reftable/block: reuse buffer to compute record keys

When iterating over entries in the block iterator we compute the key of
each of the entries and write it into a buffer. We do not reuse the
buffer though and thus re-allocate it on every iteration, which is
wasteful.

Refactor the code to reuse the buffer.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/reftable/block.c b/reftable/block.c
index 8c6a8c77fc0f444e4a9bd2456bbb809dacfebc14..1df3d8a0f09671c74143e655cb2963adda872545 100644 (file)
--- a/reftable/block.c
+++ b/reftable/block.c
@@ -323,30 +323,28 @@ int block_iter_next(struct block_iter *it, struct reftable_record *rec)
                .len = it->br->block_len - it->next_off,
        };
        struct string_view start = in;
-       struct strbuf key = STRBUF_INIT;
        uint8_t extra = 0;
        int n = 0;
 
        if (it->next_off >= it->br->block_len)
                return 1;
 
-       n = reftable_decode_key(&key, &extra, it->last_key, in);
+       n = reftable_decode_key(&it->key, &extra, it->last_key, in);
        if (n < 0)
                return -1;
 
-       if (!key.len)
+       if (!it->key.len)
                return REFTABLE_FORMAT_ERROR;
 
        string_view_consume(&in, n);
-       n = reftable_record_decode(rec, key, extra, in, it->br->hash_size);
+       n = reftable_record_decode(rec, it->key, extra, in, it->br->hash_size);
        if (n < 0)
                return -1;
        string_view_consume(&in, n);
 
        strbuf_reset(&it->last_key);
-       strbuf_addbuf(&it->last_key, &key);
+       strbuf_addbuf(&it->last_key, &it->key);
        it->next_off += start.len - in.len;
-       strbuf_release(&key);
        return 0;
 }
 
@@ -377,6 +375,7 @@ int block_iter_seek(struct block_iter *it, struct strbuf *want)
 void block_iter_close(struct block_iter *it)
 {
        strbuf_release(&it->last_key);
+       strbuf_release(&it->key);
 }
 
 int block_reader_seek(struct block_reader *br, struct block_iter *it,
@@ -387,7 +386,6 @@ int block_reader_seek(struct block_reader *br, struct block_iter *it,
                .r = br,
        };
        struct reftable_record rec = reftable_new_record(block_reader_type(br));
-       struct strbuf key = STRBUF_INIT;
        int err = 0;
        struct block_iter next = BLOCK_ITER_INIT;
 
@@ -414,8 +412,8 @@ int block_reader_seek(struct block_reader *br, struct block_iter *it,
                if (err < 0)
                        goto done;
 
-               reftable_record_key(&rec, &key);
-               if (err > 0 || strbuf_cmp(&key, want) >= 0) {
+               reftable_record_key(&rec, &it->key);
+               if (err > 0 || strbuf_cmp(&it->key, want) >= 0) {
                        err = 0;
                        goto done;
                }
@@ -424,8 +422,7 @@ int block_reader_seek(struct block_reader *br, struct block_iter *it,
        }
 
 done:
-       strbuf_release(&key);
-       strbuf_release(&next.last_key);
+       block_iter_close(&next);
        reftable_record_release(&rec);
 
        return err;

diff --git a/reftable/block.h b/reftable/block.h
index 51699af233d823fafe681f3d7cbb20cf61b88d8a..17481e6331979cc31972ee3dad576e9c594a1769 100644 (file)
--- a/reftable/block.h
+++ b/reftable/block.h
@@ -84,10 +84,12 @@ struct block_iter {
 
        /* key for last entry we read. */
        struct strbuf last_key;
+       struct strbuf key;
 };
 
 #define BLOCK_ITER_INIT { \
        .last_key = STRBUF_INIT, \
+       .key = STRBUF_INIT, \
 }
 
 /* initializes a block reader. */