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Annotation of 43BSD/contrib/mh/miscellany/less/position.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Routines dealing with the "position" table.
        !             3:  * This is a table which tells the position (in the input file) of the
        !             4:  * first char on each currently displayed line.
        !             5:  *
        !             6:  * {{ The position table is scrolled by moving all the entries.
        !             7:  *    Would be better to have a circular table 
        !             8:  *    and just change a couple of pointers. }}
        !             9:  */
        !            10: 
        !            11: #include "less.h"
        !            12: #include "position.h"
        !            13: 
        !            14: #define        NPOS    100             /* {{ sc_height must be less than NPOS }} */
        !            15: static POSITION table[NPOS];   /* The position table */
        !            16: 
        !            17: extern int sc_width, sc_height;
        !            18: 
        !            19: /*
        !            20:  * Return the position of one of:
        !            21:  *     the top (first) line on the screen
        !            22:  *     the second line on the screen
        !            23:  *     the bottom line on the screen
        !            24:  *     the line after the bottom line on the screen
        !            25:  */
        !            26:        public POSITION
        !            27: position(where)
        !            28:        int where;
        !            29: {
        !            30:        switch (where)
        !            31:        {
        !            32:        case BOTTOM:
        !            33:                where = sc_height - 2;
        !            34:                break;
        !            35:        case BOTTOM_PLUS_ONE:
        !            36:                where = sc_height - 1;
        !            37:                break;
        !            38:        }
        !            39:        return (table[where]);
        !            40: }
        !            41: 
        !            42: /*
        !            43:  * Add a new file position to the bottom of the position table.
        !            44:  */
        !            45:        public void
        !            46: add_forw_pos(pos)
        !            47:        POSITION pos;
        !            48: {
        !            49:        register int i;
        !            50: 
        !            51:        /*
        !            52:         * Scroll the position table up.
        !            53:         */
        !            54:        for (i = 1;  i < sc_height;  i++)
        !            55:                table[i-1] = table[i];
        !            56:        table[sc_height - 1] = pos;
        !            57: }
        !            58: 
        !            59: /*
        !            60:  * Add a new file position to the top of the position table.
        !            61:  */
        !            62:        public void
        !            63: add_back_pos(pos)
        !            64:        POSITION pos;
        !            65: {
        !            66:        register int i;
        !            67: 
        !            68:        /*
        !            69:         * Scroll the position table down.
        !            70:         */
        !            71:        for (i = sc_height - 1;  i > 0;  i--)
        !            72:                table[i] = table[i-1];
        !            73:        table[0] = pos;
        !            74: }
        !            75: 
        !            76: /*
        !            77:  * Initialize the position table, done whenever we clear the screen.
        !            78:  */
        !            79:        public void
        !            80: pos_clear()
        !            81: {
        !            82:        register int i;
        !            83: 
        !            84:        for (i = 0;  i < sc_height;  i++)
        !            85:                table[i] = NULL_POSITION;
        !            86: }
        !            87: 
        !            88: /*
        !            89:  * See if the byte at a specified position is currently on the screen.
        !            90:  * Check the position table to see if the position falls within its range.
        !            91:  * Return the position table entry if found, -1 if not.
        !            92:  */
        !            93:        public int
        !            94: onscreen(pos)
        !            95:        POSITION pos;
        !            96: {
        !            97:        register int i;
        !            98: 
        !            99:        if (pos < table[0])
        !           100:                return (-1);
        !           101:        for (i = 1;  i < sc_height;  i++)
        !           102:                if (pos < table[i])
        !           103:                        return (i-1);
        !           104:        return (-1);
        !           105: }

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