[alsa-devel] [PATCH - PCM 3/3] pcm: Provide areas_copy function which handles buffer wrap around

[twischer at de.adit-jv.com]

From: Timo Wischer <twischer at de.adit-jv.com>

Signed-off-by: Timo Wischer <twischer at de.adit-jv.com>

diff --git a/include/pcm.h b/include/pcm.h
index 2619c8c..d880a1c 100644
--- a/include/pcm.h
+++ b/include/pcm.h
@@ -1147,6 +1147,9 @@ int snd_pcm_area_copy(const snd_pcm_channel_area_t *dst_channel, snd_pcm_uframes
 int snd_pcm_areas_copy(const snd_pcm_channel_area_t *dst_channels, snd_pcm_uframes_t dst_offset,
 		       const snd_pcm_channel_area_t *src_channels, snd_pcm_uframes_t src_offset,
 		       unsigned int channels, snd_pcm_uframes_t frames, snd_pcm_format_t format);
+int snd_pcm_areas_copy_wrap(const snd_pcm_channel_area_t *dst_channels, snd_pcm_uframes_t dst_offset, const snd_pcm_uframes_t dst_size,
+		       const snd_pcm_channel_area_t *src_channels, snd_pcm_uframes_t src_offset, const snd_pcm_uframes_t src_size,
+		       const unsigned int channels, snd_pcm_uframes_t frames, const snd_pcm_format_t format);
 
 /** \} */
 
diff --git a/src/pcm/pcm.c b/src/pcm/pcm.c
index d53ed98..77898db 100644
--- a/src/pcm/pcm.c
+++ b/src/pcm/pcm.c
@@ -3289,6 +3289,36 @@ int snd_pcm_areas_copy(const snd_pcm_channel_area_t *dst_areas, snd_pcm_uframes_
 	return 0;
 }
 
+int snd_pcm_areas_copy_wrap(const snd_pcm_channel_area_t *dst_channels, snd_pcm_uframes_t dst_offset, const snd_pcm_uframes_t dst_size,
+		       const snd_pcm_channel_area_t *src_channels, snd_pcm_uframes_t src_offset, const snd_pcm_uframes_t src_size,
+		       const unsigned int channels, snd_pcm_uframes_t frames, const snd_pcm_format_t format)
+{
+	while (frames > 0) {
+		int err;
+		snd_pcm_uframes_t xfer = frames;
+		/* do not write above the destination buffer */
+		if ( (dst_offset + xfer) > dst_size )
+			xfer = dst_size - dst_offset;
+		/* do not read from above the source buffer */
+		if ( (src_offset + xfer) > src_size )
+			xfer = src_size - src_offset;
+		err = snd_pcm_areas_copy(dst_channels, dst_offset, src_channels,
+		                              src_offset, channels, xfer, format);
+		if (err < 0)
+			return err;
+
+		dst_offset += xfer;
+		if (dst_offset >= dst_size)
+			dst_offset = 0;
+		src_offset += xfer;
+		if (src_offset >= src_size)
+			src_offset = 0;
+		frames -= xfer;
+	}
+
+	return 0;
+}
+
 static void dump_one_param(snd_pcm_hw_params_t *params, unsigned int k, snd_output_t *out)
 {
 	snd_output_printf(out, "%s: ", snd_pcm_hw_param_name(k));
-- 
2.7.4