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