Ref-count the filespecs used by diffcore

Rather than copy the filespecs when introducing new versions of them
(for rename or copy detection), use a refcount and increment the count
when reusing the diff_filespec.

This avoids unnecessary allocations, but the real reason behind this is
a future enhancement: we will want to track shared data across the
copy/rename detection.  In order to efficiently notice when a filespec
is used by a rename, the rename machinery wants to keep track of a
rename usage count which is shared across all different users of the
filespec.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/diff.c b/diff.c
index dfb8595b7086c71b3be0ece408d65a7285f42e9f..0b320f6b96fab017c2b32f3aa45921216d3f1e25 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -1440,9 +1440,18 @@ struct diff_filespec *alloc_filespec(const char *path)
        memset(spec, 0, sizeof(*spec));
        spec->path = (char *)(spec + 1);
        memcpy(spec->path, path, namelen+1);
+       spec->count = 1;
        return spec;
 }
 
+void free_filespec(struct diff_filespec *spec)
+{
+       if (!--spec->count) {
+               diff_free_filespec_data(spec);
+               free(spec);
+       }
+}
+
 void fill_filespec(struct diff_filespec *spec, const unsigned char *sha1,
                   unsigned short mode)
 {
@@ -2435,10 +2444,8 @@ struct diff_filepair *diff_queue(struct diff_queue_struct *queue,
 
 void diff_free_filepair(struct diff_filepair *p)
 {
-       diff_free_filespec_data(p->one);
-       diff_free_filespec_data(p->two);
-       free(p->one);
-       free(p->two);
+       free_filespec(p->one);
+       free_filespec(p->two);
        free(p);
 }
 

diff --git a/diffcore-rename.c b/diffcore-rename.c
index 2077a9b981945dd2a75cbf8a867738ccf1de30c8..3da06b702bf2ee0381f1bb75ff5a7d04026d14ac 100644 (file)
--- a/diffcore-rename.c
+++ b/diffcore-rename.c
@@ -209,21 +209,19 @@ static int estimate_similarity(struct diff_filespec *src,
 
 static void record_rename_pair(int dst_index, int src_index, int score)
 {
-       struct diff_filespec *one, *two, *src, *dst;
+       struct diff_filespec *src, *dst;
        struct diff_filepair *dp;
 
        if (rename_dst[dst_index].pair)
                die("internal error: dst already matched.");
 
        src = rename_src[src_index].one;
-       one = alloc_filespec(src->path);
-       fill_filespec(one, src->sha1, src->mode);
+       src->count++;
 
        dst = rename_dst[dst_index].two;
-       two = alloc_filespec(dst->path);
-       fill_filespec(two, dst->sha1, dst->mode);
+       dst->count++;
 
-       dp = diff_queue(NULL, one, two);
+       dp = diff_queue(NULL, src, dst);
        dp->renamed_pair = 1;
        if (!strcmp(src->path, dst->path))
                dp->score = rename_src[src_index].score;
@@ -526,10 +524,8 @@ void diffcore_rename(struct diff_options *options)
                }
        }
 
-       for (i = 0; i < rename_dst_nr; i++) {
-               diff_free_filespec_data(rename_dst[i].two);
-               free(rename_dst[i].two);
-       }
+       for (i = 0; i < rename_dst_nr; i++)
+               free_filespec(rename_dst[i].two);
 
        free(rename_dst);
        rename_dst = NULL;

diff --git a/diffcore.h b/diffcore.h
index eb618b1ec00113dabcd5231f141f82e1cdfdca46..30055ac5a9692f0f1f952de0754f36221cd07664 100644 (file)
--- a/diffcore.h
+++ b/diffcore.h
@@ -29,6 +29,7 @@ struct diff_filespec {
        void *cnt_data;
        const char *funcname_pattern_ident;
        unsigned long size;
+       int count;               /* Reference count */
        int xfrm_flags;          /* for use by the xfrm */
        unsigned short mode;     /* file mode */
        unsigned sha1_valid : 1; /* if true, use sha1 and trust mode;
@@ -43,6 +44,7 @@ struct diff_filespec {
 };
 
 extern struct diff_filespec *alloc_filespec(const char *);
+extern void free_filespec(struct diff_filespec *);
 extern void fill_filespec(struct diff_filespec *, const unsigned char *,
                          unsigned short);