lzo1b_r.ch

lzo-1.08-src.zip 高效的压缩解压代码

/* lzo1b_r.ch -- literal run handling for the the LZO1B/LZO1C algorithm

   This file is part of the LZO real-time data compression library.

   Copyright (C) 1996-2002 Markus Franz Xaver Johannes Oberhumer
   All Rights Reserved.

   The LZO library 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 of
   the License, or (at your option) any later version.

   The LZO library 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 the LZO library; see the file COPYING.
   If not, write to the Free Software Foundation, Inc.,
   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

   Markus F.X.J. Oberhumer
   <[e-mail]>
 */


/***********************************************************************
// store a literal run (internal)
************************************************************************/

LZO_PUBLIC(lzo_byte *)
STORE_RUN ( lzo_byte * const oo, const lzo_byte * const ii, lzo_uint r_len)
{
#if defined(LZO_OPTIMIZE_GNUC_i386)
	register lzo_byte *op __asm__("%edi");
	register const lzo_byte *ip __asm__("%esi");
	register lzo_uint t __asm__("%ecx");
#else
	register lzo_byte *op;
	register const lzo_byte *ip;
	register lzo_uint t;
#endif

	LZO_STATS(lzo_stats->literals += r_len);

	op = oo;
	ip = ii;
	assert(r_len > 0);

	/* code a long R0 run */
	if (r_len >= 512)
	{
		unsigned r_bits = 6;		/* 256 << 6 == 16384 */
		lzo_uint tt = 32768u;

		while (r_len >= (t = tt))
		{
			r_len -= t;
			*op++ = 0; *op++ = (R0FAST - R0MIN) + 7;
			MEMCPY8_DS(op, ip, t);
			LZO_STATS(lzo_stats->r0long_runs++);
		}
		tt >>= 1;
		do {
			if (r_len >= (t = tt))
			{
				r_len -= t;
				*op++ = 0; *op++ = LZO_BYTE((R0FAST - R0MIN) + r_bits);
				MEMCPY8_DS(op, ip, t);
				LZO_STATS(lzo_stats->r0long_runs++);
			}
			tt >>= 1;
		} while (--r_bits > 0);
	}
	assert(r_len < 512);

	while (r_len >= (t = R0FAST))
	{
		r_len -= t;
		*op++ = 0; *op++ = (R0FAST - R0MIN);
		MEMCPY8_DS(op, ip, t);
		LZO_STATS(lzo_stats->r0fast_runs++);
	}

	t = r_len;
	if (t >= R0MIN)
	{
		/* code a short R0 run */
		*op++ = 0; *op++ = LZO_BYTE(t - R0MIN);
		MEMCPY_DS(op, ip, t);
		LZO_STATS(lzo_stats->r0short_runs++);
	}
	else if (t > 0)
	{
		/* code a short literal run */
		LZO_STATS(lzo_stats->lit_runs++);
		LZO_STATS(lzo_stats->lit_run[t]++);
		*op++ = LZO_BYTE(t);
		MEMCPY_DS(op, ip, t);
	}

	return op;
}


/*
vi:ts=4:et
*/