Translating from X'00' to X'40' directly in memory

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  • 1. worse code ever
    i had a client once that named all of their files filxxx where xxx was a number from 001 to 999. en to make things even better, their fields were fld00 -fld999 with no duplicates between files. When they ran out of fldxxx they went to fxxxxx(f00001 - f99999) I lasted about 2 weeks before I finished the little project I was on and ran like hell.
  • 2. Zoned vs packed - Advantages and disadvantages?
    Hi, As far as I know (I'm somewhat new to RPG), a field declared as a packed numeric takes half the memory that a field of the same length declared as a zoned-decimal would take. This concept was never explained where I learned RPG programming, and at the place where I work now, the use of "p" and "s" fields seems... random. I'm sure there are drawbacks to using a data type that takes less memory than another, but what are they? What would be the differences between a RPG program (or a physical file) where all the numeric fields would be declared as packed and another where they would be declared as zoned?
  • 3. Anyone upgrade to v5r3 yet?
    Just wondering if anyone has performed the 5.3 upgrade yet. If so, any problems? Thanks, Jim
  • 4. AS400 & Netgear PS101
    Does anyone know what port to use to print using a Netgear PS101? I tried port 9100, but it does not work. Thank you, Ivan
  • 5. chgprtf
    I'm getting a CPA4072 max records hit error on several jobs since upgrading from v4r5 to v5r2. Trying to use the chgprtf on qsysprt in qsys but it is always in use. Any way around this? No batch jobs are running, don't know what has it in use,possible asyncs. These jobs are running overnight and I really need some sleep. Thanks

Translating from X'00' to X'40' directly in memory

Postby Ewout » Sat, 12 Nov 2005 18:56:38 GMT

We have a service program that is used to put messages on a WebSphere
MQ message queue. The program receives a pointer as an input parameter
(i.e. not the text of the message itself). The messages are build (in
other programs) from data in the database. Some fields in the database
may have low values (hexadecimal 00's). These values can end up in the
message, and we think those values might cause problems when the
messages are processed on the target system. Therefore, we want to
replace the hexadecimal 00's by hexadecimal 40's (i.e. blanks). Now, in
the service program, I could define a field and base the field on the
pointer, but the maximum size of a field in RPG is about 65.000
characters. However, the messages can be much larger. The length might
even be in the megabytes. Of course, I could scan through the message
by first positioning the field on the address of the pointer, do the
scan, and then position the field on the address of the pointer plus
the length of the field, repeat the scan, and so on, until the length
of the message is completely covered, but this does not seem a very
elegant solution to me.

In fact, I am looking for a way to search an area in memory, without
having to use a field. Does anyone have a suggestion that could help me
out?

Ewout


Re: Translating from X'00' to X'40' directly in memory

Postby walker.l2 » Sat, 12 Nov 2005 19:35:07 GMT

Just thinking out loud:

Could User Spaces help somehow?
How about SQL's TRANSLATE function?

Still, if your RPG field is 65k long, you wouldn't need to do many
scans unless the message is tens of megabytes or more.


Walker.


Re: Translating from X'00' to X'40' directly in memory

Postby walker.l2 » Sat, 12 Nov 2005 20:45:56 GMT

I'm also wondering if you could do something clever with a customised
CCSID / translation table...

I'm sorry I'm not giving you anything more concrete.


Walker.


Re: Translating from X'00' to X'40' directly in memory

Postby Jonathan Bailey » Sat, 12 Nov 2005 20:51:05 GMT

The APIs I found which looked at all useful required an input & output
buffer & I assume you need to translate in place. I think that walking
your pointer is going to be as fast & efficient as you could get. I
suppost you are talking about xlate when you say scan ? I dont know if
xlateing 65k then moving is as good or better than pointing to a single
byte char , testing & converting then incrementing the pointer. I think
the xlate would be better but its just a guess.

Jonathan


Re: Translating from X'00' to X'40' directly in memory

Postby datacrush » Sat, 12 Nov 2005 23:37:52 GMT

I think it was as of V5R1 (or was it V4R4?) that you could solve your 
problem this way:

D Msg             S          65535A   Dim(100)
D MsgPtr          S               *   Inz(%Addr(Msg))

Where in debug the attribute is:
TYPE = ARRAY, LENGTH = 6553500 BYTES

This way MsgPtr should be able to point to your MQGET parameter, and you 
could %SCAN the array for X'00'. The largest I've ever declared using 
this method was 12MB.

I don't think you can access the memory directly. You could try 
accessing some MI functions, but I really don't think IBM provides such 
a thing for security reasons.




Re: Translating from X'00' to X'40' directly in memory

Postby Barbara Morris » Sun, 13 Nov 2005 10:04:56 GMT



You could use the _XLATEB MI builtin function (see QSYSINC/MIH XLATEB). 
It takes a 256 byte translate table where you list all the characters
from x'00' to x'ff'; for the characters you want translated, you replace
them with the to-character.

D xlateTable       ds
D   xlatechars               3u 0   dim(256)

D xlateb           pr               extproc('_XLATEB')
D   data                      *     value
D   table                  256a     const
D   len                     10u 0   value

    // setup translate table
    for i = 1 to 256;
       xlatechars(i) = i - 1;  // setup with all the characters from
x'00' to x'ff'
    endfor;
    xlatechars(1) = x'40';     // replace x'00' by x'40' (blank)

    // translate x'00's to blanks
    xlateb (pointerToData : xlateTable : dataLength);

Re: Translating from X'00' to X'40' directly in memory

Postby Ewout » Sun, 13 Nov 2005 20:52:31 GMT

This seems really great! The for-loop is intended to initialize the
array? And I just need to change the entries that I want to be
translated?

I am not at the office right now, but I will try implement this
solution first thing in the (Monday) morning!


Ewout


Re: Translating from X'00' to X'40' directly in memory

Postby Lou » Mon, 14 Nov 2005 03:02:11 GMT

The AS/400 has a feature, which will do this scrubbing for you much
faster than spinning through the message 1 byte at a time.

You define a tranlsation table with from and to byte values. In this
case you would start with the tranlsation table for your code set
(EBCDIC, ASCII, TCPEBD, TCPASC, etc.). Make of copy of that table.
Change the output mapping to be the same as the input mapping except
map x'00' to x'40'.

The call is to a program (not a bound procedure). The program is
QDCXLATE. This program takes several parameters, but only three are
required.

1. Length of data being converted	Input	Packed(5,0)
2. Conversion data			I/O	Char(*)
4. Conversion table name		Input	Char(10)

If you are stuck using RPG, below is a function prototype of the call:

d translate       pr                  extpgm('QDCXLATE')
d  length                        5P 0 const
d  data                      32766A   options(*varsize)
d  table                        10A   const


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