githubmirror/dosfstools

src/io.c
218 строк6 KB
Steven J. Magnani
Adding support for limited-memory embedded systems.
23 янв 2013, 15:50
23 янв 2013, 15:50ff1b24e
/* io.c - Virtual disk input/output

   Copyright (C) 1993 Werner Almesberger <werner.almesberger@lrc.di.epfl.ch>
   Copyright (C) 1998 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>

   This program 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 3 of the License, or
   (at your option) any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program. If not, see <http://www.gnu.org/licenses/>.

   On Debian systems, the complete text of the GNU General Public License
   can be found in /usr/share/common-licenses/GPL-3 file.
*/

/*
 * Thu Feb 26 01:15:36 CET 1998: Martin Schulze <joey@infodrom.north.de>
 *	Fixed nasty bug that caused every file with a name like
 *	xxxxxxxx.xxx to be treated as bad name that needed to be fixed.
 */

/* FAT32, VFAT, Atari format support, and various fixes additions May 1998
 * by Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de> */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/fd.h>

#include "dosfsck.h"
#include "common.h"
#include "io.h"


typedef struct _change {
    void *data;
    loff_t pos;
    int size;
    struct _change *next;
} CHANGE;


static CHANGE *changes,*last;
static int fd,did_change = 0;

unsigned device_no;


#ifdef __DJGPP__
#include "volume.h"	/* DOS lowlevel disk access functions */
#undef llseek
static loff_t llseek( int fd, loff_t offset, int whence )
{
    if ((whence != SEEK_SET) || (fd == 4711)) return -1; /* only those supported */
    return VolumeSeek(offset);
}
#define open OpenVolume
#define close CloseVolume
#define read(a,b,c) ReadVolume(b,c)
#define write(a,b,c) WriteVolume(b,c)
#endif

void fs_open(char *path,int rw)
{
    struct stat stbuf;

    if ((fd = open(path,rw ? O_RDWR : O_RDONLY)) < 0)
	pdie("open %s",path);
    changes = last = NULL;
    did_change = 0;

#ifndef _DJGPP_
    if (fstat(fd,&stbuf) < 0)
	pdie("fstat %s",path);
    device_no = S_ISBLK(stbuf.st_mode) ? (stbuf.st_rdev >> 8) & 0xff : 0;
#else
    if (IsWorkingOnImageFile()) {
	if (fstat(GetVolumeHandle(),&stbuf) < 0)
	    pdie("fstat image %s",path);
	device_no = 0;
    }
    else {
        /* return 2 for floppy, 1 for ramdisk, 7 for loopback  */
        /* used by boot.c in Atari mode: floppy always FAT12,  */
        /* loopback / ramdisk only FAT12 if usual floppy size, */
        /* harddisk always FAT16 on Atari... */
        device_no = (GetVolumeHandle() < 2) ? 2 : 1;
        /* telling "floppy" for A:/B:, "ramdisk" for the rest */
    }
#endif
}


/**
 * Read data from the partition, accounting for any pending updates that are
 * queued for writing.
 *
 * @param[in]   pos     Byte offset, relative to the beginning of the partition,
 *                      at which to read
 * @param[in]   size    Number of bytes to read
 * @param[out]  data    Where to put the data read
 */
void fs_read(loff_t pos,int size,void *data)
{
    CHANGE *walk;
    int got;

    if (llseek(fd,pos,0) != pos) pdie("Seek to %lld",pos);
    if ((got = read(fd,data,size)) < 0) pdie("Read %d bytes at %lld",size,pos);
    if (got != size) die("Got %d bytes instead of %d at %lld",got,size,pos);
    for (walk = changes; walk; walk = walk->next) {
	if (walk->pos < pos+size && walk->pos+walk->size > pos) {
	    if (walk->pos < pos)
		memcpy(data,(char *) walk->data+pos-walk->pos,min(size,
		  walk->size-pos+walk->pos));
	    else memcpy((char *) data+walk->pos-pos,walk->data,min(walk->size,
		  size+pos-walk->pos));
	}
    }
}


int fs_test(loff_t pos,int size)
{
    void *scratch;
    int okay;

    if (llseek(fd,pos,0) != pos) pdie("Seek to %lld",pos);
    scratch = alloc(size);
    okay = read(fd,scratch,size) == size;
    free(scratch);
    return okay;
}


void fs_write(loff_t pos,int size,void *data)
{
    CHANGE *new;
    int did;

    if (write_immed) {
	did_change = 1;
	if (llseek(fd,pos,0) != pos) pdie("Seek to %lld",pos);
	if ((did = write(fd,data,size)) == size) return;
	if (did < 0) pdie("Write %d bytes at %lld",size,pos);
	die("Wrote %d bytes instead of %d at %lld",did,size,pos);
    }
    new = alloc(sizeof(CHANGE));
    new->pos = pos;
    memcpy(new->data = alloc(new->size = size),data,size);
    new->next = NULL;
    if (last) last->next = new;
    else changes = new;
    last = new;
}


static void fs_flush(void)
{
    CHANGE *this;
    int size;

    while (changes) {
	this = changes;
	changes = changes->next;
	if (llseek(fd,this->pos,0) != this->pos)
	    fprintf(stderr,"Seek to %lld failed: %s\n  Did not write %d bytes.\n",
	      (long long)this->pos,strerror(errno),this->size);
	else if ((size = write(fd,this->data,this->size)) < 0)
		fprintf(stderr,"Writing %d bytes at %lld failed: %s\n",this->size,
		  (long long)this->pos,strerror(errno));
	    else if (size != this->size)
		    fprintf(stderr,"Wrote %d bytes instead of %d bytes at %lld."
		      "\n",size,this->size,(long long)this->pos);
	free(this->data);
	free(this);
    }
}


int fs_close(int write)
{
    CHANGE *next;
    int changed;

    changed = !!changes;
    if (write) fs_flush();
    else while (changes) {
	    next = changes->next;
	    free(changes->data);
	    free(changes);
	    changes = next;
	}
    if (close(fd) < 0) pdie("closing file system");
    return changed || did_change;
}


int fs_changed(void)
{
    return !!changes || did_change;
}

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