C PROCEDURE TABLES
by Tim Berens

[LISTING ONE]


/****************************************************************************
    Name : prompter.c

    Description : A routine for prompting a user for a series of answers.
****************************************************************************/
#include<stdio.h>
#include"prompter.h"

struct group_stack group_stack[GROUP_STACK_SIZE];

prompter(pc)
    struct prcontrol * pc;
{
    int errstat;

    pc->current_question = 0;
    pc->group_stack_ptr = 0;

    for(;;){
        pc->errstat = 0;

        display_current_question(pc);

        gets(pc->response);

        if(*pc->response == 0){
            continue;
        }

        if(!(pc->errstat = 
          (*pc->current_group[pc->current_question].validate)(pc))){

            if(pc->errstat = 
              (*pc->current_group[pc->current_question].doit)(pc)){
                 if(pc->errstat == EXIT_NOW){
                    return(0);
                 }
            }
        }

        if(pc->current_group[pc->current_question].response != NULL){
            strcpy(pc->current_group[pc->current_question].response,
                   pc->response);
        }

        (*pc->current_group[pc->current_question].set)(pc);

        if(pc->current_group[pc->current_question].text == NULL){
            return(0);
        }

        if(pc->errstat){
            handle_error(pc->errstat,pc->errormess);
        }

    }

}

display_current_question(pc)    
    struct prcontrol * pc;
{
    printf("\n%s\n",pc->current_group[pc->current_question].text);
    printf("--->");

}

handle_error(errstat,errormess)
    int errstat;
    struct errormess * errormess;
{
    int i;
    int emess_offset = -1;
    char * message,messagebuff[100];
    
    for(i = 0 ; errormess[i].errstat != -1 ; ++i){
        if(errormess[i].errstat == errstat){
           emess_offset = i;
            break;
        }
    }
    message = messagebuff;
    if(emess_offset != -1){
        strcpy(message,errormess[emess_offset].message);
        if(errormess[emess_offset].build){
            (*errormess[emess_offset].build)(message);
        }
    }
    else{
        sprintf(message,"Error %d.",errstat);
    }

    puts("\n");
    puts(message);
    return(0);
}


/***************************************    
    Flow control routines
***************************************/
no_op()
{
    return(0);
}

next_question(pc)
    struct prcontrol * pc;
{
    ++pc->current_question;
    return(0);
}


pop_group(pc)
    struct prcontrol * pc;
{
    --pc->group_stack_ptr;
    pc->current_group = group_stack[pc->group_stack_ptr].group; 
    pc->current_question = group_stack[pc->group_stack_ptr].current_question;
    return(0);
}

push_current_group(pc)
    struct prcontrol * pc;
{
    group_stack[pc->group_stack_ptr].group = pc->current_group;
    group_stack[pc->group_stack_ptr].current_question = pc->current_question;
    ++pc->group_stack_ptr;
    return(0);
}

start_group(newgroup,pc)
    struct question * newgroup;
    struct prcontrol * pc;
{
    push_current_group(pc);
    pc->current_group = newgroup;
    pc->current_question = 0;
    return(0);
}

restart_group(pc)
    struct prcontrol * pc;
{
    pc->current_question = 0;
    return(0);
}


end_group(pc)   
    struct prcontrol * pc;
{
    pop_group(pc);
    ++pc->current_question;
    return(0);
}

checkerror_end_group(pc)
    struct prcontrol * pc;
{   
    if(pc->errstat){    
        return(0);
    }
    end_group(pc);
    return(0);
}

checkerror_next_question(pc)
    struct prcontrol * pc;
{   
    if(pc->errstat){    
        return(0);
    }
    next_question(pc);
    return(0);
}


[LISTING TWO]

/****************************************************************************
    Name : prompter.h 

    Description : Declarations for prompter
****************************************************************************/

struct prcontrol {
    int current_question;
    struct question * current_group;
    int group_stack_ptr;
    char response[121];
    int errstat;
    struct errormess * errormess;
    };

struct question {
    char * text;
    char * response;
    int (*validate)();
    int (*doit)();
    int (*set)();
    };

struct group_stack {
    struct question * group;
    int current_question;
    };

/************************
   errormess data structure
************************/
    
struct errormess {
    int errstat;
    char * message;
    int (*build)();
    };

#define GROUP_STACK_SIZE            50
#define NO_ERROR                    0
#define EXIT_NOW                    2001

int pop_group(),end_group(),no_op(),next_question();
int checkerror_end_group(),checkerror_next_question();


[LISTING THREE]

/****************************************************************************
    Name : prsample.c

    Description : A sample that uses the prompter() routine
****************************************************************************/
#include<stdio.h>
#include"prompter.h"
#include<ctype.h>

/**************************
    The report parameter variables 
***************************/
char report_destination[2];
char dest_filename[30];
char single_or_range[2];
char start_account[20],end_account[20];
int account_number;
char display_parmname[50];
char include_overshort[2];

/*********************
    Error Values
*********************/
#define ENTER_S_OR_R            1
#define ENTER_Y_OR_N            2
#define START_ACCOUNT_LARGER    3
#define BAD_PARM_NAME           4
#define BAD_ACCOUNT_NUMBER      5
#define ENTER_P_S_OR_D          6
#define FILE_EXISTS             7

/************************
  Report to printer, screen or disk routines
************************/
int filename_val();
struct question report_filename[] = {   
    { "What is the name of the disk file?",
        dest_filename,filename_val,no_op,checkerror_end_group},
    {   NULL,NULL,NULL,NULL,NULL }
    };

filename_val(pc)    
    struct prcontrol * pc;
{
    FILE * fp,*fopen();
    /* you should put a routine to validate that the response
       entered is a legal file name here */
    if(fp = fopen(pc->response,"r")){
        fclose(fp);
        return(FILE_EXISTS);
    }
    return(0);
}

reportdest_val(pc)
    struct prcontrol * pc;
{
    char * strchr();
    if((!strchr("PpSsDd",pc->response[0])) || (strlen(pc->response) != 1)){
        return(ENTER_P_S_OR_D);
    }
    return(0);
}

reportdest_set(pc)
    struct prcontrol * pc;
{
    char destination;
    destination = islower(*pc->response) ? *pc->response-32 : *pc->response;
    switch(destination){    
        case 'P' :
        case 'S' : next_question(pc);
                   break;
        case 'D' : start_group(report_filename,pc);
                   break;
   }
   return(0);
}

/***************************
    Account routines
***************************/
int account_val(),end_account_set(),end_account_val();

struct question account_range[] = {
    {"Enter the starting account.",
        start_account,account_val,no_op,checkerror_next_question},
    {"Enter the ending account.",
        end_account,end_account_val,no_op,end_account_set},
    { NULL,NULL,NULL,NULL,NULL }
    };

int save_account_doit(),account_set();
struct question account[] = {
    {"Enter the account.",
        start_account,account_val,save_account_doit,checkerror_end_group},
    {NULL,NULL,NULL,NULL,NULL}};

account_or_range_val(pc)
    struct prcontrol * pc;
{
    char * strchr();
    if((!strchr("SsRr",pc->response[0])) || (strlen(pc->response) > 1)){
        return(ENTER_S_OR_R);
    }
    return(0);
}

account_or_range_set(pc)
    struct prcontrol * pc;
{
    char account_or_range;
    account_or_range = islower(*pc->response) ? *pc->response-32 : 
                        *pc->response;
    if(pc->errstat){
        return(0);
    }    
    if(account_or_range == 'S'){
        start_group(account,pc);
    }
    if(account_or_range == 'R'){
        start_group(account_range,pc);
    }
    return(0);
}

save_account_doit(pc)
    struct prcontrol * pc;
{
    account_number = atoi(pc->response);
    return(0);
}

account_val(pc)
    struct prcontrol * pc;
{
    if((atoi(pc->response) < 100) || (atoi(pc->response) > 1000)){   
        return(BAD_ACCOUNT_NUMBER);
    }
    return(0);
}

end_account_val(pc)
    struct prcontrol * pc;
{
    int errstat;
    if(errstat = account_val(pc)){
        return(errstat);
    }
    if(atoi(start_account) >= atoi(pc->response)){
        return(START_ACCOUNT_LARGER);
    }
    return(0);
}

end_account_set(pc)
    struct prcontrol * pc;
{
    switch(pc->errstat){
        case NO_ERROR             : end_group(pc);
                                    break;
        case START_ACCOUNT_LARGER : restart_group(pc);
                                    break;
        case BAD_ACCOUNT_NUMBER   : break;
    }
    return(0);
}

/***************************
    Get display parameters routines
****************************/
char * legal_parmnames[] = {      /* In a "real" system, this table       */
    "default",                    /* would probably be stored in a file   */
    "daily",                      /* and parmname_val would check to see  */
    "weekly",                     /* if the name entered is in this file. */
    "yearly",
    NULL
    };

parmname_val(pc)
    struct prcontrol * pc;
{
    int i;
    for(i = 0 ; legal_parmnames[i] != NULL ; ++i){
        if(strcmp(pc->response,legal_parmnames[i]) == 0){
            return(0);
        }
    }    
    return(BAD_PARM_NAME);
}

bld_bad_parmname(message)
    char * message;
{
    sprintf(message + strlen(message)," %s, %s, %s, or %s.",
            legal_parmnames[0],legal_parmnames[1],legal_parmnames[2],
            legal_parmnames[3]);
    return(0);
}

/**************************
    yesno validation
***************************/
yesno_val(pc)
    struct prcontrol * pc;
{
    char * strchr();
    if((!strchr("YyNn",pc->response[0])) || (strlen(pc->response) != 1)){
        return(ENTER_Y_OR_N);
    }
    return(0);
}

/**************************************
    Main question array procedure table
***************************************/
struct question account_parms[] = {
    {"Do you want this report for a single account or a range of accounts? (S or R)",
        single_or_range,account_or_range_val,no_op,account_or_range_set },
    {"Enter the name of the display parameter record.",
        display_parmname,parmname_val,no_op,checkerror_next_question},
    {"Do you want to include the Over/Short Report? (Y/N)",
        NULL,yesno_val,no_op,checkerror_next_question},
    {"Do you want this report on the printer, screen, or saved to disk?(P,S or D)",
        report_destination,reportdest_val,no_op,reportdest_set},
    { NULL,NULL,NULL,NULL,NULL }
    };

struct errormess account_errormess[] = { 
    { ENTER_S_OR_R,"Please enter S or R.",NULL },
    { ENTER_Y_OR_N,"Please enter Y or N.",NULL },
    { START_ACCOUNT_LARGER,"The starting account must be smaller than the ending account.",NULL },
    { BAD_ACCOUNT_NUMBER,"The account number must be between 100 and 1000",NULL },
    { BAD_PARM_NAME,"Choose one of the following :",bld_bad_parmname },
    { ENTER_P_S_OR_D,"Please enter P, S or D",NULL },
    { FILE_EXISTS,"That file already exists.",NULL },
    { -1,NULL,NULL }
    };

main(argc,argv)
    int argc;
    char * argv[];
{
    int errstat;
    struct prcontrol prcontrol;

    prcontrol.current_group = account_parms;
    prcontrol.errormess = account_errormess;

    if(errstat = prompter(&prcontrol)){
        handle_error(errstat,account_errormess);
    }
    /*  Print the report with the gathered parameters */
}




[EXAMPLE 1]


		loop{
			display current_question->text
			
			get response from user

			execute current_question->validate

			if(no error on validate){
				execute current_question->doit
			}

			copy response to current_question->response

			execute current_question->set

			if(error from validate){
				call error handler
			}
		}