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/* Copyright (C) 1995, 1996, 1997 Aladdin Enterprises. All rights reserved.
This file is part of GNU Ghostscript.
GNU Ghostscript is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY. No author or distributor accepts responsibility to
anyone for the consequences of using it or for whether it serves any
particular purpose or works at all, unless he says so in writing. Refer to
the GNU General Public License for full details.
Everyone is granted permission to copy, modify and redistribute GNU
Ghostscript, but only under the conditions described in the GNU General
Public License. A copy of this license is supposed to have been given to
you along with GNU Ghostscript so you can know your rights and
responsibilities. It should be in a file named COPYING. Among other
things, the copyright notice and this notice must be preserved on all
copies.
Aladdin Enterprises is not affiliated with the Free Software Foundation or
the GNU Project. GNU Ghostscript, as distributed by Aladdin Enterprises,
does not depend on any other GNU software.
*/
/* srle.c */
/* RunLengthEncode filter */
#include "stdio_.h" /* includes std.h */
#include "memory_.h"
#include "strimpl.h"
#include "srlx.h"
/* ------ RunLengthEncode ------ */
private_st_RLE_state();
#define ss ((stream_RLE_state *)st)
/* Set defaults */
private void
s_RLE_set_defaults(stream_state *st)
{ s_RLE_set_defaults_inline(ss);
}
/* Initialize */
private int
s_RLE_init(stream_state *st)
{ return s_RLE_init_inline(ss);
}
/* Process a buffer */
private int
s_RLE_process(stream_state *st, stream_cursor_read *pr,
stream_cursor_write *pw, bool last)
{ register const byte *p = pr->ptr;
register byte *q = pw->ptr;
const byte *rlimit = pr->limit;
byte *wlimit = pw->limit;
int status = 0;
ulong rleft = ss->record_left;
/*
* We thought that the Genoa CET demands that the output from this
* filter be not just legal, but optimal, so we went to the trouble
* of ensuring this. It turned out that this wasn't actually
* necessary, but we didn't want to change the code back.
*
* For optimal output, we can't just break runs at buffer
* boundaries: unless we hit a record boundary or the end of the
* input, we have to look ahead far enough to know that we aren't
* breaking a run prematurely.
*/
/* Check for leftover output. */
copy: if ( ss->copy_left )
{ uint rcount = rlimit - p;
uint wcount = wlimit - q;
uint count = ss->copy_left;
if ( rcount < count )
count = rcount;
if ( wcount < count )
count = wcount;
if ( rleft < count )
count = rleft;
memcpy(q + 1, p + 1, count);
pr->ptr = p += count;
pw->ptr = q += count;
if ( (ss->record_left = rleft -= count) == 0 )
ss->record_left = rleft = ss->record_size;
if ( (ss->copy_left -= count) != 0 )
return (rcount == 0 ? 0 : 1);
}
while ( p < rlimit )
{ const byte *beg = p;
const byte *p1;
uint count = rlimit - p;
bool end = last;
byte next;
if ( count > rleft )
count = rleft, end = true;
if ( count > 128 )
count = 128, end = true;
p1 = p + count - 1;
if ( count < 3 )
{ if ( !end || count == 0 )
break; /* can't look ahead far enough */
if ( count == 1 )
{ if ( wlimit - q < 2 )
{ status = 1;
break;
}
*++q = 0;
}
else /* count == 2 */
{ if ( p[1] == p[2] )
{ if ( wlimit - q < 2 )
{ status = 1;
break;
}
*++q = 255;
}
else
{ if ( wlimit - q < 3 )
{ status = 1;
break;
}
*++q = 1;
*++q = p[1];
}
}
*++q = p1[1];
p = p1 + 1;
}
else if ( (next = p[1]) == p[2] && next == p[3] )
{ if ( wlimit - q < 2 )
{ status = 1;
break;
}
/* Recognize leading repeated byte */
do { p++; }
while ( p < p1 && p[2] == next );
if ( p == p1 && !end )
{ p = beg; /* need to look ahead further */
break;
}
p++;
*++q = (byte)(257 - (p - beg));
*++q = next;
}
else
{ p1--;
while ( p < p1 && (p[2] != p[1] || p[3] != p[1]) )
p++;
if ( p == p1 )
{ if ( !end )
{ p = beg; /* need to look ahead further */
break;
}
p += 2;
}
count = p - beg;
if ( wlimit - q < count + 1 )
{ p = beg;
if ( q >= wlimit )
{ status = 1;
break;
}
/* Copy some now and some later. */
*++q = count - 1;
ss->copy_left = count;
goto copy;
}
*++q = count - 1;
memcpy(q + 1, beg + 1, count);
q += count;
}
rleft -= p - beg;
if ( rleft == 0 )
rleft = ss->record_size;
}
if ( last && status == 0 && ss->EndOfData )
{ if ( q < wlimit )
*++q = 128;
else
status = 1;
}
pr->ptr = p;
pw->ptr = q;
ss->record_left = rleft;
return status;
}
#undef ss
/* Stream template */
const stream_template s_RLE_template =
{ &st_RLE_state, s_RLE_init, s_RLE_process, 128, 2, NULL,
s_RLE_set_defaults, s_RLE_init
};
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