XTRAN Example — Translate HP (Digital, Compaq) VAX MACRO to C

This example uses the following XTRAN rules:

• The standard set of rules for parsing VAX MACRO
• A rule for parsing invocations of the CALLNZ macro
• The standard set of rules for parsing C
• The standard set of rules for translating VAX MACRO to C
• A translation rule for the CALLNZ user macro that specifies the C code to which it should translate
• A standard set of rules for structuring C code
• The standard set of rules for rendering C
• A standard set of rules for styling rendered C code

NOTE that otherwise the translation shown below was done with default conditions.  XTRAN provides many options for controlling the way it translates.

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Process Flowchart

Here is a flowchart for this process, in which the elements are color coded:

• BLUE for XTRAN versions (runnable programs)
• ORANGE for XTRAN rules (text files)
• RED for code

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Input to XTRAN:

XFLGS   =       ^X0C                    ;SOME FLAGS
UPDT    =       5                       ;UPDATE AMOUNT
SHIFT   =       2                       ;RIGHT SHIFT TO DO
;
ENTRY:                                  ;ENTRY POINT
        MOVAL   LWS,R5                  ;POINT TO WS
LOOP:   MOVL    R1,PXADDR[R2]           ;SAVE ADDR
        BEQL    DONE                    ;IF ZERO, QUIT
        MOVL    (R5),(R1)+
        MOVW    R3,(R1)+                ;STORE VALUE..
                                        ;..AND BUMP POINTER
        BEQL    NOINC                   ;IF NO VALUE
        CALLNZ  (R1),SUBR,DONE          ;CALL IF NONZERO
        INCL    (R1)                    ;BUMP VALUE..
        INCL    A2                      ;..AND ENTRY ADDR
NOINC:
        BISW2   #XFLGS,WWS              ;ADD FLAGS
        MOVZWL  WWS,LWS                 ;SHOW OFF OPERAND TYPES
        TSTW    (R4)[R2]                ;END OF UPDATE VALS?
        BEQL    LOOP                    ;IF SO, START OVER
        MOVL    (R1),A2                 ;SET ENTRY ADDR
        BISL2   #<^C^D<14&24>!-         ;ADD SOME FLAGS..
                <^XAA@3>!<^XBB@-SHIFT>!- ;..INCLUDING SOME SHIFTS..
                <^O25!^XA3>>,R0         ;..TO RETURN VALUE
DONE:   RSB                             ;BACK TO CALLER
;
BARR:   .BYTE   1                       ;BYTE ARRAY OF VALUES
        .BYTE   2,3
        .BYTE   4
LARR:                                   ;LONGWORD ARRAY OF VALUES
        .LONG   50,600,7000,80000
STR:    .ASCII  ?String with?<13><10>/embedded/<12>
        .ASCIZ  +control characters+
WWS:    .WORD   0                       ;WORD WORKING STORAGE
LWS:    .LONG   32768                   ;LONGWORD WORKING STORAGE
        .END

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Output from XTRAN:

        extern long a2;
        extern long pxaddr[];
        extern unsigned short subr();
        extern long tmp5;
        extern long *tmp1;
        extern short tmp2;
        extern short *tmp4;
        extern unsigned long tmp0;

        static char barr[4] =
          { 1, 2, 3, 4 };                    /*byte array of values*/
        static long larr[4] =
            { 50, 600, 7000, 80000
            };                               /*longword array of values*/
        static char str[41] =
         "String with\r\nembedded\fcontrol characters";

        short wws = 0;                       /*word working storage*/
        long lws = 32768;                    /*longword working storage*/

#define XFLGS 0x0c                           /*some flags*/
#define UPDT 5                               /*update amount*/
#define SHIFT 2                              /*right shift to do*/

entry:                                       /*entry point*/
        tmp5 = &lws;                         /*point to ws*/
loop:
                                             /*save addr*/
        if ((pxaddr[tmp2] = tmp1) != 0)      /*(XTR: reversed) if zero, quit*/
            {
            *(tmp1++) = *tmp5;
                                             /*store value..*/
                                             /*..and bump pointer*/
            if ((*(tmp1++) = tmp3) != 0)     /*(XTR: reversed) if no value*/
                {
                if (*tmp1 != 0)              /*call if nonzero*/
                    {
                    if (!subr())
                        goto done;
                    }
                ++(*tmp1);                   /*bump value..*/
                ++a2;                        /*..and entry addr*/
                }
            wws |= XFLGS;                    /*add flags*/
            lws = wws;                       /*show off operand types*/
                                             /*end of update vals?*/
            if ((*tmp4)[tmp2] == 0)          /*if so, start over*/
                goto loop;
            a2 = *tmp1;                      /*set entry addr*/
            tmp0 |= ~(14 & 24) | 0xaa << 3 |
              0xbb >> SHIFT | (025 | 0xa3); /*add some flags..*/
                                             /*..including some shifts..*/
                                             /*..to return value*/
            }
done:
        return (tmp0);                       /*back to caller*/