With the new External Function feature, you can call compiled programs written in conventional language, as PL1, Assembler, and maybe more.
We closely adapted IBM’s TSO/E REXX programming services: https://www.ibm.com/support/knowledgecenter/SSLTBW_2.2.0/com.ibm.zos.v2r2.ikja300/progsrv.htm
How it works:
To call an external program, you call it in the same way as a normal BREXX function:
say load-module(argument-1,argument-2,...,argument-15)
you can pass up to 15 arguments to the external function. The size of the return value can be up to 1024 bytes.
Example:
Say RXPI()
RXPI is a load module that must be accessible within the link list chain. It does not have any arguments.
BREXX provides control blocks containing the arguments and a 1024 bytes return buffer.
The program needs to match the BREXX calling conventions to manage the argument and return value handling. To ease it, we have isolated communication control blocks and internal functions in a copybook. Once included, it will transparently provide the functionality to the program.
Example, PI calculation:
RXPI: PROCEDURE(EFPL_PTR) OPTIONS(MAIN);
%INCLUDE RXCOMM;
...
The performance of a compiled program is much higher than in BREXX. So if you have complex mathematical calculations, they will be significantly faster than code implemented in BREXX. In our testing, we implemented an algorithm for calculating PI with 500 digits. In comparison, it was over 600 times faster than the same algorithm implemented in BREXX.
Example, PI calculation:
RXPI: PROCEDURE(EFPL_PTR) OPTIONS(MAIN); 00000101
%INCLUDE RXCOMM; 00000201
/* --------------------------------------------------------------------00000301
* CALCULATE PI USING THE ALGORITHM OF S. RABINOWICZ AND S. WAGON 00000413
* INPUT VARIABLES 00000501
* ARGNUM CONTAINS NUMBER OF PROVIDED ARGUMENTS (MAX 15) 00000601
* ARG(I) CONTAINS CONTENTS OF ARGUMENT I (1 TO 15) 00000701
* ARG_LEN(I) CONTAINS LENGTH OF ARGUMENT I (1 TO 15) 00000801
* RETURN VARIABLES 00000901
* RESULT CONTAINS RESULT TO BE RETURNED TO BREXX 00001001
* THE RETURN VALUE MUST NOT EXCEED 1024 BYTES 00001112
* RESULT_LEN CONTAINS LENGTH OF RETURNED STRING 00001201
* --------------------------------------------------------------------00001301
*/ 00001401
DCL (N, LEN) FIXED BINARY; 00001505
DCL PI CHAR(512) VARYING; 00001611
DCL TEMPI CHAR(9); 00001709
DCL PREDIGIT BIN FIXED(15); 00001806
N = 500; 00001912
LEN = 10*N / 3; 00002012
PI=''; 00002112
BEGIN; 00002212
DECLARE ( I, J, K, Q, NINES) BIN FIXED(15); 00002312
DECLARE X FIXED BINARY (31); 00002412
DECLARE A(LEN) FIXED BINARY (31); 00002512
00002600
A = 2; /* START WITH 2S */ 00002712
NINES, PREDIGIT =0; /* FIRST PREDIGIT IS A 0 */ 00002812
DO J = 1 TO N; 00002912
Q = 0; 00003012
DO I = LEN TO 1 BY -1; /* WORK BACKWARDS */ 00003112
X = 10*A(I) + Q*I; 00003212
A(I) = MOD (X, (2*I-1)); 00003312
Q = X / (2*I-1); 00003412
END; 00003512
A(1) = MOD(Q, 10); Q = Q / 10; 00003612
IF Q = 9 THEN NINES = NINES + 1; 00003712
ELSE IF Q = 10 THEN DO; 00003812
TEMPI=PREDIGIT+1; 00003912
PI=PI||SUBSTR(TEMPI,9,1); 00004012
DO K = 1 TO NINES; 00004112
PI=PI||'0'; 00004212
END; 00004312
PREDIGIT=0; 00004412
NINES = 0; 00004512
END; 00004612
ELSE DO; 00004712
TEMPI=PREDIGIT; 00004812
PI=PI||SUBSTR(TEMPI,9,1); 00004912
PREDIGIT = Q; 00005012
DO K = 1 TO NINES; 00005112
PI=PI||'9'; 00005212
END; 00005312
NINES = 0; 00005412
END; 00005512
END; 00005610
END ; /* END BEGIN */ 00005712
TEMPI=PREDIGIT; 00005812
PI=PI||SUBSTR(TEMPI,9,1); 00005910
RESULT='3.'||SUBSTR(PI,3); 00006012
RESULT_LEN=LENGTH(PI); 00006112
END RXPI; 00006201
BREXX Version of the PI calculation program:
/* --------------------------------------------------------------------
* PI USING THE ALGORITHM OF S. RABINOWICZ AND S. WAGON
* --------------------------------------------------------------------
*/
RXPIR:
N = 500
LEN = (10*N/3)%1
A.=2
NINES=0
PREDIGIT = 0 /* FIRST PREDIGIT IS A 0 */
DO J = 1 TO N
Q = 0
DO I = LEN TO 1 BY -1 /* WORK BACKWARDS */
X = INT(10*A.I + Q*I)
A.I = INT(X//(2*I-1))
Q = X%(2*I-1)
END
A.1 = (Q//10)%1
Q = Q % 10
IF Q = 9 THEN NINES = NINES + 1
ELSE IF Q = 10 THEN DO
PI=PI||PREDIGIT+1
PI=PI||COPIES('0',NINES)
PREDIGIT= 0
NINES = 0
END
ELSE DO
PI=PI||PREDIGIT
PREDIGIT = Q
PI=PI||COPIES('9',NINES)
NINES = 0
END
END
PI=PI||PREDIGIT
RETURN '3.'SUBSTR(PI,3)Comparison of both implementations:
PL1 Program:: : 3.14159265358979323846264338327950288419716939937510582097494459230781640628620 8998628034825342117067982148086513282306647093844609550582231725359408128481117 4502841027019385211055596446229489549303819644288109756659334461284756482337867 8316527120190914564856692346034861045432664821339360726024914127372458700660631 5588174881520920962829254091715364367892590360011330530548820466521384146951941 5116094330572703657595919530921861173819326117931051185480744623799627495673518 857527248912279381830119491
Elapsed Time 0.49016099452972417 seconds
BREXX Program:: : 3.14159265358979323846264338327950288419716939937510582097494459230781640628620 8998628034825342117067982148086513282306647093844609550582231725359408128481117 4502841027019385211055596446229489549303819644288109756659334461284756482337867 8316527120190914564856692346034861045432664821339360726024914127372458700660631 5588174881520920962829254091715364367892590360011330530548820466521384146951941 5116094330572703657595919530921861173819326117931051185480744623799627495673518 857527248912279381830119491
Elapsed Time 300.3606059551243 seconds
For the hardcore programmer The current content of the Communication Interface follows. The long-winded coding is caused by the functionality of the old PL1-360-F compiler.
/* --------------------------------------------------------------------00000500
* REXX INTERFACE BLOCK EFPL 00000600
* --------------------------------------------------------------------00000700
*/ 00000800
DCL EFPL_PTR PTR; 00000900
DCL 1 EFPL BASED(EFPL_PTR), 00001000
2 EFPLCOM FIXED BIN(31), 00001100
2 EFPLBARG FIXED BIN(31), 00001200
2 EFPLEARG FIXED BIN(31), 00001300
2 EFPLFB FIXED BIN(31), 00001400
2 EFPLARG PTR, 00001500
2 EFPLEVAL PTR; 00001600
/* --------------------------------------------------------------------00001700
* ARGTABLE ENTRIES AND RELATED DEFINITIONS 00001800
* --------------------------------------------------------------------00001900
*/ 00002000
DCL EFPLARG_PTR PTR; 00002100
EFPLARG_PTR = EFPLARG; 00002200
DCL 1 ARGTABLE BASED(EFPLARG_PTR), 00002300
2 ARGTABLE_ENTRY(15), 00002402
3 ARGSTRING_PTR PTR, 00002500
3 ARGSTRING_LENGTH FIXED BIN(31); 00002600
00002704
DCL ARGNUM BIN FIXED(31); 00002810
DCL ARG_LEN(15) BIN FIXED(31); 00002908
DCL ARG(15) CHAR(255) VARYING; 00003010
00003104
DCL ARG_PTR PTR; 00003200
DCL ARGSTRING CHAR(255) BASED(ARG_PTR); 00003300
/* --------------------------------------------------------------------00003400
* EVALUATION BLOCK: EVALBLOCK 00003500
* --------------------------------------------------------------------00003600
*/ 00003700
DCL EFPLEVAL_ADR_PTR PTR; 00003800
DCL EFPLEVAL_PTR PTR; 00003900
EFPLEVAL_ADR_PTR = EFPLEVAL; 00004000
00004104
DCL 1 EVALBLOCK_ADR BASED(EFPLEVAL_ADR_PTR), 00004200
2 EFPLEVAL_ADR PTR; 00004300
00004400
EFPLEVAL_PTR = EFPLEVAL_ADR; 00004500
00004600
DCL 1 EVALBLOCK BASED(EFPLEVAL_PTR), 00004700
2 EVALBLOCK_EVPAD1 FIXED BIN(31), 00004800
2 EVALBLOCK_EVSIZE FIXED BIN(31), 00004900
2 EVALBLOCK_EVLEN FIXED BIN(31), 00005000
2 EVALBLOCK_EVPAD2 FIXED BIN(31), 00005100
2 EVALBLOCK_EVDATA CHAR(256); 00005200
00005300
DCL EVDATA_PTR PTR; 00005400
DCL EVDATLN_PTR PTR; 00005500
00005600
EVDATA_PTR = ADDR(EVALBLOCK_EVDATA); 00005700
EVDATLN_PTR = ADDR(EVALBLOCK_EVLEN); 00005800
00005900
DCL RESULT CHAR(1024) BASED (EVDATA_PTR); 00006009
DCL RESULT_LEN BIN FIXED(31) BASED(EVDATLN_PTR); 00006100
00006200
RESULT_LEN = 1; 00006300
/* --------------------------------------------------------------------00006400
* COPY BREXX PARMS INTO PL1 STRUCTURE 00006503
* --------------------------------------------------------------------00006600
*/ 00006703
DCL AI BIN FIXED(31); 00006804
00006904
DO AI=1 TO 15 ; 00007004
ARG_PTR = ARGSTRING_PTR(AI); 00007103
ARG_LEN(AI) = ARGSTRING_LENGTH(AI); 00007208
IF ARG_LEN(AI)<=0 THEN ARG(AI)=''; 00007308
ELSE DO 00007403
ARG(AI) = SUBSTR(ARGSTRING,1,ARG_LEN(AI)); 00007508
ARGNUM=AI; 00007605
END; 00007705
END;