COMPRESS

8.5C

The COMPRESS instruction compresses the logical string from a source variable into a destination variable. The instruction uses the following format:

Where:

label

Optional. A Program Execution Label.

source

Required. A previously defined Character String Variable that contains the input string that is compressed.

sep

Required. A comma or one of the following prepositions: BY, TO, OF, FROM, USING, WITH, IN, or INTO.

dest

Required. A previously defined character variable that receives the compressed data.

Flags Affected: EQUAL, EOS, OVER

Note the following:

1. Only the Logical String of the {source} variable is compressed.

2. The {dest} variable size must be larger than the {source} data size or the EOS flag is set. This size difference can occur because the compression control data can make the output larger than the non-compressed size. To insure that there is sufficient room in the {dest} variable, the following algorithm can be used:
   
   destlen = sourcelen + sourcelen/64 + 19
   
   

3. The EOS flag is set if the {dest} variable is too small to receive all of the compressed data. In this case, the {dest} variable is set to a Null String.

4. The EQUAL flag is set if the {source} variable was successfully compressed and stored into {dest}.

5. The OVER flag is set if a recoverable compression error occurs. The {dest} variable is set to a Null String in this case.

6. A U42 error occurs if an internal error occurs.

See Also: Example Code, DECOMPRESS, Character String Instructions