Add shm allocator

include/shm.h

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2019 - 2020 Andri Yngvason
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+ * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#pragma once
+
+#include <unistd.h>
+
+int shm_alloc_fd(size_t size);

meson.build

@@ -43,6 +43,7 @@ subdir('protocols')
 
 sources = [
 	'src/main.c',
+	'src/shm.c',
 ]
 
 dependencies = [

src/shm.c

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2019 - 2020 Andri Yngvason
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+ * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "config.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_alloc_fd(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;
+}