1 | #define _GNU_SOURCE |
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2 | |
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3 | #include <fcntl.h> |
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4 | #include <liburing.h> |
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5 | #include <stdio.h> |
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6 | #include <string.h> |
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7 | #include <unistd.h> |
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8 | |
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9 | struct io_uring ring; |
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10 | |
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11 | int main(int argc, char * argv[]) { |
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12 | if(argc != 2) { |
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13 | printf("usage: %s FILE - prints file to console.\n", argv[0]); |
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14 | return 1; |
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15 | } |
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16 | |
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17 | int fd = open(argv[1], O_DIRECT); |
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18 | if(fd < 0) { |
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19 | printf("Could not open file %s.\n", argv[1]); |
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20 | return 2; |
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21 | } |
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22 | |
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23 | /* prep the array */ |
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24 | char data[512]; |
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25 | struct iovec iov = { data, 512 }; |
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26 | |
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27 | /* init liburing */ |
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28 | io_uring_queue_init(256, &ring, IORING_SETUP_IOPOLL); |
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29 | |
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30 | /* declare required structs */ |
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31 | struct io_uring_sqe * sqe; |
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32 | struct io_uring_cqe * cqe; |
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33 | |
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34 | /* get an sqe and fill in a READV operation */ |
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35 | sqe = io_uring_get_sqe(&ring); |
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36 | io_uring_prep_readv(sqe, fd, &iov, 1, 0); |
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37 | |
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38 | sqe->user_data = data; |
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39 | |
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40 | /* tell the kernel we have an sqe ready for consumption */ |
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41 | io_uring_submit(&ring); |
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42 | |
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43 | /* wait for the sqe to complete */ |
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44 | int ret = io_uring_wait_cqe(&ring, &cqe); |
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45 | |
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46 | /* read and process cqe event */ |
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47 | if(ret == 0) { |
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48 | char * out = cqe->user_data; |
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49 | signed int len = cqe->res; |
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50 | io_uring_cqe_seen(&ring, cqe); |
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51 | |
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52 | if(len > 0) { |
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53 | printf("%.*s", len, out); |
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54 | } |
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55 | else if( len < 0 ) { |
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56 | fprintf(stderr, "readv returned error : %s\n", strerror(-len)); |
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57 | } |
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58 | } |
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59 | else { |
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60 | printf("%d\n", ret); |
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61 | io_uring_cqe_seen(&ring, cqe); |
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62 | } |
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63 | |
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64 | io_uring_queue_exit(&ring); |
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65 | |
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66 | close(fd); |
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67 | } |
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