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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 2374 | konopa | 1 | /* This file contains the procedures for opening, closing, and seeking on files. */ |
| 2 | |||
| 3 | /* Methods: |
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| 4 | * do_open: perform the OPEN system call |
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| 5 | * do_close: perform the CLOSE system call |
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| 6 | * do_lseek: perform the SEEK system call |
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| 7 | */ |
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| 8 | |||
| 9 | |||
| 10 | #include "fs.h" |
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| 11 | #include "block.h" |
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| 12 | #include "file.h" |
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| 13 | #include "fproc.h" |
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| 14 | #include "inode.h" |
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| 15 | #include "param.h" |
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| 16 | |||
| 17 | |||
| 18 | int do_open() |
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| 19 | { |
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| 20 | |||
| 21 | /* Perform the open(file_name) system call */ |
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| 22 | |||
| 23 | int r; |
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| 24 | register inode_t *rip; |
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| 25 | filp_t *fil_ptr; |
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| 26 | |||
| 27 | |||
| 28 | r = fetch_name(file_name, strlen(file_name)+1); |
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| 29 | if (r != OK) |
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| 30 | return err_code; /* name was bad */ |
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| 31 | |||
| 32 | /* See if file descriptor and filp slots are available. */ |
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| 33 | if ( (r = get_fd(0, &fd, &fil_ptr)) != OK) |
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| 34 | return r; |
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| 35 | |||
| 36 | /* Scan path name. */ |
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| 37 | if ( (rip = eat_path(user_path)) == NIL_INODE) |
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| 38 | return err_code; |
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| 39 | |||
| 40 | /* Claim the file descriptor and filp slot and fill them in. */ |
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| 41 | fp->fp_filp[fd] = fil_ptr; |
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| 42 | fil_ptr->filp_count = 1; |
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| 43 | fil_ptr->filp_ino = rip; |
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| 44 | fil_ptr->filp_flags = R_BIT; |
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| 45 | |||
| 46 | return fd; |
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| 47 | } |
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| 48 | |||
| 49 | int do_close() |
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| 50 | { |
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| 51 | |||
| 52 | /* Perform the close(fd) system call. */ |
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| 53 | |||
| 54 | register filp_t *rfilp; |
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| 55 | register inode_t *rip; |
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| 56 | |||
| 57 | |||
| 58 | /* First locate the inode that belongs to the file descriptor */ |
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| 59 | if ( (rfilp = get_filp(fd)) == NIL_FILP) |
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| 60 | return err_code; |
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| 61 | |||
| 62 | rip = rfilp->filp_ino; /* 'rip' points to the inode */ |
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| 63 | |||
| 64 | if (--rfilp->filp_count == 0) { |
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| 65 | put_inode(rip); |
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| 66 | } |
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| 67 | |||
| 68 | fp->fp_filp[fd] = NIL_FILP; |
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| 69 | |||
| 70 | return OK; |
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| 71 | } |
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| 72 | |||
| 73 | int do_lseek() |
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| 74 | { |
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| 75 | |||
| 76 | /* Perform the seek(ls_fd, offset, whence) system call. */ |
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| 77 | |||
| 78 | register filp_t *rfilp; |
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| 79 | register offset_t pos, new_pos; |
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| 80 | |||
| 81 | |||
| 82 | /* Check to see if the file descriptor is valid. */ |
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| 83 | if ( (rfilp = get_filp(fd)) == NIL_FILP) |
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| 84 | return err_code; |
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| 85 | |||
| 86 | |||
| 87 | /* The value of 'whence' determines the start position to use. */ |
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| 88 | switch(whence) { |
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| 89 | case 0: pos = 0; |
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| 90 | break; |
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| 91 | case 1: pos = rfilp->filp_pos; |
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| 92 | break; |
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| 93 | case 2: pos = rfilp->filp_ino->i_size; |
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| 94 | break; |
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| 95 | default: return FS_EINVAL; |
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| 96 | } |
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| 97 | |||
| 98 | /* Check for overflow. */ |
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| 99 | if (((long)offset > 0) && ((long)(pos + offset) < (long)pos)) |
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| 100 | return FS_EINVAL; |
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| 101 | if (((long)offset < 0) && ((long)(pos + offset) > (long)pos)) |
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| 102 | return FS_EINVAL; |
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| 103 | |||
| 104 | new_pos = pos + offset; |
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| 105 | |||
| 106 | /* Check for setting behind the end. */ |
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| 107 | if ((new_pos) > rfilp->filp_ino->i_size) { |
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| 108 | pos = rfilp->filp_ino->i_size; |
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| 109 | } |
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| 110 | else if (new_pos < 0) { |
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| 111 | pos = 0; |
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| 112 | } |
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| 113 | else { |
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| 114 | pos = new_pos; |
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| 115 | } |
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| 116 | rfilp->filp_pos = pos; |
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| 117 | |||
| 118 | return pos; |
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| 119 | } |
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| 120 |