Commit | Line | Data |
---|---|---|
7ee0f27f JA |
1 | /* |
2 | * Use vmsplice to fill some user memory into a pipe. vmsplice writes | |
3 | * to stdout, so that must be a pipe. | |
4 | */ | |
5 | #include <stdio.h> | |
6 | #include <stdlib.h> | |
7 | #include <unistd.h> | |
8 | #include <fcntl.h> | |
9 | #include <limits.h> | |
10 | #include <sys/poll.h> | |
11 | #include <sys/stat.h> | |
12 | #include <sys/types.h> | |
13 | ||
14 | #include "splice.h" | |
15 | ||
16 | #define ALIGN_BUF | |
17 | ||
18 | #ifdef ALIGN_BUF | |
19 | #define ALIGN_MASK (65535) /* 64k-1, should just be PAGE_SIZE - 1 */ | |
20 | #define ALIGN(buf) (void *) (((unsigned long) (buf) + ALIGN_MASK) & ~ALIGN_MASK) | |
21 | #else | |
22 | #define ALIGN_MASK (0) | |
23 | #define ALIGN(buf) (buf) | |
24 | #endif | |
25 | ||
26 | int do_vmsplice(int fd, void *buffer, int len) | |
27 | { | |
28 | struct pollfd pfd = { .fd = fd, .events = POLLOUT, }; | |
29 | int written; | |
30 | ||
31 | while (len) { | |
32 | /* | |
33 | * in a real app you'd be more clever with poll of course, | |
34 | * here we are basically just blocking on output room and | |
35 | * not using the free time for anything interesting. | |
36 | */ | |
37 | if (poll(&pfd, 1, -1) < 0) | |
38 | return error("poll"); | |
39 | ||
40 | written = vmsplice(fd, buffer, min(SPLICE_SIZE, len), 0); | |
41 | ||
42 | if (written <= 0) | |
43 | return error("vmsplice"); | |
44 | ||
45 | len -= written; | |
46 | } | |
47 | ||
48 | return 0; | |
49 | } | |
50 | ||
51 | int main(int argc, char *argv[]) | |
52 | { | |
53 | unsigned char *buffer; | |
54 | struct stat sb; | |
55 | long page_size; | |
56 | int i, ret; | |
57 | ||
58 | if (fstat(STDOUT_FILENO, &sb) < 0) | |
59 | return error("stat"); | |
60 | if (!S_ISFIFO(sb.st_mode)) { | |
61 | fprintf(stderr, "stdout must be a pipe\n"); | |
62 | return 1; | |
63 | } | |
64 | ||
65 | ret = fcntl(STDOUT_FILENO, F_GETPSZ); | |
66 | if (ret < 0) | |
67 | return error("F_GETPSZ"); | |
68 | ||
69 | page_size = sysconf(_SC_PAGESIZE); | |
70 | if (page_size < 0) | |
71 | return error("_SC_PAGESIZE"); | |
72 | ||
73 | fprintf(stderr, "Pipe size: %d pages / %ld bytes\n", ret, ret * page_size); | |
74 | ||
75 | buffer = ALIGN(malloc(2 * SPLICE_SIZE + ALIGN_MASK)); | |
76 | for (i = 0; i < 2 * SPLICE_SIZE; i++) | |
77 | buffer[i] = (i & 0xff); | |
78 | ||
79 | do { | |
80 | /* | |
81 | * vmsplice the first half of the buffer into the pipe | |
82 | */ | |
83 | if (do_vmsplice(STDOUT_FILENO, buffer, SPLICE_SIZE)) | |
84 | break; | |
85 | ||
86 | /* | |
87 | * first half is now in pipe, but we don't quite know when | |
88 | * we can reuse it. | |
89 | */ | |
90 | ||
91 | /* | |
92 | * vmsplice second half | |
93 | */ | |
94 | if (do_vmsplice(STDOUT_FILENO, buffer + SPLICE_SIZE, SPLICE_SIZE)) | |
95 | break; | |
96 | ||
97 | /* | |
98 | * We still don't know when we can reuse the second half of | |
99 | * the buffer, but we do now know that all parts of the first | |
100 | * half have been consumed from the pipe - so we can reuse that. | |
101 | */ | |
102 | } while (0); | |
103 | ||
104 | return 0; | |
105 | } |