This is an example of how to extend another language with functions found within the C library using the Systems/C Direct Call facility. Regular expressions are used in a variety of ways for very flexible text matching facilities. For more information on the details of the functions used below as well as regular expressions, see the Systems/C documentation.

• Regular Expression Systems/C Source -> regexp.c
• Regular Expression Example Assembler Source -> callre.asm
• Example Assembler Object deck -> callre.obj
  Save this as binary, upload as fixed 80 and linkedit, using callre.jcl as example JCL.
• Systems/C include -> regex.h
• Linkable regexp library using Systems/C -> regexp.obj
  Note that this is a non-rent version of these functions, just link it in with your application to use.

If you'd like to learn more about Systems/C, visit the Systems/C description here.

#include <sys/types.h>
#include <regex.h>


#pragma prolkey(DCCREBG,"DCALL=ALLOCATE,NOSTDIO=1")
void *
DCCREBG(void ** envp)
{
  { /* Save the created environment */
    __register(13) long * sa;
    *envp = *(long **)(sa+1);
  }

  return *envp;

}

#pragma prolkey(DCCRECO,"DCALL=SUPPLIED,FINDENV=REGFND")
int
DCCRECO(void ** envp, regex_t *preg, const char *pattern, int cflags)
{
  return regcomp(preg,pattern,cflags);
}

#pragma prolkey(DCCREXE,"DCALL=SUPPLIED,FINDENV=REGFND")
int
DCCREXE(void ** env,const regex_t *preg, const char *string, size_t nmatch,
             regmatch_t pmatch[], int eflags)
{
  return regexec(preg, string, nmatch, pmatch, eflags);
}

#pragma prolkey(DCCRERR,"DCALL=SUPPLIED,FINDENV=REGFND")
size_t
DCCRERR(void ** env,int errcode, const regex_t *preg, char *errbuf,
             size_t errbuf_size)
{
  return regerror(errcode, preg,errbuf,errbuf_size);
}


#pragma prolkey(DCCREFR,"DCALL=SUPPLIED,FINDENV=REGFND")
void
DCCREFR(void ** env, regex_t *preg)
{
  regfree(preg);
  return;
}

#pragma prolkey(DCCREND,"DCALL=DESTROY,FINDENV=REGFND")
void
DCCREND(void ** env)
{
}

__asm {
REGFND CSECT
       USING REGFND,15
       L  2,0(,1)   Get the address of the Environment
       L  0,0(,2)   The Environment
       L  15,=v(@crt9a) Get the address of CRT9A
       BR 15
       LTORG
}

callre    csect
          stm     14,12,12(13)
          lr      12,15
          using   callre,12
          st      13,savearea+4
          la      13,savearea
          using   savearea,13

          call    DCCREBG,(envp)   * create the C Environment

          call    DCCRECO,(envp,preg,pattern,0) * compile the RE
          ltr     6,15
          bz      ok1

          o       6,=a(1000)  * Indicate regcomp failed
          b       returnrc

ok1       call    DCCREXE,(envp,preg,match,0,0,0) * compare match
          ltr     6,15
          bz      ok2

          o       6,=a(2000)  * Indicate regexec of match faile

ok2       call    DCCREXE,(envp,preg,nomatch,0,0,0) * compare nomatch
          ltr     6,15
          bz      ok3

          o       6,=a(3000)  * Indicate regexec of nomatch, should fail

ok3       call    DCCREND,(envp)  * Destroy the C Environment

returnrc  lr      15,6
          l       13,4(,13)
          l       14,12(,13)
          lm      0,12,20(13)
          br      14
          ltorg
savearea  ds      18f
envp      ds      1f
preg      ds      1f
pattern   dc      C'[0-9]+',x'00'    only accept numbers
match     dc      C'0123999',x'00' this will match
nomatch   dc      C'ABCDEF',X'00'  this will not match
          end

 
//LINK EXEC PGM=IEWL,REGION=2M,PARM=('LIST',
//  'MAP,XREF',
//  'ALIASES=NO,UPCASE=NO,MSGLEVEL=4,EDIT=YES')
//SYSPRINT DD SYSOUT=*
//SYSUT1   DD UNIT=SYSDA,SPACE=(CYL,(1,1))
//SYSUT2   DD UNIT=SYSDA,SPACE=(CYL,(1,1))
//SYSLMOD  DD DISP=SHR,DSN=&SYSUID..LOAD(CALLRE)
//SYSLIN   DD DISP=SHR,DSN=&SYSUID..OBJ(CALLRE)
//    EXEC PGM=CALLRE
//STEPLIB DD DISP=SHR,DSN=&SYSUID..LOAD

If you'd like to learn more about Systems/C, visit the Systems/C description here.