Re: Reading Pipe - ASCII -> EBCDIC Conversion

[Simon Coulter <shc@xxxxxxxxxxxxxxxxx>]

On 20/07/2010, at 11:03 PM, MattLavinder@xxxxxxxxxxxxxxxxxxx wrote:

> Have been looking at writing a pipe to process log information from  
> the IBM
> HTTP.  Program reads data but it appears to be in ASCII.  Tried  
> using the
> follow code to convert it and it didn't work.  What did I do wrong?

Your prototype is wrong.

> D Translate       PR                  ExtPgm('QDCXLATE')
> D   Length                       5P 0 const
> D   Data                          *   const
> D   Table                       10A   const

The definition of parameter 2 is wrong. QDCXLATE expects [the address  
of] a variable and it limits the length of data to convert to 32K--the  
length field cannot exceed 32767. QDCXLATE is an external program  
therefore it expects the variables to be passed by reference. Ingrain  
the following:

	passing a variable by reference is EXACTLY the same as passing a  
pointer by value

Thus if you want to pass a pointer then it must be by value not const.  
You have two choices:

Define the prototype with a variable of flexible size e.g.:

D Translate       PR                  ExtPgm('QDCXLATE')
D   Length                       5P 0 const
D   Data                     32767    options(*varsize)
D   Table                       10A   const

or confuse the next person by defining it with a pointer e.g.:

D Translate       PR                  ExtPgm('QDCXLATE')
D   Length                       5P 0 const
D   Data                          *   value
D   Table                       10A   const

Note that since the main reason to use a pointer is to exceed the size  
limitations inherent in defining a variable (32K prior to VRM440, 64K  
from VRM440 to VRM540, and [hardly a limit] 16M from VRM610) and that  
QDCXLATE is limited to 32K there is no point in defining a pointer--it  
will simply confuse things.

One possible area of additional confusion is that IBM APIs with  
variable-length character parameters are documented as CHAR(*) which  
some programmers, usually those with a C mind-set, interpret as a  
pointer [i.e., char *] which is simply incorrect--a mistake fostered  
entirely by assumption. Reading the API concepts section should clear  
that up.

Regards,
Simon Coulter.
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