/* vi: set sw=4 ts=4: */
/*
 * icount.c --- an efficient inode count abstraction
 *
 * Copyright (C) 1997 Theodore Ts'o.
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Public
 * License.
 * %End-Header%
 */

#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <string.h>
#include <stdio.h>

#include "ext2_fs.h"
#include "ext2fs.h"

/*
 * The data storage strategy used by icount relies on the observation
 * that most inode counts are either zero (for non-allocated inodes),
 * one (for most files), and only a few that are two or more
 * (directories and files that are linked to more than one directory).
 *
 * Also, e2fsck tends to load the icount data sequentially.
 *
 * So, we use an inode bitmap to indicate which inodes have a count of
 * one, and then use a sorted list to store the counts for inodes
 * which are greater than one.
 *
 * We also use an optional bitmap to indicate which inodes are already
 * in the sorted list, to speed up the use of this abstraction by
 * e2fsck's pass 2.  Pass 2 increments inode counts as it finds them,
 * so this extra bitmap avoids searching the sorted list to see if a
 * particular inode is on the sorted list already.
 */

struct ext2_icount_el {
        ext2_ino_t      ino;
        __u16   count;
};

struct ext2_icount {
        errcode_t               magic;
        ext2fs_inode_bitmap     single;
        ext2fs_inode_bitmap     multiple;
        ext2_ino_t              count;
        ext2_ino_t              size;
        ext2_ino_t              num_inodes;
        ext2_ino_t              cursor;
        struct ext2_icount_el   *list;
};

void ext2fs_free_icount(ext2_icount_t icount)
{
        if (!icount)
                return;

        icount->magic = 0;
        ext2fs_free_mem(&icount->list);
        ext2fs_free_inode_bitmap(icount->single);
        ext2fs_free_inode_bitmap(icount->multiple);
        ext2fs_free_mem(&icount);
}

errcode_t ext2fs_create_icount2(ext2_filsys fs, int flags, unsigned int size,
                                ext2_icount_t hint, ext2_icount_t *ret)
{
        ext2_icount_t   icount;
        errcode_t       retval;
        size_t          bytes;
        ext2_ino_t      i;

        if (hint) {
                EXT2_CHECK_MAGIC(hint, EXT2_ET_MAGIC_ICOUNT);
                if (hint->size > size)
                        size = (size_t) hint->size;
        }

        retval = ext2fs_get_mem(sizeof(struct ext2_icount), &icount);
        if (retval)
                return retval;
        memset(icount, 0, sizeof(struct ext2_icount));

        retval = ext2fs_allocate_inode_bitmap(fs, 0,
                                              &icount->single);
        if (retval)
                goto errout;

        if (flags & EXT2_ICOUNT_OPT_INCREMENT) {
                retval = ext2fs_allocate_inode_bitmap(fs, 0,
                                                      &icount->multiple);
                if (retval)
                        goto errout;
        } else
                icount->multiple = 0;

        if (size) {
                icount->size = size;
        } else {
                /*
                 * Figure out how many special case inode counts we will
                 * have.  We know we will need one for each directory;
                 * we also need to reserve some extra room for file links
                 */
                retval = ext2fs_get_num_dirs(fs, &icount->size);
                if (retval)
                        goto errout;
                icount->size += fs->super->s_inodes_count / 50;
        }

        bytes = (size_t) (icount->size * sizeof(struct ext2_icount_el));
        retval = ext2fs_get_mem(bytes, &icount->list);
        if (retval)
                goto errout;
        memset(icount->list, 0, bytes);

        icount->magic = EXT2_ET_MAGIC_ICOUNT;
        icount->count = 0;
        icount->cursor = 0;
        icount->num_inodes = fs->super->s_inodes_count;

        /*
         * Populate the sorted list with those entries which were
         * found in the hint icount (since those are ones which will
         * likely need to be in the sorted list this time around).
         */
        if (hint) {
                for (i=0; i < hint->count; i++)
                        icount->list[i].ino = hint->list[i].ino;
                icount->count = hint->count;
        }

        *ret = icount;
        return 0;

errout:
        ext2fs_free_icount(icount);
        return retval;
}

errcode_t ext2fs_create_icount(ext2_filsys fs, int flags,
                               unsigned int size,
                               ext2_icount_t *ret)
{
        return ext2fs_create_icount2(fs, flags, size, 0, ret);
}

/*
 * insert_icount_el() --- Insert a new entry into the sorted list at a
 *      specified position.
 */
static struct ext2_icount_el *insert_icount_el(ext2_icount_t icount,
                                            ext2_ino_t ino, int pos)
{
        struct ext2_icount_el   *el;
        errcode_t               retval;
        ext2_ino_t                      new_size = 0;
        int                     num;

        if (icount->count >= icount->size) {
                if (icount->count) {
                        new_size = icount->list[(unsigned)icount->count-1].ino;
                        new_size = (ext2_ino_t) (icount->count *
                                ((float) icount->num_inodes / new_size));
                }
                if (new_size < (icount->size + 100))
                        new_size = icount->size + 100;
                retval = ext2fs_resize_mem((size_t) icount->size *
                                           sizeof(struct ext2_icount_el),
                                           (size_t) new_size *
                                           sizeof(struct ext2_icount_el),
                                           &icount->list);
                if (retval)
                        return 0;
                icount->size = new_size;
        }
        num = (int) icount->count - pos;
        if (num < 0)
                return 0;       /* should never happen */
        if (num) {
                memmove(&icount->list[pos+1], &icount->list[pos],
                        sizeof(struct ext2_icount_el) * num);
        }
        icount->count++;
        el = &icount->list[pos];
        el->count = 0;
        el->ino = ino;
        return el;
}

/*
 * get_icount_el() --- given an inode number, try to find icount
 *      information in the sorted list.  If the create flag is set,
 *      and we can't find an entry, create one in the sorted list.
 */
static struct ext2_icount_el *get_icount_el(ext2_icount_t icount,
                                            ext2_ino_t ino, int create)
{
        float   range;
        int     low, high, mid;
        ext2_ino_t      lowval, highval;

        if (!icount || !icount->list)
                return 0;

        if (create && ((icount->count == 0) ||
                       (ino > icount->list[(unsigned)icount->count-1].ino))) {
                return insert_icount_el(icount, ino, (unsigned) icount->count);
        }
        if (icount->count == 0)
                return 0;

        if (icount->cursor >= icount->count)
                icount->cursor = 0;
        if (ino == icount->list[icount->cursor].ino)
                return &icount->list[icount->cursor++];
        low = 0;
        high = (int) icount->count-1;
        while (low <= high) {
                if (low == high)
                        mid = low;
                else {
                        /* Interpolate for efficiency */
                        lowval = icount->list[low].ino;
                        highval = icount->list[high].ino;

                        if (ino < lowval)
                                range = 0;
                        else if (ino > highval)
                                range = 1;
                        else
                                range = ((float) (ino - lowval)) /
                                        (highval - lowval);
                        mid = low + ((int) (range * (high-low)));
                }
                if (ino == icount->list[mid].ino) {
                        icount->cursor = mid+1;
                        return &icount->list[mid];
                }
                if (ino < icount->list[mid].ino)
                        high = mid-1;
                else
                        low = mid+1;
        }
        /*
         * If we need to create a new entry, it should be right at
         * low (where high will be left at low-1).
         */
        if (create)
                return insert_icount_el(icount, ino, low);
        return 0;
}

errcode_t ext2fs_icount_validate(ext2_icount_t icount, FILE *out)
{
        errcode_t       ret = 0;
        unsigned int    i;
        const char *bad = "bad icount";

        EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);

        if (icount->count > icount->size) {
                fprintf(out, "%s: count > size\n", bad);
                return EXT2_ET_INVALID_ARGUMENT;
        }
        for (i=1; i < icount->count; i++) {
                if (icount->list[i-1].ino >= icount->list[i].ino) {
                        fprintf(out, "%s: list[%d].ino=%u, list[%d].ino=%u\n",
                                bad, i-1, icount->list[i-1].ino,
                                i, icount->list[i].ino);
                        ret = EXT2_ET_INVALID_ARGUMENT;
                }
        }
        return ret;
}

errcode_t ext2fs_icount_fetch(ext2_icount_t icount, ext2_ino_t ino, __u16 *ret)
{
        struct ext2_icount_el   *el;

        EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);

        if (!ino || (ino > icount->num_inodes))
                return EXT2_ET_INVALID_ARGUMENT;

        if (ext2fs_test_inode_bitmap(icount->single, ino)) {
                *ret = 1;
                return 0;
        }
        if (icount->multiple &&
            !ext2fs_test_inode_bitmap(icount->multiple, ino)) {
                *ret = 0;
                return 0;
        }
        el = get_icount_el(icount, ino, 0);
        if (!el) {
                *ret = 0;
                return 0;
        }
        *ret = el->count;
        return 0;
}

errcode_t ext2fs_icount_increment(ext2_icount_t icount, ext2_ino_t ino,
                                  __u16 *ret)
{
        struct ext2_icount_el   *el;

        EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);

        if (!ino || (ino > icount->num_inodes))
                return EXT2_ET_INVALID_ARGUMENT;

        if (ext2fs_test_inode_bitmap(icount->single, ino)) {
                /*
                 * If the existing count is 1, then we know there is
                 * no entry in the list.
                 */
                el = get_icount_el(icount, ino, 1);
                if (!el)
                        return EXT2_ET_NO_MEMORY;
                ext2fs_unmark_inode_bitmap(icount->single, ino);
                el->count = 2;
        } else if (icount->multiple) {
                /*
                 * The count is either zero or greater than 1; if the
                 * inode is set in icount->multiple, then there should
                 * be an entry in the list, so find it using
                 * get_icount_el().
                 */
                if (ext2fs_test_inode_bitmap(icount->multiple, ino)) {
                        el = get_icount_el(icount, ino, 1);
                        if (!el)
                                return EXT2_ET_NO_MEMORY;
                        el->count++;
                } else {
                        /*
                         * The count was zero; mark the single bitmap
                         * and return.
                         */
                zero_count:
                        ext2fs_mark_inode_bitmap(icount->single, ino);
                        if (ret)
                                *ret = 1;
                        return 0;
                }
        } else {
                /*
                 * The count is either zero or greater than 1; try to
                 * find an entry in the list to determine which.
                 */
                el = get_icount_el(icount, ino, 0);
                if (!el) {
                        /* No entry means the count was zero */
                        goto zero_count;
                }
                el = get_icount_el(icount, ino, 1);
                if (!el)
                        return EXT2_ET_NO_MEMORY;
                el->count++;
        }
        if (icount->multiple)
                ext2fs_mark_inode_bitmap(icount->multiple, ino);
        if (ret)
                *ret = el->count;
        return 0;
}

errcode_t ext2fs_icount_decrement(ext2_icount_t icount, ext2_ino_t ino,
                                  __u16 *ret)
{
        struct ext2_icount_el   *el;

        if (!ino || (ino > icount->num_inodes))
                return EXT2_ET_INVALID_ARGUMENT;

        EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);

        if (ext2fs_test_inode_bitmap(icount->single, ino)) {
                ext2fs_unmark_inode_bitmap(icount->single, ino);
                if (icount->multiple)
                        ext2fs_unmark_inode_bitmap(icount->multiple, ino);
                else {
                        el = get_icount_el(icount, ino, 0);
                        if (el)
                                el->count = 0;
                }
                if (ret)
                        *ret = 0;
                return 0;
        }

        if (icount->multiple &&
            !ext2fs_test_inode_bitmap(icount->multiple, ino))
                return EXT2_ET_INVALID_ARGUMENT;

        el = get_icount_el(icount, ino, 0);
        if (!el || el->count == 0)
                return EXT2_ET_INVALID_ARGUMENT;

        el->count--;
        if (el->count == 1)
                ext2fs_mark_inode_bitmap(icount->single, ino);
        if ((el->count == 0) && icount->multiple)
                ext2fs_unmark_inode_bitmap(icount->multiple, ino);

        if (ret)
                *ret = el->count;
        return 0;
}

errcode_t ext2fs_icount_store(ext2_icount_t icount, ext2_ino_t ino,
                              __u16 count)
{
        struct ext2_icount_el   *el;

        if (!ino || (ino > icount->num_inodes))
                return EXT2_ET_INVALID_ARGUMENT;

        EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);

        if (count == 1) {
                ext2fs_mark_inode_bitmap(icount->single, ino);
                if (icount->multiple)
                        ext2fs_unmark_inode_bitmap(icount->multiple, ino);
                return 0;
        }
        if (count == 0) {
                ext2fs_unmark_inode_bitmap(icount->single, ino);
                if (icount->multiple) {
                        /*
                         * If the icount->multiple bitmap is enabled,
                         * we can just clear both bitmaps and we're done
                         */
                        ext2fs_unmark_inode_bitmap(icount->multiple, ino);
                } else {
                        el = get_icount_el(icount, ino, 0);
                        if (el)
                                el->count = 0;
                }
                return 0;
        }

        /*
         * Get the icount element
         */
        el = get_icount_el(icount, ino, 1);
        if (!el)
                return EXT2_ET_NO_MEMORY;
        el->count = count;
        ext2fs_unmark_inode_bitmap(icount->single, ino);
        if (icount->multiple)
                ext2fs_mark_inode_bitmap(icount->multiple, ino);
        return 0;
}

ext2_ino_t ext2fs_get_icount_size(ext2_icount_t icount)
{
        if (!icount || icount->magic != EXT2_ET_MAGIC_ICOUNT)
                return 0;

        return icount->size;
}