/* frags.c - manage frags -

   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.  */

#include "as.h"
#include "subsegs.h"
#include "obstack.h"

struct obstack frags;		/* All, and only, frags live here. */

extern fragS zero_address_frag;
extern fragS bss_address_frag;

/* Initialization for frag routines.  */
void
frag_init ()
{
  zero_address_frag.fr_type = rs_fill;
  bss_address_frag.fr_type = rs_fill;
}

/*
 *			frag_grow()
 *
 * Try to augment current frag by nchars chars.
 * If there is no room, close of the current frag with a ".fill 0"
 * and begin a new frag. Unless the new frag has nchars chars available
 * do not return. Do not set up any fields of *now_frag.
 */
void 
frag_grow (nchars)
     unsigned int nchars;
{
  if (obstack_room (&frags) < nchars)
    {
      unsigned int n, oldn;
      long oldc;

      frag_wane (frag_now);
      frag_new (0);
      oldn = (unsigned) -1;
      oldc = frags.chunk_size;
      frags.chunk_size = 2 * nchars;
      while ((n = obstack_room (&frags)) < nchars && n < oldn)
	{
	  frag_wane (frag_now);
	  frag_new (0);
	  oldn = n;
	}
      frags.chunk_size = oldc;
    }
  if (obstack_room (&frags) < nchars)
    as_fatal ("Can't extend frag %d. chars", nchars);
}				/* frag_grow() */

/*
 *			frag_new()
 *
 * Call this to close off a completed frag, and start up a new (empty)
 * frag, in the same subsegment as the old frag.
 * [frchain_now remains the same but frag_now is updated.]
 * Because this calculates the correct value of fr_fix by
 * looking at the obstack 'frags', it needs to know how many
 * characters at the end of the old frag belong to (the maximal)
 * fr_var: the rest must belong to fr_fix.
 * It doesn't actually set up the old frag's fr_var: you may have
 * set fr_var == 1, but allocated 10 chars to the end of the frag:
 * in this case you pass old_frags_var_max_size == 10.
 *
 * Make a new frag, initialising some components. Link new frag at end
 * of frchain_now.
 */
void 
frag_new (old_frags_var_max_size)
     int old_frags_var_max_size;/* Number of chars (already allocated on
				   obstack frags) */
     /* in variable_length part of frag. */
{
  register fragS *former_last_fragP;
  register frchainS *frchP;
  long tmp;

  frag_now->fr_fix = (char *) (obstack_next_free (&frags)) -
    (frag_now->fr_literal) - old_frags_var_max_size;
  /* Fix up old frag's fr_fix. */

  obstack_finish (&frags);
  /* This will align the obstack so the next struct we allocate on it
     will begin at a correct boundary. */
  frchP = frchain_now;
  know (frchP);
  former_last_fragP = frchP->frch_last;
  know (former_last_fragP);
  know (former_last_fragP == frag_now);
  obstack_blank (&frags, SIZEOF_STRUCT_FRAG);
  /* We expect this will begin at a correct boundary for a struct. */
  tmp = obstack_alignment_mask (&frags);
  obstack_alignment_mask (&frags) = 0;	/* Turn off alignment */
  /* If we ever hit a machine where strings must be aligned, we Lose
     Big.  */
  frag_now = (fragS *) obstack_finish (&frags);
  obstack_alignment_mask (&frags) = tmp;	/* Restore alignment */

  /* Just in case we don't get zero'd bytes */
  memset (frag_now, '\0', SIZEOF_STRUCT_FRAG);

  /* Generally, frag_now->points to an address rounded up to next
     alignment.  However, characters will add to obstack frags
     IMMEDIATELY after the struct frag, even if they are not starting
     at an alignment address. */
  former_last_fragP->fr_next = frag_now;
  frchP->frch_last = frag_now;

#ifndef NO_LISTING
  {
    extern struct list_info_struct *listing_tail;
    frag_now->line = listing_tail;
  }
#endif

  frag_now->fr_next = NULL;
}				/* frag_new() */

/*
 *			frag_more()
 *
 * Start a new frag unless we have n more chars of room in the current frag.
 * Close off the old frag with a .fill 0.
 *
 * Return the address of the 1st char to write into. Advance
 * frag_now_growth past the new chars.
 */

char *
frag_more (nchars)
     int nchars;
{
  register char *retval;

  frag_grow (nchars);
  retval = obstack_next_free (&frags);
  obstack_blank_fast (&frags, nchars);
  return (retval);
}				/* frag_more() */

/*
 *			frag_var()
 *
 * Start a new frag unless we have max_chars more chars of room in the current frag.
 * Close off the old frag with a .fill 0.
 *
 * Set up a machine_dependent relaxable frag, then start a new frag.
 * Return the address of the 1st char of the var part of the old frag
 * to write into.
 */

char *
frag_var (type, max_chars, var, subtype, symbol, offset, opcode)
     relax_stateT type;
     int max_chars;
     int var;
     relax_substateT subtype;
     symbolS *symbol;
     long offset;
     char *opcode;
{
  register char *retval;

  frag_grow (max_chars);
  retval = obstack_next_free (&frags);
  obstack_blank_fast (&frags, max_chars);
  frag_now->fr_var = var;
  frag_now->fr_type = type;
  frag_now->fr_subtype = subtype;
  frag_now->fr_symbol = symbol;
  frag_now->fr_offset = offset;
  frag_now->fr_opcode = opcode;
  /* default these to zero. */
  frag_now->fr_pcrel_adjust = 0;
  frag_now->fr_bsr = 0;
  frag_new (max_chars);
  return (retval);
}

/*
 *			frag_variant()
 *
 * OVE: This variant of frag_var assumes that space for the tail has been
 *      allocated by caller.
 *      No call to frag_grow is done.
 *      Two new arguments have been added.
 */

char *
frag_variant (type, max_chars, var, subtype, symbol, offset, opcode, pcrel_adjust, bsr)
     relax_stateT type;
     int max_chars;
     int var;
     relax_substateT subtype;
     symbolS *symbol;
     long offset;
     char *opcode;
     int pcrel_adjust;
     char bsr;
{
  register char *retval;

  retval = obstack_next_free (&frags);
  frag_now->fr_var = var;
  frag_now->fr_type = type;
  frag_now->fr_subtype = subtype;
  frag_now->fr_symbol = symbol;
  frag_now->fr_offset = offset;
  frag_now->fr_opcode = opcode;
  frag_now->fr_pcrel_adjust = pcrel_adjust;
  frag_now->fr_bsr = bsr;
  frag_new (max_chars);
  return (retval);
}				/* frag_variant() */

/*
 *			frag_wane()
 *
 * Reduce the variable end of a frag to a harmless state.
 */
void 
frag_wane (fragP)
     register fragS *fragP;
{
  fragP->fr_type = rs_fill;
  fragP->fr_offset = 0;
  fragP->fr_var = 0;
}

/*
 *			frag_align()
 *
 * Make a frag for ".align foo,bar". Call is "frag_align (foo,bar);".
 * Foo & bar are absolute integers.
 *
 * Call to close off the current frag with a ".align", then start a new
 * (so far empty) frag, in the same subsegment as the last frag.
 */

void 
frag_align (alignment, fill_character)
     int alignment;
     int fill_character;
{
  char *p;
  p = frag_var (rs_align, 1, 1, (relax_substateT) 0,
		(symbolS *) 0, (long) alignment, (char *) 0);
  *p = fill_character;
}

void 
frag_align_pattern (alignment, fill_pattern, n_fill)
     int alignment;
     const char *fill_pattern;
     int n_fill;
{
  char *p;
  p = frag_var (rs_align, n_fill, n_fill, (relax_substateT) 0,
		(symbolS *) 0, (long) alignment, (char *) 0);
  memcpy (p, fill_pattern, n_fill);
}

/* end of frags.c */
