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linear.c

/*
 *  Linear conversion Plug-In
 *  Copyright (c) 1999 by Jaroslav Kysela <perex@perex.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 <linux/time.h>
#include <sound/core.h>
#include <sound/pcm.h>
#include "pcm_plugin.h"

/*
 *  Basic linear conversion plugin
 */
 
struct linear_priv {
      int cvt_endian;         /* need endian conversion? */
      unsigned int src_ofs;   /* byte offset in source format */
      unsigned int dst_ofs;   /* byte soffset in destination format */
      unsigned int copy_ofs;  /* byte offset in temporary u32 data */
      unsigned int dst_bytes;       /* byte size of destination format */
      unsigned int copy_bytes;      /* bytes to copy per conversion */
      unsigned int flip; /* MSB flip for signeness, done after endian conv */
};

static inline void do_convert(struct linear_priv *data,
                        unsigned char *dst, unsigned char *src)
{
      unsigned int tmp = 0;
      unsigned char *p = (unsigned char *)&tmp;

      memcpy(p + data->copy_ofs, src + data->src_ofs, data->copy_bytes);
      if (data->cvt_endian)
            tmp = swab32(tmp);
      tmp ^= data->flip;
      memcpy(dst, p + data->dst_ofs, data->dst_bytes);
}

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)
{
      struct linear_priv *data = (struct linear_priv *)plugin->extra_data;
      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) {
                  do_convert(data, dst, src);
                  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;

      if (snd_BUG_ON(!plugin || !src_channels || !dst_channels))
            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++) {
                  if (snd_BUG_ON(src_channels[channel].area.first % 8 ||
                               src_channels[channel].area.step % 8))
                        return -ENXIO;
                  if (snd_BUG_ON(dst_channels[channel].area.first % 8 ||
                               dst_channels[channel].area.step % 8))
                        return -ENXIO;
            }
      }
#endif
      convert(plugin, src_channels, dst_channels, frames);
      return frames;
}

static void init_data(struct linear_priv *data, int src_format, int dst_format)
{
      int src_le, dst_le, src_bytes, dst_bytes;

      src_bytes = snd_pcm_format_width(src_format) / 8;
      dst_bytes = snd_pcm_format_width(dst_format) / 8;
      src_le = snd_pcm_format_little_endian(src_format) > 0;
      dst_le = snd_pcm_format_little_endian(dst_format) > 0;

      data->dst_bytes = dst_bytes;
      data->cvt_endian = src_le != dst_le;
      data->copy_bytes = src_bytes < dst_bytes ? src_bytes : dst_bytes;
      if (src_le) {
            data->copy_ofs = 4 - data->copy_bytes;
            data->src_ofs = src_bytes - data->copy_bytes;
      } else
            data->src_ofs = snd_pcm_format_physical_width(src_format) / 8 -
                  src_bytes;
      if (dst_le)
            data->dst_ofs = 4 - data->dst_bytes;
      else
            data->dst_ofs = snd_pcm_format_physical_width(dst_format) / 8 -
                  dst_bytes;
      if (snd_pcm_format_signed(src_format) !=
          snd_pcm_format_signed(dst_format)) {
            if (dst_le)
                  data->flip = cpu_to_le32(0x80000000);
            else
                  data->flip = cpu_to_be32(0x80000000);
      }
}

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;

      if (snd_BUG_ON(!r_plugin))
            return -ENXIO;
      *r_plugin = NULL;

      if (snd_BUG_ON(src_format->rate != dst_format->rate))
            return -ENXIO;
      if (snd_BUG_ON(src_format->channels != dst_format->channels))
            return -ENXIO;
      if (snd_BUG_ON(!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;
      init_data(data, src_format->format, dst_format->format);
      plugin->transfer = linear_transfer;
      *r_plugin = plugin;
      return 0;
}

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