fast-import optimization:

Now that cmd_data acts on a strbuf, make last_object stashed buffer be a
strbuf as well. On new stash, don't free the last stashed buffer, rather
swap it with the one you will stash, this way, callers of store_object can
act on static strbufs, and at some point, fast-import won't allocate new
memory for objects buffers.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/fast-import.c b/fast-import.c
index e456eab17ce993317e6309562755dc29fe863fd7..e2a4834706659c050cdfd0d53ad3340c9522fa47 100644 (file)
--- a/fast-import.c
+++ b/fast-import.c
@@ -182,11 +182,10 @@ struct mark_set
 
 struct last_object
 {
-       void *data;
-       unsigned long len;
+       struct strbuf data;
        uint32_t offset;
        unsigned int depth;
-       unsigned no_free:1;
+       unsigned no_swap : 1;
 };
 
 struct mem_pool
@@ -310,7 +309,7 @@ static struct mark_set *marks;
 static const char* mark_file;
 
 /* Our last blob */
-static struct last_object last_blob;
+static struct last_object last_blob = { STRBUF_INIT, 0, 0, 0 };
 
 /* Tree management */
 static unsigned int tree_entry_alloc = 1000;
@@ -950,9 +949,7 @@ static void end_packfile(void)
        free(old_p);
 
        /* We can't carry a delta across packfiles. */
-       free(last_blob.data);
-       last_blob.data = NULL;
-       last_blob.len = 0;
+       strbuf_release(&last_blob.data);
        last_blob.offset = 0;
        last_blob.depth = 0;
 }
@@ -1024,8 +1021,8 @@ static int store_object(
                return 1;
        }
 
-       if (last && last->data && last->depth < max_depth) {
-               delta = diff_delta(last->data, last->len,
+       if (last && last->data.buf && last->depth < max_depth) {
+               delta = diff_delta(last->data.buf, last->data.len,
                        dat->buf, dat->len,
                        &deltalen, 0);
                if (delta && deltalen >= dat->len) {
@@ -1111,11 +1108,14 @@ static int store_object(
        free(out);
        free(delta);
        if (last) {
-               if (!last->no_free)
-                       free(last->data);
+               if (last->no_swap) {
+                       last->data = *dat;
+               } else {
+                       struct strbuf tmp = *dat;
+                       *dat = last->data;
+                       last->data = tmp;
+               }
                last->offset = e->offset;
-               last->data = dat->buf;
-               last->len = dat->len;
        }
        return 0;
 }
@@ -1242,7 +1242,7 @@ static void store_tree(struct tree_entry *root)
 {
        struct tree_content *t = root->tree;
        unsigned int i, j, del;
-       struct last_object lo;
+       struct last_object lo = { STRBUF_INIT, 0, 0, /* no_swap */ 1 };
        struct object_entry *le;
 
        if (!is_null_sha1(root->versions[1].sha1))
@@ -1254,19 +1254,11 @@ static void store_tree(struct tree_entry *root)
        }
 
        le = find_object(root->versions[0].sha1);
-       if (!S_ISDIR(root->versions[0].mode)
-               || !le
-               || le->pack_id != pack_id) {
-               lo.data = NULL;
-               lo.depth = 0;
-               lo.no_free = 0;
-       } else {
+       if (S_ISDIR(root->versions[0].mode) && le && le->pack_id == pack_id) {
                mktree(t, 0, &old_tree);
-               lo.len  = old_tree.len;
-               lo.data = old_tree.buf;
+               lo.data = old_tree;
                lo.offset = le->offset;
                lo.depth = t->delta_depth;
-               lo.no_free = 1;
        }
 
        mktree(t, 1, &new_tree);
@@ -1714,14 +1706,12 @@ static char *parse_ident(const char *buf)
 
 static void cmd_new_blob(void)
 {
-       struct strbuf buf;
+       static struct strbuf buf = STRBUF_INIT;
 
        read_next_command();
        cmd_mark();
-       strbuf_init(&buf, 0);
        cmd_data(&buf);
-       if (store_object(OBJ_BLOB, &buf, &last_blob, NULL, next_mark))
-               strbuf_release(&buf);
+       store_object(OBJ_BLOB, &buf, &last_blob, NULL, next_mark);
 }
 
 static void unload_one_branch(void)
@@ -1817,15 +1807,13 @@ static void file_change_m(struct branch *b)
        }
 
        if (inline_data) {
-               struct strbuf buf;
+               static struct strbuf buf = STRBUF_INIT;
 
                if (!p_uq)
                        p = p_uq = xstrdup(p);
                read_next_command();
-               strbuf_init(&buf, 0);
                cmd_data(&buf);
-               if (store_object(OBJ_BLOB, &buf, &last_blob, sha1, 0))
-                       strbuf_release(&buf);
+               store_object(OBJ_BLOB, &buf, &last_blob, sha1, 0);
        } else if (oe) {
                if (oe->type != OBJ_BLOB)
                        die("Not a blob (actually a %s): %s",