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Annotation of researchv10no/cmd/basic/bite/src/fetch.c, revision 1.1.1.1

1.1       root        1: /* Copyright Bell Telephone Labotatories Whippany, N.J.
                      2: 
                      3:  *     *******************************************
                      4:  *     *******************************************
                      5:  *     *** FETCH LINES FROM THE PROGRAM BUFFER ***
                      6:  *     ******* R. B. Drake WH 8C-005 X4163 *******
                      7:  *     ******** Fri Aug 24 17:25:20 1979 *********
                      8:  *     *******************************************
                      9:  *     *******************************************
                     10: 
                     11: */
                     12: /*   "@(#) fetch.c:  V 1.1  12/21/80" */
                     13: 
                     14: /*
                     15:    This routine fetches lines from the program txtbuf as described
                     16:    below:
                     17:  *
                     18:  *
                     19:  * calling sequence: fetch([0 -1 n],&ptr)
                     20:  * result: if arg1 is 0, fetches the first line of the program
                     21:  *         if arg1 is -1, fetches the next sequential line
                     22:  *         if arg1 is n, fetches line number n
                     23:  *         ptr is the adress of a character pointer to be used by fetch
                     24:  *         a zero is returned if the operation was successful
                     25:  *         a minus 1 is returned if the operation failed
                     26:  *         a minus 2 is returned if a line was found but not line n
                     27:  *         data is returned as follows:
                     28:  *         inst.thing.linno contains the line number
                     29:  *          inst.opcode.lobyte contains the operation code
                     30:  *         expr points to the first character of the expression string
                     31:  *
                     32: */
                     33: #include "bas.h"
                     34: char *expr;
                     35: extern char *curptr;
                     36: fetch(i,ptr)
                     37: int i;
                     38: char **ptr;
                     39: {
                     40:        int j;
                     41:        /* if line n is requested, search the page index for the
                     42:         * page which contains the requested line. Then search
                     43:         * that page sequentially until the line is found
                     44:        */
                     45:        curptr = *ptr;
                     46:        if(i>0)
                     47:                {
                     48:                if(!index[0].maxlin)
                     49:                {
                     50:                        curptr = *ptr = txtbuf;
                     51:                        return(-1);
                     52:                } /*empty txtbuf */
                     53:                for(j=0;j<32;j++)
                     54:                {
                     55:                        if((i>index[j].maxlin) &&  (index[j+1].maxlin != 0))
                     56:                                continue;
                     57:                        *ptr = index[j].begin;
                     58:                        inst.thing.linno=0;
                     59:                        while((i>inst.thing.linno)&&(fetch(-1,ptr) == 0));
                     60:                        if(i== inst.thing.linno) return(0);
                     61:                        return(-2);     /* -2 used to indicate that
                     62:                                         * a line was found but it
                     63:                                         * is not the one asked for */
                     64:                }
                     65:                }
                     66:        /* if the first line of the program is requested
                     67:         * set the pointer to the beginnig of the txtbuf
                     68:         * retrieve the line found there and leave the
                     69:         * pointer at the beginning of the next line
                     70:        */
                     71:        if(i==0)
                     72:                curptr= *ptr=txtbuf;
                     73:        /* otherwise use ptr to retrieve the next line */
                     74:        if(**ptr == '\0' && *(*ptr+1) == '\0' || *ptr >= linptr)
                     75:                return(-1);
                     76:        for(j=0;j<4;j++)
                     77:                inst.byte[j] = *(*ptr)++;
                     78:        expr = *ptr;
                     79:        while(*(*ptr)++);
                     80:        return(0);
                     81: }

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