Commit | Line | Data |
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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> | |
dbcd0883 JA |
10 | #include <string.h> |
11 | #include <getopt.h> | |
7ee0f27f JA |
12 | #include <sys/poll.h> |
13 | #include <sys/stat.h> | |
14 | #include <sys/types.h> | |
15 | ||
16 | #include "splice.h" | |
17 | ||
18 | #define ALIGN_BUF | |
19 | ||
20 | #ifdef ALIGN_BUF | |
21 | #define ALIGN_MASK (65535) /* 64k-1, should just be PAGE_SIZE - 1 */ | |
22 | #define ALIGN(buf) (void *) (((unsigned long) (buf) + ALIGN_MASK) & ~ALIGN_MASK) | |
23 | #else | |
24 | #define ALIGN_MASK (0) | |
25 | #define ALIGN(buf) (buf) | |
26 | #endif | |
27 | ||
dbcd0883 JA |
28 | static int do_clear; |
29 | ||
7ee0f27f JA |
30 | int do_vmsplice(int fd, void *buffer, int len) |
31 | { | |
32 | struct pollfd pfd = { .fd = fd, .events = POLLOUT, }; | |
33 | int written; | |
34 | ||
35 | while (len) { | |
36 | /* | |
37 | * in a real app you'd be more clever with poll of course, | |
38 | * here we are basically just blocking on output room and | |
39 | * not using the free time for anything interesting. | |
40 | */ | |
41 | if (poll(&pfd, 1, -1) < 0) | |
42 | return error("poll"); | |
43 | ||
44 | written = vmsplice(fd, buffer, min(SPLICE_SIZE, len), 0); | |
45 | ||
46 | if (written <= 0) | |
47 | return error("vmsplice"); | |
48 | ||
49 | len -= written; | |
ee0531f5 | 50 | buffer += written; |
7ee0f27f JA |
51 | } |
52 | ||
53 | return 0; | |
54 | } | |
55 | ||
dbcd0883 JA |
56 | static int usage(char *name) |
57 | { | |
58 | fprintf(stderr, "%s: [-c]\n", name); | |
59 | return 1; | |
60 | } | |
61 | ||
62 | static int parse_options(int argc, char *argv[]) | |
63 | { | |
64 | int c, index = 1; | |
65 | ||
66 | while ((c = getopt(argc, argv, "m")) != -1) { | |
67 | switch (c) { | |
68 | case 'c': | |
69 | do_clear = 1; | |
70 | index++; | |
71 | break; | |
72 | default: | |
73 | return -1; | |
74 | } | |
75 | } | |
76 | ||
77 | return index; | |
78 | } | |
79 | ||
7ee0f27f JA |
80 | int main(int argc, char *argv[]) |
81 | { | |
82 | unsigned char *buffer; | |
83 | struct stat sb; | |
84 | long page_size; | |
85 | int i, ret; | |
86 | ||
dbcd0883 JA |
87 | if (parse_options(argc, argv) < 0) |
88 | return usage(argv[0]); | |
89 | ||
7ee0f27f JA |
90 | if (fstat(STDOUT_FILENO, &sb) < 0) |
91 | return error("stat"); | |
92 | if (!S_ISFIFO(sb.st_mode)) { | |
93 | fprintf(stderr, "stdout must be a pipe\n"); | |
94 | return 1; | |
95 | } | |
96 | ||
97 | ret = fcntl(STDOUT_FILENO, F_GETPSZ); | |
98 | if (ret < 0) | |
99 | return error("F_GETPSZ"); | |
100 | ||
101 | page_size = sysconf(_SC_PAGESIZE); | |
102 | if (page_size < 0) | |
103 | return error("_SC_PAGESIZE"); | |
104 | ||
105 | fprintf(stderr, "Pipe size: %d pages / %ld bytes\n", ret, ret * page_size); | |
106 | ||
107 | buffer = ALIGN(malloc(2 * SPLICE_SIZE + ALIGN_MASK)); | |
108 | for (i = 0; i < 2 * SPLICE_SIZE; i++) | |
109 | buffer[i] = (i & 0xff); | |
110 | ||
111 | do { | |
112 | /* | |
113 | * vmsplice the first half of the buffer into the pipe | |
114 | */ | |
115 | if (do_vmsplice(STDOUT_FILENO, buffer, SPLICE_SIZE)) | |
116 | break; | |
117 | ||
118 | /* | |
119 | * first half is now in pipe, but we don't quite know when | |
120 | * we can reuse it. | |
121 | */ | |
122 | ||
123 | /* | |
124 | * vmsplice second half | |
125 | */ | |
126 | if (do_vmsplice(STDOUT_FILENO, buffer + SPLICE_SIZE, SPLICE_SIZE)) | |
127 | break; | |
128 | ||
129 | /* | |
130 | * We still don't know when we can reuse the second half of | |
131 | * the buffer, but we do now know that all parts of the first | |
132 | * half have been consumed from the pipe - so we can reuse that. | |
133 | */ | |
dbcd0883 JA |
134 | |
135 | /* | |
136 | * Test option - clear the first half of the buffer, should | |
137 | * be safe now | |
138 | */ | |
139 | if (do_clear) | |
140 | memset(buffer, 0x00, SPLICE_SIZE); | |
141 | ||
7ee0f27f JA |
142 | } while (0); |
143 | ||
144 | return 0; | |
145 | } |