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