Virtual VFAT support (Johannes Schindelin)

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@1426 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 1742 insertions, 0 deletions

diff --git a/block-vvfat.c b/block-vvfat.c
new file mode 100644
index 0000000..7bce91e
--- /dev/null
+++ b/block-vvfat.c
@@ -0,0 +1,1742 @@
+/*
+ * 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,
+};
+
+