lzo1f_d.ch

lzo-1.08-src.zip 高效的压缩解压代码

/* lzo1f_d.ch -- implementation of the LZO1F decompression 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]>
 */


#include "lzo1_d.ch"


/***********************************************************************
// decompress a block of data.
************************************************************************/

LZO_PUBLIC(int)
DO_DECOMPRESS  ( const lzo_byte *in , lzo_uint  in_len,
                       lzo_byte *out, lzo_uintp out_len,
                       lzo_voidp wrkmem )
{
	register lzo_byte *op;
	register const lzo_byte *ip;
	register lzo_uint t;
	register const lzo_byte *m_pos;

	const lzo_byte * const ip_end = in + in_len;
#if defined(HAVE_ANY_OP)
	lzo_byte * const op_end = out + *out_len;
#endif

	LZO_UNUSED(wrkmem);

#if defined(__LZO_QUERY_DECOMPRESS)
	if (__LZO_IS_DECOMPRESS_QUERY(in,in_len,out,out_len,wrkmem))
		return __LZO_QUERY_DECOMPRESS(in,in_len,out,out_len,wrkmem,0,0);
#endif

	*out_len = 0;

	op = out;
	ip = in;

	while (TEST_IP && TEST_OP)
	{
		t = *ip++;
		if (t > 31)
			goto match;

		/* a literal run */
		if (t == 0)
		{
			NEED_IP(1);
			while (*ip == 0)
			{
				t += 255;
				ip++;
				NEED_IP(1);
			}
			t += 31 + *ip++;
		}
		/* copy literals */
		assert(t > 0); NEED_OP(t); NEED_IP(t+1);
#if defined(LZO_UNALIGNED_OK_4)
		if (t >= 4)
		{
			do {
				* (lzo_uint32p) op = * (const lzo_uint32p) ip;
				op += 4; ip += 4; t -= 4;
			} while (t >= 4);
			if (t > 0) do *op++ = *ip++; while (--t > 0);
		}
		else
#endif
		do *op++ = *ip++; while (--t > 0);

		t = *ip++;

		while (TEST_IP && TEST_OP)
		{
			/* handle matches */
			if (t < 32)
			{
				m_pos = op - 1 - 0x800;
				m_pos -= (t >> 2) & 7;
				m_pos -= *ip++ << 3;
				TEST_LOOKBEHIND(m_pos,out); NEED_OP(3);
				*op++ = *m_pos++; *op++ = *m_pos++; *op++ = *m_pos++;
			}
			else
			{
match:
				if (t < M3_MARKER)
				{
					m_pos = op - 1;
					m_pos -= (t >> 2) & 7;
					m_pos -= *ip++ << 3;
					t >>= 5;
					TEST_LOOKBEHIND(m_pos,out); assert(t > 0); NEED_OP(t+3-1);
					goto copy_match;
				}
				else
				{
					t &= 31;
					if (t == 0)
					{
						NEED_IP(1);
						while (*ip == 0)
						{
							t += 255;
							ip++;
							NEED_IP(1);
						}
						t += 31 + *ip++;
					}
					NEED_IP(2);
					m_pos = op;
#if defined(LZO_UNALIGNED_OK_2) && (LZO_BYTE_ORDER == LZO_LITTLE_ENDIAN)
                    m_pos -= (* (const lzo_ushortp) ip) >> 2;
					ip += 2;
#else
					m_pos -= *ip++ >> 2;
					m_pos -= *ip++ << 6;
#endif
					if (m_pos == op)
						goto eof_found;
				}

				/* copy match */
				TEST_LOOKBEHIND(m_pos,out); assert(t > 0); NEED_OP(t+3-1);
#if defined(LZO_UNALIGNED_OK_4)
				if (t >= 2 * 4 - (3 - 1) && (op - m_pos) >= 4)
				{
					* (lzo_uint32p) op = * (const lzo_uint32p) m_pos;
					op += 4; m_pos += 4; t -= 4 - (3 - 1);
					do {
						* (lzo_uint32p) op = * (const lzo_uint32p) m_pos;
						op += 4; m_pos += 4; t -= 4;
					} while (t >= 4);
					if (t > 0) do *op++ = *m_pos++; while (--t > 0);
				}
				else
#endif
				{
copy_match:
				*op++ = *m_pos++; *op++ = *m_pos++;
				do *op++ = *m_pos++; while (--t > 0);
				}
			}
			t = ip[-2] & 3;
			if (t == 0)
				break;

			/* copy literals */
			assert(t > 0); NEED_OP(t); NEED_IP(t+1);
			do *op++ = *ip++; while (--t > 0);
			t = *ip++;
		}
	}

#if defined(HAVE_TEST_IP) || defined(HAVE_TEST_OP)
	/* no EOF code was found */
	*out_len = op - out;
	return LZO_E_EOF_NOT_FOUND;
#endif

eof_found:
	assert(t == 1);
	*out_len = op - out;
	return (ip == ip_end ? LZO_E_OK :
	       (ip < ip_end  ? LZO_E_INPUT_NOT_CONSUMED : LZO_E_INPUT_OVERRUN));


#if defined(HAVE_NEED_IP)
input_overrun:
	*out_len = op - out;
	return LZO_E_INPUT_OVERRUN;
#endif

#if defined(HAVE_NEED_OP)
output_overrun:
	*out_len = op - out;
	return LZO_E_OUTPUT_OVERRUN;
#endif

#if defined(LZO_TEST_DECOMPRESS_OVERRUN_LOOKBEHIND)
lookbehind_overrun:
	*out_len = op - out;
	return LZO_E_LOOKBEHIND_OVERRUN;
#endif
}


/*
vi:ts=4:et
*/