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/*

 * Copyright (c) 1993-1994 by Xerox Corporation.  All rights reserved.

 *

 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED

 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.

 *

 * Permission is hereby granted to use or copy this program

 * for any purpose,  provided the above notices are retained on all copies.

 * Permission to modify the code and to distribute modified code is granted,

 * provided the above notices are retained, and a notice that the code was

 * modified is included with the above copyright notice.

 */

/* Boehm, May 19, 1994 2:23 pm PDT */

# ifndef CORD_POSITION_H

/* The representation of CORD_position.  This is private to the */

/* implementation, but the size is known to clients.  Also      */

/* the implementation of some exported macros relies on it.     */

/* Don't use anything defined here and not in cord.h.           */

# define MAX_DEPTH 48

        /* The maximum depth of a balanced cord + 1.            */

        /* We don't let cords get deeper than MAX_DEPTH.        */

struct CORD_pe {

    CORD pe_cord;

    size_t pe_start_pos;

};

/* A structure describing an entry on the path from the root    */

/* to current position.                                         */

typedef struct CORD_Pos {

    size_t cur_pos;

    int path_len;

#       define CORD_POS_INVALID (0x55555555)

                /* path_len == INVALID <==> position invalid */

    const char *cur_leaf;       /* Current leaf, if it is a string.     */

                                /* If the current leaf is a function,   */

                                /* then this may point to function_buf  */

                                /* containing the next few characters.  */

                                /* Always points to a valid string      */

                                /* containing the current character     */

                                /* unless cur_end is 0.                 */

    size_t cur_start;   /* Start position of cur_leaf   */

    size_t cur_end;     /* Ending position of cur_leaf  */

                        /* 0 if cur_leaf is invalid.    */

    struct CORD_pe path[MAX_DEPTH + 1];

        /* path[path_len] is the leaf corresponding to cur_pos  */

        /* path[0].pe_cord is the cord we point to.             */

#   define FUNCTION_BUF_SZ 8

    char function_buf[FUNCTION_BUF_SZ]; /* Space for next few chars     */

                                        /* from function node.          */

} CORD_pos[1];

/* Extract the cord from a position:    */

CORD CORD_pos_to_cord(CORD_pos p);

/* Extract the current index from a position:   */

size_t CORD_pos_to_index(CORD_pos p);

/* Fetch the character located at the given position:   */

char CORD_pos_fetch(CORD_pos p);

/* Initialize the position to refer to the give cord and index. */

/* Note that this is the most expensive function on positions:  */

void CORD_set_pos(CORD_pos p, CORD x, size_t i);

/* Advance the position to the next character.  */

/* P must be initialized and valid.             */

/* Invalidates p if past end:                   */

void CORD_next(CORD_pos p);

/* Move the position to the preceding character.        */

/* P must be initialized and valid.                     */

/* Invalidates p if past beginning:                     */

void CORD_prev(CORD_pos p);

/* Is the position valid, i.e. inside the cord?         */

int CORD_pos_valid(CORD_pos p);

char CORD__pos_fetch(CORD_pos);

void CORD__next(CORD_pos);

void CORD__prev(CORD_pos);

#define CORD_pos_fetch(p)       \

    (((p)[0].cur_end != 0)? \

        (p)[0].cur_leaf[(p)[0].cur_pos - (p)[0].cur_start] \

        : CORD__pos_fetch(p))

#define CORD_next(p)    \

    (((p)[0].cur_pos + 1 < (p)[0].cur_end)? \

        (p)[0].cur_pos++ \

        : (CORD__next(p), 0))

#define CORD_prev(p)    \

    (((p)[0].cur_end != 0 && (p)[0].cur_pos > (p)[0].cur_start)? \

        (p)[0].cur_pos-- \

        : (CORD__prev(p), 0))

#define CORD_pos_to_index(p) ((p)[0].cur_pos)

#define CORD_pos_to_cord(p) ((p)[0].path[0].pe_cord)

#define CORD_pos_valid(p) ((p)[0].path_len != CORD_POS_INVALID)

/* Some grubby stuff for performance-critical friends:  */

#define CORD_pos_chars_left(p) ((long)((p)[0].cur_end) - (long)((p)[0].cur_pos))

        /* Number of characters in cache.  <= 0 ==> none        */

#define CORD_pos_advance(p,n) ((p)[0].cur_pos += (n) - 1, CORD_next(p))

        /* Advance position by n characters     */

        /* 0 < n < CORD_pos_chars_left(p)       */

#define CORD_pos_cur_char_addr(p) \

        (p)[0].cur_leaf + ((p)[0].cur_pos - (p)[0].cur_start)

        /* address of current character in cache.       */

#endif