/* input_file.c - Deal with Input Files -
   Copyright (C) 1987, 1990, 1991, 1992 Free Software Foundation, Inc.

   This file is part of GAS, the GNU Assembler.

   GAS is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   GAS 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with GAS; see the file COPYING.  If not, write to
   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

/*
 * Confines all details of reading source bytes to this module.
 * All O/S specific crocks should live here.
 * What we lose in "efficiency" we gain in modularity.
 * Note we don't need to #include the "as.h" file. No common coupling!
 */

#include <stdio.h>
#include <string.h>

#include "as.h"
#include "input-file.h"

/* This variable is non-zero if the file currently being read should be
   preprocessed by app.  It is zero if the file can be read straight in.
   */
int preprocess = 0;

/*
 * This code opens a file, then delivers BUFFER_SIZE character
 * chunks of the file on demand.
 * BUFFER_SIZE is supposed to be a number chosen for speed.
 * The caller only asks once what BUFFER_SIZE is, and asks before
 * the nature of the input files (if any) is known.
 */

#define BUFFER_SIZE (32 * 1024)

/*
 * We use static data: the data area is not sharable.
 */

static FILE *f_in;
static char *file_name;

/* Struct for saving the state of this module for file includes.  */
struct saved_file
  {
    FILE *f_in;
    char *file_name;
    int preprocess;
    char *app_save;
  };

/* These hooks accomodate most operating systems. */

void 
input_file_begin ()
{
  f_in = (FILE *) 0;
}

void 
input_file_end ()
{
}

/* Return BUFFER_SIZE. */
unsigned int 
input_file_buffer_size ()
{
  return (BUFFER_SIZE);
}

int 
input_file_is_open ()
{
  return f_in != (FILE *) 0;
}

/* Push the state of our input, returning a pointer to saved info that
   can be restored with input_file_pop ().  */
char *
input_file_push ()
{
  register struct saved_file *saved;

  saved = (struct saved_file *) xmalloc (sizeof *saved);

  saved->f_in = f_in;
  saved->file_name = file_name;
  saved->preprocess = preprocess;
  if (preprocess)
    saved->app_save = app_push ();

  input_file_begin ();		/* Initialize for new file */

  return (char *) saved;
}

void
input_file_pop (arg)
     char *arg;
{
  register struct saved_file *saved = (struct saved_file *) arg;

  input_file_end ();		/* Close out old file */

  f_in = saved->f_in;
  file_name = saved->file_name;
  preprocess = saved->preprocess;
  if (preprocess)
    app_pop (saved->app_save);

  free (arg);
}

void
input_file_open (filename, pre)
     char *filename;		/* "" means use stdin. Must not be 0. */
     int pre;
{
  int c;
  char buf[80];

  preprocess = pre;

  assert (filename != 0);	/* Filename may not be NULL. */
  if (filename[0])
    {				/* We have a file name. Suck it and see. */
      f_in = fopen (filename, "r");
      file_name = filename;
    }
  else
    {				/* use stdin for the input file. */
      f_in = stdin;
      file_name = "{standard input}";	/* For error messages. */
    }
  if (f_in == (FILE *) 0)
    {
      as_perror ("Can't open %s for reading", file_name);
      return;
    }

  c = getc (f_in);
  if (c == '#')
    {				/* Begins with comment, may not want to preprocess */
      c = getc (f_in);
      if (c == 'N')
	{
	  fgets (buf, 80, f_in);
	  if (!strcmp (buf, "O_APP\n"))
	    preprocess = 0;
	  if (!strchr (buf, '\n'))
	    ungetc ('#', f_in);	/* It was longer */
	  else
	    ungetc ('\n', f_in);
	}
      else if (c == '\n')
	ungetc ('\n', f_in);
      else
	ungetc ('#', f_in);
    }
  else
    ungetc (c, f_in);
}

/* Close input file.  */
void 
input_file_close ()
{
  if (f_in != NULL)
    {
      fclose (f_in);
    }				/* don't close a null file pointer */
  f_in = 0;
}				/* input_file_close() */

char *
input_file_give_next_buffer (where)
     char *where;		/* Where to place 1st character of new buffer. */
{
  char *return_value;		/* -> Last char of what we read, + 1. */
  register int size;

  if (f_in == (FILE *) 0)
    return 0;
  /*
   * fflush (stdin); could be done here if you want to synchronise
   * stdin and stdout, for the case where our input file is stdin.
   * Since the assembler shouldn't do any output to stdout, we
   * don't bother to synch output and input.
   */
  if (preprocess)
    {
      char *p;
      int n;
      int ch;
      extern FILE *scrub_file;

      scrub_file = f_in;
      for (p = where, n = BUFFER_SIZE; n; --n)
	{

	  ch = do_scrub_next_char (scrub_from_file, scrub_to_file);
	  if (ch == EOF)
	    break;
	  *p++ = ch;
	}
      size = BUFFER_SIZE - n;
    }
  else
    size = fread (where, sizeof (char), BUFFER_SIZE, f_in);
  if (size < 0)
    {
      as_perror ("Can't read from %s", file_name);
      size = 0;
    }
  if (size)
    return_value = where + size;
  else
    {
      if (fclose (f_in))
	as_perror ("Can't close %s", file_name);
      f_in = (FILE *) 0;
      return_value = 0;
    }
  return (return_value);
}

/* end of input-file.c */
