1 files changed, 90 insertions, 0 deletions
diff --git a/modules/policy/lua-aho-corasick/load_ac.lua b/modules/policy/lua-aho-corasick/load_ac.lua
new file mode 100644
index 0000000..eb70446
--- /dev/null
+++ b/modules/policy/lua-aho-corasick/load_ac.lua
@@ -0,0 +1,90 @@
+-- Helper wrappring script for loading shared object libac.so (FFI interface)
+-- from package.cpath instead of LD_LIBRARTY_PATH.
+--
+
+local ffi = require 'ffi'
+ffi.cdef[[
+  void* ac_create(const char** str_v, unsigned int* strlen_v,
+                  unsigned int v_len);
+  int ac_match2(void*, const char *str, int len);
+  void ac_free(void*);
+]]
+
+local _M = {}
+
+local string_gmatch = string.gmatch
+local string_match = string.match
+
+local ac_lib = nil
+local ac_create = nil
+local ac_match = nil
+local ac_free = nil
+
+--[[ Find shared object file package.cpath, obviating the need of setting
+   LD_LIBRARY_PATH
+]]
+local function find_shared_obj(cpath, so_name)
+    for k, v in string_gmatch(cpath, "[^;]+") do
+        local so_path = string_match(k, "(.*/)")
+        if so_path then
+            -- "so_path" could be nil. e.g, the dir path component is "."
+            so_path = so_path .. so_name
+
+            -- Don't get me wrong, the only way to know if a file exist is
+            -- trying to open it.
+            local f = io.open(so_path)
+            if f ~= nil then
+                io.close(f)
+                return so_path
+            end
+        end
+    end
+end
+
+function _M.load_ac_lib()
+    if ac_lib ~= nil then
+        return ac_lib
+    else
+        local so_path = find_shared_obj(package.cpath, "libac.so")
+        if so_path ~= nil then
+            ac_lib = ffi.load(so_path)
+            ac_create = ac_lib.ac_create
+            ac_match = ac_lib.ac_match2
+            ac_free = ac_lib.ac_free
+            return ac_lib
+        end
+    end
+end
+
+-- Create an Aho-Corasick instance, and return the instance if it was
+-- successful.
+function _M.create_ac(dict)
+    local strnum = #dict
+    if ac_lib == nil then
+        _M.load_ac_lib()
+    end
+
+    local str_v = ffi.new("const char *[?]", strnum)
+    local strlen_v = ffi.new("unsigned int [?]", strnum)
+
+    for i = 1, strnum do
+        local s = dict[i]
+        str_v[i - 1] = s
+        strlen_v[i - 1] = #s
+    end
+
+    local ac = ac_create(str_v, strlen_v, strnum);
+    if ac ~= nil then
+        return ffi.gc(ac, ac_free)
+    end
+end
+
+-- Return nil if str doesn't match the dictionary, else return non-nil.
+function _M.match(ac, str)
+    local r = ac_match(ac, str, #str);
+    if r >= 0 then
+        return r
+    end
+end
+
+return _M