fs/msdos/file.c

/* */
This source file includes following definitions.
msdos_file_read
msdos_file_write
msdos_truncate
   1 /*
   2  *  linux/fs/msdos/file.c
   3  *
   4  *  Written 1992 by Werner Almesberger
   5  *
   6  *  MS-DOS regular file handling primitives
   7  */
   8 
   9 #include <asm/segment.h>
  10 #include <asm/system.h>
  11 
  12 #include <linux/sched.h>
  13 #include <linux/fs.h>
  14 #include <linux/msdos_fs.h>
  15 #include <linux/errno.h>
  16 #include <linux/fcntl.h>
  17 #include <linux/stat.h>
  18 
  19 #define MIN(a,b) (((a) < (b)) ? (a) : (b))
  20 #define MAX(a,b) (((a) > (b)) ? (a) : (b))
  21 
  22 static int msdos_file_read(struct inode *inode,struct file *filp,char *buf,
  23     int count);
  24 static int msdos_file_write(struct inode *inode,struct file *filp,char *buf,
  25     int count);
  26 
  27 
  28 static struct file_operations msdos_file_operations = {
  29         NULL,                   /* lseek - default */
  30         msdos_file_read,        /* read */
  31         msdos_file_write,       /* write */
  32         NULL,                   /* readdir - bad */
  33         NULL,                   /* select - default */
  34         NULL,                   /* ioctl - default */
  35         NULL,                   /* mmap */
  36         NULL,                   /* no special open is needed */
  37         NULL                    /* release */
  38 };
  39 
  40 struct inode_operations msdos_file_inode_operations = {
  41         &msdos_file_operations, /* default file operations */
  42         NULL,                   /* create */
  43         NULL,                   /* lookup */
  44         NULL,                   /* link */
  45         NULL,                   /* unlink */
  46         NULL,                   /* symlink */
  47         NULL,                   /* mkdir */
  48         NULL,                   /* rmdir */
  49         NULL,                   /* mknod */
  50         NULL,                   /* rename */
  51         NULL,                   /* readlink */
  52         NULL,                   /* follow_link */
  53         msdos_bmap,             /* bmap */
  54         msdos_truncate,         /* truncate */
  55         NULL                    /* permission */
  56 };
  57 
  58 /* No bmap for MS-DOS FS' that don't align data at kByte boundaries. */
  59 
  60 struct inode_operations msdos_file_inode_operations_no_bmap = {
  61         &msdos_file_operations, /* default file operations */
  62         NULL,                   /* create */
  63         NULL,                   /* lookup */
  64         NULL,                   /* link */
  65         NULL,                   /* unlink */
  66         NULL,                   /* symlink */
  67         NULL,                   /* mkdir */
  68         NULL,                   /* rmdir */
  69         NULL,                   /* mknod */
  70         NULL,                   /* rename */
  71         NULL,                   /* readlink */
  72         NULL,                   /* follow_link */
  73         NULL,                   /* bmap */
  74         msdos_truncate,         /* truncate */
  75         NULL                    /* permission */
  76 };
  77 
  78 
  79 static int msdos_file_read(struct inode *inode,struct file *filp,char *buf,
     /*  */
  80     int count)
  81 {
  82         char *start;
  83         int left,offset,size,sector,cnt;
  84         char ch;
  85         struct buffer_head *bh;
  86         void *data;
  87 
  88 /* printk("msdos_file_read\n"); */
  89         if (!inode) {
  90                 printk("msdos_file_read: inode = NULL\n");
  91                 return -EINVAL;
  92         }
  93         if (!S_ISREG(inode->i_mode)) {
  94                 printk("msdos_file_read: mode = %07o\n",inode->i_mode);
  95                 return -EINVAL;
  96         }
  97         if (filp->f_pos >= inode->i_size || count <= 0) return 0;
  98         start = buf;
  99         while ((left = MIN(inode->i_size-filp->f_pos,count-(buf-start))) > 0){
 100                 if (!(sector = msdos_smap(inode,filp->f_pos >> SECTOR_BITS)))
 101                         break;
 102                 offset = filp->f_pos & (SECTOR_SIZE-1);
 103                 if (!(bh = msdos_sread(inode->i_dev,sector,&data))) break;
 104                 filp->f_pos += (size = MIN(SECTOR_SIZE-offset,left));
 105                 if (MSDOS_I(inode)->i_binary) {
 106                         memcpy_tofs(buf,data+offset,size);
 107                         buf += size;
 108                 }
 109                 else for (cnt = size; cnt; cnt--) {
 110                                 if ((ch = *((char *) data+offset++)) == '\r')
 111                                         size--;
 112                                 else {
 113                                         if (ch != 26) put_fs_byte(ch,buf++);
 114                                         else {
 115                                                 filp->f_pos = inode->i_size;
 116                                                 brelse(bh);
 117                                                 return buf-start;
 118                                         }
 119                                 }
 120                         }
 121                 brelse(bh);
 122         }
 123         if (start == buf) return -EIO;
 124         return buf-start;
 125 }
 126 
 127 
 128 static int msdos_file_write(struct inode *inode,struct file *filp,char *buf,
     /*  */
 129     int count)
 130 {
 131         int sector,offset,size,left,written;
 132         int error,carry;
 133         char *start,*to,ch;
 134         struct buffer_head *bh;
 135         void *data;
 136 
 137         if (!inode) {
 138                 printk("msdos_file_write: inode = NULL\n");
 139                 return -EINVAL;
 140         }
 141         if (!S_ISREG(inode->i_mode)) {
 142                 printk("msdos_file_write: mode = %07o\n",inode->i_mode);
 143                 return -EINVAL;
 144         }
 145 /*
 146  * ok, append may not work when many processes are writing at the same time
 147  * but so what. That way leads to madness anyway.
 148  */
 149         if (filp->f_flags & O_APPEND) filp->f_pos = inode->i_size;
 150         if (count <= 0) return 0;
 151         error = carry = 0;
 152         for (start = buf; count || carry; count -= size) {
 153                 while (!(sector = msdos_smap(inode,filp->f_pos >> SECTOR_BITS)))
 154                         if ((error = msdos_add_cluster(inode)) < 0) break;
 155                 if (error) {
 156                         msdos_truncate(inode);
 157                         break;
 158                 }
 159                 offset = filp->f_pos & (SECTOR_SIZE-1);
 160                 size = MIN(SECTOR_SIZE-offset,MAX(carry,count));
 161                 if (!(bh = msdos_sread(inode->i_dev,sector,&data))) {
 162                         error = -EIO;
 163                         break;
 164                 }
 165                 if (MSDOS_I(inode)->i_binary) {
 166                         memcpy_fromfs(data+(filp->f_pos & (SECTOR_SIZE-1)),
 167                             buf,written = size);
 168                         buf += size;
 169                 }
 170                 else {
 171                         written = left = SECTOR_SIZE-offset;
 172                         to = data+(filp->f_pos & (SECTOR_SIZE-1));
 173                         if (carry) {
 174                                 *to++ = '\n';
 175                                 left--;
 176                                 carry = 0;
 177                         }
 178                         for (size = 0; size < count && left; size++) {
 179                                 if ((ch = get_fs_byte(buf++)) == '\n') {
 180                                         *to++ = '\r';
 181                                         left--;
 182                                 }
 183                                 if (!left) carry = 1;
 184                                 else {
 185                                         *to++ = ch;
 186                                         left--;
 187                                 }
 188                         }
 189                         written -= left;
 190                 }
 191                 filp->f_pos += written;
 192                 if (filp->f_pos > inode->i_size) {
 193                         inode->i_size = filp->f_pos;
 194                         inode->i_dirt = 1;
 195                 }
 196                 bh->b_dirt = 1;
 197                 brelse(bh);
 198         }
 199         inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 200         MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
 201         inode->i_dirt = 1;
 202         return start == buf ? error : buf-start;
 203 }
 204 
 205 
 206 void msdos_truncate(struct inode *inode)
     /*  */
 207 {
 208         int cluster;
 209 
 210         cluster = SECTOR_SIZE*MSDOS_SB(inode->i_sb)->cluster_size;
 211         (void) fat_free(inode,(inode->i_size+(cluster-1))/cluster);
 212         MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
 213         inode->i_dirt = 1;
 214 }
/* */
root/fs/msdos/file.c

DEFINITIONS
