correct use of USBDEVFS_DISCONNECT

[qemu] / block-vvfat.c

/*
 * QEMU Block driver for virtual VFAT (shadows a local directory)
 * 
 * Copyright (c) 2004 Johannes E. Schindelin
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#include <sys/stat.h>
#include <dirent.h>
#include <assert.h>
#include "vl.h"
#include "block_int.h"

// TODO: new file
// TODO: delete file
// TODO: make root directory larger
// TODO: make directory clusters connected, so they are reserved anyway... add a member which tells how many clusters are reserved after a directory
// TODO: introduce another member in mapping_t which says where the directory resides in s->directory (for mkdir and rmdir) 
// in _read and _write, before treating direntries or file contents, get_mapping to know what it is.
// TODO: mkdir
// TODO: rmdir 

// TODO: when commit_data'ing a direntry and is_consistent, commit_remove
// TODO: reset MODE_MODIFIED when commit_remove'ing

#define DEBUG

/* dynamic array functions */
typedef struct array_t {
    char* pointer;
    unsigned int size,next,item_size;
} array_t;

static inline void array_init(array_t* array,unsigned int item_size)
{
    array->pointer=0;
    array->size=0;
    array->next=0;
    array->item_size=item_size;
}

static inline void array_free(array_t* array)
{
    if(array->pointer)
        free(array->pointer);
    array->size=array->next=0;
}

/* make sure that memory is reserved at pointer[index*item_size] */
static inline void* array_get(array_t* array,unsigned int index) {
    if((index+1)*array->item_size>array->size) {
        int new_size=(index+32)*array->item_size;
        array->pointer=realloc(array->pointer,new_size);
        if(!array->pointer)
            return 0;
        array->size=new_size;
        array->next=index+1;
    }
    return array->pointer+index*array->item_size;
}

static inline void* array_get_next(array_t* array) {
    unsigned int next=array->next;
    void* result=array_get(array,next);
    array->next=next+1;
    return result;
}

static inline void* array_insert(array_t* array,unsigned int index,unsigned int count) {
    if((array->next+count)*array->item_size>array->size) {
        int increment=count*array->item_size;
        array->pointer=realloc(array->pointer,array->size+increment);
        if(!array->pointer)
            return 0;
        array->size+=increment;
    }
    memmove(array->pointer+(index+count)*array->item_size,
                array->pointer+index*array->item_size,
                (array->next-index)*array->item_size);
    array->next+=count;
    return array->pointer+index*array->item_size;
}

/* this performs a "roll", so that the element which was at index_from becomes
 * index_to, but the order of all other elements is preserved. */
static inline int array_roll(array_t* array,int index_to,int index_from,int count)
{
    char* buf;
    char* from;
    char* to;
    int is;

    if(!array ||
            index_to<0 || index_to>=array->next ||
            index_from<0 || index_from>=array->next)
        return -1;
    
    if(index_to==index_from)
        return 0;

    is=array->item_size;
    from=array->pointer+index_from*is;
    to=array->pointer+index_to*is;
    buf=malloc(is*count);
    memcpy(buf,from,is*count);

    if(index_to<index_from)
        memmove(to+is*count,to,from-to);
    else
        memmove(from,from+is*count,to-from);
    
    memcpy(to,buf,is*count);

    free(buf);

    return 0;
}

int array_remove(array_t* array,int index)
{
    if(array_roll(array,array->next-1,index,1))
        return -1;
    array->next--;
    return 0;
}

/* These structures are used to fake a disk and the VFAT filesystem.
 * For this reason we need to use __attribute__((packed)). */

typedef struct bootsector_t {
    uint8_t jump[3];
    uint8_t name[8];
    uint16_t sector_size;
    uint8_t sectors_per_cluster;
    uint16_t reserved_sectors;
    uint8_t number_of_fats;
    uint16_t root_entries;
    uint16_t zero;
    uint8_t media_type;
    uint16_t sectors_per_fat;
    uint16_t sectors_per_track;
    uint16_t number_of_heads;
    uint32_t hidden_sectors;
    uint32_t total_sectors;
    union {
        struct {
            uint8_t drive_number;
            uint8_t current_head;
            uint8_t signature;
            uint32_t id;
            uint8_t volume_label[11];
        } __attribute__((packed)) fat16;
        struct {
            uint32_t sectors_per_fat;
            uint16_t flags;
            uint8_t major,minor;
            uint32_t first_cluster_of_root_directory;
            uint16_t info_sector;
            uint16_t backup_boot_sector;
            uint16_t ignored;
        } __attribute__((packed)) fat32;
    } u;
    uint8_t fat_type[8];
    uint8_t ignored[0x1c0];
    uint8_t magic[2];
} __attribute__((packed)) bootsector_t;

typedef struct partition_t {
    uint8_t attributes; /* 0x80 = bootable */
    uint8_t start_head;
    uint8_t start_sector;
    uint8_t start_cylinder;
    uint8_t fs_type; /* 0x6 = FAT16, 0xb = FAT32 */
    uint8_t end_head;
    uint8_t end_sector;
    uint8_t end_cylinder;
    uint32_t start_sector_long;
    uint32_t end_sector_long;
} __attribute__((packed)) partition_t;

typedef struct mbr_t {
    uint8_t ignored[0x1be];
    partition_t partition[4];
    uint8_t magic[2];
} __attribute__((packed)) mbr_t;

typedef struct direntry_t {
    uint8_t name[8];
    uint8_t extension[3];
    uint8_t attributes;
    uint8_t reserved[2];
    uint16_t ctime;
    uint16_t cdate;
    uint16_t adate;
    uint16_t begin_hi;
    uint16_t mtime;
    uint16_t mdate;
    uint16_t begin;
    uint32_t size;
} __attribute__((packed)) direntry_t;

/* this structure are used to transparently access the files */

typedef struct mapping_t {
    /* begin is the first cluster, end is the last+1,
     * offset is the offset in the file in clusters of this slice */
    off_t begin,end,offset;
    char* filename;

    /* as s->directory is growable, no pointer may be used here */
    unsigned int dir_index;
    enum { MODE_NORMAL,MODE_UNDEFINED,MODE_MODIFIED,MODE_DELETED,MODE_DIRECTORY } mode;
} mapping_t;

/* this structure is used to hold sectors which need to be written, but it's
 * not known yet where to write them. */

typedef struct commit_t {
    uint32_t cluster_num;
    uint8_t* buf;
} commit_t;

/* write support exists for fat, direntry and file contents */
typedef enum {
    WRITE_UNDEFINED,WRITE_FAT,WRITE_DIRENTRY,WRITE_DATA
} write_action_t;

/* here begins the real VVFAT driver */

typedef struct BDRVVVFATState {
    unsigned int first_sectors_number; /* 1 for a single partition, 0x40 for a disk with partition table */
    unsigned char first_sectors[0x40*0x200];
    
    int fat_type; /* 16 or 32 */
    array_t fat,directory,mapping;
   
    unsigned int cluster_size;
    unsigned int sectors_per_cluster;
    unsigned int sectors_per_fat;
    unsigned int sectors_of_root_directory;
    unsigned int sectors_for_directory;
    unsigned int faked_sectors; /* how many sectors are faked before file data */
    uint32_t sector_count; /* total number of sectors of the partition */
    uint32_t cluster_count; /* total number of clusters of this partition */
    unsigned int first_file_mapping; /* index of the first mapping which is not a directory, but a file */
    uint32_t max_fat_value;
   
    int current_fd;
    char current_fd_is_writable; /* =0 if read only, !=0 if read/writable */
    mapping_t* current_mapping;
    unsigned char* cluster;
    unsigned int current_cluster;

    /* write support */
    array_t commit;
    /* for each file, the file contents, the direntry, and the fat entries are
     * written, but not necessarily in that order */
    write_action_t action[3];
} BDRVVVFATState;


static int vvfat_probe(const uint8_t *buf, int buf_size, const char *filename)
{
    if (strstart(filename, "fat:", NULL) ||
        strstart(filename, "fatrw:", NULL))
        return 100;
    return 0;
}

static void init_mbr(BDRVVVFATState* s)
{
    /* TODO: if the files mbr.img and bootsect.img exist, use them */
    mbr_t* real_mbr=(mbr_t*)s->first_sectors;
    partition_t* partition=&(real_mbr->partition[0]);

    memset(s->first_sectors,0,512);
   
    partition->attributes=0x80; /* bootable */
    partition->start_head=1;
    partition->start_sector=1;
    partition->start_cylinder=0;
    partition->fs_type=(s->fat_type==16?0x6:0xb); /* FAT16/FAT32 */
    partition->end_head=0xf;
    partition->end_sector=0xff; /* end sector & upper 2 bits of cylinder */;
    partition->end_cylinder=0xff; /* lower 8 bits of end cylinder */;
    partition->start_sector_long=cpu_to_le32(0x3f);
    partition->end_sector_long=cpu_to_le32(s->sector_count);

    real_mbr->magic[0]=0x55; real_mbr->magic[1]=0xaa;
}

/* dest is assumed to hold 258 bytes, and pads with 0xffff up to next multiple of 26 */
static inline int short2long_name(unsigned char* dest,const char* src)
{
    int i;
    for(i=0;i<129 && src[i];i++) {
        dest[2*i]=src[i];
        dest[2*i+1]=0;
    }
    dest[2*i]=dest[2*i+1]=0;
    for(i=2*i+2;(i%26);i++)
        dest[i]=0xff;
    return i;
}

static inline direntry_t* create_long_filename(BDRVVVFATState* s,const char* filename)
{
    char buffer[258];
    int length=short2long_name(buffer,filename),
        number_of_entries=(length+25)/26,i;
    direntry_t* entry;

    for(i=0;i<number_of_entries;i++) {
        entry=array_get_next(&(s->directory));
        entry->attributes=0xf;
        entry->reserved[0]=0;
        entry->begin=0;
        entry->name[0]=(number_of_entries-i)|(i==0?0x40:0);
    }
    for(i=0;i<length;i++) {
        int offset=(i%26);
        if(offset<10) offset=1+offset;
        else if(offset<22) offset=14+offset-10;
        else offset=28+offset-22;
        entry=array_get(&(s->directory),s->directory.next-1-(i/26));
        entry->name[offset]=buffer[i];
    }
    return array_get(&(s->directory),s->directory.next-number_of_entries);
}

/* fat functions */

static inline uint8_t fat_chksum(direntry_t* entry)
{
    uint8_t chksum=0;
    int i;

    for(i=0;i<11;i++)
        chksum=(((chksum&0xfe)>>1)|((chksum&0x01)?0x80:0))
            +(unsigned char)entry->name[i];
    
    return chksum;
}

/* if return_time==0, this returns the fat_date, else the fat_time */
static uint16_t fat_datetime(time_t time,int return_time) {
    struct tm* t;
#ifdef _WIN32
    t=localtime(&time); /* this is not thread safe */
#else
    struct tm t1;
    t=&t1;
    localtime_r(&time,t);
#endif
    if(return_time)
        return cpu_to_le16((t->tm_sec/2)|(t->tm_min<<5)|(t->tm_hour<<11));
    return cpu_to_le16((t->tm_mday)|((t->tm_mon+1)<<5)|((t->tm_year-80)<<9));
}

static inline void fat_set(BDRVVVFATState* s,unsigned int cluster,uint32_t value)
{
    if(s->fat_type==12) {
        assert(0); /* TODO */
    } else if(s->fat_type==16) {
        uint16_t* entry=array_get(&(s->fat),cluster);
        *entry=cpu_to_le16(value&0xffff);
    } else {
        uint32_t* entry=array_get(&(s->fat),cluster);
        *entry=cpu_to_le32(value);
    }
}

static inline uint32_t fat_get(BDRVVVFATState* s,unsigned int cluster)
{
    //fprintf(stderr,"want to get fat for cluster %d\n",cluster);
    if(s->fat_type==12) {
        const uint8_t* x=s->fat.pointer+cluster*3/2;
        return ((x[0]|(x[1]<<8))>>(cluster&1?4:0))&0x0fff;
    } else if(s->fat_type==16) {
        uint16_t* entry=array_get(&(s->fat),cluster);
        return le16_to_cpu(*entry);
    } else {
        uint32_t* entry=array_get(&(s->fat),cluster);
        return le32_to_cpu(*entry);
    }
}

static inline int fat_eof(BDRVVVFATState* s,uint32_t fat_entry)
{
    if(fat_entry>s->max_fat_value-8)
        return -1;
    return 0;
}

static inline void init_fat(BDRVVVFATState* s)
{
    int i;
    
    array_init(&(s->fat),(s->fat_type==32?4:2));
    array_get(&(s->fat),s->sectors_per_fat*0x200/s->fat.item_size-1);
    memset(s->fat.pointer,0,s->fat.size);
    fat_set(s,0,0x7ffffff8);
    
    for(i=1;i<s->sectors_for_directory/s->sectors_per_cluster-1;i++)
        fat_set(s,i,i+1);
    fat_set(s,i,0x7fffffff);

    switch(s->fat_type) {
        case 12: s->max_fat_value=0xfff; break;
        case 16: s->max_fat_value=0xffff; break;
        case 32: s->max_fat_value=0xfffffff; break;
        default: s->max_fat_value=0; /* error... */
    }

}

static inline int long2unix_name(unsigned char* dest,int dest_size,direntry_t* direntry_short) {
    int i=-1,j;
    int chksum=fat_chksum(direntry_short);
    while(1) {
        char* buf=(char*)(direntry_short+i);
        if((buf[0]&0x3f)!=-i || direntry_short[i].reserved[1]!=chksum ||
                direntry_short[i].attributes!=0xf) {
            if(i<-1)
                return -3;
            /* take short name */
            for(j=7;j>0 && direntry_short->name[j]==' ';j--);
            if(j+1>dest_size)
                return -1;
            strncpy(dest,direntry_short->name,j+1);
            dest+=j+1; dest_size-=j+1;
            for(j=2;j>=0 && direntry_short->extension[j]==' ';j--);
            if(j>=0) {
                if(j+2>dest_size)
                    return -1;
                dest[0]='.';
                strncpy(dest+1,direntry_short->extension,j+1);
            }
            return 0;
        }
        for(j=0;j<13;j++) {
            dest_size--;
            if(dest_size<0)
                return -2;
            dest[0]=buf[2*j+((j<5)?1:(j<11)?4:6)];
            if(dest[0]==0 && (buf[0]&0x40)!=0)
                return 0;
            dest++;
        }
        /* last entry, but no trailing \0? */
        if(buf[0]&0x40)
            return -3;
        i--;
    }
}

static inline direntry_t* create_short_filename(BDRVVVFATState* s,unsigned int directory_start,const char* filename,int is_dot)
{
    int i,long_index=s->directory.next;
    direntry_t* entry=0;
    direntry_t* entry_long=0;

    if(is_dot) {
        entry=array_get_next(&(s->directory));
        memset(entry->name,0x20,11);
        memcpy(entry->name,filename,strlen(filename));
        return entry;
    }
    
    for(i=1;i<8 && filename[i] && filename[i]!='.';i++);

    entry_long=create_long_filename(s,filename);
   
    entry=array_get_next(&(s->directory));
    memset(entry->name,0x20,11);
    strncpy(entry->name,filename,i);
    
    if(filename[i]) {
        int len=strlen(filename);
        for(i=len;i>0 && filename[i-1]!='.';i--);
        if(i>0)
            memcpy(entry->extension,filename+i,(len-i>3?3:len-i));
    }

    /* upcase & remove unwanted characters */
    for(i=10;i>=0;i--) {
        if(i==10 || i==7) for(;i>1 && entry->name[i]==' ';i--);
        if(entry->name[i]<=' ' || entry->name[i]>0x7f
                || strchr("*?<>|\":/\\[];,+='",entry->name[i]))
            entry->name[i]='_';
        else if(entry->name[i]>='a' && entry->name[i]<='z')
            entry->name[i]+='A'-'a';
    }

    /* mangle duplicates */
    while(1) {
        direntry_t* entry1=array_get(&(s->directory),directory_start);
        int j;

        for(;entry1<entry;entry1++)
            if(!(entry1->attributes&0xf) && !memcmp(entry1->name,entry->name,11))
                break; /* found dupe */
        if(entry1==entry) /* no dupe found */
            break;

        /* use all 8 characters of name */      
        if(entry->name[7]==' ') {
            int j;
            for(j=6;j>0 && entry->name[j]==' ';j--)
                entry->name[j]='~';
        }

        /* increment number */
        for(j=7;j>0 && entry->name[j]=='9';j--)
            entry->name[j]='0';
        if(j>0) {
            if(entry->name[j]<'0' || entry->name[j]>'9')
                entry->name[j]='0';
            else
                entry->name[j]++;
        }
    }

    /* calculate checksum; propagate to long name */
    if(entry_long) {
        uint8_t chksum=fat_chksum(entry);

        /* calculate anew, because realloc could have taken place */
        entry_long=array_get(&(s->directory),long_index);
        while(entry_long<entry
                    && entry_long->attributes==0xf) {
            entry_long->reserved[1]=chksum;
            entry_long++;
        }
    }

    return entry;
}

static int read_directory(BDRVVVFATState* s,const char* dirname,
                int first_cluster_of_parent)
{

    DIR* dir=opendir(dirname);
    struct dirent* entry;
    struct stat st;
    unsigned int start_of_directory=s->directory.next;
    /* mappings before first_file_mapping are directories */
    unsigned int first_directory_mapping=s->first_file_mapping;
    unsigned int first_cluster=(start_of_directory/0x10/s->sectors_per_cluster);
    int i;

    if(!dir)
        return -1;
    
    while((entry=readdir(dir))) {
        unsigned int length=strlen(dirname)+2+strlen(entry->d_name);
        char* buffer;
        direntry_t* direntry;
        int is_dot=!strcmp(entry->d_name,".");
        int is_dotdot=!strcmp(entry->d_name,"..");

        if(start_of_directory==1 && (is_dotdot || is_dot))
            continue;
        
        buffer=(char*)malloc(length);
        snprintf(buffer,length,"%s/%s",dirname,entry->d_name);

        if(stat(buffer,&st)<0) {
            free(buffer);
            continue;
        }

        /* create directory entry for this file */
        //fprintf(stderr,"create direntry at %d (cluster %d) for %s\n",s->directory.next,s->directory.next/0x10/s->sectors_per_cluster,entry->d_name);
        direntry=create_short_filename(s,start_of_directory,entry->d_name,is_dot||is_dotdot);
        direntry->attributes=(S_ISDIR(st.st_mode)?0x10:0x20);
        direntry->reserved[0]=direntry->reserved[1]=0;
        direntry->ctime=fat_datetime(st.st_ctime,1);
        direntry->cdate=fat_datetime(st.st_ctime,0);
        direntry->adate=fat_datetime(st.st_atime,0);
        direntry->begin_hi=0;
        direntry->mtime=fat_datetime(st.st_mtime,1);
        direntry->mdate=fat_datetime(st.st_mtime,0);
        if(is_dotdot)
            direntry->begin=cpu_to_le16(first_cluster_of_parent);
        else if(is_dot)
            direntry->begin=cpu_to_le16(first_cluster);
        else
            direntry->begin=cpu_to_le16(0); /* do that later */
        direntry->size=cpu_to_le32(st.st_size);

        /* create mapping for this file */
        if(!is_dot && !is_dotdot) {
            if(S_ISDIR(st.st_mode))
                s->current_mapping=(mapping_t*)array_insert(&(s->mapping),s->first_file_mapping++,1);
            else
                s->current_mapping=(mapping_t*)array_get_next(&(s->mapping));
            s->current_mapping->begin=0;
            s->current_mapping->end=st.st_size;
            s->current_mapping->offset=0;
            s->current_mapping->filename=buffer;
            s->current_mapping->dir_index=s->directory.next-1;
            s->current_mapping->mode=(S_ISDIR(st.st_mode)?MODE_DIRECTORY:MODE_UNDEFINED);
        }
    }
    closedir(dir);

    /* fill with zeroes up to the end of the cluster */
    while(s->directory.next%(0x10*s->sectors_per_cluster)) {
        direntry_t* direntry=array_get_next(&(s->directory));
        memset(direntry,0,sizeof(direntry_t));
    }

    /* reserve next cluster also (for new files) */
    for(i=0;i<0x10*s->sectors_per_cluster;i++) {
        direntry_t* direntry=array_get_next(&(s->directory));
        memset(direntry,0,sizeof(direntry_t));
    }

    /* was it the first directory? */
    if(start_of_directory==1) {
        mapping_t* mapping=array_insert(&(s->mapping),0,1);
        mapping->filename=strdup(dirname);
        mapping->mode=MODE_DIRECTORY;
        mapping->begin=0;
        mapping->end=1;
        mapping->offset=0;
        mapping->dir_index=0xffffffff;
        s->sectors_of_root_directory=s->directory.next/0x10;
    }

    /* recurse directories */
    {
        int i;

        //fprintf(stderr,"iterating subdirectories of %s (first cluster %d): %d to %d\n",dirname,first_cluster,first_directory_mapping,last_directory_mapping);
        for(i=first_directory_mapping;i<s->first_file_mapping;i++) {
            mapping_t* mapping=array_get(&(s->mapping),i);
            direntry_t* direntry=array_get(&(s->directory),mapping->dir_index);
            /* the directory to be read can add more subdirectories */
            int last_dir_mapping=s->first_file_mapping;
            
            assert(mapping->mode==MODE_DIRECTORY);
            /* first, tell the mapping where the directory will start */
            mapping->begin=s->directory.next/0x10/s->sectors_per_cluster;
            if(i>0) {
                mapping[-1].end=mapping->begin;
                assert(mapping[-1].begin<mapping->begin);
            }
            /* then tell the direntry */
            direntry->begin=cpu_to_le16(mapping->begin);
            //fprintf(stderr,"read directory %s (begin %d)\n",mapping->filename,(int)mapping->begin);
            /* then read it */
            if(read_directory(s,mapping->filename,first_cluster))
                return -1;

            if(last_dir_mapping!=s->first_file_mapping) {
                int diff=s->first_file_mapping-last_dir_mapping;
                assert(diff>0);

                if(last_dir_mapping!=i+1) {
                    int count=last_dir_mapping-i-1;
                    int to=s->first_file_mapping-count;

                    assert(count>0);
                    assert(to>i+1);
                    array_roll(&(s->mapping),to,i+1,count);
                    /* could have changed due to realloc */
                    mapping=array_get(&(s->mapping),i);
                    mapping->end=mapping[1].begin;
                }
                i+=diff;
            }
        }
    }

    return 0;
}

static int init_directory(BDRVVVFATState* s,const char* dirname)
{
    bootsector_t* bootsector=(bootsector_t*)&(s->first_sectors[(s->first_sectors_number-1)*0x200]);
    unsigned int i;
    unsigned int cluster;

    memset(&(s->first_sectors[0]),0,0x40*0x200);

    /* TODO: if FAT32, this is probably wrong */
    s->sectors_per_fat=0xfc;
    s->sectors_per_cluster=0x10;
    s->cluster_size=s->sectors_per_cluster*0x200;
    s->cluster=malloc(s->cluster_size);
    
    array_init(&(s->mapping),sizeof(mapping_t));
    array_init(&(s->directory),sizeof(direntry_t));
    array_init(&(s->commit),sizeof(commit_t));

    /* add volume label */
    {
        direntry_t* entry=array_get_next(&(s->directory));
        entry->attributes=0x28; /* archive | volume label */
        snprintf(entry->name,11,"QEMU VVFAT");
    }

    if(read_directory(s,dirname,0))
        return -1;

    /* make sure that the number of directory entries is multiple of 0x200/0x20 (to fit the last sector exactly) */
    s->sectors_for_directory=s->directory.next/0x10;

    s->faked_sectors=s->first_sectors_number+s->sectors_per_fat*2+s->sectors_for_directory;
    s->cluster_count=(s->sector_count-s->faked_sectors)/s->sectors_per_cluster;

    /* Now build FAT, and write back information into directory */
    init_fat(s);

    cluster=s->sectors_for_directory/s->sectors_per_cluster;
    assert(s->sectors_for_directory%s->sectors_per_cluster==0);

    /* set the end of the last read directory */
    if(s->first_file_mapping>0) {
        mapping_t* mapping=array_get(&(s->mapping),s->first_file_mapping-1);
        mapping->end=cluster;
    }

    for(i=1;i<s->mapping.next;i++) {
        mapping_t* mapping=array_get(&(s->mapping),i);
        direntry_t* direntry=array_get(&(s->directory),mapping->dir_index);
        if(mapping->mode==MODE_DIRECTORY) {
            /* directory */
            int i;
#ifdef DEBUG
            fprintf(stderr,"assert: %s %d < %d\n",mapping->filename,(int)mapping->begin,(int)mapping->end);
#endif
            assert(mapping->begin<mapping->end);
            for(i=mapping->begin;i<mapping->end-1;i++)
                fat_set(s,i,i+1);
            fat_set(s,i,0x7fffffff);
        } else {
            /* as the space is virtual, we can be sloppy about it */
            unsigned int end_cluster=cluster+mapping->end/s->cluster_size;

            if(end_cluster>=s->cluster_count) {
                fprintf(stderr,"Directory does not fit in FAT%d\n",s->fat_type);
                return -1;
            }
            mapping->begin=cluster;
            mapping->mode=MODE_NORMAL;
            mapping->offset=0;
            direntry->size=cpu_to_le32(mapping->end);
            if(direntry->size==0) {
                direntry->begin=0;
                mapping->end=cluster;
                continue;
            }

            direntry->begin=cpu_to_le16(cluster);
            mapping->end=end_cluster+1;
            for(;cluster<end_cluster;cluster++)
                fat_set(s,cluster,cluster+1);
            fat_set(s,cluster,0x7fffffff);
            cluster++;
        }
    }

    s->current_mapping=0;

    bootsector->jump[0]=0xeb;
    bootsector->jump[1]=0x3e;
    bootsector->jump[2]=0x90;
    memcpy(bootsector->name,"QEMU    ",8);
    bootsector->sector_size=cpu_to_le16(0x200);
    bootsector->sectors_per_cluster=s->sectors_per_cluster;
    bootsector->reserved_sectors=cpu_to_le16(1);
    bootsector->number_of_fats=0x2; /* number of FATs */
    bootsector->root_entries=cpu_to_le16(s->sectors_of_root_directory*0x10);
    bootsector->zero=0;
    bootsector->media_type=(s->first_sectors_number==1?0xf0:0xf8); /* media descriptor */
    bootsector->sectors_per_fat=cpu_to_le16(s->sectors_per_fat);
    bootsector->sectors_per_track=cpu_to_le16(0x3f);
    bootsector->number_of_heads=cpu_to_le16(0x10);
    bootsector->hidden_sectors=cpu_to_le32(s->first_sectors_number==1?0:0x3f);
    /* TODO: if FAT32, adjust */
    bootsector->total_sectors=cpu_to_le32(s->sector_count);

    /* TODO: if FAT32, this is wrong */
    bootsector->u.fat16.drive_number=0x80; /* assume this is hda (TODO) */
    bootsector->u.fat16.current_head=0;
    bootsector->u.fat16.signature=0x29;
    bootsector->u.fat16.id=cpu_to_le32(0xfabe1afd);

    memcpy(bootsector->u.fat16.volume_label,"QEMU VVFAT ",11);
    memcpy(bootsector->fat_type,(s->fat_type==12?"FAT12   ":s->fat_type==16?"FAT16   ":"FAT32   "),8);
    bootsector->magic[0]=0x55; bootsector->magic[1]=0xaa;

    return 0;
}

static int vvfat_open(BlockDriverState *bs, const char* dirname)
{
    BDRVVVFATState *s = bs->opaque;
    int i;

    /* TODO: automatically determine which FAT type */
    s->fat_type=16;
    s->sector_count=0xec04f;

    s->current_cluster=0xffffffff;
    s->first_file_mapping=0;

    /* TODO: if simulating a floppy, this is 1, because there is no partition table */
    s->first_sectors_number=0x40;
    
    if (strstart(dirname, "fat:", &dirname)) {
        /* read only is the default for safety */
        bs->read_only = 1;
    } else if (strstart(dirname, "fatrw:", &dirname)) {
        /* development only for now */
        bs->read_only = 0;
    } else {
        return -1;
    }
    if(init_directory(s,dirname))
        return -1;

    if(s->first_sectors_number==0x40)
        init_mbr(s);

    /* TODO: this could be wrong for FAT32 */
    bs->cyls=1023; bs->heads=15; bs->secs=63;
    bs->total_sectors=bs->cyls*bs->heads*bs->secs;

    /* write support */
    for(i=0;i<3;i++)
        s->action[i]=WRITE_UNDEFINED;
    return 0;
}

static inline void vvfat_close_current_file(BDRVVVFATState *s)
{
    if(s->current_mapping) {
        s->current_mapping = 0;
        close(s->current_fd);
    }
}

/* mappings between index1 and index2-1 are supposed to be ordered
 * return value is the index of the last mapping for which end>cluster_num
 */
static inline int find_mapping_for_cluster_aux(BDRVVVFATState* s,int cluster_num,int index1,int index2)
{
    int index3=index1+1;
    //fprintf(stderr,"find_aux: cluster_num=%d, index1=%d,index2=%d\n",cluster_num,index1,index2);
    while(1) {
        mapping_t* mapping;
        index3=(index1+index2)/2;
        mapping=array_get(&(s->mapping),index3);
        //fprintf(stderr,"index3: %d = (%d+%d)/2, end: %d\n",index3,index1,index2,(int)mapping->end);
        if(mapping->end>cluster_num) {
            assert(index2!=index3 || index2==0);
            if(index2==index3)
                return index2;
            index2=index3;
        } else {
            if(index1==index3)
                return index2;
            index1=index3;
        }
        assert(index1<=index2);
    }
}

static inline mapping_t* find_mapping_for_cluster(BDRVVVFATState* s,int cluster_num)
{
    int index=find_mapping_for_cluster_aux(s,cluster_num,0,s->mapping.next);
    mapping_t* mapping;
    if(index>=s->mapping.next)
        return 0;
    mapping=array_get(&(s->mapping),index);
    if(mapping->begin>cluster_num)
        return 0;
    return mapping;
}

static int open_file(BDRVVVFATState* s,mapping_t* mapping,int flags)
{
    if(!mapping)
        return -1;
    assert(flags==O_RDONLY || flags==O_RDWR);
    if(!s->current_mapping ||
            strcmp(s->current_mapping->filename,mapping->filename) ||
            (flags==O_RDWR && !s->current_fd_is_writable)) {
        /* open file */
        int fd = open(mapping->filename, flags | O_BINARY | O_LARGEFILE);
        if(fd<0)
            return -1;
        vvfat_close_current_file(s);
        s->current_fd = fd;
        s->current_fd_is_writable = (flags==O_RDWR?-1:0);
        s->current_mapping = mapping;
    }
    return 0;
}

static inline int read_cluster(BDRVVVFATState *s,int cluster_num)
{
    if(s->current_cluster != cluster_num) {
        int result=0;
        off_t offset;
        if(!s->current_mapping
                || s->current_mapping->begin>cluster_num
                || s->current_mapping->end<=cluster_num) {
            /* binary search of mappings for file */
            mapping_t* mapping=find_mapping_for_cluster(s,cluster_num);
            if(open_file(s,mapping,O_RDONLY))
                return -2;
        }

        offset=s->cluster_size*(cluster_num-s->current_mapping->begin+s->current_mapping->offset);
        if(lseek(s->current_fd, offset, SEEK_SET)!=offset)
            return -3;
        result=read(s->current_fd,s->cluster,s->cluster_size);
        if(result<0) {
            s->current_cluster = -1;
            return -1;
        }
        s->current_cluster = cluster_num;
    }
    return 0;
}

static int vvfat_read(BlockDriverState *bs, int64_t sector_num, 
                    uint8_t *buf, int nb_sectors)
{
    BDRVVVFATState *s = bs->opaque;
    int i;

    //    fprintf(stderr,"vvfat_read: sector %d+%d\n",(int)sector_num,nb_sectors);

    for(i=0;i<nb_sectors;i++,sector_num++) {
        if(sector_num<s->faked_sectors) {
                if(sector_num<s->first_sectors_number)
                    memcpy(buf+i*0x200,&(s->first_sectors[sector_num*0x200]),0x200);
                else if(sector_num-s->first_sectors_number<s->sectors_per_fat)
                        memcpy(buf+i*0x200,&(s->fat.pointer[(sector_num-s->first_sectors_number)*0x200]),0x200);
                else if(sector_num-s->first_sectors_number-s->sectors_per_fat<s->sectors_per_fat)
                        memcpy(buf+i*0x200,&(s->fat.pointer[(sector_num-s->first_sectors_number-s->sectors_per_fat)*0x200]),0x200);
                else if(sector_num-s->first_sectors_number-s->sectors_per_fat*2<s->sectors_for_directory)
                        memcpy(buf+i*0x200,&(s->directory.pointer[(sector_num-s->first_sectors_number-s->sectors_per_fat*2)*0x200]),0x200);
        } else {
            uint32_t sector=sector_num-s->first_sectors_number-s->sectors_per_fat*2,
                sector_offset_in_cluster=(sector%s->sectors_per_cluster),
                cluster_num=sector/s->sectors_per_cluster;
                if(read_cluster(s, cluster_num) != 0) {
                        //fprintf(stderr,"failed to read cluster %d\n",(int)cluster_num);
                        // TODO: strict: return -1;
                        memset(buf+i*0x200,0,0x200);
                        continue;
                }
                memcpy(buf+i*0x200,s->cluster+sector_offset_in_cluster*0x200,0x200);
        }
    }
    return 0;
}

static void print_direntry(direntry_t* direntry)
{
    if(!direntry)
        return;
    if(direntry->attributes==0xf) {
        unsigned char* c=(unsigned char*)direntry;
        int i;
        for(i=1;i<11 && c[i] && c[i]!=0xff;i+=2)
            fputc(c[i],stderr);
        for(i=14;i<26 && c[i] && c[i]!=0xff;i+=2)
            fputc(c[i],stderr);
        for(i=28;i<32 && c[i] && c[i]!=0xff;i+=2)
            fputc(c[i],stderr);
        fputc('\n',stderr);
    } else {
        int i;
        for(i=0;i<11;i++)
            fputc(direntry->name[i],stderr);
        fprintf(stderr,"attributes=0x%02x begin=%d size=%d\n",
                direntry->attributes,
                direntry->begin,direntry->size);
    }
}

static void print_changed_sector(BlockDriverState *bs,int64_t sector_num,const uint8_t *buf)
{
    BDRVVVFATState *s = bs->opaque;

    if(sector_num<s->first_sectors_number)
        return;
    if(sector_num<s->first_sectors_number+s->sectors_per_fat*2) {
        int first=((sector_num-s->first_sectors_number)%s->sectors_per_fat);
        int first_fat_entry=first*0x200/2;
        int i;

        fprintf(stderr, "fat:\n");
        for(i=0;i<0x200;i+=2) {
            uint16_t* f=array_get(&(s->fat),first_fat_entry+i/2);
            if(memcmp(buf+i,f,2))
                fprintf(stderr,"%d(%d->%d) ",first_fat_entry+i/2,*f,*(uint16_t*)(buf+i));
        }
        fprintf(stderr, "\n");
    } else if(sector_num<s->faked_sectors) {
        direntry_t* d=(direntry_t*)buf;
        int i;
        fprintf(stderr, "directory:\n");
        for(i=0;i<0x200/sizeof(direntry_t);i++) {
            direntry_t* d_old=(direntry_t*)(s->directory.pointer+0x200*(sector_num-s->first_sectors_number-s->sectors_per_fat*2)+i*sizeof(direntry_t));
            if(memcmp(d+i,d_old,sizeof(direntry_t))) {
                fprintf(stderr, "old: "); print_direntry(d_old);
                fprintf(stderr, "new: "); print_direntry(d+i);
                fprintf(stderr, "\n");
            }
        }
    } else {
        int sec=(sector_num-s->first_sectors_number-2*s->sectors_per_fat);
        fprintf(stderr, "\tcluster: %d(+%d sectors)\n",sec/s->sectors_per_cluster,sec%s->sectors_per_cluster);
    }
}

char direntry_is_free(const direntry_t* direntry)
{
    return direntry->name[0]==0 || direntry->name[0]==0xe5;
}

/* TODO: use this everywhere */
static inline uint32_t begin_of_direntry(direntry_t* direntry)
{
    return le16_to_cpu(direntry->begin)|(le16_to_cpu(direntry->begin_hi)<<16);
}

int consistency_check1(BDRVVVFATState *s) {
    /* check all mappings */
    int i;
    for(i=0;i<s->mapping.next;i++) {
        mapping_t* mapping=array_get(&(s->mapping),i);
        int j;
        for(j=mapping->begin;j<mapping->end-1;j++)
            assert(fat_get(s,j)==j+1);
        assert(fat_get(s,j)==(0x7fffffff&s->max_fat_value));
    }
    return 0;
}

int consistency_check2(BDRVVVFATState *s) {
    /* check fat entries: consecutive fat entries should be mapped in one mapping */
    int i;
    /* TODO: i=0 (mappings for direntries have to be sorted) */
    for(i=s->sectors_for_directory/s->sectors_per_cluster;i<s->fat.next-1;i++) {
        uint32_t j=fat_get(s,i);
        if(j!=i+1 && j!=0 && !fat_eof(s,j)) {
            mapping_t* mapping=find_mapping_for_cluster(s,i+1);
            assert(mapping->begin==i+1);
        }
    }
    return 0;
}

int consistency_check3(BDRVVVFATState *s) {
    /* check that for each file there is exactly one mapping per cluster */
    int i,count_non_next=0;
    for(i=0;i<s->mapping.next;i++) {
        mapping_t* mapping=array_get(&(s->mapping),i);
        /* TODO: when directories are correctly adapted, add them here */
        assert(mapping->begin<mapping->end);
        if(mapping->mode==MODE_NORMAL) {
            int j,count=0,count_next=0;
            for(j=0;j<s->mapping.next;j++) {
                mapping_t* other=array_get(&(s->mapping),j);
                if(mapping->begin<other->end&&mapping->end>other->begin)
                    count++;
                if(mapping->end==other->begin)
                    count_next++;
            }
            assert(count==1); /* no overlapping mappings */
            assert(count_next==1 || count_next==0); /* every mapping except the last one has a successor */
            if(!count_next)
                count_non_next++;
        }
    }
    assert(count_non_next==1); /* only one last mapping */
    return 0;
}

static inline commit_t* commit_get_next(BDRVVVFATState* s)
{
    commit_t* commit=array_get_next(&(s->commit));
    if((commit->buf=malloc(s->cluster_size))==0) {
        /* out of memory */
        s->commit.next--;
        return 0;
    }
    return commit;
}

int commit_remove(BDRVVVFATState* s,commit_t* commit)
{
    int index=commit-(commit_t*)s->commit.pointer;
    free(commit->buf);
    if(array_roll(&(s->commit),s->commit.next-1,index,1))
        return -1;
    s->commit.next--;
    return 0;
}

/* TODO: the plan for write support:
 *
 * it seems that the direntries are written first, then the data is committed
 * to the free sectors, then fat 1 is updated, then fat2.
 *
 * Plan: when sectors are written, do the following:
 *
 * - if they are in a directory, check if the entry has changed. if yes,
 *   look what has changed (different strategies for name, begin & size).
 *
 *   if it is new (old entry is only 0's or has E5 at the start), create it,
 *   and also create mapping, but in a special mode "undefined" (TODO),
 *   because we cannot know which clusters belong to it yet.
 *
 *   if it is zeroed, or has E5 at the start, look if has just moved. If yes,
 *   copy the entry to the new position. If no, delete the file.
 *
 * - if they are in data, and the cluster is undefined, add it to the commit
 *   list. if the cluster is defined (find_mapping), then write it into the
 *   corresponding file.
 *
 *   If it is the last cluster (TODO: add a function
 *   fat_get(s,cluster); ), make sure not to write a complete cluster_size.
 *
 *   If the data is in current_cluster, update s->cluster.
 *
 * - if they are in fat 1, update mappings, look in the commit list
 *   (assertions!) and if the cluster is now known (or changed from undefined
 *   state to defined state, like when begin or size changed in a direntry),
 *   write it.
 *
 * - if they are in fat 2, make sure they match with current fat.
 *
 */

void mapping_modify_from_direntry(BDRVVVFATState* s,mapping_t* mapping,direntry_t* direntry)
{
    int begin=le16_to_cpu(direntry->begin),
        end=begin+le32_to_cpu(direntry->size)/s->cluster_size+1,
        i;
    mapping->mode = MODE_MODIFIED;
    /* TODO: what if begin==0 (size==0)? */
    mapping->begin = begin;
    /* TODO: why not just mapping->end = begin+1 ? */
    for(i=begin+1;i<end && (fat_get(s,i)==0 || fat_get(s,i)==i+1);i++);
    mapping->end = i;
}

mapping_t* find_mapping_for_direntry(BDRVVVFATState* s,direntry_t* direntry)
{
    int i;
    int dir_index=direntry-((direntry_t*)s->directory.pointer);
    
    /* TODO: support allocation for new clusters for directories (new/larger directory */
    assert(dir_index<0x200/0x20*s->sectors_for_directory);
    
    for(i=0;i<s->mapping.next;i++) {
        mapping_t* mapping=array_get(&(s->mapping),i);
        if(mapping->dir_index==dir_index && mapping->offset==0 &&
                mapping->mode!=MODE_UNDEFINED)
            return mapping;
    }
    return 0;
}

static inline uint32_t sector2cluster(BDRVVVFATState* s,off_t sector_num)
{
    return (sector_num-s->first_sectors_number-2*s->sectors_per_fat)/s->sectors_per_cluster;
}

static inline uint32_t sector_offset_in_cluster(BDRVVVFATState* s,off_t sector_num)
{
    return (sector_num-s->first_sectors_number-2*s->sectors_per_fat)%s->sectors_per_cluster;
}

static commit_t* get_commit_for_cluster(BDRVVVFATState* s,uint32_t cluster_num)
{
    int i;
    for(i=0;i<s->commit.next;i++) {
        commit_t* commit=array_get(&(s->commit),i);
        if(commit->cluster_num==cluster_num)
            return commit;
    }
    return 0;
}

static inline commit_t* create_or_get_commit_for_sector(BDRVVVFATState* s,off_t sector_num)
{
    int i;
    commit_t* commit;
    uint32_t cluster_num=sector2cluster(s,sector_num);

    for(i=0;i<s->commit.next;i++) {
        commit=array_get(&(s->commit),i);
        if(commit->cluster_num==cluster_num)
            return commit;
    }

    commit=commit_get_next(s);
    commit->cluster_num=cluster_num;
    /* we can ignore read errors here */
    read_cluster(s,cluster_num);
    memcpy(commit->buf,s->cluster,s->cluster_size);
    return commit;
}

static direntry_t* get_direntry_for_mapping(BDRVVVFATState* s,mapping_t* mapping)
{
    if(mapping->mode==MODE_UNDEFINED)
        return 0;
    if(mapping->dir_index>=0x200/0x20*s->sectors_for_directory)
        return 0;
    return (direntry_t*)(s->directory.pointer+sizeof(direntry_t)*mapping->dir_index);
}

static void print_mappings(BDRVVVFATState* s)
{
    int i;
    fprintf(stderr,"mapping:\n");
    for(i=0;i<s->mapping.next;i++) {
        mapping_t* m=array_get(&(s->mapping),i);
        direntry_t* d=get_direntry_for_mapping(s,m);
        fprintf(stderr,"%02d %d-%d (%d) %s (dir: %d)",i,(int)m->begin,(int)m->end,(int)m->offset,m->filename,m->dir_index);
        print_direntry(d);
        fprintf(stderr,"\n");
    }
    fprintf(stderr,"mappings end.\n");
}

/* TODO: statify all functions */

/* This function is only meant for file contents.
 * It will return an error if used for other sectors. */
static int write_cluster(BDRVVVFATState* s,uint32_t cluster_num,const uint8_t* buf)
{
    /* sector_offset is the sector_num relative to the first cluster */
    mapping_t* mapping=find_mapping_for_cluster(s,cluster_num);
    direntry_t* direntry;
    int next_cluster,write_size,last_cluster;
    off_t offset;

    /* if this cluster is free, return error */
    next_cluster=fat_get(s,cluster_num);
    if(next_cluster<2)
        return -1;
    
    /* TODO: MODE_DIRECTORY */
    if(!mapping || mapping->mode==MODE_UNDEFINED || mapping->mode==MODE_DIRECTORY)
        return -1;
    direntry=get_direntry_for_mapping(s,mapping);
    if(!direntry)
        return -2;

    /* get size to write */
    last_cluster=fat_eof(s,next_cluster);
    write_size=!last_cluster?s->cluster_size:
        (le32_to_cpu(direntry->size)%s->cluster_size);
    if(write_size<=0)
        return 0;
    //fprintf(stderr,"next_cluster: %d (%d), write_size: %d, %d, %d\n",next_cluster,s->max_fat_value-8,write_size,direntry->size,s->cluster_size);

    if(open_file(s,mapping,O_RDWR))
        return -4;
   
    offset=(cluster_num-mapping->begin+mapping->offset)*s->cluster_size;
    if(lseek(s->current_fd,offset,SEEK_SET)!=offset)
        return -3;
    if(write(s->current_fd,buf,write_size)!=write_size) {
        lseek(s->current_fd,0,SEEK_END);
        vvfat_close_current_file(s);
        return -2;
    }

    /* seek to end of file, so it doesn't get truncated */
    if(!last_cluster)
        lseek(s->current_fd,0,SEEK_END);
    else {
        ftruncate(s->current_fd,le32_to_cpu(direntry->size));
        vvfat_close_current_file(s);
    }

    /* update s->cluster if necessary */
    if(cluster_num==s->current_cluster && s->cluster!=buf)
        memcpy(s->cluster,buf,s->cluster_size);

    return 0;
}

/* this function returns !=0 on error */
int mapping_is_consistent(BDRVVVFATState* s,mapping_t* mapping)
{
    direntry_t* direntry=get_direntry_for_mapping(s,mapping);
    uint32_t cluster_count=0;
    int commit_count=0; /* number of commits for this file (we also write incomplete files; think "append") */
    //fprintf(stderr,"check direntry for %s\n",mapping->filename);
    while(mapping) {
        int i;
        assert(mapping->begin<mapping->end);
        for(i=mapping->begin;i<mapping->end-1;i++) {
            if(i<=0 || fat_get(s,i)!=i+1) {
                /*fprintf(stderr,"the fat mapping of %d is not %d, but %d\n",
                        i,i+1,fat_get(s,i));*/
                return -1;
            }
            if(get_commit_for_cluster(s,i))
                commit_count++;
        }
        if(get_commit_for_cluster(s,i))
            commit_count++;

        cluster_count+=mapping->end-mapping->begin;
        
        i=fat_get(s,mapping->end-1);
        if(fat_eof(s,i))
            break;

        mapping=find_mapping_for_cluster(s,i);
        if(!mapping) {
            //fprintf(stderr,"No mapping found for %d\n",i);
            print_mappings(s);
            return -2;
        }
    }

    if(cluster_count!=(le32_to_cpu(direntry->size)+s->cluster_size-1)/s->cluster_size) {
        //fprintf(stderr,"cluster_count is %d, but size is %d\n",cluster_count,le32_to_cpu(direntry->size));
        return -3;
    }

    if(commit_count==0)
        return -4;

    //fprintf(stderr,"okay\n");
    return 0;
}

/* TODO: remember what comes third, and what's first in this OS:
 * FAT, direntry or data.
 * If the last written sector is either last in cluster or sector_num+nb_sectors-1,
 *      - commit every cluster for this file if mapping_is_consistent()==0
 *      - if the last written sector is first_action, and last_action=third_action, clear commit
 */

static int commit_cluster_aux(BDRVVVFATState* s,commit_t* commit)
{
    int result=write_cluster(s,commit->cluster_num,commit->buf);
    return result;
}


static int commit_cluster(BDRVVVFATState* s,uint32_t cluster_num)
{
    commit_t* commit;

    /* commit the sectors of this cluster */
    commit=get_commit_for_cluster(s,cluster_num);
    if(commit)
        return commit_cluster_aux(s,commit);
    return 0;
}

/* this function checks the consistency for the direntry which belongs to
 * the mapping. if everything is found consistent, the data is committed.
 * this returns 0 if no error occurred (even if inconsistencies were found) */
static inline int commit_data_if_consistent(BDRVVVFATState* s,mapping_t* mapping,write_action_t action)
{
    direntry_t* direntry;
    
    if(!mapping)
        return 0;

    //fprintf(stderr,"7\n");
#define d(x) fprintf(stderr,#x "\n")
    direntry=get_direntry_for_mapping(s,mapping);

    //d(8);

    assert(action==WRITE_FAT || action==WRITE_DIRENTRY || action==WRITE_DATA);

    //d(9);
    //fprintf(stderr,"mapping: 0x%x s=0x%x\n",(uint32_t)mapping,(uint32_t)s);
    /*fprintf(stderr,"commit? file=%s, action=%s\n",
            mapping->filename,action==WRITE_FAT?"fat":action==WRITE_DIRENTRY?"direntry":"data");*/

    //d(10);
    if(s->action[2]==WRITE_UNDEFINED) {
        int i;
        for(i=2;i>0 && s->action[i-1]==WRITE_UNDEFINED;i--);
        if(i>0 && action!=s->action[i-1])
            s->action[i]=action;
        assert(i<2 || s->action[0]!=s->action[2]);
    }
    //d(11);
    
    if(mapping_is_consistent(s,mapping)==0) {
        uint32_t cluster_num=begin_of_direntry(direntry);
        off_t remaining_bytes=le32_to_cpu(direntry->size);
        //fprintf(stderr,"the data for %s was found consistent\n",mapping->filename);
        while(remaining_bytes>0) {
            commit_t* commit=get_commit_for_cluster(s,cluster_num);
            if(!commit)
                continue;
                
            //fprintf(stderr,"commit_cluster %d (%d), remaining: %d\n",cluster_num,s->max_fat_value-15,(int)remaining_bytes);
            assert(cluster_num>1);
            assert(cluster_num<s->max_fat_value-15);
            if(commit_cluster(s,cluster_num)) {
                fprintf(stderr,"error committing cluster %d\n",cluster_num);
                return -1;
            }
            cluster_num=fat_get(s,cluster_num);
            remaining_bytes-=s->cluster_size;
            /* TODO: if(action==s->action[2]) {
                commit_t* commit=get_commit_for_cluster(s,cluster_num);
                commit_remove(s,commit);
            } */
        }
    }
    //print_mappings(s);
    //fprintf(stderr,"finish vvfat_write\n");
    return 0;
}

static int vvfat_write(BlockDriverState *bs, int64_t sector_num, 
                    const uint8_t *buf, int nb_sectors)
{
    BDRVVVFATState *s = bs->opaque;
    int i;

    /* fprintf(stderr,"vvfat_write %d+%d (%s)\n",(int)sector_num,nb_sectors,
                    (sector_num>=s->faked_sectors?"data":
                     (sector_num>=s->first_sectors_number+2*s->sectors_per_fat?"directory":
                      (sector_num>=s->first_sectors_number+s->sectors_per_fat?"fat 2":
                       (sector_num>=s->first_sectors_number?"fat 1":"boot sector"))))); */

    for(i=0;i<nb_sectors;i++,sector_num++,buf+=0x200) {
        print_changed_sector(bs,sector_num,buf);

        if(sector_num<s->first_sectors_number) {
            /* change the bootsector or partition table? no! */
            return -1;
        } else if(sector_num<s->first_sectors_number+s->sectors_per_fat) {
            /* FAT 1 */
            int fat_entries_per_cluster=s->cluster_size*8/s->fat_type;
            int first_cluster=(sector_num-s->first_sectors_number)*fat_entries_per_cluster,i;
            mapping_t* mapping=0;

            /* write back */
            memcpy(s->fat.pointer+0x200*(sector_num-s->first_sectors_number),
                    buf,0x200);

            /* for each changed FAT entry, */
            for(i=0;i<fat_entries_per_cluster;i++) {
                int new_value;
                
                /* TODO: MODE_DIRENTRY */
                if(first_cluster+i<s->sectors_for_directory/s->sectors_per_cluster)
                    continue;

                new_value=fat_get(s,first_cluster+i);

                /* check the current fat entry */
                if(new_value<2 || (new_value>=s->max_fat_value-0xf && !fat_eof(s,new_value))) {
                    /* free, reserved or bad cluster */
                    mapping=find_mapping_for_cluster(s,first_cluster+i);
                    //assert(!mapping || mapping->mode==MODE_DELETED);
                    if(mapping && mapping->mode==MODE_DELETED &&
                            first_cluster+i+1==mapping->end)
                        array_remove(&(s->mapping),mapping-(mapping_t*)s->mapping.pointer);
                    mapping=0;
                    continue;
                }

                /* get the mapping for the current entry */
                if(!mapping || mapping->begin>new_value || mapping->end<=new_value) {
                    mapping=find_mapping_for_cluster(s,first_cluster+i);
                }

                print_mappings(s);
                fprintf(stderr,"fat_get(%d)=%d\n",first_cluster+i,new_value);
                /* TODO: what if there's no mapping? this is valid. */
                /* TODO: refactor the rest of this clause so it can be called when the direntry changes, too */
                assert(mapping);

                if(new_value>1 && new_value<s->max_fat_value-0xf) {
                    /* the cluster new_value points to is valid */

                    if(first_cluster+i+1==new_value) {
                        /* consecutive cluster */
                        if(mapping->end<=new_value)
                            mapping->end=new_value+1;
                    } else {
                        mapping_t* next_mapping;
                        
                        /* the current mapping ends here */
                        mapping->end=first_cluster+i+1;
                        
                        /* the next mapping */
                        next_mapping=find_mapping_for_cluster(s,new_value);
                        if(next_mapping) {
                            assert(mapping!=next_mapping);
                            /* assert next mapping's filename is the same */
                            assert(next_mapping->filename==mapping->filename);
                            assert(next_mapping->dir_index==mapping->dir_index);
                            /* assert next mapping is MODIFIED or UNDEFINED */
                            assert(next_mapping->mode==MODE_MODIFIED || next_mapping->mode==MODE_UNDEFINED);
                        } else {
                            int index=find_mapping_for_cluster_aux(s,new_value,0,s->mapping.next);
                            next_mapping=array_insert(&(s->mapping),index,1);
                            next_mapping->filename=mapping->filename;
                            next_mapping->dir_index=mapping->dir_index;
                            next_mapping->mode=MODE_MODIFIED;
                            next_mapping->begin=0;
                        }
                        /* adjust offset of next mapping */
                        next_mapping->offset=mapping->offset+mapping->end-mapping->begin;
                        /* set begin and possible end */
                        if(next_mapping->begin!=new_value) {
                            next_mapping->begin=new_value;
                            next_mapping->end=new_value+1;
                        }
                        if(commit_data_if_consistent(s,mapping,WRITE_FAT))
                            return -4;
                        mapping=0;
                    }
                } else if(fat_eof(s,new_value)) {
                    /* the last cluster of the file */
                    mapping->end=first_cluster+i+1;
                    if(commit_data_if_consistent(s,mapping,WRITE_FAT))
                        return -4;
                    mapping=0;
                }
            }
        } else if(sector_num<s->first_sectors_number+2*s->sectors_per_fat) {
            /* FAT 2: check if it is the same as FAT 1 */
            if(memcmp(array_get(&(s->fat),sector_num-s->first_sectors_number),buf,0x200))
                return -1; /* mismatch */
        } else if(sector_num<s->faked_sectors) {
            /* direntry */
            /* - if they are in a directory, check if the entry has changed.
             *   if yes, look what has changed (different strategies for name,
             *   begin & size).
             *
             *   if it is new (old entry is only 0's or has E5 at the start),
             *   create it, and also create mapping, but in a special mode
             *   "undefined", because we cannot know which clusters belong
             *   to it yet.
             *
             *   if it is zeroed, or has E5 at the start, look if has just
             *   moved. If yes, copy the entry to the new position. If no,
             *   delete the file.
             */
            mapping_t* dir_mapping=find_mapping_for_cluster(s,sector2cluster(s,sector_num));
            direntry_t *original=array_get(&(s->directory),sector_num-s->first_sectors_number-2*s->sectors_per_fat);
            direntry_t *new_=(direntry_t*)buf;
            int first_dir_index=(sector_num-s->first_sectors_number-2*s->sectors_per_fat)*0x200/0x20;
            int j;

#if 0
            fprintf(stderr,"direntry: consistency check\n");

            if(s->commit.next==0) {
                consistency_check1(s);
                consistency_check2(s);
                consistency_check3(s);
            }
#endif

            assert(sizeof(direntry_t)==0x20);

            for(j=0;j<0x200/0x20;j++) {
                //fprintf(stderr,"compare direntry %d: 0x%x,0x%x\n",j,(uint32_t)original+j,(uint32_t)new_+j);
                if(memcmp(original+j,new_+j,sizeof(direntry_t))) {
                    //fprintf(stderr,"different\n");
                    /* TODO: in create_short_filename, 0xe5->0x05 is not yet handled! */
                    if(direntry_is_free(original+j)) {
                        mapping_t* mapping;
                        char buffer[4096];
                        int fd,i;

                        if(new_[j].attributes==0xf)
                            continue; /* long entry */

                        print_mappings(s);
                        //fprintf(stderr,"sector: %d cluster: %d\n",(int)sector_num,(int)sector2cluster(s,sector_num));

                        /* construct absolute path */
                        strncpy(buffer,dir_mapping->filename,4096);
                        i=strlen(buffer);
                        if(i+2>=4096)
                                return -1;
                        buffer[i]='/';
                        if(long2unix_name(buffer+i+1,4096-i-1,new_+j))
                                return -2;

                        /* new file/directory */
                        if(new_[j].attributes&0x10) {
#ifdef _WIN32
#define SEVENFIVEFIVE
#else
#define SEVENFIVEFIVE ,0755
#endif
                            if(mkdir(buffer SEVENFIVEFIVE))
                                return -3;
                            /* TODO: map direntry.begin as directory, together with new array_t direntries */
                            assert(0);
                        } else {
                            fd=open(buffer,O_CREAT|O_EXCL,0644);
                            if(!fd)
                                return -3;
                            close(fd);
                        }

                        /* create mapping */
                        i=find_mapping_for_cluster_aux(s,begin_of_direntry(new_+j),0,s->mapping.next);
                        mapping=array_insert(&(s->mapping),i,1);
                        mapping->filename=strdup(buffer);
                        mapping->offset=0;
                        /* back pointer to direntry */
                        mapping->dir_index=first_dir_index+j;
                        /* set mode to modified */
                        mapping->mode=MODE_MODIFIED;
                        /* set begin to direntry.begin */
                        mapping->begin=begin_of_direntry(new_+j);
                        /* set end to begin+1 */
                        mapping->end=mapping->begin+1;
                        /* commit file contents */
                        if(commit_data_if_consistent(s,mapping,WRITE_DIRENTRY)) {
                            fprintf(stderr,"error committing file contents for new file %s!\n",buffer);
                            return -4;
                        }
                    } else if(direntry_is_free(new_+j)) {
                        assert(0);
                        /* TODO: delete file */
                        /* TODO: write direntry */
                        /* TODO: modify mapping: set mode=deleted */
                    } else {
                        /* modified file */
                        mapping_t* mapping=0;
                        /* if direntry.begin has changed,
                         * set mode to modified,
                         * adapt begin,
                         * adapt end */
                        /* TODO: handle rename */
                        assert(!memcmp(new_[j].name,original[j].name,11));
                        //fprintf(stderr,"1\n");
                        if(new_[j].begin!=original[j].begin || new_[j].size/s->cluster_size!=original[j].size/s->cluster_size) {
                        //fprintf(stderr,"2\n");
                            mapping = find_mapping_for_direntry(s,original+j);
                        //fprintf(stderr,"3\n");
                            if(!mapping) /* this should never happen! */
                                return -2;
                            mapping_modify_from_direntry(s,mapping,new_+j);
                            //fprintf(stderr,"4\n");
                            if(commit_data_if_consistent(s,mapping,WRITE_DIRENTRY)) {
                                fprintf(stderr,"big error\n");
                                return -4;
                            }
                        }
                        /* TODO: handle modified times and other attributes */

                        //fprintf(stderr,"5: mapping=0x%x, s=0x%x, s->mapping.pointer=0x%x\n",(uint32_t)mapping,(uint32_t)s,(uint32_t)s->mapping.pointer);
                        //fprintf(stderr,"6\n");
                    }
                }
            }
            /* write back direntries */
            memcpy(original,new_,0x200);
        } else {
            /* data */
            off_t sector=sector_num-s->first_sectors_number-2*s->sectors_per_fat;
            off_t cluster=sector/s->sectors_per_cluster;
            mapping_t* mapping=find_mapping_for_cluster(s,cluster);
            if(mapping && mapping->mode==MODE_DELETED)
                return -3; /* this is an error: no writes to these clusters before committed */
            {
                /* as of yet, undefined: put into commits */
                commit_t* commit=create_or_get_commit_for_sector(s,sector_num);

                if(!commit)
                    return -1; /* out of memory */
                memcpy(commit->buf+0x200*sector_offset_in_cluster(s,sector_num),buf,0x200);

                //fprintf(stderr,"mapping: 0x%x\n",(uint32_t)mapping);
                if(commit_data_if_consistent(s,mapping,WRITE_DATA))
                    return -4;
            }
        }
    }
    return 0;
}

static void vvfat_close(BlockDriverState *bs)
{
    BDRVVVFATState *s = bs->opaque;

    vvfat_close_current_file(s);
    array_free(&(s->fat));
    array_free(&(s->directory));
    array_free(&(s->mapping));
    if(s->cluster)
        free(s->cluster);
}

BlockDriver bdrv_vvfat = {
    "vvfat",
    sizeof(BDRVVVFATState),
    vvfat_probe,
    vvfat_open,
    vvfat_read,
    vvfat_write,
    vvfat_close,
};