add evict call back func in lrucache

lib/resty/lrucache.lua

@@ -151,7 +151,7 @@ local function ptr2num(ptr)
 end
 
 
-function _M.new(size)
+function _M.new(size, evict_cb)
     if size < 1 then
         return nil, "size too small"
     end
@@ -164,6 +164,7 @@ function _M.new(size)
         node2key = {},
         num_items = 0,
         max_items = size,
+        evict_cb = evict_cb,
     }
     return setmetatable(self, mt)
 end
@@ -241,6 +242,9 @@ function _M.set(self, key, value, ttl, flags)
             -- print(key, ": evicting oldkey: ", oldkey, ", oldnode: ",
             --         tostring(node))
             if oldkey then
+                if self.evict_cb then
+                    self.evict_cb(oldkey, hasht[oldkey])
+                end
                 hasht[oldkey] = nil
                 key2node[oldkey] = nil
             end

lib/resty/lrucache/pureffi.lua

@@ -318,7 +318,7 @@ local mt = { __index = _M }
 -- load-factor is specified, it will be clamped to the range of [0.1, 1](i.e.
 -- if load-factor is greater than 1, it will be saturated to 1, likewise,
 -- if load-factor is smaller than 0.1, it will be clamped to 0.1).
-function _M.new(size, load_factor)
+function _M.new(size, load_factor, evict_cb)
     if size < 1 then
         return nil, "size too small"
     end
@@ -350,6 +350,7 @@ function _M.new(size, load_factor)
         val_v = new_tab(size, 0),
         bucket_v = ffi_new(int_array_t, bucket_sz),
         num_items = 0,
+        evict_cb = evict_cb,
     }
     -- "note_v" is an array of all the nodes used in the LRU queue. Exprpession
     -- node_v[i] evaluates to the element of ID "i".
@@ -526,6 +527,9 @@ function _M.set(self, key, value, ttl, flags)
             -- evict the least recently used key
             -- assert(not queue_is_empty(self.cache_queue))
             node = queue_last(self.cache_queue)
+            if self.evict_cb then
+                self.evict_cb(self.key_v[node.id], self.val_v[node.id])
+            end
             remove_key(self, self.key_v[node.id])
         else
             -- take a free queue node

t/009-evict-call-back.t

@@ -0,0 +1,31 @@
+# vim:set ft= ts=4 sw=4 et fdm=marker:
+use lib '.';
+use t::TestLRUCache;
+
+repeat_each(2);
+
+plan tests => repeat_each() * (blocks() * 3);
+
+no_long_string();
+run_tests();
+
+__DATA__
+
+=== TEST 1: evict with call back
+--- config
+    location = /t {
+        content_by_lua '
+            local function evict_cb(k,v)
+                ngx.say(k, v)
+            end
+            local lrucache = require "resty.lrucache"
+            local c = lrucache.new(1, evict_cb)
+
+            collectgarbage()
+
+            c:set("dog", 12)
+            c:set("cat", 14)
+        ';
+    }
+--- response_body
+dog12

t/100-pureffi/009-evict-call-back.t

@@ -0,0 +1,31 @@
+# vim:set ft= ts=4 sw=4 et fdm=marker:
+use lib '.';
+use t::TestLRUCache;
+
+repeat_each(2);
+
+plan tests => repeat_each() * (blocks() * 3);
+
+no_long_string();
+run_tests();
+
+__DATA__
+
+=== TEST 1: evict with call back
+--- config
+    location = /t {
+        content_by_lua '
+            local function evict_cb(k,v)
+                ngx.say(k, v)
+            end
+            local lrucache = require "resty.lrucache.pureffi"
+            local c = lrucache.new(1, nil, evict_cb)
+
+            collectgarbage()
+
+            c:set("dog", 12)
+            c:set("cat", 14)
+        ';
+    }
+--- response_body
+dog12