busybox/archival/lzo1x_c.c

/* implementation of the LZO1[XY]-1 compression algorithm

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

   Copyright (C) 1996..2008 Markus Franz Xaver Johannes Oberhumer
   All Rights Reserved.

   Markus F.X.J. Oberhumer <markus@oberhumer.com>
   http://www.oberhumer.com/opensource/lzo/

   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.,
   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

/***********************************************************************
// compress a block of data.
************************************************************************/
static NOINLINE unsigned
do_compress(const uint8_t* in, unsigned in_len,
		uint8_t* out, unsigned* out_len,
		void* wrkmem)
{
	register const uint8_t* ip;
	uint8_t* op;
	const uint8_t* const in_end = in + in_len;
	const uint8_t* const ip_end = in + in_len - M2_MAX_LEN - 5;
	const uint8_t* ii;
	const void* *const dict = (const void**) wrkmem;

	op = out;
	ip = in;
	ii = ip;

	ip += 4;
	for (;;) {
		register const uint8_t* m_pos;
		unsigned m_off;
		unsigned m_len;
		unsigned dindex;

		D_INDEX1(dindex,ip);
		GINDEX(m_pos,m_off,dict,dindex,in);
		if (LZO_CHECK_MPOS_NON_DET(m_pos,m_off,in,ip,M4_MAX_OFFSET))
			goto literal;
#if 1
		if (m_off <= M2_MAX_OFFSET || m_pos[3] == ip[3])
			goto try_match;
		D_INDEX2(dindex,ip);
#endif
		GINDEX(m_pos,m_off,dict,dindex,in);
		if (LZO_CHECK_MPOS_NON_DET(m_pos,m_off,in,ip,M4_MAX_OFFSET))
			goto literal;
		if (m_off <= M2_MAX_OFFSET || m_pos[3] == ip[3])
			goto try_match;
		goto literal;

 try_match:
#if 1 && defined(LZO_UNALIGNED_OK_2)
		if (* (const lzo_ushortp) m_pos != * (const lzo_ushortp) ip)
#else
		if (m_pos[0] != ip[0] || m_pos[1] != ip[1])
#endif
		{
		} else {
			if (m_pos[2] == ip[2]) {
#if 0
				if (m_off <= M2_MAX_OFFSET)
					goto match;
				if (lit <= 3)
					goto match;
				if (lit == 3) {			  /* better compression, but slower */
					assert(op - 2 > out); op[-2] |= (uint8_t)(3);
					*op++ = *ii++; *op++ = *ii++; *op++ = *ii++;
					goto code_match;
				}
				if (m_pos[3] == ip[3])
#endif
					goto match;
			}
			else {
				/* still need a better way for finding M1 matches */
#if 0
				/* a M1 match */
#if 0
				if (m_off <= M1_MAX_OFFSET && lit > 0 && lit <= 3)
#else
				if (m_off <= M1_MAX_OFFSET && lit == 3)
#endif
				{
					register unsigned t;

					t = lit;
					assert(op - 2 > out); op[-2] |= (uint8_t)(t);
					do *op++ = *ii++; while (--t > 0);
					assert(ii == ip);
					m_off -= 1;
					*op++ = (uint8_t)(M1_MARKER | ((m_off & 3) << 2));
					*op++ = (uint8_t)(m_off >> 2);
					ip += 2;
					goto match_done;
				}
#endif
			}
		}

		/* a literal */
 literal:
		UPDATE_I(dict, 0, dindex, ip, in);
		++ip;
		if (ip >= ip_end)
			break;
		continue;

		/* a match */
match:
		UPDATE_I(dict, 0, dindex, ip, in);
		/* store current literal run */
		if (pd(ip, ii) > 0) {
			register unsigned t = pd(ip, ii);

			if (t <= 3) {
				assert(op - 2 > out);
				op[-2] |= (uint8_t)(t);
			}
			else if (t <= 18)
				*op++ = (uint8_t)(t - 3);
			else {
				register unsigned tt = t - 18;

				*op++ = 0;
				while (tt > 255) {
					tt -= 255;
					*op++ = 0;
				}
				assert(tt > 0);
				*op++ = (uint8_t)(tt);
			}
			do *op++ = *ii++; while (--t > 0);
		}

		/* code the match */
		assert(ii == ip);
		ip += 3;
		if (m_pos[3] != *ip++ || m_pos[4] != *ip++ || m_pos[5] != *ip++
		 || m_pos[6] != *ip++ || m_pos[7] != *ip++ || m_pos[8] != *ip++
#ifdef LZO1Y
		 || m_pos[ 9] != *ip++ || m_pos[10] != *ip++ || m_pos[11] != *ip++
		 || m_pos[12] != *ip++ || m_pos[13] != *ip++ || m_pos[14] != *ip++
#endif
		) {
			--ip;
			m_len = pd(ip, ii);
			assert(m_len >= 3);
			assert(m_len <= M2_MAX_LEN);

			if (m_off <= M2_MAX_OFFSET) {
				m_off -= 1;
#if defined(LZO1X)
				*op++ = (uint8_t)(((m_len - 1) << 5) | ((m_off & 7) << 2));
				*op++ = (uint8_t)(m_off >> 3);
#elif defined(LZO1Y)
				*op++ = (uint8_t)(((m_len + 1) << 4) | ((m_off & 3) << 2));
				*op++ = (uint8_t)(m_off >> 2);
#endif
			}
			else if (m_off <= M3_MAX_OFFSET) {
				m_off -= 1;
				*op++ = (uint8_t)(M3_MARKER | (m_len - 2));
				goto m3_m4_offset;
			} else {
#if defined(LZO1X)
				m_off -= 0x4000;
				assert(m_off > 0);
				assert(m_off <= 0x7fff);
				*op++ = (uint8_t)(M4_MARKER | ((m_off & 0x4000) >> 11) | (m_len - 2));
				goto m3_m4_offset;
#elif defined(LZO1Y)
				goto m4_match;
#endif
			}
		}
		else {
			{
				const uint8_t* end = in_end;
				const uint8_t* m = m_pos + M2_MAX_LEN + 1;
				while (ip < end && *m == *ip)
					m++, ip++;
				m_len = pd(ip, ii);
			}
			assert(m_len > M2_MAX_LEN);

			if (m_off <= M3_MAX_OFFSET) {
				m_off -= 1;
				if (m_len <= 33)
					*op++ = (uint8_t)(M3_MARKER | (m_len - 2));
				else {
					m_len -= 33;
					*op++ = M3_MARKER | 0;
					goto m3_m4_len;
				}
			} else {
#if defined(LZO1Y)
 m4_match:
#endif
				m_off -= 0x4000;
				assert(m_off > 0);
				assert(m_off <= 0x7fff);
				if (m_len <= M4_MAX_LEN)
					*op++ = (uint8_t)(M4_MARKER | ((m_off & 0x4000) >> 11) | (m_len - 2));
				else {
					m_len -= M4_MAX_LEN;
					*op++ = (uint8_t)(M4_MARKER | ((m_off & 0x4000) >> 11));
 m3_m4_len:
					while (m_len > 255) {
						m_len -= 255;
						*op++ = 0;
					}
					assert(m_len > 0);
					*op++ = (uint8_t)(m_len);
				}
			}
 m3_m4_offset:
			*op++ = (uint8_t)((m_off & 63) << 2);
			*op++ = (uint8_t)(m_off >> 6);
		}
#if 0
 match_done:
#endif
		ii = ip;
		if (ip >= ip_end)
			break;
	}

	*out_len = pd(op, out);
	return pd(in_end, ii);
}

/***********************************************************************
// public entry point
************************************************************************/
int DO_COMPRESS(const uint8_t* in, unsigned in_len,
		uint8_t* out, unsigned* out_len,
		void* wrkmem)
{
	uint8_t* op = out;
	unsigned t;

	if (in_len <= M2_MAX_LEN + 5)
		t = in_len;
	else {
		t = do_compress(in,in_len,op,out_len,wrkmem);
		op += *out_len;
	}

	if (t > 0) {
		const uint8_t* ii = in + in_len - t;

		if (op == out && t <= 238)
			*op++ = (uint8_t)(17 + t);
		else if (t <= 3)
			op[-2] |= (uint8_t)(t);
		else if (t <= 18)
			*op++ = (uint8_t)(t - 3);
		else {
			unsigned tt = t - 18;

			*op++ = 0;
			while (tt > 255) {
				tt -= 255;
				*op++ = 0;
			}
			assert(tt > 0);
			*op++ = (uint8_t)(tt);
		}
		do *op++ = *ii++; while (--t > 0);
	}

	*op++ = M4_MARKER | 1;
	*op++ = 0;
	*op++ = 0;

	*out_len = pd(op, out);
	return 0; /*LZO_E_OK*/
}