Return to bitmap.c CVS log

Up to [local] / src / usr.bin / ssh

Switch to recallocarray() for a few operations.  Both growth and shrinkage
are handled safely, and there also is no need for preallocation dances.
Future changes in this area will be less error prone.
Review and one bug found by markus

/*
 * Copyright (c) 2015 Damien Miller <djm@mindrot.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>
#include <string.h>
#include <stdlib.h>

#include "bitmap.h"

#define BITMAP_WTYPE	u_int
#define BITMAP_MAX	(1<<24)
#define BITMAP_BYTES	(sizeof(BITMAP_WTYPE))
#define BITMAP_BITS	(sizeof(BITMAP_WTYPE) * 8)
#define BITMAP_WMASK	((BITMAP_WTYPE)BITMAP_BITS - 1)
struct bitmap {
	BITMAP_WTYPE *d;
	size_t len; /* number of words allocated */
	size_t top; /* index of top word allocated */
};

struct bitmap *
bitmap_new(void)
{
	struct bitmap *ret;

	if ((ret = calloc(1, sizeof(*ret))) == NULL)
		return NULL;
	if ((ret->d = calloc(1, BITMAP_BYTES)) == NULL) {
		free(ret);
		return NULL;
	}
	ret->len = 1;
	ret->top = 0;
	return ret;
}

void
bitmap_free(struct bitmap *b)
{
	if (b != NULL && b->d != NULL) {
		bitmap_zero(b);
		free(b->d);
		b->d = NULL;
	}
	free(b);
}

void
bitmap_zero(struct bitmap *b)
{
	memset(b->d, 0, b->len * BITMAP_BYTES);
	b->top = 0;
}

int
bitmap_test_bit(struct bitmap *b, u_int n)
{
	if (b->top >= b->len)
		return 0; /* invalid */
	if (b->len == 0 || (n / BITMAP_BITS) > b->top)
		return 0;
	return (b->d[n / BITMAP_BITS] >> (n & BITMAP_WMASK)) & 1;
}

static int
reserve(struct bitmap *b, u_int n)
{
	BITMAP_WTYPE *tmp;
	size_t nlen;

	if (b->top >= b->len || n > BITMAP_MAX)
		return -1; /* invalid */
	nlen = (n / BITMAP_BITS) + 1;
	if (b->len < nlen) {
		if ((tmp = recallocarray(b->d, b->len, nlen, BITMAP_BYTES)) == NULL)
			return -1;
		b->d = tmp;
		memset(b->d + b->len, 0, (nlen - b->len) * BITMAP_BYTES);
		b->len = nlen;
	}
	return 0;
}

int
bitmap_set_bit(struct bitmap *b, u_int n)
{
	int r;
	size_t offset;

	if ((r = reserve(b, n)) != 0)
		return r;
	offset = n / BITMAP_BITS;
	if (offset > b->top)
		b->top = offset;
	b->d[offset] |= (BITMAP_WTYPE)1 << (n & BITMAP_WMASK);
	return 0;
}

/* Resets b->top to point to the most significant bit set in b->d */
static void
retop(struct bitmap *b)
{
	if (b->top >= b->len)
		return;
	while (b->top > 0 && b->d[b->top] == 0)
		b->top--;
}

void
bitmap_clear_bit(struct bitmap *b, u_int n)
{
	size_t offset;

	if (b->top >= b->len || n > BITMAP_MAX)
		return; /* invalid */
	offset = n / BITMAP_BITS;
	if (offset > b->top)
		return;
	b->d[offset] &= ~((BITMAP_WTYPE)1 << (n & BITMAP_WMASK));
	/* The top may have changed as a result of the clear */
	retop(b);
}

size_t
bitmap_nbits(struct bitmap *b)
{
	size_t bits;
	BITMAP_WTYPE w;

	retop(b);
	if (b->top >= b->len)
		return 0; /* invalid */
	if (b->len == 0 || (b->top == 0 && b->d[0] == 0))
		return 0;
	/* Find MSB set */
	w = b->d[b->top];
	bits = (b->top + 1) * BITMAP_BITS;
	while (!(w & ((BITMAP_WTYPE)1 << (BITMAP_BITS - 1)))) {
		w <<= 1;
		bits--;
	}
	return bits;
}

size_t
bitmap_nbytes(struct bitmap *b)
{
	return (bitmap_nbits(b) + 7) / 8;
}

int
bitmap_to_string(struct bitmap *b, void *p, size_t l)
{
	u_char *s = (u_char *)p;
	size_t i, j, k, need = bitmap_nbytes(b);

	if (l < need || b->top >= b->len)
		return -1;
	if (l > need)
		l = need;
	/* Put the bytes from LSB backwards */
	for (i = k = 0; i < b->top + 1; i++) {
		for (j = 0; j < BITMAP_BYTES; j++) {
			if (k >= l)
				break;
			s[need - 1 - k++] = (b->d[i] >> (j * 8)) & 0xff;
		}
	}
	return 0;
}

int
bitmap_from_string(struct bitmap *b, const void *p, size_t l)
{
	int r;
	size_t i, offset, shift;
	u_char *s = (u_char *)p;

	if (l > BITMAP_MAX / 8)
		return -1;
	if ((r = reserve(b, l * 8)) != 0)
		return r;
	bitmap_zero(b);
	if (l == 0)
		return 0;
	b->top = offset = ((l + (BITMAP_BYTES - 1)) / BITMAP_BYTES) - 1;
	shift = ((l + (BITMAP_BYTES - 1)) % BITMAP_BYTES) * 8;
	for (i = 0; i < l; i++) {
		b->d[offset] |= (BITMAP_WTYPE)s[i] << shift;
		if (shift == 0) {
			offset--;
			shift = BITMAP_BITS - 8;
		} else
			shift -= 8;
	}
	retop(b);
	return 0;
}