From 770deae6cd0f25d7fa7f5e74f730f15cd6c0c323 Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <goliath@infraroot.at>
Date: Tue, 19 Jul 2022 21:45:36 +0200
Subject: [PATCH] Force blocking stdout

Signed-off-by: David Oberhollenzer <goliath@infraroot.at>
---
 shadermeh.c | 40 ++++++++++++++++++++++++++++++++++++++++
 shadermeh.h |  1 +
 2 files changed, 41 insertions(+)

diff --git a/shadermeh.c b/shadermeh.c
index 6249922..c2be88c 100644
--- a/shadermeh.c
+++ b/shadermeh.c
@@ -48,6 +48,39 @@ static void convert_for_ffmpeg(const uint8_t *in, uint8_t *out,
 	}
 }
 
+static int wait_fd_event(int fd, int events)
+{
+	struct pollfd pfd;
+	int ret;
+
+	for (;;) {
+		pfd.fd = fd;
+		pfd.events = events;
+		pfd.revents = 0;
+
+		ret = poll(&pfd, 1, -1);
+
+		if (ret > 0) {
+			if (pfd.revents & events)
+				break;
+
+			if (pfd.revents & (POLLERR | POLLHUP)) {
+				fputs("poll reported error\n", stderr);
+				return -1;
+			}
+		}
+
+		if (ret < 0) {
+			if (errno == EINTR)
+				continue;
+			perror("poll");
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
 static int write_retry(int fd, const void *buffer, size_t size)
 {
 	while (size > 0) {
@@ -56,6 +89,13 @@ static int write_retry(int fd, const void *buffer, size_t size)
 		if (ret < 0) {
 			if (errno == EINTR)
 				continue;
+
+			if (errno == EAGAIN) {
+				if (wait_fd_event(fd, POLLOUT))
+					return -1;
+				continue;
+			}
+
 			perror("write");
 			return -1;
 		}
diff --git a/shadermeh.h b/shadermeh.h
index aa5c5cd..df43001 100644
--- a/shadermeh.h
+++ b/shadermeh.h
@@ -23,6 +23,7 @@
 #include <unistd.h>
 #include <stdio.h>
 #include <errno.h>
+#include <poll.h>
 #include <time.h>
 
 #define AUDIO_SAMPLES (512)