[PATCH] Add -B flag to diff-* brothers.

[git.git] / diffcore-break.c

diff --git a/diffcore-break.c b/diffcore-break.c
new file mode 100644 (file)
index 0000000..c5e006d
--- /dev/null
+++ b/diffcore-break.c
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2005 Junio C Hamano
+ */
+#include "cache.h"
+#include "diff.h"
+#include "diffcore.h"
+#include "delta.h"
+#include "count-delta.h"
+
+static int very_different(struct diff_filespec *src,
+                         struct diff_filespec *dst,
+                         int min_score)
+{
+       /* dst is recorded as a modification of src.  Are they so
+        * different that we are better off recording this as a pair
+        * of delete and create?  min_score is the minimum amount of
+        * new material that must exist in the dst and not in src for
+        * the pair to be considered a complete rewrite, and recommended
+        * to be set to a very high value, 99% or so.
+        *
+        * The value we return represents the amount of new material
+        * that is in dst and not in src.  We return 0 when we do not
+        * want to get the filepair broken.
+        */
+       void *delta;
+       unsigned long delta_size, base_size;
+
+       if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
+               return 0; /* leave symlink rename alone */
+
+       if (diff_populate_filespec(src, 1) || diff_populate_filespec(dst, 1))
+               return 0; /* error but caught downstream */
+
+       delta_size = ((src->size < dst->size) ?
+                     (dst->size - src->size) : (src->size - dst->size));
+
+       /* Notice that we use max of src and dst as the base size,
+        * unlike rename similarity detection.  This is so that we do
+        * not mistake a large addition as a complete rewrite.
+        */
+       base_size = ((src->size < dst->size) ? dst->size : src->size);
+
+       /*
+        * If file size difference is too big compared to the
+        * base_size, we declare this a complete rewrite.
+        */
+       if (base_size * min_score < delta_size * MAX_SCORE)
+               return MAX_SCORE;
+
+       if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
+               return 0; /* error but caught downstream */
+
+       delta = diff_delta(src->data, src->size,
+                          dst->data, dst->size,
+                          &delta_size);
+
+       /* A delta that has a lot of literal additions would have
+        * big delta_size no matter what else it does.
+        */
+       if (base_size * min_score < delta_size * MAX_SCORE)
+               return MAX_SCORE;
+
+       /* Estimate the edit size by interpreting delta. */
+       delta_size = count_delta(delta, delta_size);
+       free(delta);
+       if (delta_size == UINT_MAX)
+               return 0; /* error in delta computation */
+
+       if (base_size < delta_size)
+               return MAX_SCORE;
+
+       return delta_size * MAX_SCORE / base_size; 
+}
+
+void diffcore_break(int min_score)
+{
+       struct diff_queue_struct *q = &diff_queued_diff;
+       struct diff_queue_struct outq;
+       int i;
+
+       if (!min_score)
+               min_score = DEFAULT_BREAK_SCORE;
+
+       outq.nr = outq.alloc = 0;
+       outq.queue = NULL;
+
+       for (i = 0; i < q->nr; i++) {
+               struct diff_filepair *p = q->queue[i];
+               int score;
+
+               /* We deal only with in-place edit of non directory.
+                * We do not break anything else.
+                */
+               if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two) &&
+                   !S_ISDIR(p->one->mode) && !S_ISDIR(p->two->mode) &&
+                   !strcmp(p->one->path, p->two->path)) {
+                       score = very_different(p->one, p->two, min_score);
+                       if (min_score <= score) {
+                               /* Split this into delete and create */
+                               struct diff_filespec *null_one, *null_two;
+                               struct diff_filepair *dp;
+
+                               /* deletion of one */
+                               null_one = alloc_filespec(p->one->path);
+                               dp = diff_queue(&outq, p->one, null_one);
+                               dp->score = score;
+                               dp->broken_pair = 1;
+
+                               /* creation of two */
+                               null_two = alloc_filespec(p->two->path);
+                               dp = diff_queue(&outq, null_two, p->two);
+                               dp->score = score;
+                               dp->broken_pair = 1;
+
+                               free(p); /* not diff_free_filepair(), we are
+                                         * reusing one and two here.
+                                         */
+                               continue;
+                       }
+               }
+               diff_q(&outq, p);
+       }
+       free(q->queue);
+       *q = outq;
+
+       return;
+}