servers/fs/filedes.c

   1 /* This file contains the procedures that manipulate file descriptors.
   2  *
   3  * The entry points into this file are
   4  *   get_fd:     look for free file descriptor and free filp slots
   5  *   get_filp:   look up the filp entry for a given file descriptor
   6  *   find_filp:  find a filp slot that points to a given inode
   7  *   inval_filp: invalidate a filp and associated fd's, only let close()
   8  *               happen on it
   9  */
  10
  11 #include <sys/select.h>
  12
  13 #include "fs.h"
  14 #include "file.h"
  15 #include "fproc.h"
  16 #include "inode.h"
  17
  18 /*===========================================================================*
  19  *                              get_fd                                       *
  20  *===========================================================================*/
  21 PUBLIC int get_fd(int start, mode_t bits, int *k, struct filp **fpt)
  22 {
  23 /* Look for a free file descriptor and a free filp slot.  Fill in the mode word
  24  * in the latter, but don't claim either one yet, since the open() or creat()
  25  * may yet fail.
  26  */
  27
  28   register struct filp *f;
  29   register int i;
  30
  31   *k = -1;                      /* we need a way to tell if file desc found */
  32
  33   /* Search the fproc fp_filp table for a free file descriptor. */
  34   for (i = start; i < OPEN_MAX; i++) {
  35         if (fp->fp_filp[i] == NIL_FILP && !FD_ISSET(i, &fp->fp_filp_inuse)) {
  36                 /* A file descriptor has been located. */
  37                 *k = i;
  38                 break;
  39         }
  40   }
  41
  42   /* Check to see if a file descriptor has been found. */
  43   if (*k < 0) return(EMFILE);   /* this is why we initialized k to -1 */
  44
  45   /* Now that a file descriptor has been found, look for a free filp slot. */
  46   for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
  47         if (f->filp_count == 0) {
  48                 f->filp_mode = bits;
  49                 f->filp_pos = 0L;
  50                 f->filp_selectors = 0;
  51                 f->filp_select_ops = 0;
  52                 f->filp_pipe_select_ops = 0;
  53                 f->filp_flags = 0;
  54                 *fpt = f;
  55                 return(OK);
  56         }
  57   }
  58
  59   /* If control passes here, the filp table must be full.  Report that back. */
  60   return(ENFILE);
  61 }
  62
  63 /*===========================================================================*
  64  *                              get_filp                                     *
  65  *===========================================================================*/
  66 PUBLIC struct filp *get_filp(fild)
  67 int fild;                       /* file descriptor */
  68 {
  69 /* See if 'fild' refers to a valid file descr.  If so, return its filp ptr. */
  70
  71   return get_filp2(fp, fild);
  72 }
  73
  74 /*===========================================================================*
  75  *                              get_filp2                                    *
  76  *===========================================================================*/
  77 PUBLIC struct filp *get_filp2(rfp, fild)
  78 register struct fproc *rfp;
  79 int fild;                       /* file descriptor */
  80 {
  81 /* See if 'fild' refers to a valid file descr.  If so, return its filp ptr. */
  82
  83   err_code = EBADF;
  84   if (fild < 0 || fild >= OPEN_MAX ) return(NIL_FILP);
  85   return(rfp->fp_filp[fild]);   /* may also be NIL_FILP */
  86 }
  87
  88 /*===========================================================================*
  89  *                              find_filp                                    *
  90  *===========================================================================*/
  91 PUBLIC struct filp *find_filp(register struct inode *rip, mode_t bits)
  92 {
  93 /* Find a filp slot that refers to the inode 'rip' in a way as described
  94  * by the mode bit 'bits'. Used for determining whether somebody is still
  95  * interested in either end of a pipe.  Also used when opening a FIFO to
  96  * find partners to share a filp field with (to shared the file position).
  97  * Like 'get_fd' it performs its job by linear search through the filp table.
  98  */
  99
 100   register struct filp *f;
 101
 102   for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
 103         if (f->filp_count != 0 && f->filp_ino == rip && (f->filp_mode & bits)){
 104                 return(f);
 105         }
 106   }
 107
 108   /* If control passes here, the filp wasn't there.  Report that back. */
 109   return(NIL_FILP);
 110 }
 111
 112 /*===========================================================================*
 113  *                              inval_filp                                   *
 114  *===========================================================================*/
 115 PUBLIC int inval_filp(struct filp *fp)
 116 {
 117         int f, fd, n = 0;
 118         for(f = 0; f < NR_PROCS; f++) {
 119                 if(fproc[f].fp_pid == PID_FREE) continue;
 120                 for(fd = 0; fd < OPEN_MAX; fd++) {
 121                         if(fproc[f].fp_filp[fd] && fproc[f].fp_filp[fd] == fp) {
 122                                 fproc[f].fp_filp[fd] = NIL_FILP;
 123                                 n++;
 124                         }
 125                 }
 126         }
 127
 128         return n;
 129 }