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#define _POSIX_C_SOURCE 200112L
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <sys/mman.h>
#include <time.h>
#include <unistd.h>
static void randname(char *buf) {
struct timespec ts;
clock_gettime(CLOCK_REALTIME, &ts);
long r = ts.tv_nsec;
for (int i = 0; i < 6; ++i) {
buf[i] = 'A'+(r&15)+(r&16)*2;
r >>= 5;
}
}
int create_shm_file(void) {
int retries = 100;
do {
char name[] = "/wev-XXXXXX";
randname(name + strlen(name) - 6);
--retries;
// CLOEXEC is guaranteed to be set by shm_open
int fd = shm_open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
if (fd >= 0) {
shm_unlink(name);
return fd;
}
} while (retries > 0 && errno == EEXIST);
return -1;
}
int allocate_shm_file(size_t size) {
int fd = create_shm_file();
if (fd < 0) {
return -1;
}
int ret;
do {
ret = ftruncate(fd, size);
} while (ret < 0 && errno == EINTR);
if (ret < 0) {
close(fd);
return -1;
}
return fd;
}
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