From f3bf686a529b4f42bde189b66137103feac817af Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <goliath@infraroot.at>
Date: Tue, 19 Jul 2022 22:10:23 +0200
Subject: [PATCH] Read 32 bit float audio PCM samples from stdin

Signed-off-by: David Oberhollenzer <goliath@infraroot.at>
---
 shadermeh.c | 52 +++++++++++++++++++++++++++++++++++++++++++++-------
 shadermeh.h |  1 +
 2 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/shadermeh.c b/shadermeh.c
index c2be88c..cbeaf2c 100644
--- a/shadermeh.c
+++ b/shadermeh.c
@@ -23,6 +23,39 @@ static GLfloat vertex_buffer[] = {
 static GLubyte audio_buffer[AUDIO_SAMPLES * AUDIO_CHANNELS];
 static float audio_sample_data[AUDIO_SAMPLES];
 
+static int try_fetch_audio(void)
+{
+	size_t i, count = 0;
+	int ret;
+
+	for (;;) {
+		ret = read(STDIN_FILENO,
+			   (char *)audio_sample_data + count,
+			   sizeof(audio_sample_data) - count);
+
+		if (ret < 0) {
+			if (errno == EINTR)
+				continue;
+			if (errno == EAGAIN)
+				break;
+			perror("stdin");
+			return -1;
+		}
+
+		if (ret == 0)
+			break;
+
+		count += ret;
+	}
+
+	for (i = 0; i < (count / sizeof(float)); ++i) {
+		audio_buffer[i + AUDIO_SAMPLES] = audio_sample_data[i] * 127.0f	+ 127.0f;
+		audio_buffer[i] = 0.0f;
+	}
+
+	return 0;
+}
+
 static double diff_timespec(const struct timespec *time1,
 			    const struct timespec *time0)
 {
@@ -181,6 +214,15 @@ int main(int argc, char **argv)
 		}
 	}
 
+	if (have_audio) {
+		int flags = fcntl(STDIN_FILENO, F_GETFL, 0);
+
+		if (fcntl(STDIN_FILENO, F_SETFL, flags | O_NONBLOCK)) {
+			perror("making stdin non-blocking");
+			return EXIT_FAILURE;
+		}
+	}
+
 	if (!shader_file) {
 		fputs(usage_str, stderr);
 		fputs("No shader file specified!\n", stderr);
@@ -323,15 +365,11 @@ int main(int argc, char **argv)
 		glClear(GL_COLOR_BUFFER_BIT);
 
 		if (have_audio) {
+			if (try_fetch_audio())
+				break;
+
 			glBindTexture(GL_TEXTURE_2D, sound_tex);
 
-			for (i = 0; i < AUDIO_SAMPLES; ++i) {
-				audio_buffer[i] = 255.0f * audio_sample_data[i];
-
-				audio_buffer[AUDIO_SAMPLES + i] =
-					audio_buffer[i];
-			}
-
 			glTexImage2D(GL_TEXTURE_2D, 0, GL_R8,
 				     AUDIO_SAMPLES, AUDIO_CHANNELS, 0,
 				     GL_RED, GL_UNSIGNED_BYTE, audio_buffer);
diff --git a/shadermeh.h b/shadermeh.h
index df43001..88b0c8a 100644
--- a/shadermeh.h
+++ b/shadermeh.h
@@ -23,6 +23,7 @@
 #include <unistd.h>
 #include <stdio.h>
 #include <errno.h>
+#include <fcntl.h>
 #include <poll.h>
 #include <time.h>