/* xdelta 3 - delta compression tools and library
 * Copyright (C) 2002, 2003, 2006, 2007.  Joshua P. MacDonald
 *
 *  This program 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.
 *
 *  This program 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 this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifndef _XDELTA3_SECOND_H_
#define _XDELTA3_SECOND_H_

/******************************************************************************************
 Secondary compression
 ******************************************************************************************/

#define xd3_sec_data(s) ((s)->sec_stream_d)
#define xd3_sec_inst(s) ((s)->sec_stream_i)
#define xd3_sec_addr(s) ((s)->sec_stream_a)

struct _xd3_sec_type
{
  int         id;
  const char *name;
  xd3_secondary_flags flags;

  /* xd3_sec_stream is opaque to the generic code */
  xd3_sec_stream* (*alloc)   (xd3_stream     *stream);
  void            (*destroy) (xd3_stream     *stream,
			      xd3_sec_stream *sec);
  void            (*init)    (xd3_sec_stream *sec);
  int             (*decode)  (xd3_stream     *stream,
			      xd3_sec_stream *sec_stream,
			      const uint8_t **input,
			      const uint8_t  *input_end,
			      uint8_t       **output,
			      const uint8_t  *output_end);
#if XD3_ENCODER
  int             (*encode)  (xd3_stream     *stream,
			      xd3_sec_stream *sec_stream,
			      xd3_output     *input,
			      xd3_output     *output,
			      xd3_sec_cfg    *cfg);
#endif
};

#define BIT_STATE_ENCODE_INIT { 0, 1 }
#define BIT_STATE_DECODE_INIT { 0, 0x100 }

typedef struct _bit_state bit_state;
struct _bit_state
{
  usize_t cur_byte;
  usize_t cur_mask;
};

static inline void xd3_bit_state_encode_init  (bit_state       *bits)
{
  bits->cur_byte = 0;
  bits->cur_mask = 1;
}

static inline int xd3_decode_bits     (xd3_stream     *stream,
				       bit_state      *bits,
				       const uint8_t **input,
				       const uint8_t  *input_max,
				       usize_t          nbits,
				       usize_t         *valuep)
{
  usize_t value = 0;
  usize_t vmask = 1 << nbits;

  if (bits->cur_mask == 0x100) { goto next_byte; }

  for (;;)
    {
      do
	{
	  vmask >>= 1;

	  if (bits->cur_byte & bits->cur_mask)
	    {
	      value |= vmask;
	    }

	  bits->cur_mask <<= 1;

	  if (vmask == 1) { goto done; }
	}
      while (bits->cur_mask != 0x100);

    next_byte:

      if (*input == input_max)
	{
	  stream->msg = "secondary decoder end of input";
	  return XD3_INTERNAL;
	}

      bits->cur_byte = *(*input)++;
      bits->cur_mask = 1;
    }

 done:

  IF_DEBUG2 (DP(RINT "(d) %u ", value));

  (*valuep) = value;
  return 0;
}

#if REGRESSION_TEST
/* There may be extra bits at the end of secondary decompression, this macro checks for
 * non-zero bits.  This is overly strict, but helps pass the single-bit-error regression
 * test. */
static int
xd3_test_clean_bits (xd3_stream *stream, bit_state *bits)
{
  for (; bits->cur_mask != 0x100; bits->cur_mask <<= 1)
    {
      if (bits->cur_byte & bits->cur_mask)
	{
	  stream->msg = "secondary decoder garbage";
	  return XD3_INTERNAL;
	}
    }

  return 0;
}
#endif

static xd3_sec_stream*
xd3_get_secondary (xd3_stream *stream, xd3_sec_stream **sec_streamp)
{
  xd3_sec_stream *sec_stream;

  if ((sec_stream = *sec_streamp) == NULL)
    {
      if ((*sec_streamp = stream->sec_type->alloc (stream)) == NULL)
	{
	  return NULL;
	}

      sec_stream = *sec_streamp;

      /* If cuumulative stats, init once. */
      stream->sec_type->init (sec_stream);
    }

  return sec_stream;
}

static int
xd3_decode_secondary (xd3_stream      *stream,
		      xd3_desect      *sect,
		      xd3_sec_stream **sec_streamp)
{
  xd3_sec_stream *sec_stream;
  uint32_t dec_size;
  uint8_t *out_used;
  int ret;

  if ((sec_stream = xd3_get_secondary (stream, sec_streamp)) == NULL) { return ENOMEM; }

  /* Decode the size, allocate the buffer. */
  if ((ret = xd3_read_size (stream, & sect->buf, sect->buf_max, & dec_size)) ||
      (ret = xd3_decode_allocate (stream, dec_size, & sect->copied2, & sect->alloc2)))
    {
      return ret;
    }

  out_used = sect->copied2;

  if ((ret = stream->sec_type->decode (stream, sec_stream,
				       & sect->buf, sect->buf_max,
				       & out_used, out_used + dec_size))) { return ret; }

  if (sect->buf != sect->buf_max)
    {
      stream->msg = "secondary decoder finished with unused input";
      return XD3_INTERNAL;
    }

  if (out_used != sect->copied2 + dec_size)
    {
      stream->msg = "secondary decoder short output";
      return XD3_INTERNAL;
    }

  sect->buf     = sect->copied2;
  sect->buf_max = sect->copied2 + dec_size;
  sect->size = dec_size;

  return 0;
}

#if XD3_ENCODER
/* OPT: Should these be inline? */
static inline int xd3_encode_bit       (xd3_stream      *stream,
					xd3_output     **output,
					bit_state       *bits,
					int              bit)
{
  int ret;

  if (bit)
    {
      bits->cur_byte |= bits->cur_mask;
    }

  /* OPT: Might help to buffer more than 8 bits at once. */
  if (bits->cur_mask == 0x80)
    {
      if ((ret = xd3_emit_byte (stream, output, bits->cur_byte)) != 0) { return ret; }

      bits->cur_mask = 1;
      bits->cur_byte = 0;
    }
  else
    {
      bits->cur_mask <<= 1;
    }

  return 0;
}

static inline int xd3_flush_bits       (xd3_stream      *stream,
					xd3_output     **output,
					bit_state       *bits)
{
  return (bits->cur_mask == 1) ? 0 : xd3_emit_byte (stream, output, bits->cur_byte);
}

static inline int xd3_encode_bits      (xd3_stream      *stream,
					xd3_output     **output,
					bit_state       *bits,
					usize_t           nbits,
					usize_t           value)
{
  int ret;
  usize_t mask = 1 << nbits;

  XD3_ASSERT (nbits > 0);
  XD3_ASSERT (nbits < sizeof (usize_t) * 8);
  XD3_ASSERT (value < mask);

  do
    {
      mask >>= 1;

      if ((ret = xd3_encode_bit (stream, output, bits, value & mask))) { return ret; }
    }
  while (mask != 1);

  IF_DEBUG2 (DP(RINT "(e) %u ", value));

  return 0;
}

static int
xd3_encode_secondary (xd3_stream      *stream,
		      xd3_output     **head,
		      xd3_output     **tail,
		      xd3_sec_stream **sec_streamp,
		      xd3_sec_cfg     *cfg,
		      int             *did_it)
{
  xd3_sec_stream *sec_stream;
  xd3_output     *tmp_head;
  xd3_output     *tmp_tail;

  usize_t comp_size;
  usize_t orig_size;

  int ret;

  orig_size = xd3_sizeof_output (*head);

  if (orig_size < SECONDARY_MIN_INPUT) { return 0; }

  if ((sec_stream = xd3_get_secondary (stream, sec_streamp)) == NULL) { return ENOMEM; }

  tmp_head = xd3_alloc_output (stream, NULL);

  /* Encode the size, encode the data.  @@ Encoding the size makes it simpler, but is a
   * little gross.  Should not need the entire section in contiguous memory, but it is
   * much easier this way. */
  if ((ret = xd3_emit_size (stream, & tmp_head, orig_size)) ||
      (ret = stream->sec_type->encode (stream, sec_stream, *head, tmp_head, cfg))) { goto getout; }

  /* If the secondary compressor determines its no good, it returns XD3_NOSECOND. */

  /* Setup tmp_tail, comp_size */
  tmp_tail  = tmp_head;
  comp_size = tmp_head->next;

  while (tmp_tail->next_page != NULL)
    {
      tmp_tail = tmp_tail->next_page;
      comp_size += tmp_tail->next;
    }

  XD3_ASSERT (comp_size == xd3_sizeof_output (tmp_head));
  XD3_ASSERT (tmp_tail != NULL);

  if (comp_size < (orig_size - SECONDARY_MIN_SAVINGS))
    {
      IF_DEBUG1(DP(RINT "secondary saved %u bytes: %u -> %u (%0.2f%%)\n",
			 orig_size - comp_size, orig_size, comp_size,
			 (double) comp_size / (double) orig_size));

      xd3_free_output (stream, *head);

      *head = tmp_head;
      *tail = tmp_tail;
      *did_it = 1;
    }
  else
    {
    getout:
      if (ret == XD3_NOSECOND) { ret = 0; }
      xd3_free_output (stream, tmp_head);
    }

  return ret;
}
#endif /* XD3_ENCODER */
#endif /* _XDELTA3_SECOND_H_ */