cordbscs.c

A garbage collector for C and C

/* See cord.h for definition.  We assume i is in range.	*/
int CORD_iter5(CORD x, size_t i, CORD_iter_fn f1,
			 CORD_batched_iter_fn f2, void * client_data)
{
    if (x == 0) return(0);
    if (CORD_IS_STRING(x)) {
    	register const char *p = x+i;
    	
    	if (*p == '\0') ABORT("2nd arg to CORD_iter5 too big");
        if (f2 != CORD_NO_FN) {
            return((*f2)(p, client_data));
        } else {
	    while (*p) {
                if ((*f1)(*p, client_data)) return(1);
                p++;
	    }
	    return(0);
        }
    } else if (IS_CONCATENATION(x)) {
    	register struct Concatenation * conc
    			= &(((CordRep *)x) -> concatenation);
    	
    	
    	if (i > 0) {
    	    register size_t left_len = LEFT_LEN(conc);
    	    
    	    if (i >= left_len) {
    	        return(CORD_iter5(conc -> right, i - left_len, f1, f2,
    	        		  client_data));
    	    }
    	}
    	if (CORD_iter5(conc -> left, i, f1, f2, client_data)) {
    	    return(1);
    	}
    	return(CORD_iter5(conc -> right, 0, f1, f2, client_data));
    } else /* function */ {
        register struct Function * f = &(((CordRep *)x) -> function);
        register size_t j;
        register size_t lim = f -> len;
        
        for (j = i; j < lim; j++) {
            if ((*f1)((*(f -> fn))(j, f -> client_data), client_data)) {
                return(1);
            }
        }
        return(0);
    }
}
			
#undef CORD_iter
int CORD_iter(CORD x, CORD_iter_fn f1, void * client_data)
{
    return(CORD_iter5(x, 0, f1, CORD_NO_FN, client_data));
}

int CORD_riter4(CORD x, size_t i, CORD_iter_fn f1, void * client_data)
{
    if (x == 0) return(0);
    if (CORD_IS_STRING(x)) {
	register const char *p = x + i;
	register char c;
               
	for(;;) {
	    c = *p;
	    if (c == '\0') ABORT("2nd arg to CORD_riter4 too big");
            if ((*f1)(c, client_data)) return(1);
	    if (p == x) break;
            p--;
	}
	return(0);
    } else if (IS_CONCATENATION(x)) {
    	register struct Concatenation * conc
    			= &(((CordRep *)x) -> concatenation);
    	register CORD left_part = conc -> left;
    	register size_t left_len;
    	
    	left_len = LEFT_LEN(conc);
    	if (i >= left_len) {
    	    if (CORD_riter4(conc -> right, i - left_len, f1, client_data)) {
    	    	return(1);
    	    }
    	    return(CORD_riter4(left_part, left_len - 1, f1, client_data));
    	} else {
    	    return(CORD_riter4(left_part, i, f1, client_data));
    	}
    } else /* function */ {
        register struct Function * f = &(((CordRep *)x) -> function);
        register size_t j;
        
        for (j = i; ; j--) {
            if ((*f1)((*(f -> fn))(j, f -> client_data), client_data)) {
                return(1);
            }
            if (j == 0) return(0);
        }
    }
}

int CORD_riter(CORD x, CORD_iter_fn f1, void * client_data)
{
    return(CORD_riter4(x, CORD_len(x) - 1, f1, client_data));
}

/*
 * The following functions are concerned with balancing cords.
 * Strategy:
 * Scan the cord from left to right, keeping the cord scanned so far
 * as a forest of balanced trees of exponentialy decreasing length.
 * When a new subtree needs to be added to the forest, we concatenate all
 * shorter ones to the new tree in the appropriate order, and then insert
 * the result into the forest.
 * Crucial invariants:
 * 1. The concatenation of the forest (in decreasing order) with the
 *     unscanned part of the rope is equal to the rope being balanced.
 * 2. All trees in the forest are balanced.
 * 3. forest[i] has depth at most i.
 */

typedef struct {
    CORD c;
    size_t len;		/* Actual length of c 	*/
} ForestElement;

static size_t min_len [ MAX_DEPTH ];

static int min_len_init = 0;

int CORD_max_len;

typedef ForestElement Forest [ MAX_DEPTH ];
			/* forest[i].len >= fib(i+1)	        */
			/* The string is the concatenation	*/
			/* of the forest in order of DECREASING */
			/* indices.				*/

void CORD_init_min_len()
{
    register int i;
    register size_t last, previous, current;
        
    min_len[0] = previous = 1;
    min_len[1] = last = 2;
    for (i = 2; i < MAX_DEPTH; i++) {
    	current = last + previous;
    	if (current < last) /* overflow */ current = last;
    	min_len[i] = current;
    	previous = last;
    	last = current;
    }
    CORD_max_len = last - 1;
    min_len_init = 1;
}


void CORD_init_forest(ForestElement * forest, size_t max_len)
{
    register int i;
    
    for (i = 0; i < MAX_DEPTH; i++) {
    	forest[i].c = 0;
    	if (min_len[i] > max_len) return;
    }
    ABORT("Cord too long");
}

/* Add a leaf to the appropriate level in the forest, cleaning		*/
/* out lower levels as necessary.					*/
/* Also works if x is a balanced tree of concatenations; however	*/
/* in this case an extra concatenation node may be inserted above x;	*/
/* This node should not be counted in the statement of the invariants.	*/
void CORD_add_forest(ForestElement * forest, CORD x, size_t len)
{
    register int i = 0;
    register CORD sum = CORD_EMPTY;
    register size_t sum_len = 0;
    
    while (len > min_len[i + 1]) {
    	if (forest[i].c != 0) {
    	    sum = CORD_cat(forest[i].c, sum);
    	    sum_len += forest[i].len;
    	    forest[i].c = 0;
    	}
        i++;
    }
    /* Sum has depth at most 1 greter than what would be required 	*/
    /* for balance.							*/
    sum = CORD_cat(sum, x);
    sum_len += len;
    /* If x was a leaf, then sum is now balanced.  To see this		*/
    /* consider the two cases in which forest[i-1] either is or is 	*/
    /* not empty.							*/
    while (sum_len >= min_len[i]) {
    	if (forest[i].c != 0) {
    	    sum = CORD_cat(forest[i].c, sum);
    	    sum_len += forest[i].len;
    	    /* This is again balanced, since sum was balanced, and has	*/
    	    /* allowable depth that differs from i by at most 1.	*/
    	    forest[i].c = 0;
    	}
        i++;
    }
    i--;
    forest[i].c = sum;
    forest[i].len = sum_len;
}

CORD CORD_concat_forest(ForestElement * forest, size_t expected_len)
{
    register int i = 0;
    CORD sum = 0;
    size_t sum_len = 0;
    
    while (sum_len != expected_len) {
    	if (forest[i].c != 0) {
    	    sum = CORD_cat(forest[i].c, sum);
    	    sum_len += forest[i].len;
    	}
        i++;
    }
    return(sum);
}

/* Insert the frontier of x into forest.  Balanced subtrees are	*/
/* treated as leaves.  This potentially adds one to the depth	*/
/* of the final tree.						*/
void CORD_balance_insert(CORD x, size_t len, ForestElement * forest)
{
    register int depth;
    
    if (CORD_IS_STRING(x)) {
        CORD_add_forest(forest, x, len);
    } else if (IS_CONCATENATION(x)
               && ((depth = DEPTH(x)) >= MAX_DEPTH
                   || len < min_len[depth])) {
    	register struct Concatenation * conc
    			= &(((CordRep *)x) -> concatenation);
    	size_t left_len = LEFT_LEN(conc);
    	
    	CORD_balance_insert(conc -> left, left_len, forest);
    	CORD_balance_insert(conc -> right, len - left_len, forest);
    } else /* function or balanced */ {
    	CORD_add_forest(forest, x, len);
    }
}


CORD CORD_balance(CORD x)
{
    Forest forest;
    register size_t len;
    
    if (x == 0) return(0);
    if (CORD_IS_STRING(x)) return(x);
    if (!min_len_init) CORD_init_min_len();
    len = LEN(x);
    CORD_init_forest(forest, len);
    CORD_balance_insert(x, len, forest);
    return(CORD_concat_forest(forest, len));
}


/* Position primitives	*/

/* Private routines to deal with the hard cases only: */

/* P contains a prefix of the  path to cur_pos.	Extend it to a full	*/
/* path and set up leaf info.						*/
/* Return 0 if past the end of cord, 1 o.w.				*/
void CORD__extend_path(register CORD_pos p)
{
     register struct CORD_pe * current_pe = &(p[0].path[p[0].path_len]);
     register CORD top = current_pe -> pe_cord;
     register size_t pos = p[0].cur_pos;
     register size_t top_pos = current_pe -> pe_start_pos;
     register size_t top_len = GEN_LEN(top);
     
     /* Fill in the rest of the path. */
       while(!CORD_IS_STRING(top) && IS_CONCATENATION(top)) {
     	 register struct Concatenation * conc =
     	 		&(((CordRep *)top) -> concatenation);
     	 register size_t left_len;
     	 
     	 left_len = LEFT_LEN(conc);
     	 current_pe++;
     	 if (pos >= top_pos + left_len) {
     	     current_pe -> pe_cord = top = conc -> right;
     	     current_pe -> pe_start_pos = top_pos = top_pos + left_len;
     	     top_len -= left_len;
     	 } else {
     	     current_pe -> pe_cord = top = conc -> left;
     	     current_pe -> pe_start_pos = top_pos;
     	     top_len = left_len;
     	 }
     	 p[0].path_len++;
       }
     /* Fill in leaf description for fast access. */
       if (CORD_IS_STRING(top)) {
         p[0].cur_leaf = top;
         p[0].cur_start = top_pos;
         p[0].cur_end = top_pos + top_len;
       } else {
         p[0].cur_end = 0;
       }
       if (pos >= top_pos + top_len) p[0].path_len = CORD_POS_INVALID;
}

char CORD__pos_fetch(register CORD_pos p)
{
    /* Leaf is a function node */
    struct CORD_pe * pe = &((p)[0].path[(p)[0].path_len]);
    CORD leaf = pe -> pe_cord;
    register struct Function * f = &(((CordRep *)leaf) -> function);
    
    if (!IS_FUNCTION(leaf)) ABORT("CORD_pos_fetch: bad leaf");
    return ((*(f -> fn))(p[0].cur_pos - pe -> pe_start_pos, f -> client_data));
}

void CORD__next(register CORD_pos p)
{
    register size_t cur_pos = p[0].cur_pos + 1;
    register struct CORD_pe * current_pe = &((p)[0].path[(p)[0].path_len]);
    register CORD leaf = current_pe -> pe_cord;
    
    /* Leaf is not a string or we're at end of leaf */
    p[0].cur_pos = cur_pos;
    if (!CORD_IS_STRING(leaf)) {
    	/* Function leaf	*/
    	register struct Function * f = &(((CordRep *)leaf) -> function);
    	register size_t start_pos = current_pe -> pe_start_pos;
    	register size_t end_pos = start_pos + f -> len;
    	
    	if (cur_pos < end_pos) {
    	  /* Fill cache and return. */
    	    register size_t i;
    	    register size_t limit = cur_pos + FUNCTION_BUF_SZ;
    	    register CORD_fn fn = f -> fn;
    	    register void * client_data = f -> client_data;
    	    
    	    if (limit > end_pos) {
    	        limit = end_pos;
    	    }
    	    for (i = cur_pos; i < limit; i++) {
    	        p[0].function_buf[i - cur_pos] =
    	        	(*fn)(i - start_pos, client_data);
    	    }
    	    p[0].cur_start = cur_pos;
    	    p[0].cur_leaf = p[0].function_buf;
    	    p[0].cur_end = limit;
    	    return;
    	}
    }
    /* End of leaf	*/
    /* Pop the stack until we find two concatenation nodes with the 	*/
    /* same start position: this implies we were in left part.		*/
    {
    	while (p[0].path_len > 0
    	       && current_pe[0].pe_start_pos != current_pe[-1].pe_start_pos) {
    	    p[0].path_len--;
    	    current_pe--;
    	}
    	if (p[0].path_len == 0) {
	    p[0].path_len = CORD_POS_INVALID;
            return;
	}
    }
    p[0].path_len--;
    CORD__extend_path(p);
}

void CORD__prev(register CORD_pos p)
{
    register struct CORD_pe * pe = &(p[0].path[p[0].path_len]);
    
    if (p[0].cur_pos == 0) {
        p[0].path_len = CORD_POS_INVALID;
        return;
    }
    p[0].cur_pos--;
    if (p[0].cur_pos >= pe -> pe_start_pos) return;
    
    /* Beginning of leaf	*/
    
    /* Pop the stack until we find two concatenation nodes with the 	*/
    /* different start position: this implies we were in right part.	*/
    {
    	register struct CORD_pe * current_pe = &((p)[0].path[(p)[0].path_len]);
    	
    	while (p[0].path_len > 0
    	       && current_pe[0].pe_start_pos == current_pe[-1].pe_start_pos) {
    	    p[0].path_len--;
    	    current_pe--;
    	}
    }
    p[0].path_len--;
    CORD__extend_path(p);
}

#undef CORD_pos_fetch
#undef CORD_next
#undef CORD_prev
#undef CORD_pos_to_index
#undef CORD_pos_to_cord
#undef CORD_pos_valid

char CORD_pos_fetch(register CORD_pos p)
{
    if (p[0].cur_start <= p[0].cur_pos && p[0].cur_pos < p[0].cur_end) {
    	return(p[0].cur_leaf[p[0].cur_pos - p[0].cur_start]);
    } else {
        return(CORD__pos_fetch(p));
    }
}

void CORD_next(CORD_pos p)
{
    if (p[0].cur_pos < p[0].cur_end - 1) {
    	p[0].cur_pos++;
    } else {
    	CORD__next(p);
    }
}

void CORD_prev(CORD_pos p)
{
    if (p[0].cur_end != 0 && p[0].cur_pos > p[0].cur_start) {
    	p[0].cur_pos--;
    } else {
    	CORD__prev(p);
    }
}

size_t CORD_pos_to_index(CORD_pos p)
{
    return(p[0].cur_pos);
}

CORD CORD_pos_to_cord(CORD_pos p)
{
    return(p[0].path[0].pe_cord);
}

int CORD_pos_valid(CORD_pos p)
{
    return(p[0].path_len != CORD_POS_INVALID);
}

void CORD_set_pos(CORD_pos p, CORD x, size_t i)
{
    if (x == CORD_EMPTY) {
    	p[0].path_len = CORD_POS_INVALID;
    	return;
    }
    p[0].path[0].pe_cord = x;
    p[0].path[0].pe_start_pos = 0;
    p[0].path_len = 0;
    p[0].cur_pos = i;
    CORD__extend_path(p);
}