298 lines
6.3 KiB
C
298 lines
6.3 KiB
C
/*
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* LZO1X Decompressor from LZO
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*
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* Copyright (C) 1996-2012 Markus F.X.J. Oberhumer <markus@oberhumer.com>
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*
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* The full LZO package can be found at:
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* http://www.oberhumer.com/opensource/lzo/
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*
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* Changed for Linux kernel use by:
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* Nitin Gupta <nitingupta910@gmail.com>
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* Richard Purdie <rpurdie@openedhand.com>
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*/
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#ifndef STATIC
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#include <linux/module.h>
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#include <linux/kernel.h>
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#endif
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#include <asm/unaligned.h>
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#include <linux/lzo.h>
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#include "lzodefs.h"
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#define HAVE_IP(x) ((size_t)(ip_end - ip) >= (size_t)(x))
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#define HAVE_OP(x) ((size_t)(op_end - op) >= (size_t)(x))
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#define NEED_IP(x) if (!HAVE_IP(x)) goto input_overrun
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#define NEED_OP(x) if (!HAVE_OP(x)) goto output_overrun
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#define TEST_LB(m_pos) if ((m_pos) < out) goto lookbehind_overrun
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/* This MAX_255_COUNT is the maximum number of times we can add 255 to a base
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* count without overflowing an integer. The multiply will overflow when
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* multiplying 255 by more than MAXINT/255. The sum will overflow earlier
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* depending on the base count. Since the base count is taken from a u8
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* and a few bits, it is safe to assume that it will always be lower than
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* or equal to 2*255, thus we can always prevent any overflow by accepting
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* two less 255 steps. See Documentation/lzo.txt for more information.
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*/
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#define MAX_255_COUNT ((((size_t)~0) / 255) - 2)
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int lzo1x_decompress_safe(const unsigned char *in, size_t in_len,
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unsigned char *out, size_t *out_len)
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{
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unsigned char *op;
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const unsigned char *ip;
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size_t t, next;
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size_t state = 0;
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const unsigned char *m_pos;
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const unsigned char * const ip_end = in + in_len;
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unsigned char * const op_end = out + *out_len;
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unsigned char bitstream_version;
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op = out;
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ip = in;
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if (unlikely(in_len < 3))
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goto input_overrun;
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if (likely(*ip == 17)) {
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bitstream_version = ip[1];
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ip += 2;
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if (unlikely(in_len < 5))
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goto input_overrun;
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} else {
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bitstream_version = 0;
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}
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if (*ip > 17) {
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t = *ip++ - 17;
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if (t < 4) {
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next = t;
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goto match_next;
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}
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goto copy_literal_run;
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}
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for (;;) {
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t = *ip++;
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if (t < 16) {
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if (likely(state == 0)) {
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if (unlikely(t == 0)) {
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size_t offset;
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const unsigned char *ip_last = ip;
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while (unlikely(*ip == 0)) {
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ip++;
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NEED_IP(1);
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}
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offset = ip - ip_last;
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if (unlikely(offset > MAX_255_COUNT))
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return LZO_E_ERROR;
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offset = (offset << 8) - offset;
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t += offset + 15 + *ip++;
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}
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t += 3;
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copy_literal_run:
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#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
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if (likely(HAVE_IP(t + 15) && HAVE_OP(t + 15))) {
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const unsigned char *ie = ip + t;
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unsigned char *oe = op + t;
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do {
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COPY8(op, ip);
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op += 8;
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ip += 8;
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COPY8(op, ip);
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op += 8;
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ip += 8;
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} while (ip < ie);
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ip = ie;
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op = oe;
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} else
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#endif
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{
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NEED_OP(t);
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NEED_IP(t + 3);
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do {
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*op++ = *ip++;
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} while (--t > 0);
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}
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state = 4;
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continue;
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} else if (state != 4) {
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next = t & 3;
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m_pos = op - 1;
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m_pos -= t >> 2;
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m_pos -= *ip++ << 2;
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TEST_LB(m_pos);
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NEED_OP(2);
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op[0] = m_pos[0];
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op[1] = m_pos[1];
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op += 2;
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goto match_next;
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} else {
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next = t & 3;
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m_pos = op - (1 + M2_MAX_OFFSET);
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m_pos -= t >> 2;
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m_pos -= *ip++ << 2;
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t = 3;
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}
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} else if (t >= 64) {
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next = t & 3;
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m_pos = op - 1;
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m_pos -= (t >> 2) & 7;
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m_pos -= *ip++ << 3;
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t = (t >> 5) - 1 + (3 - 1);
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} else if (t >= 32) {
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t = (t & 31) + (3 - 1);
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if (unlikely(t == 2)) {
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size_t offset;
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const unsigned char *ip_last = ip;
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while (unlikely(*ip == 0)) {
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ip++;
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NEED_IP(1);
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}
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offset = ip - ip_last;
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if (unlikely(offset > MAX_255_COUNT))
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return LZO_E_ERROR;
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offset = (offset << 8) - offset;
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t += offset + 31 + *ip++;
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NEED_IP(2);
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}
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m_pos = op - 1;
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next = get_unaligned_le16(ip);
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ip += 2;
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m_pos -= next >> 2;
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next &= 3;
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} else {
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NEED_IP(2);
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next = get_unaligned_le16(ip);
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if (((next & 0xfffc) == 0xfffc) &&
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((t & 0xf8) == 0x18) &&
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likely(bitstream_version)) {
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NEED_IP(3);
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t &= 7;
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t |= ip[2] << 3;
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t += MIN_ZERO_RUN_LENGTH;
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NEED_OP(t);
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memset(op, 0, t);
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op += t;
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next &= 3;
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ip += 3;
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goto match_next;
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} else {
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m_pos = op;
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m_pos -= (t & 8) << 11;
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t = (t & 7) + (3 - 1);
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if (unlikely(t == 2)) {
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size_t offset;
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const unsigned char *ip_last = ip;
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while (unlikely(*ip == 0)) {
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ip++;
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NEED_IP(1);
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}
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offset = ip - ip_last;
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if (unlikely(offset > MAX_255_COUNT))
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return LZO_E_ERROR;
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offset = (offset << 8) - offset;
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t += offset + 7 + *ip++;
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NEED_IP(2);
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next = get_unaligned_le16(ip);
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}
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ip += 2;
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m_pos -= next >> 2;
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next &= 3;
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if (m_pos == op)
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goto eof_found;
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m_pos -= 0x4000;
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}
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}
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TEST_LB(m_pos);
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#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
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if (op - m_pos >= 8) {
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unsigned char *oe = op + t;
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if (likely(HAVE_OP(t + 15))) {
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do {
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COPY8(op, m_pos);
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op += 8;
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m_pos += 8;
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COPY8(op, m_pos);
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op += 8;
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m_pos += 8;
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} while (op < oe);
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op = oe;
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if (HAVE_IP(6)) {
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state = next;
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COPY4(op, ip);
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op += next;
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ip += next;
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continue;
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}
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} else {
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NEED_OP(t);
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do {
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*op++ = *m_pos++;
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} while (op < oe);
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}
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} else
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#endif
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{
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unsigned char *oe = op + t;
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NEED_OP(t);
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op[0] = m_pos[0];
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op[1] = m_pos[1];
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op += 2;
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m_pos += 2;
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do {
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*op++ = *m_pos++;
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} while (op < oe);
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}
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match_next:
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state = next;
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t = next;
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#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
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if (likely(HAVE_IP(6) && HAVE_OP(4))) {
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COPY4(op, ip);
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op += t;
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ip += t;
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} else
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#endif
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{
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NEED_IP(t + 3);
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NEED_OP(t);
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while (t > 0) {
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*op++ = *ip++;
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t--;
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}
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}
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}
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eof_found:
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*out_len = op - out;
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return (t != 3 ? LZO_E_ERROR :
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ip == ip_end ? LZO_E_OK :
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ip < ip_end ? LZO_E_INPUT_NOT_CONSUMED : LZO_E_INPUT_OVERRUN);
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input_overrun:
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*out_len = op - out;
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return LZO_E_INPUT_OVERRUN;
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output_overrun:
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*out_len = op - out;
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return LZO_E_OUTPUT_OVERRUN;
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lookbehind_overrun:
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*out_len = op - out;
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return LZO_E_LOOKBEHIND_OVERRUN;
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}
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#ifndef STATIC
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EXPORT_SYMBOL_GPL(lzo1x_decompress_safe);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("LZO1X Decompressor");
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#endif
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