From 51bbf779ba2c9d5954e2c9470a8eae7c1ddd38a5 Mon Sep 17 00:00:00 2001
From: Phil Jones <philj56@gmail.com>
Date: Tue, 7 Jun 2022 13:47:35 +0100
Subject: Switch from using (E)GL to wl_shm.

eglInitialize() is slow (~50-100ms), and uses a fair amount of memory
(~100 MB). For such a small, simple program that just wants to launch as
quickly as possible, wl_shm performs better.
---
 src/shm.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 src/shm.c

(limited to 'src/shm.c')

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;
+}
-- 
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