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> | |
7ee0f27f | 8 | #include <limits.h> |
dbcd0883 JA |
9 | #include <string.h> |
10 | #include <getopt.h> | |
7ee0f27f | 11 | #include <sys/poll.h> |
7ee0f27f JA |
12 | #include <sys/types.h> |
13 | ||
14 | #include "splice.h" | |
15 | ||
88a9ff87 | 16 | #define ALIGN(buf) (void *) (((unsigned long) (buf) + align_mask) & ~align_mask) |
7ee0f27f | 17 | |
dbcd0883 | 18 | static int do_clear; |
88a9ff87 | 19 | static int align_mask = 65535; |
dbcd0883 | 20 | |
88a9ff87 | 21 | int do_vmsplice(int fd, void *b1, void *b2, int len) |
7ee0f27f JA |
22 | { |
23 | struct pollfd pfd = { .fd = fd, .events = POLLOUT, }; | |
88a9ff87 JA |
24 | struct iovec iov[] = { |
25 | { | |
26 | .iov_base = b1, | |
27 | .iov_len = len / 2, | |
28 | }, | |
29 | { | |
30 | .iov_base = b2, | |
31 | .iov_len = len / 2, | |
32 | }, | |
33 | }; | |
34 | int written, idx = 0; | |
7ee0f27f JA |
35 | |
36 | while (len) { | |
37 | /* | |
38 | * in a real app you'd be more clever with poll of course, | |
39 | * here we are basically just blocking on output room and | |
40 | * not using the free time for anything interesting. | |
41 | */ | |
42 | if (poll(&pfd, 1, -1) < 0) | |
43 | return error("poll"); | |
44 | ||
88a9ff87 | 45 | written = vmsplice(fd, &iov[idx], 2 - idx, 0); |
7ee0f27f JA |
46 | |
47 | if (written <= 0) | |
48 | return error("vmsplice"); | |
49 | ||
50 | len -= written; | |
88a9ff87 JA |
51 | if (written >= iov[idx].iov_len) { |
52 | int extra = written - iov[idx].iov_len; | |
53 | ||
54 | idx++; | |
55 | iov[idx].iov_len -= extra; | |
56 | iov[idx].iov_base += extra; | |
57 | } else { | |
58 | iov[idx].iov_len -= written; | |
59 | iov[idx].iov_base += written; | |
60 | } | |
7ee0f27f JA |
61 | } |
62 | ||
63 | return 0; | |
64 | } | |
65 | ||
dbcd0883 JA |
66 | static int usage(char *name) |
67 | { | |
f91353a3 | 68 | fprintf(stderr, "%s: [-c(lear)] [-u(nalign)] | ...\n", name); |
dbcd0883 JA |
69 | return 1; |
70 | } | |
71 | ||
72 | static int parse_options(int argc, char *argv[]) | |
73 | { | |
74 | int c, index = 1; | |
75 | ||
88a9ff87 | 76 | while ((c = getopt(argc, argv, "cu")) != -1) { |
dbcd0883 JA |
77 | switch (c) { |
78 | case 'c': | |
79 | do_clear = 1; | |
80 | index++; | |
81 | break; | |
88a9ff87 JA |
82 | case 'u': |
83 | align_mask = 0; | |
84 | index++; | |
85 | break; | |
dbcd0883 JA |
86 | default: |
87 | return -1; | |
88 | } | |
89 | } | |
90 | ||
91 | return index; | |
92 | } | |
93 | ||
7ee0f27f JA |
94 | int main(int argc, char *argv[]) |
95 | { | |
88a9ff87 | 96 | unsigned char *b1, *b2; |
7ee0f27f | 97 | |
dbcd0883 JA |
98 | if (parse_options(argc, argv) < 0) |
99 | return usage(argv[0]); | |
100 | ||
76797253 | 101 | if (check_output_pipe()) |
f91353a3 | 102 | return usage(argv[0]); |
7ee0f27f | 103 | |
88a9ff87 JA |
104 | b1 = ALIGN(malloc(SPLICE_SIZE + align_mask)); |
105 | b2 = ALIGN(malloc(SPLICE_SIZE + align_mask)); | |
106 | ||
107 | memset(b1, 0xaa, SPLICE_SIZE); | |
108 | memset(b2, 0xbb, SPLICE_SIZE); | |
7ee0f27f JA |
109 | |
110 | do { | |
88a9ff87 JA |
111 | int half = SPLICE_SIZE / 2; |
112 | ||
7ee0f27f JA |
113 | /* |
114 | * vmsplice the first half of the buffer into the pipe | |
115 | */ | |
88a9ff87 | 116 | if (do_vmsplice(STDOUT_FILENO, b1, b2, SPLICE_SIZE)) |
7ee0f27f JA |
117 | break; |
118 | ||
119 | /* | |
120 | * first half is now in pipe, but we don't quite know when | |
121 | * we can reuse it. | |
122 | */ | |
123 | ||
124 | /* | |
125 | * vmsplice second half | |
126 | */ | |
88a9ff87 | 127 | if (do_vmsplice(STDOUT_FILENO, b1 + half, b2 + half, SPLICE_SIZE)) |
7ee0f27f JA |
128 | break; |
129 | ||
130 | /* | |
131 | * We still don't know when we can reuse the second half of | |
132 | * the buffer, but we do now know that all parts of the first | |
133 | * half have been consumed from the pipe - so we can reuse that. | |
134 | */ | |
dbcd0883 JA |
135 | |
136 | /* | |
137 | * Test option - clear the first half of the buffer, should | |
138 | * be safe now | |
139 | */ | |
88a9ff87 JA |
140 | if (do_clear) { |
141 | memset(b1, 0x00, SPLICE_SIZE); | |
142 | memset(b2, 0x00, SPLICE_SIZE); | |
143 | } | |
7ee0f27f JA |
144 | } while (0); |
145 | ||
146 | return 0; | |
147 | } |