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 JA |
11 | #include <sys/poll.h> |
12 | #include <sys/stat.h> | |
13 | #include <sys/types.h> | |
14 | ||
15 | #include "splice.h" | |
16 | ||
88a9ff87 | 17 | #define ALIGN(buf) (void *) (((unsigned long) (buf) + align_mask) & ~align_mask) |
7ee0f27f | 18 | |
dbcd0883 | 19 | static int do_clear; |
88a9ff87 | 20 | static int align_mask = 65535; |
dbcd0883 | 21 | |
88a9ff87 | 22 | int do_vmsplice(int fd, void *b1, void *b2, int len) |
7ee0f27f JA |
23 | { |
24 | struct pollfd pfd = { .fd = fd, .events = POLLOUT, }; | |
88a9ff87 JA |
25 | struct iovec iov[] = { |
26 | { | |
27 | .iov_base = b1, | |
28 | .iov_len = len / 2, | |
29 | }, | |
30 | { | |
31 | .iov_base = b2, | |
32 | .iov_len = len / 2, | |
33 | }, | |
34 | }; | |
35 | int written, idx = 0; | |
7ee0f27f JA |
36 | |
37 | while (len) { | |
38 | /* | |
39 | * in a real app you'd be more clever with poll of course, | |
40 | * here we are basically just blocking on output room and | |
41 | * not using the free time for anything interesting. | |
42 | */ | |
43 | if (poll(&pfd, 1, -1) < 0) | |
44 | return error("poll"); | |
45 | ||
88a9ff87 | 46 | written = vmsplice(fd, &iov[idx], 2 - idx, 0); |
7ee0f27f JA |
47 | |
48 | if (written <= 0) | |
49 | return error("vmsplice"); | |
50 | ||
51 | len -= written; | |
88a9ff87 JA |
52 | if (written >= iov[idx].iov_len) { |
53 | int extra = written - iov[idx].iov_len; | |
54 | ||
55 | idx++; | |
56 | iov[idx].iov_len -= extra; | |
57 | iov[idx].iov_base += extra; | |
58 | } else { | |
59 | iov[idx].iov_len -= written; | |
60 | iov[idx].iov_base += written; | |
61 | } | |
7ee0f27f JA |
62 | } |
63 | ||
64 | return 0; | |
65 | } | |
66 | ||
dbcd0883 JA |
67 | static int usage(char *name) |
68 | { | |
88a9ff87 | 69 | fprintf(stderr, "%s: [-c(lear)] [-u(nalign)\n", name); |
dbcd0883 JA |
70 | return 1; |
71 | } | |
72 | ||
73 | static int parse_options(int argc, char *argv[]) | |
74 | { | |
75 | int c, index = 1; | |
76 | ||
88a9ff87 | 77 | while ((c = getopt(argc, argv, "cu")) != -1) { |
dbcd0883 JA |
78 | switch (c) { |
79 | case 'c': | |
80 | do_clear = 1; | |
81 | index++; | |
82 | break; | |
88a9ff87 JA |
83 | case 'u': |
84 | align_mask = 0; | |
85 | index++; | |
86 | break; | |
dbcd0883 JA |
87 | default: |
88 | return -1; | |
89 | } | |
90 | } | |
91 | ||
92 | return index; | |
93 | } | |
94 | ||
7ee0f27f JA |
95 | int main(int argc, char *argv[]) |
96 | { | |
88a9ff87 | 97 | unsigned char *b1, *b2; |
7ee0f27f | 98 | struct stat sb; |
7ee0f27f | 99 | |
dbcd0883 JA |
100 | if (parse_options(argc, argv) < 0) |
101 | return usage(argv[0]); | |
102 | ||
7ee0f27f JA |
103 | if (fstat(STDOUT_FILENO, &sb) < 0) |
104 | return error("stat"); | |
105 | if (!S_ISFIFO(sb.st_mode)) { | |
106 | fprintf(stderr, "stdout must be a pipe\n"); | |
107 | return 1; | |
108 | } | |
109 | ||
88a9ff87 JA |
110 | b1 = ALIGN(malloc(SPLICE_SIZE + align_mask)); |
111 | b2 = ALIGN(malloc(SPLICE_SIZE + align_mask)); | |
112 | ||
113 | memset(b1, 0xaa, SPLICE_SIZE); | |
114 | memset(b2, 0xbb, SPLICE_SIZE); | |
7ee0f27f JA |
115 | |
116 | do { | |
88a9ff87 JA |
117 | int half = SPLICE_SIZE / 2; |
118 | ||
7ee0f27f JA |
119 | /* |
120 | * vmsplice the first half of the buffer into the pipe | |
121 | */ | |
88a9ff87 | 122 | if (do_vmsplice(STDOUT_FILENO, b1, b2, SPLICE_SIZE)) |
7ee0f27f JA |
123 | break; |
124 | ||
125 | /* | |
126 | * first half is now in pipe, but we don't quite know when | |
127 | * we can reuse it. | |
128 | */ | |
129 | ||
130 | /* | |
131 | * vmsplice second half | |
132 | */ | |
88a9ff87 | 133 | if (do_vmsplice(STDOUT_FILENO, b1 + half, b2 + half, SPLICE_SIZE)) |
7ee0f27f JA |
134 | break; |
135 | ||
136 | /* | |
137 | * We still don't know when we can reuse the second half of | |
138 | * the buffer, but we do now know that all parts of the first | |
139 | * half have been consumed from the pipe - so we can reuse that. | |
140 | */ | |
dbcd0883 JA |
141 | |
142 | /* | |
143 | * Test option - clear the first half of the buffer, should | |
144 | * be safe now | |
145 | */ | |
88a9ff87 JA |
146 | if (do_clear) { |
147 | memset(b1, 0x00, SPLICE_SIZE); | |
148 | memset(b2, 0x00, SPLICE_SIZE); | |
149 | } | |
7ee0f27f JA |
150 | } while (0); |
151 | ||
152 | return 0; | |
153 | } |