/*-------------- Telecommunications & Signal Processing Lab ---------------
                             McGill University

Routine:
  int AFreadTA (AFILE *AFp, long int offs, float Fbuff[], int Nreq)

Purpose:
  Read samples (text data) from an audio file (return float values)

Description:
  This routine reads a specified number of samples from an audio file.  The
  data in the file is converted to float format on output. The file must have
  been opened using subroutine AFopenRead.

Parameters:
  <-  int AFreadTX
      Number of data values transferred from the file.  On reaching the end of
      the file, this value may be less than Nreq.
   -> AFILE *AFp
      Audio file pointer for an audio file opened by AFopenRead
   -> long int offs
      Offset into the file in samples.  The parameter offs must be non-
      negative.
  <-  float Fbuff[]
      Array of floats to receive the samples
   -> int Nreq
      Number of samples requested.  Nreq may be zero.

Author / revision:
  P. Kabal  Copyright (C) 1996
  $Revision: 1.2 $  $Date: 1996/04/28 22:23:57 $

-------------------------------------------------------------------------*/

static char rcsid [] = "$Id: AFreadTA.c 1.2 1996/04/28 AFsp-V2R1 $";

#include <libtsp.h>
#include <libtsp/nucleus.h>
#include <libtsp/AFpar.h>

#ifndef SEEK_SET	/* normally defined in stdio.h */
#  include <unistd.h>
#endif

#define MINV(a, b)	(((a) < (b)) ? (a) : (b))

int
AFreadTA (AFp, offs, Fbuff, Nreq)

     AFILE *AFp;
     long int offs;
     float Fbuff[];
     int Nreq;

{
  char *line;
  int n, m, Nd;
  char c;
  float Fv;

/*
   This routine spends most of its time in sscanf.  Consider a rather large
   file of some 24 Mb, with 4.7M samples.
   - read data, copy to another file, 912 sec CPU
   - read data (sscanf commented out), copy to another file, 88 sec CPU
*/

  offs = MINV (offs, AFp->Nsamp);

/* Rewind if the position is before the current postion */
  if (offs < AFp->Isamp) {
    if (fseek (AFp->fp, AFp->Start, SEEK_SET) != 0)
      UTerror ("AFreadTA: Error from fseek");
    AFp->Isamp = 0L;
  }

/* Move forward to the desired position */
  for (; AFp->Isamp < offs; ++AFp->Isamp) {
    line = FLgetLine (AFp->fp);
    if (line == NULL)
      UThalt ("AFreadTA: Unexpected end-of-file");
  }

/* Read the data */
  Nd = (int) MINV (Nreq, AFp->Nsamp - AFp->Isamp);
  c = '\0';
  for (n = 0; n < Nd; ++n) {
    line = FLgetLine (AFp->fp);
    if (line == NULL)
      UThalt ("AFreadTA: Unexpected end-of-file");
    m = sscanf (line, "%g%c", &Fv, &c);
    if (m != 1 || c != '\0')
      UThalt ("AFreadTA: Data format error, sample: %ld", offs+n);
    Fbuff[n] = AFp->ScaleF * Fv;
  }

  AFp->Isamp += n;
  return n;
}