRIBUTE_READ AND xml_element_name = "r" AND xml_attribute_name = "time" AND state = STATE_IN_RECORD
        xml_record_time(record_counter) = xml_value
      EndIf
     
      If xml_response_code = XML_ATTRIBUTE_READ AND xml_element_name = "r" AND xml_attribute_name = "no" AND state = STATE_IN_RECORD
        xml_record_number(record_counter) = xml_value
      EndIf
     
      If xml_response_code = XML_END_OF_ELEMENT AND xml_element_name = "v1" AND state = STATE_IN_RECORD
        xml_data_value_1(record_counter) = xml_value
      EndIf

      If xml_response_code = XML_END_OF_ELEMENT AND xml_element_name = "v2" AND state = STATE_IN_RECORD
        xml_data_value_2(record_counter) = xml_value
      EndIf

      If (xml_record_time(record_counter) <> "") AND (xml_data_value_1(record_counter) <> 0) _
        AND (xml_data_value_2(record_counter) <> 0) AND (xml_record_number <> "") AND (record_counter <> 10) Then       
        record_counter = record_counter + 1
      EndIf  

    Wend 'end of XMLParse

  'delete our xml file now that we are done with it
  FileManage( XML_FILE_NAME, 8 )

  NextScan
EndProg