/*

convert to/from ulaw audio encoding

handles only 8000 Hz. 8-bit single channel data

R. Perry, March 2005

*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <errno.h>

#include "g711.h"

/* global argv[0] for error messages */

char *progname;

/* input buffer for encoding */

double *buf = NULL;
int size = 0;
int n = 0;

int push( double s)
{
  if( n == size)
  {
    int newsize = 1.5*size + 65536;
    double *newbuf;

    if( newsize > 1048576)
    {
      fprintf( stderr, "%s: buffer limit reached\n", progname);
      return 1;
    }

    newbuf = realloc( buf, newsize*sizeof(double));

    if( newbuf == NULL)
    {
      fprintf( stderr, "%s: realloc() failed\n", progname);
      exit(1);
    }
    size = newsize;
    buf = newbuf;
  }

  buf[n++] = s;

  return 0;
}

/* au file header */

typedef struct
{
 unsigned int magic;	/* file magic ".snd" */
 unsigned int offset;	/* offset to start of data */
 unsigned int nbytes;	/* number of bytes of data */
 unsigned int format;	/* data format code */
 unsigned int rate;	/* sampling rate */
 unsigned int nchan;	/* number of channels */
 unsigned int info;	/* optional text info */
}
au_header;

/* for little-endian systems only, e.g. Intel,
 * swap bytes of a 32-bit int
 * (since the Sun audio file header data format is bigendian)
 */
int swap( int x)
{
  return  ((x << 24) & 0xFF000000)
	| ((x <<  8) & 0x00FF0000)
	| ((x >>  8) & 0x0000FF00)
	| ((x >> 24) & 0x000000FF);
}

// pick one:
//
   #define SWAP(x) swap(x)
// #define SWAP(x) (x)

/* convert au file to text/PCM samples */

void do_decode( void)
{
  int c, s;
  double d;
  au_header auh;

  errno = 0;

  if( fread( &auh, sizeof(auh), 1, stdin) != 1)
  {
    fprintf( stderr, "%s: can't read au header: %s\n", progname, strerror( errno));
    exit(1);
  }

  if( SWAP(auh.format) != 1)
  {
    fprintf( stderr, "%s: au format %u != 1\n", progname, SWAP(auh.format));
    exit(1);
  }

  if( SWAP(auh.nchan) != 1)
  {
    fprintf( stderr, "%s: au nchan %u != 1\n", progname, SWAP(auh.nchan));
    exit(1);
  }

  if( fseek( stdin, SWAP(auh.offset) - sizeof(auh), SEEK_CUR))
  {
    fprintf( stderr, "%s: fseek: %s\n", progname, strerror( errno));
    exit(1);
  }

  while( (c = getchar()) >= 0)
  {
    s = ulaw2linear( c);
    d = s/32767.0;
    printf( "%18.9e\n", d);
  }  
}

/* convert text/PCM samples to au file */

void do_encode( void)
{
  int i, c;
  double s, t, max;
  au_header auh;

  while( scanf( "%lf", &s) == 1)
    if( push(s)) break;

  memcpy( &auh.magic, ".snd", 4);
  auh.offset = SWAP(sizeof(auh));
  auh.nbytes = SWAP(n);
  auh.format = SWAP(1);
  auh.rate = SWAP(8000);
  auh.nchan = SWAP(1);
  auh.info = SWAP(0);

  if( fwrite( &auh, sizeof(auh), 1, stdout) != 1)
  {
    fprintf( stderr, "%s: can't write au header: %s\n", progname, strerror( errno));
    exit(1);
  }

  max = fabs( buf[0]);

  for( i = 1; i < n; ++i)
  {
    t = fabs( buf[i]);
    if( t > max) max = t;
  }

#if 0
  fprintf( stderr, "max = %g\n", max);
#endif

  for( i = 0; i < n; ++i)
  {
    t = 32767.0*(buf[i]/max);
    if( t > 0) t += 0.5; else t -= 0.5;
    c = linear2ulaw( (int) t);
    putchar( c);
  }
}

int main( int argc, char *argv[])
{
  int encode = 1; // default is to encode

  progname = argv[0];

  if( argc == 2)
  {
    if( strcmp( argv[1], "-e") == 0)
      encode = 1;
    else if( strcmp( argv[1], "-d") == 0)
      encode = 0;
    else
      encode = -1;
  }
  else if( argc > 2)
  {
    encode = -1;
  }

  if( encode < 0)
  {
    fprintf( stderr, "Usage: %s [-e|-d]\n", progname);
    return 1;
  }

  if( encode) do_encode();
   else do_decode();

  return 0;
}