/*
 * QEMU 64-bit address ranges
 *
 * Copyright (c) 2015-2016 Red Hat, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
 *
 */

#ifndef QEMU_RANGE_H
#define QEMU_RANGE_H

#include "qemu/queue.h"

/*
 * Operations on 64 bit address ranges.
 * Notes:
 *   - ranges must not wrap around 0, but can include the last byte ~0x0LL.
 *   - this can not represent a full 0 to ~0x0LL range.
 */

/* A structure representing a range of addresses. */
struct Range {
    uint64_t begin; /* First byte of the range, or 0 if empty. */
    uint64_t end;   /* 1 + the last byte. 0 if range empty or ends at ~0x0LL. */
};

static inline void range_invariant(Range *range)
{
    assert((!range->begin && !range->end) /* empty */
           || range->begin <= range->end - 1); /* non-empty */
}

/* Compound literal encoding the empty range */
#define range_empty ((Range){ .begin = 0, .end = 0 })

/* Is @range empty? */
static inline bool range_is_empty(Range *range)
{
    range_invariant(range);
    return !range->begin && !range->end;
}

/* Does @range contain @val? */
static inline bool range_contains(Range *range, uint64_t val)
{
    return !range_is_empty(range)
        && val >= range->begin && val <= range->end - 1;
}

/* Initialize @range to the empty range */
static inline void range_make_empty(Range *range)
{
    *range = range_empty;
    assert(range_is_empty(range));
}

/*
 * Initialize @range to span the interval [@lob,@upb].
 * Both bounds are inclusive.
 * The interval must not be empty, i.e. @lob must be less than or
 * equal @upb.
 * The interval must not be [0,UINT64_MAX], because Range can't
 * represent that.
 */
static inline void range_set_bounds(Range *range, uint64_t lob, uint64_t upb)
{
    assert(lob <= upb);
    range->begin = lob;
    range->end = upb + 1;       /* may wrap to zero, that's okay */
    assert(!range_is_empty(range));
}

/*
 * Initialize @range to span the interval [@lob,@upb_plus1).
 * The lower bound is inclusive, the upper bound is exclusive.
 * Zero @upb_plus1 is special: if @lob is also zero, set @range to the
 * empty range.  Else, set @range to [@lob,UINT64_MAX].
 */
static inline void range_set_bounds1(Range *range,
                                     uint64_t lob, uint64_t upb_plus1)
{
    range->begin = lob;
    range->end = upb_plus1;
    range_invariant(range);
}

/* Return @range's lower bound.  @range must not be empty. */
static inline uint64_t range_lob(Range *range)
{
    assert(!range_is_empty(range));
    return range->begin;
}

/* Return @range's upper bound.  @range must not be empty. */
static inline uint64_t range_upb(Range *range)
{
    assert(!range_is_empty(range));
    return range->end - 1;
}

/*
 * Extend @range to the smallest interval that includes @extend_by, too.
 * This must not extend @range to cover the interval [0,UINT64_MAX],
 * because Range can't represent that.
 */
static inline void range_extend(Range *range, Range *extend_by)
{
    if (range_is_empty(extend_by)) {
        return;
    }
    if (range_is_empty(range)) {
        *range = *extend_by;
        return;
    }
    if (range->begin > extend_by->begin) {
        range->begin = extend_by->begin;
    }
    /* Compare last byte in case region ends at ~0x0LL */
    if (range->end - 1 < extend_by->end - 1) {
        range->end = extend_by->end;
    }
    /* Must not extend to { .begin = 0, .end = 0 }: */
    assert(!range_is_empty(range));
}

/* Get last byte of a range from offset + length.
 * Undefined for ranges that wrap around 0. */
static inline uint64_t range_get_last(uint64_t offset, uint64_t len)
{
    return offset + len - 1;
}

/* Check whether a given range covers a given byte. */
static inline int range_covers_byte(uint64_t offset, uint64_t len,
                                    uint64_t byte)
{
    return offset <= byte && byte <= range_get_last(offset, len);
}

/* Check whether 2 given ranges overlap.
 * Undefined if ranges that wrap around 0. */
static inline int ranges_overlap(uint64_t first1, uint64_t len1,
                                 uint64_t first2, uint64_t len2)
{
    uint64_t last1 = range_get_last(first1, len1);
    uint64_t last2 = range_get_last(first2, len2);

    return !(last2 < first1 || last1 < first2);
}

GList *range_list_insert(GList *list, Range *data);

#endif