root/fs/read_write.c

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DEFINITIONS

This source file includes following definitions.
  1. sys_readdir
  2. sys_lseek
  3. sys_read
  4. sys_write

   1 /*
   2  *  linux/fs/read_write.c
   3  *
   4  *  (C) 1991  Linus Torvalds
   5  */
   6 
   7 #include <errno.h>
   8 #include <sys/types.h>
   9 #include <sys/stat.h>
  10 #include <sys/dirent.h>
  11 
  12 #include <linux/kernel.h>
  13 #include <linux/sched.h>
  14 #include <linux/minix_fs.h>
  15 #include <asm/segment.h>
  16 
  17 /*
  18  * Count is not yet used: but we'll probably support reading several entries
  19  * at once in the future. Use count=1 in the library for future expansions.
  20  */
  21 int sys_readdir(unsigned int fd, struct dirent * dirent, unsigned int count)
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  22 {
  23         struct file * file;
  24         struct inode * inode;
  25 
  26         if (fd >= NR_OPEN || !(file = current->filp[fd]) ||
  27             !(inode = file->f_inode))
  28                 return -EBADF;
  29         if (file->f_op && file->f_op->readdir) {
  30                 verify_area(dirent, sizeof (*dirent));
  31                 return file->f_op->readdir(inode,file,dirent,count);
  32         }
  33         return -ENOTDIR;
  34 }
  35 
  36 int sys_lseek(unsigned int fd, off_t offset, unsigned int origin)
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  37 {
  38         struct file * file;
  39         int tmp;
  40 
  41         if (fd >= NR_OPEN || !(file=current->filp[fd]) || !(file->f_inode))
  42                 return -EBADF;
  43         if (origin > 2)
  44                 return -EINVAL;
  45         if (file->f_op && file->f_op->lseek)
  46                 return file->f_op->lseek(file->f_inode,file,offset,origin);
  47 
  48 /* this is the default handler if no lseek handler is present */
  49         switch (origin) {
  50                 case 0:
  51                         tmp = offset;
  52                         break;
  53                 case 1:
  54                         tmp = file->f_pos + offset;
  55                         break;
  56                 case 2:
  57                         if (!file->f_inode)
  58                                 return -EINVAL;
  59                         tmp = file->f_inode->i_size + offset;
  60                         break;
  61         }
  62         if (tmp < 0)
  63                 return -EINVAL;
  64         file->f_pos = tmp;
  65         return file->f_pos;
  66 }
  67 
  68 int sys_read(unsigned int fd,char * buf,unsigned int count)
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  69 {
  70         struct file * file;
  71         struct inode * inode;
  72 
  73         if (fd>=NR_OPEN || !(file=current->filp[fd]) || !(inode=file->f_inode))
  74                 return -EBADF;
  75         if (!(file->f_mode & 1))
  76                 return -EBADF;
  77         if (!count)
  78                 return 0;
  79         verify_area(buf,count);
  80         if (file->f_op && file->f_op->read)
  81                 return file->f_op->read(inode,file,buf,count);
  82         printk("(Read)inode->i_mode=%06o\n\r",inode->i_mode);
  83         return -EINVAL;
  84 }
  85 
  86 int sys_write(unsigned int fd,char * buf,unsigned int count)
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  87 {
  88         struct file * file;
  89         struct inode * inode;
  90         
  91         if (fd>=NR_OPEN || !(file=current->filp[fd]) || !(inode=file->f_inode))
  92                 return -EBADF;
  93         if (!(file->f_mode&2))
  94                 return -EBADF;
  95         if (!count)
  96                 return 0;
  97         if (file->f_op && file->f_op->write)
  98                 return file->f_op->write(inode,file,buf,count);
  99         printk("(Write)inode->i_mode=%06o\n\r",inode->i_mode);
 100         return -EINVAL;
 101 }

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