1 | /* Copyright 2002, Red Hat Inc. */ |
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2 | |
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3 | #include <mqueue.h> |
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4 | #include <fcntl.h> |
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5 | #include <errno.h> |
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6 | #include <sys/ipc.h> |
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7 | #include <sys/sem.h> |
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8 | #include <string.h> |
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9 | #define _LIBC 1 |
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10 | #include <sys/lock.h> |
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11 | #undef _LIBC |
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12 | |
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13 | #include "mqlocal.h" |
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14 | |
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15 | __LOCK_INIT(static, mq_rdbuf_lock); |
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16 | |
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17 | ssize_t |
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18 | mq_receive (mqd_t msgid, char *msg, size_t msg_len, unsigned int *msg_prio) |
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19 | { |
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20 | struct libc_mq *info; |
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21 | struct sembuf sb2 = {2, 1, 0}; |
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22 | struct sembuf sb3 = {3, -1, IPC_NOWAIT}; |
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23 | struct sembuf sb5 = {5, 1, IPC_NOWAIT}; |
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24 | ssize_t num_bytes; |
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25 | int ipcflag; |
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26 | |
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27 | info = __find_mq (msgid); |
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28 | |
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29 | if (info == NULL || (info->oflag & O_ACCMODE) == O_WRONLY) |
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30 | { |
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31 | errno = EBADF; |
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32 | return -1; |
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33 | } |
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34 | |
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35 | if (msg_len < info->attr->mq_msgsize) |
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36 | { |
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37 | errno = EMSGSIZE; |
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38 | return -1; |
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39 | } |
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40 | |
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41 | __lock_acquire (mq_rdbuf_lock); |
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42 | |
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43 | ipcflag = (info->attr->mq_flags & O_NONBLOCK) ? IPC_NOWAIT : 0; |
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44 | |
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45 | semop (info->semid, &sb5, 1); /* increase number of readers */ |
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46 | num_bytes = msgrcv (info->msgqid, info->rdbuf, msg_len, -MQ_PRIO_MAX, ipcflag); |
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47 | sb5.sem_op = -1; |
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48 | semop (info->semid, &sb5, 1); /* decrease number of readers */ |
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49 | |
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50 | if (num_bytes != (ssize_t)-1) |
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51 | { |
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52 | semop (info->semid, &sb2, 1); /* add one to messages left to write */ |
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53 | semop (info->semid, &sb3, 1); /* subtract one from messages to read */ |
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54 | memcpy (msg, info->rdbuf->text, num_bytes); |
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55 | if (msg_prio != NULL) |
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56 | *msg_prio = MQ_PRIO_MAX - info->rdbuf->type; |
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57 | } |
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58 | |
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59 | __lock_release (mq_rdbuf_lock); |
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60 | return num_bytes; |
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61 | } |
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62 | |
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63 | |
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64 | |
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65 | |
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66 | |
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67 | |
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