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linear.c

/*
 *  Linear conversion Plug-In
 *  Copyright (c) 1999 by Jaroslav Kysela <perex@suse.cz>,
 *                  Abramo Bagnara <abramo@alsa-project.org>
 *
 *
 *   This library is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Library General Public License as
 *   published by the Free Software Foundation; either version 2 of
 *   the License, or (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU Library General Public License for more details.
 *
 *   You should have received a copy of the GNU Library General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 */

#include <sound/driver.h>

#ifdef CONFIG_SND_PCM_OSS_PLUGINS

#include <linux/time.h>
#include <sound/core.h>
#include <sound/pcm.h>
#include "pcm_plugin.h"

/*
 *  Basic linear conversion plugin
 */
 
struct linear_priv {
      int conv;
};

static void convert(struct snd_pcm_plugin *plugin,
                const struct snd_pcm_plugin_channel *src_channels,
                struct snd_pcm_plugin_channel *dst_channels,
                snd_pcm_uframes_t frames)
{
#define CONV_LABELS
#include "plugin_ops.h"
#undef CONV_LABELS
      struct linear_priv *data = (struct linear_priv *)plugin->extra_data;
      void *conv = conv_labels[data->conv];
      int channel;
      int nchannels = plugin->src_format.channels;
      for (channel = 0; channel < nchannels; ++channel) {
            char *src;
            char *dst;
            int src_step, dst_step;
            snd_pcm_uframes_t frames1;
            if (!src_channels[channel].enabled) {
                  if (dst_channels[channel].wanted)
                        snd_pcm_area_silence(&dst_channels[channel].area, 0, frames, plugin->dst_format.format);
                  dst_channels[channel].enabled = 0;
                  continue;
            }
            dst_channels[channel].enabled = 1;
            src = src_channels[channel].area.addr + src_channels[channel].area.first / 8;
            dst = dst_channels[channel].area.addr + dst_channels[channel].area.first / 8;
            src_step = src_channels[channel].area.step / 8;
            dst_step = dst_channels[channel].area.step / 8;
            frames1 = frames;
            while (frames1-- > 0) {
                  goto *conv;
#define CONV_END after
#include "plugin_ops.h"
#undef CONV_END
            after:
                  src += src_step;
                  dst += dst_step;
            }
      }
}

static snd_pcm_sframes_t linear_transfer(struct snd_pcm_plugin *plugin,
                         const struct snd_pcm_plugin_channel *src_channels,
                         struct snd_pcm_plugin_channel *dst_channels,
                         snd_pcm_uframes_t frames)
{
      struct linear_priv *data;

      snd_assert(plugin != NULL && src_channels != NULL && dst_channels != NULL, return -ENXIO);
      data = (struct linear_priv *)plugin->extra_data;
      if (frames == 0)
            return 0;
#ifdef CONFIG_SND_DEBUG
      {
            unsigned int channel;
            for (channel = 0; channel < plugin->src_format.channels; channel++) {
                  snd_assert(src_channels[channel].area.first % 8 == 0 &&
                           src_channels[channel].area.step % 8 == 0,
                           return -ENXIO);
                  snd_assert(dst_channels[channel].area.first % 8 == 0 &&
                           dst_channels[channel].area.step % 8 == 0,
                           return -ENXIO);
            }
      }
#endif
      convert(plugin, src_channels, dst_channels, frames);
      return frames;
}

static int conv_index(int src_format, int dst_format)
{
      int src_endian, dst_endian, sign, src_width, dst_width;

      sign = (snd_pcm_format_signed(src_format) !=
            snd_pcm_format_signed(dst_format));
#ifdef SNDRV_LITTLE_ENDIAN
      src_endian = snd_pcm_format_big_endian(src_format);
      dst_endian = snd_pcm_format_big_endian(dst_format);
#else
      src_endian = snd_pcm_format_little_endian(src_format);
      dst_endian = snd_pcm_format_little_endian(dst_format);
#endif

      if (src_endian < 0)
            src_endian = 0;
      if (dst_endian < 0)
            dst_endian = 0;

      src_width = snd_pcm_format_width(src_format) / 8 - 1;
      dst_width = snd_pcm_format_width(dst_format) / 8 - 1;

      return src_width * 32 + src_endian * 16 + sign * 8 + dst_width * 2 + dst_endian;
}

int snd_pcm_plugin_build_linear(struct snd_pcm_substream *plug,
                        struct snd_pcm_plugin_format *src_format,
                        struct snd_pcm_plugin_format *dst_format,
                        struct snd_pcm_plugin **r_plugin)
{
      int err;
      struct linear_priv *data;
      struct snd_pcm_plugin *plugin;

      snd_assert(r_plugin != NULL, return -ENXIO);
      *r_plugin = NULL;

      snd_assert(src_format->rate == dst_format->rate, return -ENXIO);
      snd_assert(src_format->channels == dst_format->channels, return -ENXIO);
      snd_assert(snd_pcm_format_linear(src_format->format) &&
               snd_pcm_format_linear(dst_format->format), return -ENXIO);

      err = snd_pcm_plugin_build(plug, "linear format conversion",
                           src_format, dst_format,
                           sizeof(struct linear_priv), &plugin);
      if (err < 0)
            return err;
      data = (struct linear_priv *)plugin->extra_data;
      data->conv = conv_index(src_format->format, dst_format->format);
      plugin->transfer = linear_transfer;
      *r_plugin = plugin;
      return 0;
}

#endif

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