ITT Rule IDL Version 7.0 User Manual download pdf (Page 243)

Chapter 9: Creating a File Reader 243

iTool Developer’s Guide Creating a New File Reader

Example IsA Method

FUNCTION ExampleReader::IsA, strFilename

iDot = STRPOS(strFilename, '.', /REVERSE_SEARCH)

IF (iDot GT 0) THEN BEGIN

fileSuffix = STRUPCASE(STRMID(strFilename, iDot + 1))

IF (STRUPCASE(fileSuffix) EQ 'PPM') THEN RETURN, 1

ENDIF

self->IDLitIMessaging::ErrorMessage, $

["The specified file is not a PPM file."], $

SEVERITY = 0, TITLE="Wrong File Type"

RETURN, 0

END

Discussion

Note

Our example IsA method will simply check the filename for the presence of the

proper filename extension. A more sophisticated IsA method would actually inspect

the contents of the specified file.

The IsA method accepts a string that contains a file name. Using the supplied file

name, we first search backwards from the end of the name until we locate a dot

character. If the filename contains a dot, we extract the string that follows the dot and

convert it to upper case. If the extracted string is

'PPM', we return success; if the

extracted string is not

'PPM' or if there is no dot in the file name, we issue an error

using the IDLitIMessaging::ErrorMessage method and return failure.

Creating a GetData Method

The file reader GetData method does the work of the file reader, first creating an IDL

variable or variables to contain the data read from the file, then placing the data into

an iTool data object. If this process is successful, the GetData method must place the

created data object in the variable supplied as the method’s only argument and return

1 for success. If the process is not successful, the GetData method must return 0.

See “IDLitReader::GetData” (IDL Reference Guide) for additional details.

Example GetData Method

FUNCTION ExampleReader::GetData, oImageData

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ITT Rule IDL Version 7.0 User Manual Page 243