Library: Character encodings, Base 64 (OMFFBASE64) Import: omffbase64.xmd

Return type: Source Returns:  A scannable input source for streaming data.

Declaration

  export external source function reader
                    from value source input-data

Use reader to read a value source, its argument, and return the binary data of that file converted from a Base 64 encoding to "raw" binary octets. That is, the provided source is in Base 64, but the program sees binary data.

Any input data not recognized as part of a Base 64 encoding is ignored. This is appropriate for white space and for characters used to quote the encoding (such as ">" in email messages), but may erroneously accept input that is not a valid Base 64 encoding.

Usage Note

To use reader, you must import omffbase64.xmd into your program using a statement like this:

  import "omffbase64.xmd" prefixed by base64.

(Please see the import topic for more on importing.)

Example

  ; Read as much BASE64 encoded data as can be found in #current-input,
  ; pass it through the BASE64 reader -- which converts it from
  ; BASE64 to raw data -- and return the raw data as a function's
  ; result.
  import "omffbase64.xmd" prefixed by base64.
  define stream function read-attachment as
     as
     return base64.reader from
        (#current-input take [letter | digit | "+/=%10#%13#"]+)

Related Syntax    base64.writer

Other Library Functions    base64.reader    base64.writer

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