[PATCH] Alsa-plugins: Pulse: Fix snd_pcm_avail returning 0 in some cases

[David Henningsson <david.henningsson@canonical.com>]

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Due to a round-off error, snd_pcm_avail could in some cases
return 0 even though more data could be written to the stream.

This was discovered by Maarten Lankhorst [1], and there is also a test 
program available that triggers this error [2].

[1] 
https://tango.0pointer.de/pipermail/pulseaudio-discuss/2011-April/009935.html

[2] 
https://tango.0pointer.de/pipermail/pulseaudio-discuss/attachments/20110420/3c852d6e/attachment.c


-- 
David Henningsson, Canonical Ltd.
http://launchpad.net/~diwic

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>From 73ff6f83e1e4c53181e1794bf2cec3baee7c81b7 Mon Sep 17 00:00:00 2001
From: David Henningsson <david.henningsson@canonical.com>
Date: Thu, 21 Apr 2011 15:10:19 +0200
Subject: [PATCH] Pulse: Fix snd_pcm_avail returning 0 in some cases

Due to a round-off error, snd_pcm_avail could in some cases
return 0 even though more data could be written to the stream.

Reported-by: Maarten Lankhorst <m.b.lankhorst@gmail.com>
Signed-off-by: David Henningsson <david.henningsson@canonical.com>
---
 pulse/pcm_pulse.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/pulse/pcm_pulse.c b/pulse/pcm_pulse.c
index 2df0a80..9105d4d 100644
--- a/pulse/pcm_pulse.c
+++ b/pulse/pcm_pulse.c
@@ -92,8 +92,8 @@ static int update_ptr(snd_pcm_pulse_t *pcm)
 		size -= pcm->offset;
 
 	/* Prevent accidental overrun of the fake ringbuffer */
-	if (size >= pcm->buffer_attr.tlength)
-		size = pcm->buffer_attr.tlength-1;
+	if (size > pcm->buffer_attr.tlength - pcm->frame_size)
+		size = pcm->buffer_attr.tlength - pcm->frame_size;
 
 	if (size > pcm->last_size) {
 		pcm->ptr += size - pcm->last_size;
-- 
1.7.4.1


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