/*
 * Block handling for 2.xBSD filesystem.
 *
 * Copyright (C) 2006-2014 Serge Vakulenko, <serge@vak.ru>
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for any purpose and without fee is hereby
 * granted, provided that the above copyright notice appear in all
 * copies and that both that the copyright notice and this
 * permission notice and warranty disclaimer appear in supporting
 * documentation, and that the name of the author not be used in
 * advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 *
 * The author disclaim 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, 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 <stdio.h>
#include <time.h>
#include "bsdfs.h"

extern int verbose;

int fs_read_block (fs_t *fs, unsigned bnum, unsigned char *data)
{
    if (verbose > 3)
        printf ("read block %d\n", bnum);
    if (bnum < fs->isize)
        return 0;
    if (! fs_seek (fs, bnum * BSDFS_BSIZE))
        return 0;
    if (! fs_read (fs, data, BSDFS_BSIZE))
        return 0;
    return 1;
}

int fs_write_block (fs_t *fs, unsigned bnum, unsigned char *data)
{
    if (verbose > 3)
        printf ("write block %d\n", bnum);
    if (! fs->writable || bnum < fs->isize)
        return 0;
    if (! fs_seek (fs, bnum * BSDFS_BSIZE))
        return 0;
    if (! fs_write (fs, data, BSDFS_BSIZE))
        return 0;
    fs->modified = 1;
    return 1;
}

/*
 * Add a block to free list.
 */
int fs_block_free (fs_t *fs, unsigned int bno)
{
    int i;
    unsigned buf [BSDFS_BSIZE / 4];

    if (verbose > 1)
        printf ("free block %d, total %d\n", bno, fs->nfree);
    if (fs->nfree >= NICFREE) {
        buf[0] = fs->nfree;
        for (i=0; i<NICFREE; i++)
            buf[i+1] = fs->free[i];
        if (! fs_write_block (fs, bno, (unsigned char*) buf)) {
            fprintf (stderr, "block_free: write error at block %d\n", bno);
            return 0;
        }
        fs->nfree = 0;
    }
    fs->free [fs->nfree] = bno;
    fs->nfree++;
    fs->dirty = 1;
    if (bno)            /* Count total free blocks. */
        ++fs->tfree;
    return 1;
}

/*
 * Free an indirect block.
 */
int fs_indirect_block_free (fs_t *fs, unsigned int bno, int nblk)
{
    unsigned nb;
    unsigned char data [BSDFS_BSIZE];
    int i;

    if (! fs_read_block (fs, bno, data)) {
        fprintf (stderr, "inode_clear: read error at block %d\n", bno);
        return 0;
    }
    for (i=BSDFS_BSIZE-4; i>=0; i-=4) {
        if (i/4 < nblk) {
            /* Truncate up to required size. */
            return 0;
        }
        nb = data [i+3] << 24 | data [i+2] << 16 |
             data [i+1] << 8  | data [i];
        if (nb)
            fs_block_free (fs, nb);
    }
    fs_block_free (fs, bno);
    return 1;
}

/*
 * Free a double indirect block.
 */
int fs_double_indirect_block_free (fs_t *fs, unsigned int bno, int nblk)
{
    unsigned nb;
    unsigned char data [BSDFS_BSIZE];
    int i;

    if (! fs_read_block (fs, bno, data)) {
        fprintf (stderr, "inode_clear: read error at block %d\n", bno);
        return 0;
    }
    for (i=BSDFS_BSIZE-4; i>=0; i-=4) {
        if (i/4 * BSDFS_BSIZE/4 < nblk) {
            /* Truncate up to required size. */
            return 0;
        }
        nb = data [i+3] << 24 | data [i+2] << 16 |
             data [i+1] << 8  | data [i];
        if (nb)
            fs_indirect_block_free (fs, nb,
                nblk - i/4 * BSDFS_BSIZE/4);
    }
    fs_block_free (fs, bno);
    return 1;
}

/*
 * Free a triple indirect block.
 */
int fs_triple_indirect_block_free (fs_t *fs, unsigned int bno, int nblk)
{
    unsigned nb;
    unsigned char data [BSDFS_BSIZE];
    int i;

    if (! fs_read_block (fs, bno, data)) {
        fprintf (stderr, "inode_clear: read error at block %d\n", bno);
        return 0;
    }
    for (i=BSDFS_BSIZE-4; i>=0; i-=4) {
        if (i/4 * BSDFS_BSIZE/4 * BSDFS_BSIZE/4 < nblk) {
            /* Truncate up to required size. */
            return 0;
        }
        nb = data [i+3] << 24 | data [i+2] << 16 |
             data [i+1] << 8  | data [i];
        if (nb)
            fs_double_indirect_block_free (fs, nb,
                nblk - i/4 * BSDFS_BSIZE/4 * BSDFS_BSIZE/4);
    }
    fs_block_free (fs, bno);
    return 1;
}

/*
 * Get a block from free list.
 */
int fs_block_alloc (fs_t *fs, unsigned int *bno)
{
    int i;
    unsigned buf [BSDFS_BSIZE / 4];
again:
    if (fs->nfree == 0)
        return 0;
    fs->nfree--;
    --fs->tfree;            /* Count total free blocks. */
    *bno = fs->free [fs->nfree];
    if (verbose)
        printf ("allocate new block %d from slot %d\n", *bno, fs->nfree);
    fs->free [fs->nfree] = 0;
    fs->dirty = 1;
    if (fs->nfree <= 0) {
        if (! fs_read_block (fs, *bno, (unsigned char*) buf))
            return 0;
        fs->nfree = buf[0];
        for (i=0; i<NICFREE; i++)
            fs->free[i] = buf[i+1];
    }
    if (*bno == 0)
        goto again;
    return 1;
}