From: Takashi Iwai <tiwai@suse.de>
Date: Thu, 20 Sep 2007 11:20:03 +0000 (+0200)
Subject: Fix wrong offset calculation in snd_pcm_{read|write}_mmap()
X-Git-Tag: v1.0.15rc3~1
X-Git-Url: https://git.alsa-project.org/?a=commitdiff_plain;h=67399e35ff47269c324c251e611531c70c8e71ef;p=alsa-lib.git

Fix wrong offset calculation in snd_pcm_{read|write}_mmap()

The offset used in snd_pcm_{read|write}_mmap() is not the linear offset
but the offset in a ring buffer.  It has to be rounded.
---

diff --git a/src/pcm/pcm_mmap.c b/src/pcm/pcm_mmap.c
index d07a0806..4621fe6f 100644
--- a/src/pcm/pcm_mmap.c
+++ b/src/pcm/pcm_mmap.c
@@ -575,7 +575,7 @@ snd_pcm_sframes_t snd_pcm_write_mmap(snd_pcm_t *pcm, snd_pcm_uframes_t offset,
 		if (err < 0)
 			break;
 		xfer += frames;
-		offset += frames;
+		offset = (offset + frames) % pcm->buffer_size;
 	}
 	if (xfer > 0)
 		return xfer;
@@ -625,7 +625,7 @@ snd_pcm_sframes_t snd_pcm_read_mmap(snd_pcm_t *pcm, snd_pcm_uframes_t offset,
 		if (err < 0)
 			break;
 		xfer += frames;
-		offset += frames;
+		offset = (offset + frames) % pcm->buffer_size;
 	}
 	if (xfer > 0)
 		return xfer;