60 lines
1001 B
C
60 lines
1001 B
C
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/* The following is based on code puublished under public domain by Drew DeVault
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* here: https://wayland-book.com/book/surfaces/shared-memory.html
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*/
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#include <errno.h>
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#include <fcntl.h>
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#include <sys/mman.h>
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#include <time.h>
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#include <unistd.h>
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static void randname(char *buf)
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{
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struct timespec ts;
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clock_gettime(CLOCK_REALTIME, &ts);
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long r = ts.tv_nsec;
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for (int i = 0; i < 6; ++i) {
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buf[i] = 'A'+(r&15)+(r&16)*2;
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r >>= 5;
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}
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}
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static int create_shm_file(void)
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{
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int retries = 100;
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do {
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char name[] = "/wl_shm-XXXXXX";
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randname(name + sizeof(name) - 7);
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--retries;
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int fd = shm_open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
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if (fd >= 0) {
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shm_unlink(name);
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return fd;
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}
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} while (retries > 0 && errno == EEXIST);
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return -1;
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}
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int shm_alloc_fd(size_t size)
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{
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int fd = create_shm_file();
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if (fd < 0)
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return -1;
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int ret;
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do {
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ret = ftruncate(fd, size);
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} while (ret < 0 && errno == EINTR);
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if (ret < 0) {
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close(fd);
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return -1;
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}
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return fd;
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}
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