Move generic vector comparison routines into diffseq.h.

1 files changed, 1 insertions, 433 deletions

diff --git a/gnulib-local/lib/fstrcmp.c b/gnulib-local/lib/fstrcmp.c
index 230cfd1..90141d9 100644
--- a/gnulib-local/lib/fstrcmp.c
+++ b/gnulib-local/lib/fstrcmp.c
@@ -72,439 +72,7 @@
 #define NOTE_INSERT(ctxt, yoff) ctxt->yvec_edit_count++
 /* We don't need USE_HEURISTIC, since it is unlikely in typical uses of
    fstrcmp().  */
-
-/* Before including this file, you need to define:
-     ELEMENT                 The element type of the vectors being compared.
-     EQUAL                   A two-argument macro that tests two elements for
-                             equality.
-     OFFSET                  A signed integer type sufficient to hold the
-                             difference between two indices. Usually
-                             something like ssize_t.
-     EXTRA_CONTEXT_FIELDS    Declarations of fields for 'struct context'.
-     NOTE_DELETE(ctxt, xoff) Record the removal of the object xvec[xoff].
-     NOTE_INSERT(ctxt, yoff) Record the insertion of the object yvec[yoff].
-     USE_HEURISTIC           (Optional) Define if you want to support the
-                             heuristic for large vectors.  */
-
-/* Maximum value of type OFFSET.  */
-#define OFFSET_MAX \
-  ((((OFFSET)1 << (sizeof (OFFSET) * CHAR_BIT - 2)) - 1) * 2 + 1)
-
-/* Use this to suppress gcc's `...may be used before initialized' warnings. */
-#ifndef IF_LINT
-# ifdef lint
-#  define IF_LINT(Code) Code
-# else
-#  define IF_LINT(Code) /* empty */
-# endif
-#endif
-
-/*
- * Context of comparison operation.
- */
-struct context
-{
-  /* Vectors being compared. */
-  const ELEMENT *xvec;
-  const ELEMENT *yvec;
-
-  /* The number of elements inserted or deleted. */
-  int xvec_edit_count;
-  int yvec_edit_count;
-
-  /* Vector, indexed by diagonal, containing 1 + the X coordinate of the point
-     furthest along the given diagonal in the forward search of the edit
-     matrix.  */
-  OFFSET *fdiag;
-
-  /* Vector, indexed by diagonal, containing the X coordinate of the point
-     furthest along the given diagonal in the backward search of the edit
-     matrix.  */
-  OFFSET *bdiag;
-
-  #ifdef USE_HEURISTIC
-  /* This corresponds to the diff -H flag.  With this heuristic, for
-     vectors with a constant small density of changes, the algorithm is
-     linear in the vectors size.  */
-  bool heuristic;
-  #endif
-
-  /* Edit scripts longer than this are too expensive to compute.  */
-  OFFSET too_expensive;
-
-  /* Snakes bigger than this are considered `big'.  */
-  #define SNAKE_LIMIT	20
-};
-
-struct partition
-{
-  /* Midpoints of this partition.  */
-  OFFSET xmid;
-  OFFSET ymid;
-
-  /* True if low half will be analyzed minimally.  */
-  bool lo_minimal;
-
-  /* Likewise for high half.  */
-  bool hi_minimal;
-};
-
-
-/* Find the midpoint of the shortest edit script for a specified portion
-   of the two vectors.
-
-   Scan from the beginnings of the vectors, and simultaneously from the ends,
-   doing a breadth-first search through the space of edit-sequence.
-   When the two searches meet, we have found the midpoint of the shortest
-   edit sequence.
-
-   If FIND_MINIMAL is true, find the minimal edit script regardless of
-   expense.  Otherwise, if the search is too expensive, use heuristics to
-   stop the search and report a suboptimal answer.
-
-   Set PART->(xmid,ymid) to the midpoint (XMID,YMID).  The diagonal number
-   XMID - YMID equals the number of inserted elements minus the number
-   of deleted elements (counting only elements before the midpoint).
-
-   Set PART->lo_minimal to true iff the minimal edit script for the
-   left half of the partition is known; similarly for PART->hi_minimal.
-
-   This function assumes that the first elements of the specified portions
-   of the two vectors do not match, and likewise that the last elements do not
-   match.  The caller must trim matching elements from the beginning and end
-   of the portions it is going to specify.
-
-   If we return the "wrong" partitions, the worst this can do is cause
-   suboptimal diff output.  It cannot cause incorrect diff output.  */
-
-static void
-diag (OFFSET xoff, OFFSET xlim, OFFSET yoff, OFFSET ylim, bool find_minimal,
-      struct partition *part, struct context *ctxt)
-{
-  OFFSET *const fd = ctxt->fdiag;	/* Give the compiler a chance. */
-  OFFSET *const bd = ctxt->bdiag;	/* Additional help for the compiler. */
-  const ELEMENT *const xv = ctxt->xvec;	/* Still more help for the compiler. */
-  const ELEMENT *const yv = ctxt->yvec;	/* And more and more . . . */
-  const OFFSET dmin = xoff - ylim;	/* Minimum valid diagonal. */
-  const OFFSET dmax = xlim - yoff;	/* Maximum valid diagonal. */
-  const OFFSET fmid = xoff - yoff;	/* Center diagonal of top-down search. */
-  const OFFSET bmid = xlim - ylim;	/* Center diagonal of bottom-up search. */
-  OFFSET fmin = fmid;
-  OFFSET fmax = fmid;		/* Limits of top-down search. */
-  OFFSET bmin = bmid;
-  OFFSET bmax = bmid;		/* Limits of bottom-up search. */
-  OFFSET c;			/* Cost. */
-  bool odd = (fmid - bmid) & 1;	/* True if southeast corner is on an odd
-				   diagonal with respect to the northwest. */
-
-  fd[fmid] = xoff;
-  bd[bmid] = xlim;
-
-  for (c = 1;; ++c)
-    {
-      OFFSET d;			/* Active diagonal. */
-      bool big_snake = false;
-
-      /* Extend the top-down search by an edit step in each diagonal. */
-      if (fmin > dmin)
-	fd[--fmin - 1] = -1;
-      else
-	++fmin;
-      if (fmax < dmax)
-	fd[++fmax + 1] = -1;
-      else
-	--fmax;
-      for (d = fmax; d >= fmin; d -= 2)
-	{
-	  OFFSET x;
-	  OFFSET y;
-	  OFFSET oldx;
-	  OFFSET tlo = fd[d - 1];
-	  OFFSET thi = fd[d + 1];
-
-	  if (tlo >= thi)
-	    x = tlo + 1;
-	  else
-	    x = thi;
-	  oldx = x;
-	  y = x - d;
-	  while (x < xlim && y < ylim && xv[x] == yv[y])
-	    {
-	      ++x;
-	      ++y;
-	    }
-	  if (x - oldx > SNAKE_LIMIT)
-	    big_snake = true;
-	  fd[d] = x;
-	  if (odd && bmin <= d && d <= bmax && bd[d] <= x)
-	    {
-	      part->xmid = x;
-	      part->ymid = y;
-	      part->lo_minimal = part->hi_minimal = true;
-	      return;
-	    }
-	}
-      /* Similarly extend the bottom-up search.  */
-      if (bmin > dmin)
-	bd[--bmin - 1] = OFFSET_MAX;
-      else
-	++bmin;
-      if (bmax < dmax)
-	bd[++bmax + 1] = OFFSET_MAX;
-      else
-	--bmax;
-      for (d = bmax; d >= bmin; d -= 2)
-	{
-	  OFFSET x;
-	  OFFSET y;
-	  OFFSET oldx;
-	  OFFSET tlo = bd[d - 1];
-	  OFFSET thi = bd[d + 1];
-
-	  if (tlo < thi)
-	    x = tlo;
-	  else
-	    x = thi - 1;
-	  oldx = x;
-	  y = x - d;
-	  while (x > xoff && y > yoff && xv[x - 1] == yv[y - 1])
-	    {
-	      --x;
-	      --y;
-	    }
-	  if (oldx - x > SNAKE_LIMIT)
-	    big_snake = true;
-	  bd[d] = x;
-	  if (!odd && fmin <= d && d <= fmax && x <= fd[d])
-	    {
-	      part->xmid = x;
-	      part->ymid = y;
-	      part->lo_minimal = part->hi_minimal = true;
-	      return;
-	    }
-	}
-
-      if (find_minimal)
-	continue;
-
-#ifdef USE_HEURISTIC
-      /* Heuristic: check occasionally for a diagonal that has made lots
-	 of progress compared with the edit distance.  If we have any
-	 such, find the one that has made the most progress and return it
-	 as if it had succeeded.
-
-	 With this heuristic, for vectors with a constant small density
-	 of changes, the algorithm is linear in the vector size.  */
-
-      if (c > 200 && big_snake && ctxt->heuristic)
-	{
-	  OFFSET best;
-
-	  best = 0;
-	  for (d = fmax; d >= fmin; d -= 2)
-	    {
-	      OFFSET dd = d - fmid;
-	      OFFSET x = fd[d];
-	      OFFSET y = x - d;
-	      OFFSET v = (x - xoff) * 2 - dd;
-
-	      if (v > 12 * (c + (dd < 0 ? -dd : dd)))
-		{
-		  if (v > best
-		      && xoff + SNAKE_LIMIT <= x && x < xlim
-		      && yoff + SNAKE_LIMIT <= y && y < ylim)
-		    {
-		      /* We have a good enough best diagonal; now insist
-			 that it end with a significant snake.  */
-		      int k;
-
-		      for (k = 1; xv[x - k] == yv[y - k]; k++)
-			if (k == SNAKE_LIMIT)
-			  {
-			    best = v;
-			    part->xmid = x;
-			    part->ymid = y;
-			    break;
-			  }
-		    }
-		}
-	    }
-	  if (best > 0)
-	    {
-	      part->lo_minimal = true;
-	      part->hi_minimal = false;
-	      return;
-	    }
-
-	  best = 0;
-	  for (d = bmax; d >= bmin; d -= 2)
-	    {
-	      OFFSET dd = d - bmid;
-	      OFFSET x = bd[d];
-	      OFFSET y = x - d;
-	      OFFSET v = (xlim - x) * 2 + dd;
-
-	      if (v > 12 * (c + (dd < 0 ? -dd : dd)))
-		{
-		  if (v > best
-		      && xoff < x && x <= xlim - SNAKE_LIMIT
-		      && yoff < y && y <= ylim - SNAKE_LIMIT)
-		    {
-		      /* We have a good enough best diagonal; now insist
-			 that it end with a significant snake.  */
-		      int k;
-
-		      for (k = 0; xv[x + k] == yv[y + k]; k++)
-			if (k == SNAKE_LIMIT - 1)
-			  {
-			    best = v;
-			    part->xmid = x;
-			    part->ymid = y;
-			    break;
-			  }
-		    }
-		}
-	    }
-	  if (best > 0)
-	    {
-	      part->lo_minimal = false;
-	      part->hi_minimal = true;
-	      return;
-	    }
-	}
-#endif /* USE_HEURISTIC */
-
-      /* Heuristic: if we've gone well beyond the call of duty, give up
-	 and report halfway between our best results so far.  */
-      if (c >= ctxt->too_expensive)
-	{
-	  OFFSET fxybest;
-	  OFFSET fxbest IF_LINT (= 0);
-	  OFFSET bxybest;
-	  OFFSET bxbest IF_LINT (= 0);
-
-	  /* Find forward diagonal that maximizes X + Y.  */
-	  fxybest = -1;
-	  for (d = fmax; d >= fmin; d -= 2)
-	    {
-	      OFFSET x;
-	      OFFSET y;
-
-	      x = MIN (fd[d], xlim);
-	      y = x - d;
-	      if (ylim < y)
-		{
-		  x = ylim + d;
-		  y = ylim;
-		}
-	      if (fxybest < x + y)
-		{
-		  fxybest = x + y;
-		  fxbest = x;
-		}
-	    }
-
-	  /* Find backward diagonal that minimizes X + Y.  */
-	  bxybest = OFFSET_MAX;
-	  for (d = bmax; d >= bmin; d -= 2)
-	    {
-	      OFFSET x;
-	      OFFSET y;
-
-	      x = MAX (xoff, bd[d]);
-	      y = x - d;
-	      if (y < yoff)
-		{
-		  x = yoff + d;
-		  y = yoff;
-		}
-	      if (x + y < bxybest)
-		{
-		  bxybest = x + y;
-		  bxbest = x;
-		}
-	    }
-
-	  /* Use the better of the two diagonals.  */
-	  if ((xlim + ylim) - bxybest < fxybest - (xoff + yoff))
-	    {
-	      part->xmid = fxbest;
-	      part->ymid = fxybest - fxbest;
-	      part->lo_minimal = true;
-	      part->hi_minimal = false;
-	    }
-	  else
-	    {
-	      part->xmid = bxbest;
-	      part->ymid = bxybest - bxbest;
-	      part->lo_minimal = false;
-	      part->hi_minimal = true;
-	    }
-	  return;
-	}
-    }
-}
-
-
-/* Compare in detail contiguous subsequences of the two vectors
-   which are known, as a whole, to match each other.
-
-   The subsequence of vector 0 is [XOFF, XLIM) and likewise for vector 1.
-
-   Note that XLIM, YLIM are exclusive bounds.  All indices into the vectors
-   are origin-0.
-
-   If FIND_MINIMAL, find a minimal difference no matter how
-   expensive it is.
-
-   The results are recorded by invoking NOTE_DELETE and NOTE_INSERT.  */
-
-static void
-compareseq (OFFSET xoff, OFFSET xlim, OFFSET yoff, OFFSET ylim,
-	    bool find_minimal, struct context *ctxt)
-{
-  const ELEMENT *const xv = ctxt->xvec;	/* Help the compiler.  */
-  const ELEMENT *const yv = ctxt->yvec;
-
-  /* Slide down the bottom initial diagonal. */
-  while (xoff < xlim && yoff < ylim && xv[xoff] == yv[yoff])
-    {
-      ++xoff;
-      ++yoff;
-    }
-
-  /* Slide up the top initial diagonal. */
-  while (xlim > xoff && ylim > yoff && xv[xlim - 1] == yv[ylim - 1])
-    {
-      --xlim;
-      --ylim;
-    }
-
-  /* Handle simple cases. */
-  if (xoff == xlim)
-    while (yoff < ylim)
-      {
-	NOTE_INSERT (ctxt, yoff);
-	yoff++;
-      }
-  else if (yoff == ylim)
-    while (xoff < xlim)
-      {
-	NOTE_DELETE (ctxt, xoff);
-	xoff++;
-      }
-  else
-    {
-      struct partition part;
-
-      /* Find a point of correspondence in the middle of the vectors.  */
-      diag (xoff, xlim, yoff, ylim, find_minimal, &part, ctxt);
-
-      /* Use the partitions to split this problem into subproblems.  */
-      compareseq (xoff, part.xmid, yoff, part.ymid, part.lo_minimal, ctxt);
-      compareseq (part.xmid, xlim, part.ymid, ylim, part.hi_minimal, ctxt);
-    }
-}
+#include "diffseq.h"
 
 
 /* Because fstrcmp is typically called multiple times, attempt to minimize