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| 2404 | konopa | 1 | /* |
| 2 | * Copyright (c) 1987,1997, Prentice Hall |
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| 3 | * All rights reserved. |
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| 4 | * |
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| 5 | * Redistribution and use of the MINIX operating system in source and |
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| 6 | * binary forms, with or without modification, are permitted provided |
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| 7 | * that the following conditions are met: |
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| 8 | |||
| 9 | * - Redistributions of source code must retain the above copyright |
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| 10 | * notice, this list of conditions and the following disclaimer. |
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| 11 | |||
| 12 | * - Redistributions in binary form must reproduce the above |
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| 13 | * copyright notice, this list of conditions and the following |
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| 14 | * disclaimer in the documentation and/or other materials provided |
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| 15 | * with the distribution. |
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| 16 | |||
| 17 | * - Neither the name of Prentice Hall nor the names of the software |
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| 18 | * authors or contributors may be used to endorse or promote |
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| 19 | * products derived from this software without specific prior |
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| 20 | * written permission. |
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| 21 | |||
| 22 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS, AUTHORS, AND |
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| 23 | * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, |
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| 24 | * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
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| 25 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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| 26 | * IN NO EVENT SHALL PRENTICE HALL OR ANY AUTHORS OR CONTRIBUTORS BE |
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| 27 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
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| 28 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
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| 29 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR |
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| 30 | * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
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| 31 | * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE |
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| 32 | * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, |
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| 33 | * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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| 34 | */ |
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| 35 | |||
| 36 | |||
| 2374 | konopa | 37 | /* This file contains the procedures for opening, closing, and seeking on files. */ |
| 38 | |||
| 39 | /* Methods: |
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| 40 | * do_open: perform the OPEN system call |
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| 41 | * do_close: perform the CLOSE system call |
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| 42 | * do_lseek: perform the SEEK system call |
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| 43 | */ |
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| 44 | |||
| 45 | |||
| 46 | #include "fs.h" |
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| 47 | #include "block.h" |
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| 48 | #include "file.h" |
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| 49 | #include "fproc.h" |
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| 50 | #include "inode.h" |
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| 51 | #include "param.h" |
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| 52 | |||
| 53 | |||
| 54 | int do_open() |
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| 55 | { |
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| 56 | |||
| 57 | /* Perform the open(file_name) system call */ |
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| 58 | |||
| 59 | int r; |
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| 60 | register inode_t *rip; |
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| 61 | filp_t *fil_ptr; |
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| 62 | |||
| 63 | |||
| 64 | r = fetch_name(file_name, strlen(file_name)+1); |
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| 65 | if (r != OK) |
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| 66 | return err_code; /* name was bad */ |
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| 67 | |||
| 68 | /* See if file descriptor and filp slots are available. */ |
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| 69 | if ( (r = get_fd(0, &fd, &fil_ptr)) != OK) |
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| 70 | return r; |
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| 71 | |||
| 72 | /* Scan path name. */ |
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| 73 | if ( (rip = eat_path(user_path)) == NIL_INODE) |
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| 74 | return err_code; |
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| 75 | |||
| 76 | /* Claim the file descriptor and filp slot and fill them in. */ |
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| 77 | fp->fp_filp[fd] = fil_ptr; |
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| 78 | fil_ptr->filp_count = 1; |
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| 79 | fil_ptr->filp_ino = rip; |
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| 80 | fil_ptr->filp_flags = R_BIT; |
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| 81 | |||
| 82 | return fd; |
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| 83 | } |
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| 84 | |||
| 85 | int do_close() |
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| 86 | { |
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| 87 | |||
| 88 | /* Perform the close(fd) system call. */ |
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| 89 | |||
| 90 | register filp_t *rfilp; |
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| 91 | register inode_t *rip; |
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| 92 | |||
| 93 | |||
| 94 | /* First locate the inode that belongs to the file descriptor */ |
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| 95 | if ( (rfilp = get_filp(fd)) == NIL_FILP) |
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| 96 | return err_code; |
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| 97 | |||
| 98 | rip = rfilp->filp_ino; /* 'rip' points to the inode */ |
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| 99 | |||
| 100 | if (--rfilp->filp_count == 0) { |
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| 101 | put_inode(rip); |
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| 102 | } |
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| 103 | |||
| 104 | fp->fp_filp[fd] = NIL_FILP; |
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| 105 | |||
| 106 | return OK; |
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| 107 | } |
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| 108 | |||
| 109 | int do_lseek() |
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| 110 | { |
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| 111 | |||
| 112 | /* Perform the seek(ls_fd, offset, whence) system call. */ |
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| 113 | |||
| 114 | register filp_t *rfilp; |
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| 115 | register offset_t pos, new_pos; |
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| 116 | |||
| 117 | |||
| 118 | /* Check to see if the file descriptor is valid. */ |
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| 119 | if ( (rfilp = get_filp(fd)) == NIL_FILP) |
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| 120 | return err_code; |
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| 121 | |||
| 122 | |||
| 123 | /* The value of 'whence' determines the start position to use. */ |
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| 124 | switch(whence) { |
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| 125 | case 0: pos = 0; |
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| 126 | break; |
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| 127 | case 1: pos = rfilp->filp_pos; |
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| 128 | break; |
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| 129 | case 2: pos = rfilp->filp_ino->i_size; |
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| 130 | break; |
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| 131 | default: return FS_EINVAL; |
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| 132 | } |
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| 133 | |||
| 134 | /* Check for overflow. */ |
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| 135 | if (((long)offset > 0) && ((long)(pos + offset) < (long)pos)) |
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| 136 | return FS_EINVAL; |
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| 137 | if (((long)offset < 0) && ((long)(pos + offset) > (long)pos)) |
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| 138 | return FS_EINVAL; |
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| 139 | |||
| 140 | new_pos = pos + offset; |
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| 141 | |||
| 142 | /* Check for setting behind the end. */ |
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| 143 | if ((new_pos) > rfilp->filp_ino->i_size) { |
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| 144 | pos = rfilp->filp_ino->i_size; |
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| 145 | } |
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| 146 | else if (new_pos < 0) { |
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| 147 | pos = 0; |
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| 148 | } |
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| 149 | else { |
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| 150 | pos = new_pos; |
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| 151 | } |
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| 152 | rfilp->filp_pos = pos; |
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| 153 | |||
| 154 | return pos; |
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| 155 | } |
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| 156 |