text: /*
  ** Copyright (c) 2002-2016, Erik de Castro Lopo <erikd@mega-nerd.com>
  ** All rights reserved.
  **
  ** This code is released under 2-clause BSD license. Please see the
  ** file at : https://github.com/erikd/libsamplerate/blob/master/COPYING
  */
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  
  //#include "config.h"
  #include "float_cast.h"
  #include "common.h"
  
  static int linear_vari_process (SRC_PRIVATE *psrc, SRC_DATA *data) ;
  static void linear_reset (SRC_PRIVATE *psrc) ;
  static int linear_copy (SRC_PRIVATE *from, SRC_PRIVATE *to) ;
  
  /*========================================================================================
  */
  
  #define	LINEAR_MAGIC_MARKER	MAKE_MAGIC ('l', 'i', 'n', 'e', 'a', 'r')
  
  #define	SRC_DEBUG	0
  
  typedef struct
  {	int		linear_magic_marker ;
  	int		channels ;
  	int		reset ;
  	long	in_count, in_used ;
  	long	out_count, out_gen ;
  	float	last_value [1] ;
  } LINEAR_DATA ;
  
  /*----------------------------------------------------------------------------------------
  */
  
  static int
  linear_vari_process (SRC_PRIVATE *psrc, SRC_DATA *data)
  {	LINEAR_DATA *priv ;
  	double		src_ratio, input_index, rem ;
  	int			ch ;
  
  	if (data->input_frames <= 0)
  		return SRC_ERR_NO_ERROR ;
  
  	if (psrc->private_data == NULL)
  		return SRC_ERR_NO_PRIVATE ;
  
  	priv = (LINEAR_DATA*) psrc->private_data ;
  
  	if (priv->reset)
  	{	/* If we have just been reset, set the last_value data. */
  		for (ch = 0 ; ch < priv->channels ; ch++)
  			priv->last_value [ch] = data->data_in [ch] ;
  		priv->reset = 0 ;
  		} ;
  
  	priv->in_count = data->input_frames * priv->channels ;
  	priv->out_count = data->output_frames * priv->channels ;
  	priv->in_used = priv->out_gen = 0 ;
  
  	src_ratio = psrc->last_ratio ;
  
  	if (is_bad_src_ratio (src_ratio))
  		return SRC_ERR_BAD_INTERNAL_STATE ;
  
  	input_index = psrc->last_position ;
  
  	/* Calculate samples before first sample in input array. */
  	while (input_index < 1.0 && priv->out_gen < priv->out_count)
  	{
  		if (priv->in_used + priv->channels * (1.0 + input_index) >= priv->in_count)
  			break ;
  
  		if (priv->out_count > 0 && fabs (psrc->last_ratio - data->src_ratio) > SRC_MIN_RATIO_DIFF)
  			src_ratio = psrc->last_ratio + priv->out_gen * (data->src_ratio - psrc->last_ratio) / priv->out_count ;
  
  		for (ch = 0 ; ch < priv->channels ; ch++)
  		{	data->data_out [priv->out_gen] = (float) (priv->last_value [ch] + input_index *
  										(data->data_in [ch] - priv->last_value [ch])) ;
  			priv->out_gen ++ ;
  			} ;
  
  		/* Figure out the next index. */
  		input_index += 1.0 / src_ratio ;
  		} ;
  
  	rem = fmod_one (input_index) ;
  	priv->in_used += priv->channels * lrint (input_index - rem) ;
  	input_index = rem ;
  
  	/* Main processing loop. */
  	while (priv->out_gen < priv->out_count && priv->in_used + priv->channels * input_index < priv->in_count)
  	{
  		if (priv->out_count > 0 && fabs (psrc->last_ratio - data->src_ratio) > SRC_MIN_RATIO_DIFF)
  			src_ratio = psrc->last_ratio + priv->out_gen * (data->src_ratio - psrc->last_ratio) / priv->out_count ;
  
  		if (SRC_DEBUG && priv->in_used < priv->channels && input_index < 1.0)
  		{	printf ("Whoops!!!!   in_used : %ld     channels : %d     input_index : %f\n", priv->in_used, priv->channels, input_index) ;
  			exit (1) ;
  			} ;
  
  		for (ch = 0 ; ch < priv->channels ; ch++)
  		{	data->data_out [priv->out_gen] = (float) (data->data_in [priv->in_used - priv->channels + ch] + input_index *
  						(data->data_in [priv->in_used + ch] - data->data_in [priv->in_used - priv->channels + ch])) ;
  			priv->out_gen ++ ;
  			} ;
  
  		/* Figure out the next index. */
  		input_index += 1.0 / src_ratio ;
  		rem = fmod_one (input_index) ;
  
  		priv->in_used += priv->channels * lrint (input_index - rem) ;
  		input_index = rem ;
  		} ;
  
  	if (priv->in_used > priv->in_count)
  	{	input_index += (priv->in_used - priv->in_count) / priv->channels ;
  		priv->in_used = priv->in_count ;
  		} ;
  
  	psrc->last_position = input_index ;
  
  	if (priv->in_used > 0)
  		for (ch = 0 ; ch < priv->channels ; ch++)
  			priv->last_value [ch] = data->data_in [priv->in_used - priv->channels + ch] ;
  
  	/* Save current ratio rather then target ratio. */
  	psrc->last_ratio = src_ratio ;
  
  	data->input_frames_used = priv->in_used / priv->channels ;
  	data->output_frames_gen = priv->out_gen / priv->channels ;
  
  	return SRC_ERR_NO_ERROR ;
  } /* linear_vari_process */
  
  /*------------------------------------------------------------------------------
  */
  
  const char*
  linear_get_name (int src_enum)
  {
  	if (src_enum == SRC_LINEAR)
  		return "Linear Interpolator" ;
  
  	return NULL ;
  } /* linear_get_name */
  
  const char*
  linear_get_description (int src_enum)
  {
  	if (src_enum == SRC_LINEAR)
  		return "Linear interpolator, very fast, poor quality." ;
  
  	return NULL ;
  } /* linear_get_descrition */
  
  int
  linear_set_converter (SRC_PRIVATE *psrc, int src_enum)
  {	LINEAR_DATA *priv = NULL ;
  
  	if (src_enum != SRC_LINEAR)
  		return SRC_ERR_BAD_CONVERTER ;
  
  	if (psrc->private_data != NULL)
  	{	free (psrc->private_data) ;
  		psrc->private_data = NULL ;
  		} ;
  
  	if (psrc->private_data == NULL)
  	{	priv = (LINEAR_DATA*)calloc (1, sizeof (*priv) + psrc->channels * sizeof (float)) ;
  		psrc->private_data = priv ;
  		} ;
  
  	if (priv == NULL)
  		return SRC_ERR_MALLOC_FAILED ;
  
  	priv->linear_magic_marker = LINEAR_MAGIC_MARKER ;
  	priv->channels = psrc->channels ;
  
  	psrc->const_process = linear_vari_process ;
  	psrc->vari_process = linear_vari_process ;
  	psrc->reset = linear_reset ;
  	psrc->copy = linear_copy ;
  
  	linear_reset (psrc) ;
  
  	return SRC_ERR_NO_ERROR ;
  } /* linear_set_converter */
  
  /*===================================================================================
  */
  
  static void
  linear_reset (SRC_PRIVATE *psrc)
  {	LINEAR_DATA *priv = NULL ;
  
  	priv = (LINEAR_DATA*) psrc->private_data ;
  	if (priv == NULL)
  		return ;
  
  	priv->channels = psrc->channels ;
  	priv->reset = 1 ;
  	memset (priv->last_value, 0, sizeof (priv->last_value [0]) * priv->channels) ;
  
  	return ;
  } /* linear_reset */
  
  static int
  linear_copy (SRC_PRIVATE *from, SRC_PRIVATE *to)
  {
  	if (from->private_data == NULL)
  		return SRC_ERR_NO_PRIVATE ;
  
  	LINEAR_DATA *to_priv = NULL ;
  	LINEAR_DATA* from_priv = (LINEAR_DATA*) from->private_data ;
  	size_t private_size = sizeof (*to_priv) + from_priv->channels * sizeof (float) ;
  
  	if ((to_priv = (LINEAR_DATA*)calloc (1, private_size)) == NULL)
  		return SRC_ERR_MALLOC_FAILED ;
  
  	memcpy (to_priv, from_priv, private_size) ;
  	to->private_data = to_priv ;
  
  	return SRC_ERR_NO_ERROR ;
  } /* linear_copy */
  