lzx-compress.c: Don't update recent offset queue unnecessarily

[wimlib] / src / lzx-compress.c

diff --git a/src/lzx-compress.c b/src/lzx-compress.c
index 070e2bfc005e0211dbe6e8e6b95e8fdb9978ce6a..565dc863c92cb74c3eb76e3893e011168120fc60 100644 (file)
--- a/src/lzx-compress.c
+++ b/src/lzx-compress.c
@@ -1712,16 +1712,19 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c)
                 * length.  */
                for (unsigned i = 0, len = 2; i < num_matches; i++) {
                        u32 offset;
-                       struct lzx_lru_queue queue;
                        u32 position_cost;
                        unsigned position_slot;
                        unsigned num_extra_bits;
 
                        offset = matches[i].offset;
-                       queue = optimum[cur_pos].queue;
                        position_cost = optimum[cur_pos].cost;
 
-                       position_slot = lzx_get_position_slot(offset, &queue);
+                       for (position_slot = 0; position_slot < LZX_NUM_RECENT_OFFSETS; position_slot++)
+                               if (offset == optimum[cur_pos].queue.R[position_slot])
+                                       goto have_position_cost;
+
+                       position_slot = lzx_get_position_slot_raw(offset + LZX_OFFSET_OFFSET);
+
                        num_extra_bits = lzx_get_num_extra_bits(position_slot);
                        if (num_extra_bits >= 3) {
                                position_cost += num_extra_bits - 3;
@@ -1731,6 +1734,8 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c)
                                position_cost += num_extra_bits;
                        }
 
+               have_position_cost:
+
                        do {
                                unsigned len_header;
                                unsigned main_symbol;
@@ -1749,7 +1754,16 @@ lzx_choose_near_optimal_item(struct lzx_compressor *c)
                                                        LZX_NUM_PRIMARY_LENS];
                                }
                                if (cost < optimum[cur_pos + len].cost) {
-                                       optimum[cur_pos + len].queue = queue;
+
+                                       if (position_slot < LZX_NUM_RECENT_OFFSETS) {
+                                               optimum[cur_pos + len].queue = optimum[cur_pos].queue;
+                                               swap(optimum[cur_pos + len].queue.R[0],
+                                                    optimum[cur_pos + len].queue.R[position_slot]);
+                                       } else {
+                                               optimum[cur_pos + len].queue.R[0] = offset;
+                                               optimum[cur_pos + len].queue.R[1] = optimum[cur_pos].queue.R[0];
+                                               optimum[cur_pos + len].queue.R[2] = optimum[cur_pos].queue.R[1];
+                                       }
                                        optimum[cur_pos + len].prev.link = cur_pos;
                                        optimum[cur_pos + len].prev.match_offset = offset;
                                        optimum[cur_pos + len].cost = cost;