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| Rev | Author | Line No. | Line |
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| 4973 | right-hear | 1 | /* Copyright (C) 1995 DJ Delorie, see COPYING.DJ for details */ |
| 2 | /* An implementation of select() |
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| 3 | |||
| 4 | Copyright 1995 by Morten Welinder |
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| 5 | This file maybe freely distributed and modified as long as the |
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| 6 | copyright notice remains. |
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| 7 | |||
| 8 | Notes: In a single process system as Dos this really boils down to |
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| 9 | something that can check whether a character from standard input |
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| 10 | is ready. However, the code is organised in a way to make it easy |
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| 11 | to extend to multi process systems like WinNT and OS/2. */ |
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| 12 | |||
| 13 | #include |
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| 14 | #include |
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| 15 | #include |
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| 16 | #include |
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| 17 | #include |
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| 18 | #include |
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| 19 | #include |
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| 20 | #include |
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| 21 | #include |
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| 22 | #include |
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| 23 | |||
| 24 | inline static int fp_output_ready(FILE *fp) |
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| 25 | { |
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| 26 | return !ferror(fp); |
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| 27 | } |
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| 28 | |||
| 29 | /* This is as close as we get, I think. For a file connected to a printer |
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| 30 | we could of course go ask the BIOS, but this should be enough. */ |
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| 31 | |||
| 32 | inline static int fp_except_ready(FILE *fp) |
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| 33 | { |
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| 34 | return ferror (fp); |
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| 35 | } |
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| 36 | |||
| 37 | inline static int fp_input_ready (FILE *fp) |
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| 38 | { |
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| 39 | /* I think if there is something in the buffer, we should return |
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| 40 | ``ready'', even if some error was encountered. Let him consume |
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| 41 | the buffered characters, *then* return ``not ready''. */ |
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| 42 | if (fp->_cnt) |
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| 43 | return 1; |
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| 44 | |||
| 45 | /* The `feof' part is only correct in a single-tasked environment. */ |
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| 46 | if (ferror (fp) || feof (fp)) |
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| 47 | return 0; |
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| 48 | |||
| 49 | /* There is nothing in the buffer (perhaps because we read unbuffered). |
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| 50 | We don't know if we are ready. Return ``ready'' anyway and let |
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| 51 | read() or write() tell the truth. */ |
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| 52 | return 1; |
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| 53 | } |
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| 54 | |||
| 55 | /* The Dos call 4407 always returns TRUE for disk files. So the |
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| 56 | following really is meaningful for character devices only... */ |
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| 57 | |||
| 58 | inline static int fd_output_ready(int fd) |
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| 59 | { |
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| 60 | return 0; |
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| 61 | } |
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| 62 | |||
| 63 | inline static int fd_input_ready(int fd) |
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| 64 | { |
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| 65 | return 0; |
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| 66 | } |
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| 67 | |||
| 68 | int select(int nfds,fd_set *readfds,fd_set *writefds,fd_set *exceptfds, |
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| 69 | struct timeval *timeout) |
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| 70 | { |
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| 71 | int ready; |
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| 72 | fd_set oread, owrite, oexcept; |
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| 73 | struct timeval now, then; |
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| 74 | |||
| 75 | if (nfds > FD_SETSIZE) |
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| 76 | { |
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| 77 | errno = EINVAL; |
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| 78 | return -1; |
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| 79 | } |
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| 80 | |||
| 81 | FD_ZERO (&oread); |
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| 82 | FD_ZERO (&owrite); |
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| 83 | FD_ZERO (&oexcept); |
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| 84 | ready = 0; |
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| 85 | |||
| 86 | if (timeout) |
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| 87 | { |
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| 88 | if (timeout->tv_usec < 0) |
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| 89 | { |
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| 90 | errno = EINVAL; |
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| 91 | return -1; |
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| 92 | } |
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| 93 | gettimeofday (&now, 0); |
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| 94 | then.tv_usec = timeout->tv_usec + now.tv_usec; |
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| 95 | then.tv_sec = timeout->tv_sec + now.tv_sec + then.tv_usec / 1000000; |
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| 96 | then.tv_usec %= 1000000; |
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| 97 | } |
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| 98 | |||
| 99 | do { |
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| 100 | int i; |
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| 101 | int fd0 = 0; |
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| 102 | __file_rec *fr = __file_rec_list; |
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| 103 | FILE *fp; |
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| 104 | |||
| 105 | /* First, check the file handles with low-level DOS calls. */ |
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| 106 | for (i = 0; i < nfds; i++) |
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| 107 | { |
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| 108 | register int ioctl_result; |
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| 109 | __FSEXT_Function *func = __FSEXT_get_function(i); |
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| 110 | int fsext_ready = -1; |
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| 111 | |||
| 112 | if (func) |
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| 113 | func(__FSEXT_ready, &fsext_ready, &i); |
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| 114 | |||
| 115 | if (readfds && FD_ISSET (i, readfds)) |
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| 116 | { |
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| 117 | if (fsext_ready != -1) |
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| 118 | { |
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| 119 | if (fsext_ready & __FSEXT_ready_read) |
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| 120 | ready++, FD_SET(i, &oread); |
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| 121 | } |
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| 122 | else if ((ioctl_result = fd_input_ready (i)) == -1) |
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| 123 | return -1; |
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| 124 | else if (ioctl_result) |
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| 125 | ready++, FD_SET (i, &oread); |
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| 126 | } |
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| 127 | if (writefds && FD_ISSET (i, writefds)) |
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| 128 | { |
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| 129 | if (fsext_ready != -1) |
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| 130 | { |
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| 131 | if (fsext_ready & __FSEXT_ready_write) |
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| 132 | ready++, FD_SET(i, &owrite); |
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| 133 | } |
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| 134 | else if ((ioctl_result = fd_output_ready (i)) == -1) |
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| 135 | return -1; |
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| 136 | else if (ioctl_result) |
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| 137 | ready++, FD_SET (i, &owrite); |
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| 138 | } |
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| 139 | if (exceptfds && FD_ISSET (i, exceptfds)) |
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| 140 | { |
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| 141 | if (fsext_ready != -1) |
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| 142 | { |
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| 143 | if (fsext_ready & __FSEXT_ready_error) |
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| 144 | ready++, FD_SET(i, &oexcept); |
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| 145 | } |
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| 146 | } |
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| 147 | } |
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| 148 | |||
| 149 | /* Now look at the table of FILE ptrs and reset the bits for file |
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| 150 | descriptors which we *thought* are ready, but for which the flags |
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| 151 | say they're NOT ready. */ |
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| 152 | for (i = 0; fr; i++) |
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| 153 | { |
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| 154 | if (i >= fd0 + fr->count) /* done with this subtable, go to next */ |
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| 155 | { |
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| 156 | fd0 += fr->count; |
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| 157 | fr = fr->next; |
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| 158 | } |
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| 159 | if (fr) |
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| 160 | { |
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| 161 | fp = fr->files[i - fd0]; |
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| 162 | if (fp->_flag) |
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| 163 | { |
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| 164 | int this_fd = fileno(fp); |
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| 165 | |||
| 166 | if (this_fd < nfds) |
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| 167 | { |
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| 168 | if (readfds && FD_ISSET (this_fd, readfds) && |
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| 169 | FD_ISSET (this_fd, &oread) && !fp_input_ready (fp)) |
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| 170 | ready--, FD_CLR (this_fd, &oread); |
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| 171 | if (writefds && FD_ISSET (this_fd, writefds) && |
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| 172 | FD_ISSET (this_fd, &owrite) && !fp_output_ready (fp)) |
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| 173 | ready--, FD_CLR (this_fd, &owrite); |
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| 174 | |||
| 175 | /* For exceptional conditions, ferror() is the only one |
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| 176 | which can tell us an exception is pending. */ |
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| 177 | if (exceptfds && FD_ISSET (this_fd, exceptfds) && |
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| 178 | fp_except_ready (fp)) |
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| 179 | ready++, FD_SET (this_fd, &oexcept); |
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| 180 | } |
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| 181 | } |
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| 182 | } |
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| 183 | } |
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| 184 | |||
| 185 | /* Exit if we found what we were waiting for. */ |
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| 186 | if (ready > 0) |
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| 187 | { |
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| 188 | if (readfds) |
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| 189 | *readfds = oread; |
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| 190 | if (writefds) |
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| 191 | *writefds = owrite; |
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| 192 | if (exceptfds) |
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| 193 | *exceptfds = oexcept; |
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| 194 | return ready; |
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| 195 | } |
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| 196 | |||
| 197 | /* Exit if we hit the time limit. */ |
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| 198 | if (timeout) |
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| 199 | { |
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| 200 | gettimeofday (&now, 0); |
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| 201 | if (now.tv_sec > then.tv_sec |
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| 202 | || (now.tv_sec = then.tv_sec && now.tv_usec >= then.tv_usec)) |
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| 203 | return 0; |
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| 204 | } |
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| 205 | } while (1); |
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| 206 | } |