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[/] [System09/] [trunk/] [Tools/] [as09/] [ifd.c] - Rev 149
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/* IfMachine() --- This function implements the IFD & IFND conditional assembly machine. version 1.0 made for release TER_2.0 cross assembler 27 Jun 89 */ #define FALSE_BLOCK 0 /* values for state variable */ #define TRUE_BLOCK 1 #define POP_TEST 2 #define ELSE_TEST 3 #define FALSE 0 #define TRUE 1 void IfMachine(Token) int Token; /* input token from calling machine */ /* See file as.h for definition (globals) */ { static int State = TRUE_BLOCK, StackPt = 0, IfStack[MAXIFD]; /* State variable, pointer to "IF stack pointer" and "Stack" */ int Hiatus; /* flag to break out of FSM & resume normal processing */ Hiatus=FALSE; /* infinite loop to operate machine until time to break out */ do /* test at end */ { #ifdef DEBUG3 printf("IfMachine state=%u , token=%u\n",State,Token); #endif if (State == TRUE_BLOCK) /* a block of statements processed normally */ switch(Token) { case IF_TRUE: IfStack[StackPt]=TRUE; if (++StackPt > MAXIFD) { /* check for over flow */ StackPt = MAXIFD; error("Error:IFD/IFND nested too deep"); } /* print_line() will be done in normal processing */ Hiatus = TRUE; /* resume normal line processing */ break; case IF_FALSE: IfStack[StackPt]=TRUE; if (++StackPt > MAXIFD) { /* check for over flow */ StackPt = MAXIFD; error("Error:IFD/IFND nested too deep"); } if (Pass == 2 && Lflag && !N_page) /* need to print here */ print_line(); /* cuz will not return to normal */ Token = GetToken(); /* get next line & examine for IF */ State = FALSE_BLOCK; /* change state */ break; case IF_ELSE: if (StackPt == 0) /* bad IF nesting */ error("Error: ELSE without IF"); if (Pass == 2 && Lflag && !N_page) print_line(); Token = GetToken(); /* get next line & examine for IF */ State = FALSE_BLOCK; break; case IF_ENDIF: if (StackPt == 0) /* bad IF nesting */ error("Error: ENDIF without IF"); else StackPt--; /* popped state must be TRUE */ Hiatus = TRUE; break; /* case NORMAL is not implemented as it represents normal line processing. */ case IF_END: /* file ended with improperly nested IFD */ /* this code can't actually be reached at present in a TRUE_BLOCK */ fatal("Error: file ended before IFD/IFND/ELSE/ENDIF"); break; default: /* This code can't be reached at the present. Logically would happen if EOF but handled else where */ fatal("Can't get here from there."); break; } else if (State == FALSE_BLOCK) /* statements not processed */ switch(Token) { case IF_TRUE: /* doesn't make any diff. Just nest IFs */ case IF_FALSE: IfStack[StackPt]=FALSE; if (++StackPt > MAXIFD) { StackPt = MAXIFD; error("Error:IFD/IFND nested too deep"); } if (Pass == 2 && Lflag && !N_page) print_line(); Token = GetToken(); break; case IF_ELSE: /* if (Pass == 2 && Lflag && !N_page) */ /* print_line(); */ State = ELSE_TEST; break; case IF_ENDIF: State = POP_TEST; break; case IF_END: /* file ended with improperly nested IFD */ fatal("Fatal Error: file ended before last ENDIF"); /* Fatal will exit assembler. Things are too messed up. Include file handling is else where and don't want to duplicate here. */ break; case IF_NORMAL: /* normal line in a FALSE BLOCK */ if (Pass == 2 && Lflag && !N_page) print_line(); Token = GetToken(); break; default: fatal("Fatal Error: file ended before last ENDIF"); /* must be EOF or something else terrible */ break; } else if (State == POP_TEST) { /* pop up outside nest state */ if (StackPt == 0) { /* bad IF nesting */ error("Error: ENDIF without IF"); if (Pass == 2 && Lflag && !N_page) print_line(); State = TRUE; } else { StackPt--; /* pop stack */ if (IfStack[StackPt] == TRUE) { /* back to normal */ /* had to come from FALSE block cuz TRUE block cannot be inside FALSE block */ if (Pass == 2 && Lflag && !N_page) print_line(); State = TRUE; Hiatus = TRUE; /* sleep for normal line processing */ } else { /* gotta be that stack == FALSE, still inside FALSE nest */ if (Pass == 2 && Lflag && !N_page) print_line(); State = FALSE; Token = GetToken(); } } } else if (State == ELSE_TEST) { /* change state */ if (IfStack[StackPt-1] == TRUE) { State = TRUE_BLOCK; Hiatus = TRUE; } else State = FALSE_BLOCK; } } while (Hiatus == FALSE); /* loop if not exit */ } /* GetToken() --- get another line from within False Block and extract token as would be done in pseudo.c. Returns token id: IF_TRUE IFD/IFND evaluated to TRUE IF_FALSE IFD/IFND evaluated to FALSE IF_ELSE ELSE pseudo op IF_ENDIF ENDIF pseudo op IF_END END pseudo op IF_NORMAL none of the above, perhaps assy code IF_EOF encountered end of file This function exists because conditional assembly was added as pseudo op rather than with key character ("%") and did not want to disturb original software topology */ int GetToken() /* get another line and find token in it */ { /* similar to make_pass() except one line at a time */ /* most variables & constants are global */ #ifndef IBM if (FGETS(Line,MAXBUF-1,Fd) == (char *)NULL) #else if (fgets(Line,MAXBUF,Fd) == (char *)NULL) #endif return(IF_EOF); /* banged into eof */ Line_num++; P_force=0; N_page=0; if (!parse_line()) return(IF_NORMAL); /* comment line */ if (*Op==EOS) /* skipping over label, probably. */ return(IF_NORMAL); /* strcmp() returns 0 if arg1 is NULL string */ if (strcmp(Op,"ifd")==0) return(eval_ifd()); else if (strcmp(Op,"ifnd")==0) return(eval_ifnd()); else if (strcmp(Op,"else")==0) return(IF_ELSE); else if (strcmp(Op,"endif")==0) return(IF_ENDIF); else if (strcmp(Op,"end")==0) return(IF_END); else return(IF_NORMAL); /* or might be garbage...but who cares? This is FALSE BLOCK */ } /* * eval_ifd() --- evaluate an if define statement for TRUE or FALSE */ int eval_ifd() { struct nlist *np; /* symbol structure */ if (*Operand==EOS) { warn("No symbol for IFD"); return(IF_FALSE); /* nothing to check */ } if ((np=lookup(Operand)) == NULL) return(IF_FALSE); /* not defined at all...yet */ else if(np->def2 == Pass) return(IF_TRUE); /* defined for this pass */ return(IF_FALSE); /* not defined this pass */ } /* * eval_ifnd() --- evaluate an if not define statement for TRUE or FALSE */ int eval_ifnd() { struct nlist *np; /* symbol structure */ if (*Operand==EOS) { warn("No symbol for IFND"); return(IF_TRUE); /* nothing to check */ } if ((np=lookup(Operand)) == NULL) return(IF_TRUE); /* not defined at all...yet */ else if(np->def2 == Pass) return(IF_FALSE); /* defined for this pass */ return(IF_TRUE); /* not defined this pass */ }
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