100 lines
3.2 KiB
C
100 lines
3.2 KiB
C
/* This file contains the procedures that manipulate file descriptors.
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*
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* The entry points into this file are
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* get_fd: look for free file descriptor and free filp slots
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* get_filp: look up the filp entry for a given file descriptor
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* find_filp: find a filp slot that points to a given inode
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*/
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#include "fs.h"
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#include "file.h"
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#include "fproc.h"
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#include "inode.h"
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/*===========================================================================*
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* get_fd *
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*===========================================================================*/
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PUBLIC int get_fd(start, bits, k, fpt)
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int start; /* start of search (used for F_DUPFD) */
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mode_t bits; /* mode of the file to be created (RWX bits) */
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int *k; /* place to return file descriptor */
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struct filp **fpt; /* place to return filp slot */
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{
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/* Look for a free file descriptor and a free filp slot. Fill in the mode word
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* in the latter, but don't claim either one yet, since the open() or creat()
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* may yet fail.
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*/
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register struct filp *f;
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register int i;
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*k = -1; /* we need a way to tell if file desc found */
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/* Search the fproc fp_filp table for a free file descriptor. */
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for (i = start; i < OPEN_MAX; i++) {
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if (fp->fp_filp[i] == NIL_FILP) {
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/* A file descriptor has been located. */
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*k = i;
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break;
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}
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}
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/* Check to see if a file descriptor has been found. */
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if (*k < 0) return(EMFILE); /* this is why we initialized k to -1 */
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/* Now that a file descriptor has been found, look for a free filp slot. */
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for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
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if (f->filp_count == 0) {
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f->filp_mode = bits;
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f->filp_pos = 0L;
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f->filp_flags = 0;
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*fpt = f;
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return(OK);
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}
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}
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/* If control passes here, the filp table must be full. Report that back. */
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return(ENFILE);
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}
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/*===========================================================================*
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* get_filp *
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*===========================================================================*/
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PUBLIC struct filp *get_filp(fild)
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int fild; /* file descriptor */
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{
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/* See if 'fild' refers to a valid file descr. If so, return its filp ptr. */
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err_code = EBADF;
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if (fild < 0 || fild >= OPEN_MAX ) return(NIL_FILP);
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return(fp->fp_filp[fild]); /* may also be NIL_FILP */
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}
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/*===========================================================================*
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* find_filp *
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*===========================================================================*/
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PUBLIC struct filp *find_filp(rip, bits)
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register struct inode *rip; /* inode referred to by the filp to be found */
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Mode_t bits; /* mode of the filp to be found (RWX bits) */
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{
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/* Find a filp slot that refers to the inode 'rip' in a way as described
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* by the mode bit 'bits'. Used for determining whether somebody is still
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* interested in either end of a pipe. Also used when opening a FIFO to
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* find partners to share a filp field with (to shared the file position).
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* Like 'get_fd' it performs its job by linear search through the filp table.
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*/
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register struct filp *f;
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for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
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if (f->filp_count != 0 && f->filp_ino == rip && (f->filp_mode & bits)){
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return(f);
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}
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}
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/* If control passes here, the filp wasn't there. Report that back. */
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return(NIL_FILP);
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}
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