1 files changed, 49 insertions, 0 deletions
diff --git a/src/shm.c b/src/shm.c
new file mode 100644
index 0000000..e145d4a
--- /dev/null
+++ b/src/shm.c
@@ -0,0 +1,49 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <time.h>
+#include <unistd.h>
+#include "shm.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;
+	}
+}
+
+static int create_shm_file(void)
+{
+	int retries = 100;
+	do {
+		char name[] = "/wl_shm-XXXXXX";
+		randname(name + sizeof(name) - 7);
+		--retries;
+		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 shm_allocate_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;
+}