/*

 *  LibXDiff by Davide Libenzi ( File Differential Library )

 *  Copyright (C) 2003  Davide Libenzi

 *

 *  This library is free software; you can redistribute it and/or

 *  modify it under the terms of the GNU Lesser General Public

 *  License as published by the Free Software Foundation; either

 *  version 2.1 of the License, or (at your option) any later version.

 *

 *  This 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

 *  Lesser General Public License for more details.

 *

 *  You should have received a copy of the GNU Lesser General Public

 *  License along with this library; if not, see

 *  <http://www.gnu.org/licenses/>.

 *

 *  Davide Libenzi <davidel@xmailserver.org>

 *

 */

#include "xinclude.h"

#define XDL_KPDIS_RUN 4

#define XDL_MAX_EQLIMIT 1024

#define XDL_SIMSCAN_WINDOW 100

#define XDL_GUESS_NLINES1 256

#define XDL_GUESS_NLINES2 20

#define DISCARD 0

#define KEEP 1

#define INVESTIGATE 2

typedef struct s_xdlclass {

  uint64_t line_hash;

  struct s_xdlclass *next;

  const uint8_t *ptr;

  size_t size;

  long idx;

  long len1, len2;

} xdlclass_t;

typedef struct s_xdlclassifier {

  unsigned int hbits;

  long hsize;

  xdlclass_t **rchash;

  chastore_t ncha;

  xdlclass_t **rcrecs;

  long alloc;

  long count;

  long flags;

} xdlclassifier_t;

static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags) {

  cf->flags = flags;

  cf->hbits = xdl_hashbits((unsigned int) size);

  cf->hsize = 1 << cf->hbits;

  if (xdl_cha_init(&cf->ncha, sizeof(xdlclass_t), size / 4 + 1) < 0) {

    return -1;

  }

  if (!XDL_CALLOC_ARRAY(cf->rchash, cf->hsize)) {

    xdl_cha_free(&cf->ncha);

    return -1;

  }

  cf->alloc = size;

  if (!XDL_ALLOC_ARRAY(cf->rcrecs, cf->alloc)) {

    xdl_free(cf->rchash);

    xdl_cha_free(&cf->ncha);

    return -1;

  }

  cf->count = 0;

  return 0;

}

static void xdl_free_classifier(xdlclassifier_t *cf) {

  xdl_free(cf->rcrecs);

  xdl_free(cf->rchash);

  xdl_cha_free(&cf->ncha);

}

static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t *rec,

             uint64_t line_hash) {

  size_t hi;

  xdlclass_t *rcrec;

  hi = XDL_HASHLONG(line_hash, cf->hbits);

  for (rcrec = cf->rchash[hi]; rcrec; rcrec = rcrec->next)

    if (rcrec->line_hash == line_hash &&

        xdl_recmatch((const char *)rcrec->ptr, (long)rcrec->size,

          (const char *)rec->ptr, (long)rec->size, cf->flags))

      break;

  if (!rcrec) {

    if (!(rcrec = xdl_cha_alloc(&cf->ncha))) {

      return -1;

    }

    rcrec->idx = cf->count++;

    if (XDL_ALLOC_GROW(cf->rcrecs, cf->count, cf->alloc))

        return -1;

    cf->rcrecs[rcrec->idx] = rcrec;

    rcrec->line_hash = line_hash;

    rcrec->ptr = rec->ptr;

    rcrec->size = rec->size;

    rcrec->len1 = rcrec->len2 = 0;

    rcrec->next = cf->rchash[hi];

    cf->rchash[hi] = rcrec;

  }

  (pass == 1) ? rcrec->len1++ : rcrec->len2++;

  rec->minimal_perfect_hash = (size_t)rcrec->idx;

  return 0;

}

static void xdl_free_ctx(xdfile_t *xdf)

{

  xdl_free(xdf->reference_index);

  xdl_free(xdf->changed - 1);

  xdl_free(xdf->recs);

}

static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_t const *xpp,

         xdlclassifier_t *cf, xdfile_t *xdf) {

  long bsize;

  uint64_t hav;

  uint8_t const *blk, *cur, *top, *prev;

  xrecord_t *crec;

  xdf->reference_index = NULL;

  xdf->changed = NULL;

  xdf->recs = NULL;

  if (!XDL_ALLOC_ARRAY(xdf->recs, narec))

    goto abort;

  xdf->nrec = 0;

  if ((cur = blk = xdl_mmfile_first(mf, &bsize))) {

    for (top = blk + bsize; cur < top; ) {

      prev = cur;

      hav = xdl_hash_record(&cur, top, xpp->flags);

      if (XDL_ALLOC_GROW(xdf->recs, (long)xdf->nrec + 1, narec))

        goto abort;

      crec = &xdf->recs[xdf->nrec++];

      crec->ptr = prev;

      crec->size = cur - prev;

      if (xdl_classify_record(pass, cf, crec, hav) < 0)

        goto abort;

    }

  }

  if (!XDL_CALLOC_ARRAY(xdf->changed, xdf->nrec + 2))

    goto abort;

  if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&

      (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF)) {

    if (!XDL_ALLOC_ARRAY(xdf->reference_index, xdf->nrec + 1))

      goto abort;

  }

  xdf->changed += 1;

  xdf->nreff = 0;

  xdf->dstart = 0;

  xdf->dend = xdf->nrec - 1;

  return 0;

abort:

  xdl_free_ctx(xdf);

  return -1;

}

void xdl_free_env(xdfenv_t *xe) {

  xdl_free_ctx(&xe->xdf2);

  xdl_free_ctx(&xe->xdf1);

}

static bool xdl_clean_mmatch(uint8_t const *action, long i, long s, long e) {

  long r, rdis0, rpdis0, rdis1, rpdis1;

  /*

   * Limits the window that is examined during the similar-lines

   * scan. The loops below stops when action[i - r] == KEEP

   * (line that has no match), but there are corner cases where

   * the loop proceed all the way to the extremities by causing

   * huge performance penalties in case of big files.

   */

  if (i - s > XDL_SIMSCAN_WINDOW)

    s = i - XDL_SIMSCAN_WINDOW;

  if (e - i > XDL_SIMSCAN_WINDOW)

    e = i + XDL_SIMSCAN_WINDOW;

  /*

   * Scans the lines before 'i' to find a run of lines that either

   * have no match (action[j] == DISCARD) or have multiple matches

   * (action[j] == INVESTIGATE). Note that we always call this

   * function with action[i] == INVESTIGATE, so the current line

   * (i) is already a multimatch line.

   */

  for (r = 1, rdis0 = 0, rpdis0 = 1; (i - r) >= s; r++) {

    if (action[i - r] == DISCARD)

      rdis0++;

    else if (action[i - r] == INVESTIGATE)

      rpdis0++;

    else if (action[i - r] == KEEP)

      break;

    else

      BUG("Illegal value for action[i - r]");

  }

  /*

   * If the run before the line 'i' found only multimatch lines,

   * we return false and hence we don't make the current line (i)

   * discarded. We want to discard multimatch lines only when

   * they appear in the middle of runs with nomatch lines

   * (action[j] == DISCARD).

   */

  if (rdis0 == 0)

    return 0;

  for (r = 1, rdis1 = 0, rpdis1 = 1; (i + r) <= e; r++) {

    if (action[i + r] == DISCARD)

      rdis1++;

    else if (action[i + r] == INVESTIGATE)

      rpdis1++;

    else if (action[i + r] == KEEP)

      break;

    else

      BUG("Illegal value for action[i + r]");

  }

  /*

   * If the run after the line 'i' found only multimatch lines,

   * we return false and hence we don't make the current line (i)

   * discarded.

   */

  if (rdis1 == 0)

    return false;

  rdis1 += rdis0;

  rpdis1 += rpdis0;

  return rpdis1 * XDL_KPDIS_RUN < (rpdis1 + rdis1);

}

/*

 * Try to reduce the problem complexity, discard records that have no

 * matches on the other file. Also, lines that have multiple matches

 * might be potentially discarded if they appear in a run of discardable.

 */

static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {

  long i, nm, mlim;

  xrecord_t *recs;

  xdlclass_t *rcrec;

  uint8_t *action1 = NULL, *action2 = NULL;

  bool need_min = !!(cf->flags & XDF_NEED_MINIMAL);

  int ret = 0;

  /*

   * Create temporary arrays that will help us decide if

   * changed[i] should remain false, or become true.

   */

  if (!XDL_CALLOC_ARRAY(action1, xdf1->nrec + 1)) {

    ret = -1;

    goto cleanup;

  }

  if (!XDL_CALLOC_ARRAY(action2, xdf2->nrec + 1)) {

    ret = -1;

    goto cleanup;

  }

  /*

   * Initialize temporary arrays with DISCARD, KEEP, or INVESTIGATE.

   */

  if ((mlim = xdl_bogosqrt((long)xdf1->nrec)) > XDL_MAX_EQLIMIT)

    mlim = XDL_MAX_EQLIMIT;

  for (i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart]; i <= xdf1->dend; i++, recs++) {

    rcrec = cf->rcrecs[recs->minimal_perfect_hash];

    nm = rcrec ? rcrec->len2 : 0;

    action1[i] = (nm == 0) ? DISCARD: (nm >= mlim && !need_min) ? INVESTIGATE: KEEP;

  }

  if ((mlim = xdl_bogosqrt((long)xdf2->nrec)) > XDL_MAX_EQLIMIT)

    mlim = XDL_MAX_EQLIMIT;

  for (i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart]; i <= xdf2->dend; i++, recs++) {

    rcrec = cf->rcrecs[recs->minimal_perfect_hash];

    nm = rcrec ? rcrec->len1 : 0;

    action2[i] = (nm == 0) ? DISCARD: (nm >= mlim && !need_min) ? INVESTIGATE: KEEP;

  }

  /*

   * Use temporary arrays to decide if changed[i] should remain

   * false, or become true.

   */

  xdf1->nreff = 0;

  for (i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart];

       i <= xdf1->dend; i++, recs++) {

    if (action1[i] == KEEP ||

        (action1[i] == INVESTIGATE && !xdl_clean_mmatch(action1, i, xdf1->dstart, xdf1->dend))) {

      xdf1->reference_index[xdf1->nreff++] = i;

      /* changed[i] remains false, i.e. keep */

    } else

      xdf1->changed[i] = true;

      /* i.e. discard */

  }

  xdf2->nreff = 0;

  for (i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart];

       i <= xdf2->dend; i++, recs++) {

    if (action2[i] == KEEP ||

        (action2[i] == INVESTIGATE && !xdl_clean_mmatch(action2, i, xdf2->dstart, xdf2->dend))) {

      xdf2->reference_index[xdf2->nreff++] = i;

      /* changed[i] remains false, i.e. keep */

    } else

      xdf2->changed[i] = true;

      /* i.e. discard */

  }

cleanup:

  xdl_free(action1);

  xdl_free(action2);

  return ret;

}

/*

 * Early trim initial and terminal matching records.

 */

static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2) {

  long i, lim;

  xrecord_t *recs1, *recs2;

  recs1 = xdf1->recs;

  recs2 = xdf2->recs;

  for (i = 0, lim = (long)XDL_MIN(xdf1->nrec, xdf2->nrec); i < lim;

       i++, recs1++, recs2++)

    if (recs1->minimal_perfect_hash != recs2->minimal_perfect_hash)

      break;

  xdf1->dstart = xdf2->dstart = i;

  recs1 = xdf1->recs + xdf1->nrec - 1;

  recs2 = xdf2->recs + xdf2->nrec - 1;

  for (lim -= i, i = 0; i < lim; i++, recs1--, recs2--)

    if (recs1->minimal_perfect_hash != recs2->minimal_perfect_hash)

      break;

  xdf1->dend = (long)xdf1->nrec - i - 1;

  xdf2->dend = (long)xdf2->nrec - i - 1;

  return 0;

}

static int xdl_optimize_ctxs(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {

  if (xdl_trim_ends(xdf1, xdf2) < 0 ||

      xdl_cleanup_records(cf, xdf1, xdf2) < 0) {

    return -1;

  }

  return 0;

}

int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,

        xdfenv_t *xe) {

  long enl1, enl2, sample;

  xdlclassifier_t cf;

  memset(&cf, 0, sizeof(cf));

  /*

   * For histogram diff, we can afford a smaller sample size and

   * thus a poorer estimate of the number of lines, as the hash

   * table (rhash) won't be filled up/grown. The number of lines

   * (nrecs) will be updated correctly anyway by

   * xdl_prepare_ctx().

   */

  sample = (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF

      ? XDL_GUESS_NLINES2 : XDL_GUESS_NLINES1);

  enl1 = xdl_guess_lines(mf1, sample) + 1;

  enl2 = xdl_guess_lines(mf2, sample) + 1;

  if (xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0)

    return -1;

  if (xdl_prepare_ctx(1, mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {

    xdl_free_classifier(&cf);

    return -1;

  }

  if (xdl_prepare_ctx(2, mf2, enl2, xpp, &cf, &xe->xdf2) < 0) {

    xdl_free_ctx(&xe->xdf1);

    xdl_free_classifier(&cf);

    return -1;

  }

  if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&

      (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF) &&

      xdl_optimize_ctxs(&cf, &xe->xdf1, &xe->xdf2) < 0) {

    xdl_free_ctx(&xe->xdf2);

    xdl_free_ctx(&xe->xdf1);

    xdl_free_classifier(&cf);

    return -1;

  }

  xdl_free_classifier(&cf);

  return 0;

}