/*

 *  LZO1X Decompressor from LZO

 *

 *  Copyright (C) 1996-2012 Markus F.X.J. Oberhumer <markus@oberhumer.com>

 *

 *  The full LZO package can be found at:

 *  http://www.oberhumer.com/opensource/lzo/

 *

 *  Changed for Linux kernel use by:

 *  Nitin Gupta <nitingupta910@gmail.com>

 *  Richard Purdie <rpurdie@openedhand.com>

 */

#include <asm/unaligned.h>

#include <common.h>

#include <lzo.h>

#include "lzodefs.h"

#define HAVE_IP(x)      ((size_t)(ip_end - ip) >= (size_t)(x))

#define HAVE_OP(x)      ((size_t)(op_end - op) >= (size_t)(x))

#define NEED_IP(x)      if (!HAVE_IP(x)) goto input_overrun

#define NEED_OP(x)      if (!HAVE_OP(x)) goto output_overrun

#define TEST_LB(m_pos)  if ((m_pos) < out) goto lookbehind_overrun

/* This MAX_255_COUNT is the maximum number of times we can add 255 to a base

 * count without overflowing an integer. The multiply will overflow when

 * multiplying 255 by more than MAXINT/255. The sum will overflow earlier

 * depending on the base count. Since the base count is taken from a u8

 * and a few bits, it is safe to assume that it will always be lower than

 * or equal to 2*255, thus we can always prevent any overflow by accepting

 * two less 255 steps. See Documentation/lzo.txt for more information.

 */

#define MAX_255_COUNT      ((((size_t)~0) / 255) - 2)

int lzo1x_decompress_safe(const unsigned char *in, size_t in_len,

      unsigned char *out, size_t *out_len)

{

  unsigned char *op;

  const unsigned char *ip;

  size_t t, next;

  size_t state = 0;

  const unsigned char *m_pos;

  const unsigned char * const ip_end = in + in_len;

  unsigned char * const op_end = out + *out_len;

  op = out;

  ip = in;

  if (unlikely(in_len < 3))

    goto input_overrun;

  if (*ip > 17) {

    t = *ip++ - 17;

    if (t < 4) {

      next = t;

      goto match_next;

    }

    goto copy_literal_run;

  }

  for (;;) {

    t = *ip++;

    if (t < 16) {

      if (likely(state == 0)) {

        if (unlikely(t == 0)) {

          size_t offset;

          const unsigned char *ip_last = ip;

          while (unlikely(*ip == 0)) {

            ip++;

            NEED_IP(1);

          }

          offset = ip - ip_last;

          if (unlikely(offset > MAX_255_COUNT))

            return LZO_E_ERROR;

          offset = (offset << 8) - offset;

          t += offset + 15 + *ip++;

        }

        t += 3;

copy_literal_run:

#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)

        if (likely(HAVE_IP(t + 15) && HAVE_OP(t + 15))) {

          const unsigned char *ie = ip + t;

          unsigned char *oe = op + t;

          do {

            COPY8(op, ip);

            op += 8;

            ip += 8;

            COPY8(op, ip);

            op += 8;

            ip += 8;

          } while (ip < ie);

          ip = ie;

          op = oe;

        } else

#endif

        {

          NEED_OP(t);

          NEED_IP(t + 3);

          do {

            *op++ = *ip++;

          } while (--t > 0);

        }

        state = 4;

        continue;

      } else if (state != 4) {

        next = t & 3;

        m_pos = op - 1;

        m_pos -= t >> 2;

        m_pos -= *ip++ << 2;

        TEST_LB(m_pos);

        NEED_OP(2);

        op[0] = m_pos[0];

        op[1] = m_pos[1];

        op += 2;

        goto match_next;

      } else {

        next = t & 3;

        m_pos = op - (1 + M2_MAX_OFFSET);

        m_pos -= t >> 2;

        m_pos -= *ip++ << 2;

        t = 3;

      }

    } else if (t >= 64) {

      next = t & 3;

      m_pos = op - 1;

      m_pos -= (t >> 2) & 7;

      m_pos -= *ip++ << 3;

      t = (t >> 5) - 1 + (3 - 1);

    } else if (t >= 32) {

      t = (t & 31) + (3 - 1);

      if (unlikely(t == 2)) {

        size_t offset;

        const unsigned char *ip_last = ip;

        while (unlikely(*ip == 0)) {

          ip++;

          NEED_IP(1);

        }

        offset = ip - ip_last;

        if (unlikely(offset > MAX_255_COUNT))

          return LZO_E_ERROR;

        offset = (offset << 8) - offset;

        t += offset + 31 + *ip++;

        NEED_IP(2);

      }

      m_pos = op - 1;

      next = get_unaligned_le16(ip);

      ip += 2;

      m_pos -= next >> 2;

      next &= 3;

    } else {

      m_pos = op;

      m_pos -= (t & 8) << 11;

      t = (t & 7) + (3 - 1);

      if (unlikely(t == 2)) {

        size_t offset;

        const unsigned char *ip_last = ip;

        while (unlikely(*ip == 0)) {

          ip++;

          NEED_IP(1);

        }

        offset = ip - ip_last;

        if (unlikely(offset > MAX_255_COUNT))

          return LZO_E_ERROR;

        offset = (offset << 8) - offset;

        t += offset + 7 + *ip++;

        NEED_IP(2);

      }

      next = get_unaligned_le16(ip);

      ip += 2;

      m_pos -= next >> 2;

      next &= 3;

      if (m_pos == op)

        goto eof_found;

      m_pos -= 0x4000;

    }

    TEST_LB(m_pos);

#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)

    if (op - m_pos >= 8) {

      unsigned char *oe = op + t;

      if (likely(HAVE_OP(t + 15))) {

        do {

          COPY8(op, m_pos);

          op += 8;

          m_pos += 8;

          COPY8(op, m_pos);

          op += 8;

          m_pos += 8;

        } while (op < oe);

        op = oe;

        if (HAVE_IP(6)) {

          state = next;

          COPY4(op, ip);

          op += next;

          ip += next;

          continue;

        }

      } else {

        NEED_OP(t);

        do {

          *op++ = *m_pos++;

        } while (op < oe);

      }

    } else

#endif

    {

      unsigned char *oe = op + t;

      NEED_OP(t);

      op[0] = m_pos[0];

      op[1] = m_pos[1];

      op += 2;

      m_pos += 2;

      do {

        *op++ = *m_pos++;

      } while (op < oe);

    }

match_next:

    state = next;

    t = next;

#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)

    if (likely(HAVE_IP(6) && HAVE_OP(4))) {

      COPY4(op, ip);

      op += t;

      ip += t;

    } else

#endif

    {

      NEED_IP(t + 3);

      NEED_OP(t);

      while (t > 0) {

        *op++ = *ip++;

        t--;

      }

    }

  }

eof_found:

  *out_len = op - out;

  return (t != 3       ? LZO_E_ERROR :

    ip == ip_end ? LZO_E_OK :

    ip <  ip_end ? LZO_E_INPUT_NOT_CONSUMED : LZO_E_INPUT_OVERRUN);

input_overrun:

  *out_len = op - out;

  return LZO_E_INPUT_OVERRUN;

output_overrun:

  *out_len = op - out;

  return LZO_E_OUTPUT_OVERRUN;

lookbehind_overrun:

  *out_len = op - out;

  return LZO_E_LOOKBEHIND_OVERRUN;

}

EXPORT_SYMBOL(lzo1x_decompress_safe);