source: mainline/uspace/srv/fs/fat/fat_fat.c@ b1178d0

/*
 * Copyright (c) 2008 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup fs
 * @{
 */ 

/**
 * @file        fat_fat.c
 * @brief       Functions that manipulate the file allocation tables.
 */

#include "fat_fat.h"
#include "fat_dentry.h"
#include "fat.h"
#include "../../vfs/vfs.h"
#include <libfs.h>
#include <errno.h>
#include <byteorder.h>
#include <align.h>
#include <assert.h>

block_t *
_fat_block_get(dev_handle_t dev_handle, fat_cluster_t firstc, off_t offset)
{
        block_t *bb;
        block_t *b;
        unsigned bps;
        unsigned spc;
        unsigned rscnt;         /* block address of the first FAT */
        unsigned fatcnt;
        unsigned rde;
        unsigned rds;           /* root directory size */
        unsigned sf;
        unsigned ssa;           /* size of the system area */
        unsigned clusters;
        fat_cluster_t clst = firstc;
        unsigned i;

        bb = block_get(dev_handle, BS_BLOCK, BS_SIZE);
        bps = uint16_t_le2host(FAT_BS(bb)->bps);
        spc = FAT_BS(bb)->spc;
        rscnt = uint16_t_le2host(FAT_BS(bb)->rscnt);
        fatcnt = FAT_BS(bb)->fatcnt;
        rde = uint16_t_le2host(FAT_BS(bb)->root_ent_max);
        sf = uint16_t_le2host(FAT_BS(bb)->sec_per_fat);
        block_put(bb);

        rds = (sizeof(fat_dentry_t) * rde) / bps;
        rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
        ssa = rscnt + fatcnt * sf + rds;

        if (firstc == FAT_CLST_ROOT) {
                /* root directory special case */
                assert(offset < rds);
                b = block_get(dev_handle, rscnt + fatcnt * sf + offset, bps);
                return b;
        }

        clusters = offset / spc; 
        for (i = 0; i < clusters; i++) {
                unsigned fsec;  /* sector offset relative to FAT1 */
                unsigned fidx;  /* FAT1 entry index */

                assert(clst >= FAT_CLST_FIRST && clst < FAT_CLST_BAD);
                fsec = (clst * sizeof(fat_cluster_t)) / bps;
                fidx = clst % (bps / sizeof(fat_cluster_t));
                /* read FAT1 */
                b = block_get(dev_handle, rscnt + fsec, bps);
                clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
                assert(clst != FAT_CLST_BAD);
                assert(clst < FAT_CLST_LAST1);
                block_put(b);
        }

        b = block_get(dev_handle, ssa + (clst - FAT_CLST_FIRST) * spc +
            offset % spc, bps);

        return b;
}

/** Return number of blocks allocated to a file.
 *
 * @param dev_handle    Device handle of the device with the file.
 * @param firstc        First cluster of the file.
 *
 * @return              Number of blocks allocated to the file.
 */
uint16_t 
_fat_blcks_get(dev_handle_t dev_handle, fat_cluster_t firstc)
{
        block_t *bb;
        block_t *b;
        unsigned bps;
        unsigned spc;
        unsigned rscnt;         /* block address of the first FAT */
        unsigned clusters = 0;
        fat_cluster_t clst = firstc;

        bb = block_get(dev_handle, BS_BLOCK, BS_SIZE);
        bps = uint16_t_le2host(FAT_BS(bb)->bps);
        spc = FAT_BS(bb)->spc;
        rscnt = uint16_t_le2host(FAT_BS(bb)->rscnt);
        block_put(bb);

        if (firstc == FAT_CLST_RES0) {
                /* No space allocated to the file. */
                return 0;
        }

        while (clst < FAT_CLST_LAST1) {
                unsigned fsec;  /* sector offset relative to FAT1 */
                unsigned fidx;  /* FAT1 entry index */

                assert(clst >= FAT_CLST_FIRST);
                fsec = (clst * sizeof(fat_cluster_t)) / bps;
                fidx = clst % (bps / sizeof(fat_cluster_t));
                /* read FAT1 */
                b = block_get(dev_handle, rscnt + fsec, bps);
                clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
                assert(clst != FAT_CLST_BAD);
                block_put(b);
                clusters++;
        }

        return clusters * spc;
}

uint16_t fat_bps_get(dev_handle_t dev_handle)
{
        block_t *bb;
        uint16_t bps;
        
        bb = block_get(dev_handle, BS_BLOCK, BS_SIZE);
        assert(bb != NULL);
        bps = uint16_t_le2host(FAT_BS(bb)->bps);
        block_put(bb);

        return bps;
}

/** Fill the gap between EOF and a new file position.
 *
 * @param nodep         FAT node with the gap.
 * @param mcl           First cluster in an independent cluster chain that will
 *                      be later appended to the end of the node's own cluster
 *                      chain. If pos is still in the last allocated cluster,
 *                      this argument is ignored.
 * @param pos           Position in the last node block.
 */
void fat_fill_gap(fat_node_t *nodep, fat_cluster_t mcl, off_t pos)
{
        uint16_t bps;
        unsigned spc;
        block_t *bb, *b;
        off_t o, boundary;

        bb = block_get(nodep->idx->dev_handle, BS_BLOCK, BS_SIZE);
        bps = uint16_t_le2host(FAT_BS(bb)->bps);
        spc = FAT_BS(bb)->spc;
        block_put(bb);
        
        boundary = ROUND_UP(nodep->size, bps * spc);

        /* zero out already allocated space */
        for (o = nodep->size - 1; o < pos && o < boundary;
            o = ALIGN_DOWN(o + bps, bps)) {
                b = fat_block_get(nodep, o / bps);
                memset(b->data + o % bps, 0, bps - o % bps);
                b->dirty = true;                /* need to sync node */
                block_put(b);
        }
        
        if (o >= pos)
                return;
        
        /* zero out the initial part of the new cluster chain */
        for (o = boundary; o < pos; o += bps) {
                b = _fat_block_get(nodep->idx->dev_handle, mcl,
                    (o - boundary) / bps);
                memset(b->data, 0, min(bps, pos - o));
                b->dirty = true;                /* need to sync node */
                block_put(b);
        }
}

void
fat_mark_cluster(dev_handle_t dev_handle, unsigned fatno, fat_cluster_t clst,
    fat_cluster_t value)
{
        /* TODO */
}

void fat_alloc_shadow_clusters(dev_handle_t dev_handle, fat_cluster_t *lifo,
    unsigned nclsts)
{
        uint8_t fatcnt;
        uint8_t fatno;
        unsigned c;
        block_t *bb;

        bb = block_get(dev_handle, BS_BLOCK, BS_SIZE);
        fatcnt = FAT_BS(bb)->fatcnt;
        block_put(bb);
        
        for (fatno = FAT1 + 1; fatno < fatcnt; fatno++) {
                for (c = 0; c < nclsts; c++) {
                        fat_mark_cluster(dev_handle, fatno, lifo[c],
                            c == 0 ? FAT_CLST_LAST1 : lifo[c - 1]);
                }
        }
}

int
fat_alloc_clusters(dev_handle_t dev_handle, unsigned nclsts, fat_cluster_t *mcl,
    fat_cluster_t *lcl)
{
        uint16_t bps;
        uint16_t rscnt;
        uint16_t sf;
        block_t *bb, *blk;
        fat_cluster_t *lifo;    /* stack for storing free cluster numbers */ 
        unsigned found = 0;     /* top of the free cluster number stack */
        unsigned b, c, cl; 

        lifo = (fat_cluster_t *) malloc(nclsts * sizeof(fat_cluster_t));
        if (lifo)
                return ENOMEM;
        
        bb = block_get(dev_handle, BS_BLOCK, BS_SIZE);
        bps = uint16_t_le2host(FAT_BS(bb)->bps);
        rscnt = uint16_t_le2host(FAT_BS(bb)->rscnt);
        sf = uint16_t_le2host(FAT_BS(bb)->sec_per_fat);
        block_put(bb);
        
        /*
         * Search FAT1 for unused clusters.
         */
        for (b = 0, cl = 0; b < sf; blk++) {
                blk = block_get(dev_handle, rscnt + b, bps);
                for (c = 0; c < bps / sizeof(fat_cluster_t); c++, cl++) {
                        fat_cluster_t *clst = (fat_cluster_t *)blk->data + c;
                        if (*clst == FAT_CLST_RES0) {
                                /*
                                 * The cluster is free. Put it into our stack
                                 * of found clusters and mark it as non-free.
                                 */
                                lifo[found] = cl;
                                if (found == 0)
                                        *clst = FAT_CLST_LAST1;
                                else
                                        *clst = lifo[found - 1];
                                blk->dirty = true;      /* need to sync block */
                                if (++found == nclsts) {
                                        /* we are almost done */
                                        block_put(blk);
                                        /* update the shadow copies of FAT */
                                        fat_alloc_shadow_clusters(dev_handle,
                                            lifo, nclsts);
                                        *mcl = lifo[found - 1];
                                        *lcl = lifo[0];
                                        free(lifo);
                                        return EOK;
                                }
                        }
                }
                block_put(blk);
        }

        /*
         * We could not find enough clusters. Now we need to free the clusters
         * we have allocated so far.
         */
        while (found--)
                fat_mark_cluster(dev_handle, FAT1, lifo[found], FAT_CLST_RES0);
        
        free(lifo);
        return ENOSPC;
}

void fat_append_clusters(fat_node_t *nodep, fat_cluster_t mcl)
{
}

/**
 * @}
 */