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About CVT101 |
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Reading or writing an IFS stream file is not much of a job for a RPG programmer.
IBM i provides an automated way to translate character strings from the job CCSID (example: 37. But it must not be 65535!) to the IFS stream file CCSID (example: 819, US ASCII).
This automated translation takes place whenever a stream file is opened with the open flag O_TEXTDATA.
See the following example:
- Reading non-unicode stream files
Reading an IFS stream file through an ILE-RPG program is usually no problem, as the stream file data can be automatically
translated from the stream file code page to the job CCSID.
Let us take, as an example, the stream file containing this page, intro.htm, code page 819.
The ILE-RPG code to read it is pretty simple (See CVT101/SAMPLERPG member STMFREAD):
/copy CVT101/qrpglesrc,hspecs
/copy CVT101/qrpglesrc,hspecsbnd
D Stmf s 256 inz('/cvt101/html/intro.htm')
D Handle s 10i 0
D Buffer s 10000
D DataLen s 10i 0
D rc s 10i 0
D O_RDONLY s 10i 0 inz(1)
D O_TEXTDATA s 10i 0 inz(16777216)
D open pr 10i 0 extproc('open')
D filename * value options(*string)
D openflags 10i 0 value
D mode 10u 0 value options(*nopass)
D codepage 10u 0 value options(*nopass)
D read pr 10i 0 extproc('read')
D filehandle 10i 0 value
D datareceived * value
D nbytes 10u 0 value
D close pr 10i 0 extproc('close')
D filehandle 10i 0 value
/free
Handle=open(%trim(Stmf):O_RDONLY + O_TEXTDATA); // Open the stream file
// Loop reading the stream file into "Buffer"
DataLen=1;
dow DataLen>0;
DataLen=read(Handle:%addr(Buffer):%size(Buffer));
// ... process the stream file data ...
enddo;
rc=close(Handle); // Close the stream file
return; // Back to caller |
The data read into the buffer are automatically converted to the job CCSID (or to the job default CCSID, if the job CCSID is 65535).
This is why the program can understand and process (if needed) that data.
This is done by specifying the flag O_TEXTDATA
on the open() of the stream file.
However, if the IFS stream file is a UNICODE or a BASE64 encoded one, it is necessary to convert it to a "regular" CCSID stream file, in order to take advantage from the automated
translation to the job CCSID provided with the open flag O_TEXTDATA.
This CVT101 utility provides tools to perform UNICODE and BASE64 transform to a "regular" CCSID.
See the next pages.
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