460 lines
13 KiB
C
460 lines
13 KiB
C
/* frags.c - manage frags -
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Copyright (C) 1987-2015 Free Software Foundation, Inc.
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This file is part of GAS, the GNU Assembler.
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GAS is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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GAS is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GAS; see the file COPYING. If not, write to the Free
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Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
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02110-1301, USA. */
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#include "as.h"
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#include "subsegs.h"
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#include "obstack.h"
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extern fragS zero_address_frag;
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extern fragS predefined_address_frag;
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static int totalfrags;
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int
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get_frag_count (void)
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{
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return totalfrags;
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}
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void
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clear_frag_count (void)
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{
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totalfrags = 0;
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}
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/* Initialization for frag routines. */
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void
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frag_init (void)
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{
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zero_address_frag.fr_type = rs_fill;
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predefined_address_frag.fr_type = rs_fill;
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}
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/* Check that we're not trying to assemble into a section that can't
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allocate frags (currently, this is only possible in the absolute
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section), or into an mri common. */
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static void
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frag_alloc_check (const struct obstack *ob)
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{
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if (ob->chunk_size == 0)
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{
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as_bad (_("attempt to allocate data in absolute section"));
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subseg_set (text_section, 0);
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}
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if (mri_common_symbol != NULL)
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{
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as_bad (_("attempt to allocate data in common section"));
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mri_common_symbol = NULL;
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}
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}
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/* Allocate a frag on the specified obstack.
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Call this routine from everywhere else, so that all the weird alignment
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hackery can be done in just one place. */
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fragS *
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frag_alloc (struct obstack *ob)
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{
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fragS *ptr;
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int oalign;
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(void) obstack_alloc (ob, 0);
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oalign = obstack_alignment_mask (ob);
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obstack_alignment_mask (ob) = 0;
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ptr = (fragS *) obstack_alloc (ob, SIZEOF_STRUCT_FRAG);
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obstack_alignment_mask (ob) = oalign;
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memset (ptr, 0, SIZEOF_STRUCT_FRAG);
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totalfrags++;
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return ptr;
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}
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/* Try to augment current frag by nchars chars.
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If there is no room, close of the current frag with a ".fill 0"
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and begin a new frag. Unless the new frag has nchars chars available
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do not return. Do not set up any fields of *now_frag. */
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void
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frag_grow (size_t nchars)
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{
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if (obstack_room (&frchain_now->frch_obstack) < nchars)
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{
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size_t oldc;
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size_t newc;
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/* Try to allocate a bit more than needed right now. But don't do
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this if we would waste too much memory. Especially necessary
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for extremely big (like 2GB initialized) frags. */
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if (nchars < 0x10000)
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newc = 2 * nchars;
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else
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newc = nchars + 0x10000;
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newc += SIZEOF_STRUCT_FRAG;
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/* Check for possible overflow. */
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if (newc < nchars)
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as_fatal (_("can't extend frag %lu chars"), (unsigned long) nchars);
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/* Force to allocate at least NEWC bytes, but not less than the
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default. */
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oldc = obstack_chunk_size (&frchain_now->frch_obstack);
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if (newc > oldc)
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obstack_chunk_size (&frchain_now->frch_obstack) = newc;
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while (obstack_room (&frchain_now->frch_obstack) < nchars)
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{
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/* Not enough room in this frag. Close it and start a new one.
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This must be done in a loop because the created frag may not
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be big enough if the current obstack chunk is used. */
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frag_wane (frag_now);
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frag_new (0);
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}
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/* Restore the old chunk size. */
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obstack_chunk_size (&frchain_now->frch_obstack) = oldc;
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}
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}
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/* Call this to close off a completed frag, and start up a new (empty)
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frag, in the same subsegment as the old frag.
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[frchain_now remains the same but frag_now is updated.]
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Because this calculates the correct value of fr_fix by
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looking at the obstack 'frags', it needs to know how many
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characters at the end of the old frag belong to the maximal
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variable part; The rest must belong to fr_fix.
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It doesn't actually set up the old frag's fr_var. You may have
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set fr_var == 1, but allocated 10 chars to the end of the frag;
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In this case you pass old_frags_var_max_size == 10.
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In fact, you may use fr_var for something totally unrelated to the
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size of the variable part of the frag; None of the generic frag
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handling code makes use of fr_var.
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Make a new frag, initialising some components. Link new frag at end
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of frchain_now. */
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void
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frag_new (size_t old_frags_var_max_size
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/* Number of chars (already allocated on obstack frags) in
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variable_length part of frag. */)
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{
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fragS *former_last_fragP;
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frchainS *frchP;
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gas_assert (frchain_now->frch_last == frag_now);
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/* Fix up old frag's fr_fix. */
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frag_now->fr_fix = frag_now_fix_octets () - old_frags_var_max_size;
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/* Make sure its type is valid. */
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gas_assert (frag_now->fr_type != 0);
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/* This will align the obstack so the next struct we allocate on it
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will begin at a correct boundary. */
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obstack_finish (&frchain_now->frch_obstack);
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frchP = frchain_now;
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know (frchP);
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former_last_fragP = frchP->frch_last;
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gas_assert (former_last_fragP != 0);
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gas_assert (former_last_fragP == frag_now);
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frag_now = frag_alloc (&frchP->frch_obstack);
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as_where (&frag_now->fr_file, &frag_now->fr_line);
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/* Generally, frag_now->points to an address rounded up to next
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alignment. However, characters will add to obstack frags
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IMMEDIATELY after the struct frag, even if they are not starting
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at an alignment address. */
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former_last_fragP->fr_next = frag_now;
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frchP->frch_last = frag_now;
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#ifndef NO_LISTING
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{
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extern struct list_info_struct *listing_tail;
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frag_now->line = listing_tail;
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}
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#endif
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gas_assert (frchain_now->frch_last == frag_now);
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frag_now->fr_next = NULL;
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}
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/* Start a new frag unless we have n more chars of room in the current frag.
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Close off the old frag with a .fill 0.
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Return the address of the 1st char to write into. Advance
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frag_now_growth past the new chars. */
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char *
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frag_more (size_t nchars)
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{
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char *retval;
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frag_alloc_check (&frchain_now->frch_obstack);
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frag_grow (nchars);
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retval = obstack_next_free (&frchain_now->frch_obstack);
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obstack_blank_fast (&frchain_now->frch_obstack, nchars);
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return retval;
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}
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/* Close the current frag, setting its fields for a relaxable frag. Start a
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new frag. */
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static void
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frag_var_init (relax_stateT type, size_t max_chars, size_t var,
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relax_substateT subtype, symbolS *symbol, offsetT offset,
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char *opcode)
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{
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frag_now->fr_var = var;
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frag_now->fr_type = type;
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frag_now->fr_subtype = subtype;
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frag_now->fr_symbol = symbol;
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frag_now->fr_offset = offset;
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frag_now->fr_opcode = opcode;
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#ifdef USING_CGEN
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frag_now->fr_cgen.insn = 0;
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frag_now->fr_cgen.opindex = 0;
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frag_now->fr_cgen.opinfo = 0;
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#endif
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#ifdef TC_FRAG_INIT
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TC_FRAG_INIT (frag_now);
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#endif
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as_where (&frag_now->fr_file, &frag_now->fr_line);
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frag_new (max_chars);
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}
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/* Start a new frag unless we have max_chars more chars of room in the
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current frag. Close off the old frag with a .fill 0.
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Set up a machine_dependent relaxable frag, then start a new frag.
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Return the address of the 1st char of the var part of the old frag
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to write into. */
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char *
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frag_var (relax_stateT type, size_t max_chars, size_t var,
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relax_substateT subtype, symbolS *symbol, offsetT offset,
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char *opcode)
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{
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char *retval;
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frag_grow (max_chars);
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retval = obstack_next_free (&frchain_now->frch_obstack);
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obstack_blank_fast (&frchain_now->frch_obstack, max_chars);
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frag_var_init (type, max_chars, var, subtype, symbol, offset, opcode);
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return retval;
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}
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/* OVE: This variant of frag_var assumes that space for the tail has been
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allocated by caller.
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No call to frag_grow is done. */
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char *
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frag_variant (relax_stateT type, size_t max_chars, size_t var,
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relax_substateT subtype, symbolS *symbol, offsetT offset,
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char *opcode)
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{
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char *retval;
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retval = obstack_next_free (&frchain_now->frch_obstack);
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frag_var_init (type, max_chars, var, subtype, symbol, offset, opcode);
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return retval;
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}
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/* Reduce the variable end of a frag to a harmless state. */
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void
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frag_wane (fragS *fragP)
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{
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fragP->fr_type = rs_fill;
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fragP->fr_offset = 0;
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fragP->fr_var = 0;
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}
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/* Return the number of bytes by which the current frag can be grown. */
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size_t
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frag_room (void)
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{
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return obstack_room (&frchain_now->frch_obstack);
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}
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/* Make an alignment frag. The size of this frag will be adjusted to
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force the next frag to have the appropriate alignment. ALIGNMENT
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is the power of two to which to align. FILL_CHARACTER is the
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character to use to fill in any bytes which are skipped. MAX is
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the maximum number of characters to skip when doing the alignment,
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or 0 if there is no maximum. */
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void
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frag_align (int alignment, int fill_character, int max)
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{
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if (now_seg == absolute_section)
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{
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addressT new_off;
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addressT mask;
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mask = (~(addressT) 0) << alignment;
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new_off = (abs_section_offset + ~mask) & mask;
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if (max == 0 || new_off - abs_section_offset <= (addressT) max)
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abs_section_offset = new_off;
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}
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else
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{
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char *p;
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p = frag_var (rs_align, 1, 1, (relax_substateT) max,
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(symbolS *) 0, (offsetT) alignment, (char *) 0);
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*p = fill_character;
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}
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}
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/* Make an alignment frag like frag_align, but fill with a repeating
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pattern rather than a single byte. ALIGNMENT is the power of two
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to which to align. FILL_PATTERN is the fill pattern to repeat in
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the bytes which are skipped. N_FILL is the number of bytes in
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FILL_PATTERN. MAX is the maximum number of characters to skip when
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doing the alignment, or 0 if there is no maximum. */
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void
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frag_align_pattern (int alignment, const char *fill_pattern,
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size_t n_fill, int max)
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{
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char *p;
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p = frag_var (rs_align, n_fill, n_fill, (relax_substateT) max,
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(symbolS *) 0, (offsetT) alignment, (char *) 0);
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memcpy (p, fill_pattern, n_fill);
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}
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/* The NOP_OPCODE is for the alignment fill value. Fill it with a nop
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instruction so that the disassembler does not choke on it. */
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#ifndef NOP_OPCODE
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#define NOP_OPCODE 0x00
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#endif
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/* Use this to restrict the amount of memory allocated for representing
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the alignment code. Needs to be large enough to hold any fixed sized
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prologue plus the replicating portion. */
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#ifndef MAX_MEM_FOR_RS_ALIGN_CODE
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/* Assume that if HANDLE_ALIGN is not defined then no special action
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is required to code fill, which means that we get just repeat the
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one NOP_OPCODE byte. */
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# ifndef HANDLE_ALIGN
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# define MAX_MEM_FOR_RS_ALIGN_CODE 1
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# else
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# define MAX_MEM_FOR_RS_ALIGN_CODE ((1 << alignment) - 1)
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# endif
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#endif
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void
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frag_align_code (int alignment, int max)
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{
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char *p;
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p = frag_var (rs_align_code, MAX_MEM_FOR_RS_ALIGN_CODE, 1,
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(relax_substateT) max, (symbolS *) 0,
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(offsetT) alignment, (char *) 0);
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*p = NOP_OPCODE;
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}
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addressT
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frag_now_fix_octets (void)
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{
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if (now_seg == absolute_section)
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return abs_section_offset;
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return ((char *) obstack_next_free (&frchain_now->frch_obstack)
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- frag_now->fr_literal);
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}
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addressT
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frag_now_fix (void)
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{
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return frag_now_fix_octets () / OCTETS_PER_BYTE;
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}
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void
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frag_append_1_char (int datum)
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{
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frag_alloc_check (&frchain_now->frch_obstack);
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if (obstack_room (&frchain_now->frch_obstack) <= 1)
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{
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frag_wane (frag_now);
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frag_new (0);
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}
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obstack_1grow (&frchain_now->frch_obstack, datum);
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}
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/* Return TRUE if FRAG1 and FRAG2 have a fixed relationship between
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their start addresses. Set OFFSET to the difference in address
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not already accounted for in the frag FR_ADDRESS. */
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bfd_boolean
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frag_offset_fixed_p (const fragS *frag1, const fragS *frag2, offsetT *offset)
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{
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const fragS *frag;
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offsetT off;
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/* Start with offset initialised to difference between the two frags.
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Prior to assigning frag addresses this will be zero. */
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off = frag1->fr_address - frag2->fr_address;
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if (frag1 == frag2)
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{
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*offset = off;
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return TRUE;
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}
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/* Maybe frag2 is after frag1. */
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frag = frag1;
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while (frag->fr_type == rs_fill)
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{
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off += frag->fr_fix + frag->fr_offset * frag->fr_var;
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frag = frag->fr_next;
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if (frag == NULL)
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break;
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if (frag == frag2)
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{
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*offset = off;
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return TRUE;
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}
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}
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/* Maybe frag1 is after frag2. */
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off = frag1->fr_address - frag2->fr_address;
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frag = frag2;
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while (frag->fr_type == rs_fill)
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{
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off -= frag->fr_fix + frag->fr_offset * frag->fr_var;
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frag = frag->fr_next;
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if (frag == NULL)
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break;
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if (frag == frag1)
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{
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*offset = off;
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return TRUE;
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}
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}
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return FALSE;
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}
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