/* $OpenBSD: bitmap.c,v 1.9 2017/10/20 01:56:39 djm Exp $ */
/*
 * 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;
                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;
        const u_char *s = (const 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;
}