phat12.c

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/*
 * Copyright (C) 2005 by egnite Software GmbH. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of the copyright holders nor the names of
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY EGNITE SOFTWARE GMBH AND CONTRIBUTORS
 * ``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 EGNITE
 * SOFTWARE GMBH OR CONTRIBUTORS 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.
 *
 * For additional information see http://www.ethernut.de/
 */

#include <errno.h>

#include <fs/phatfs.h>
#include <fs/phatvol.h>
#include <fs/phatio.h>


static void PhatTableLoc(PHATVOL * vol, uint32_t clust, int tabnum, uint32_t * sect, uint32_t * pos)
{
    uint32_t tabpos = clust + (clust / 2);

    *sect = vol->vol_tab_sect[tabnum] + tabpos / vol->vol_sectsz;
    *pos = tabpos % vol->vol_sectsz;
}

int Phat12GetClusterLink(NUTDEVICE * dev, uint32_t clust, uint32_t * link)
{
    uint32_t sect;
    uint32_t pos;
    int sbn;
    PHATVOL *vol = (PHATVOL *) dev->dev_dcb;

    /* Do not seek beyond the end of the chain. */
    if (clust >= (PHATEOC & PHAT12CMASK)) {
        return -1;
    }

    /* Load the sector that contains the table entry. */
    PhatTableLoc(vol, clust, 0, &sect, &pos);
    if ((sbn = PhatSectorLoad(dev, sect)) < 0) {
        return -1;
    }

    /* Read the link value. Be aware, that entries may cross sector boundaries. */
    *link = vol->vol_buf[sbn].sect_data[pos++];
    if (pos >= vol->vol_sectsz) {
        if ((sbn = PhatSectorLoad(dev, sect + 1)) < 0) {
            return -1;
        }
        pos = 0;
    }
    *link += (uint32_t)(vol->vol_buf[sbn].sect_data[pos]) << 8;

    /* Adjust the 12 bit position within the 16 bit result. */
    if (clust & 1) {
        *link >>= 4;
    }
    *link &= PHAT12CMASK;

    return 0;
}

int Phat12SetClusterLink(NUTDEVICE * dev, uint32_t clust, uint32_t link)
{
    int tabnum;
    uint32_t sect;
    uint32_t pos;
    uint32_t tval;
    int sbn;
    PHATVOL *vol = (PHATVOL *) dev->dev_dcb;

    for (tabnum = 0; tabnum < 2 && vol->vol_tab_sect[tabnum]; tabnum++) {

        /* Load the sector containing the table entry to set. */
        PhatTableLoc(vol, clust, tabnum, &sect, &pos);
        if ((sbn = PhatSectorLoad(dev, sect)) < 0) {
            return -1;
        }

        /* The new value is 12 bit only. Thus we must load the
         * old value and keep the upper or lower 4 bit part. */
        tval = vol->vol_buf[sbn].sect_data[pos];
        if (pos + 1 < vol->vol_sectsz) {
            tval += (uint32_t)(vol->vol_buf[sbn].sect_data[pos + 1]) << 8;
        } else {
            if ((sbn = PhatSectorLoad(dev, sect + 1)) < 0) {
                return -1;
            }
            tval += (uint32_t)(vol->vol_buf[sbn].sect_data[0]) << 8;
        }

        link &= PHAT12CMASK;
        if (clust & 1) {
            tval &= 0x000F;
            link <<= 4;
        } else {
            tval &= 0xF000;
        }
        tval |= link;

        /* Save the modified entry. Again maintain sector boundaries. */
        if (pos + 1 < vol->vol_sectsz) {
            vol->vol_buf[sbn].sect_data[pos + 1] = (uint8_t) (tval >> 8);
        } else {
            vol->vol_buf[sbn].sect_data[0] = (uint8_t) (tval >> 8);
            vol->vol_buf[sbn].sect_dirty = 1;
            if ((sbn = PhatSectorLoad(dev, sect)) < 0) {
                return -1;
            }
        }
        vol->vol_buf[sbn].sect_data[pos] = (uint8_t) tval;
        vol->vol_buf[sbn].sect_dirty = 1;
    }

    return 0;
}

int Phat12ReleaseChain(NUTDEVICE * dev, uint32_t first)
{
    uint32_t next;
    PHATVOL *vol = (PHATVOL *) dev->dev_dcb;

    while (first < (PHATEOC & PHAT12CMASK)) {
        if (Phat12GetClusterLink(dev, first, &next)) {
            /* Read error. */
            return -1;
        }
        if (next < 2) {
            /* Incomplete chain, should not happen. */
            break;
        }
        if (Phat12SetClusterLink(dev, first, 0)) {
            /* Write error. */
            return -1;
        }
        vol->vol_numfree++;
        first = next;
    }
    return 0;
}