1 // Copyright 2012 Google Inc.
2 // All rights reserved.
3 //
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5 // modification, are permitted provided that the following conditions are
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7 //
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10 // * Redistributions in binary form must reproduce the above copyright
11 // notice, this list of conditions and the following disclaimer in the
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14 // may be used to endorse or promote products derived from this software
15 // without specific prior written permission.
16 //
17 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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26 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28
29 #include "utils/config/lua_module.hpp"
30
31 #include <lutok/stack_cleaner.hpp>
32 #include <lutok/state.ipp>
33
34 #include "utils/config/exceptions.hpp"
35 #include "utils/config/tree.ipp"
36
37 namespace config = utils::config;
38
39
40 namespace {
41
42
43 /// Gets the tree singleton stored in the Lua state.
44 ///
45 /// \param state The Lua state. The registry must contain a key named
46 /// "tree" with a pointer to the singleton.
47 ///
48 /// \return A reference to the tree associated with the Lua state.
49 ///
50 /// \throw syntax_error If the tree cannot be located.
51 config::tree&
get_global_tree(lutok::state & state)52 get_global_tree(lutok::state& state)
53 {
54 lutok::stack_cleaner cleaner(state);
55
56 state.push_value(lutok::registry_index);
57 state.push_string("tree");
58 state.get_table(-2);
59 if (state.is_nil())
60 throw config::syntax_error("Cannot find tree singleton; global state "
61 "corrupted?");
62 config::tree& tree = **state.to_userdata< config::tree* >();
63 state.pop(1);
64 return tree;
65 }
66
67
68 /// Gets a fully-qualified tree key from the state.
69 ///
70 /// \param state The Lua state.
71 /// \param table_index An index to the Lua stack pointing to the table being
72 /// accessed. If this table contains a tree_key metadata property, this is
73 /// considered to be the prefix of the tree key.
74 /// \param field_index An index to the Lua stack pointing to the entry
75 /// containing the name of the field being indexed.
76 ///
77 /// \return A dotted key.
78 ///
79 /// \throw invalid_key_error If the name of the key is invalid.
80 static std::string
get_tree_key(lutok::state & state,const int table_index,const int field_index)81 get_tree_key(lutok::state& state, const int table_index, const int field_index)
82 {
83 PRE(state.is_string(field_index));
84 const std::string field = state.to_string(field_index);
85 if (!field.empty() && field[0] == '_')
86 throw config::invalid_key_error(
87 F("Configuration key cannot have an underscore as a prefix; "
88 "found %s") % field);
89
90 std::string tree_key;
91 if (state.get_metafield(table_index, "tree_key")) {
92 tree_key = state.to_string(-1) + "." + state.to_string(field_index - 1);
93 state.pop(1);
94 } else
95 tree_key = state.to_string(field_index);
96 return tree_key;
97 }
98
99
100 static int redirect_newindex(lutok::state&);
101 static int redirect_index(lutok::state&);
102
103
104 /// Creates a table for a new configuration inner node.
105 ///
106 /// \post state(-1) Contains the new table.
107 ///
108 /// \param state The Lua state in which to push the table.
109 /// \param tree_key The key to which the new table corresponds.
110 static void
new_table_for_key(lutok::state & state,const std::string & tree_key)111 new_table_for_key(lutok::state& state, const std::string& tree_key)
112 {
113 state.new_table();
114 {
115 state.new_table();
116 {
117 state.push_string("__index");
118 state.push_cxx_function(redirect_index);
119 state.set_table(-3);
120
121 state.push_string("__newindex");
122 state.push_cxx_function(redirect_newindex);
123 state.set_table(-3);
124
125 state.push_string("tree_key");
126 state.push_string(tree_key);
127 state.set_table(-3);
128 }
129 state.set_metatable(-2);
130 }
131 }
132
133
134 /// Sets the value of an configuration node.
135 ///
136 /// \pre state(-3) The table to index. If this is not _G, then the table
137 /// metadata must contain a tree_key property describing the path to
138 /// current level.
139 /// \pre state(-2) The field to index into the table. Must be a string.
140 /// \pre state(-1) The value to set the indexed table field to.
141 ///
142 /// \param state The Lua state in which to operate.
143 ///
144 /// \return The number of result values on the Lua stack; always 0.
145 ///
146 /// \throw invalid_key_error If the provided key is invalid.
147 /// \throw unknown_key_error If the key cannot be located.
148 /// \throw value_error If the value has an unsupported type or cannot be
149 /// set on the key, or if the input table or index are invalid.
150 static int
redirect_newindex(lutok::state & state)151 redirect_newindex(lutok::state& state)
152 {
153 if (!state.is_table(-3))
154 throw config::value_error("Indexed object is not a table");
155 if (!state.is_string(-2))
156 throw config::value_error("Invalid field in configuration object "
157 "reference; must be a string");
158
159 const std::string dotted_key = get_tree_key(state, -3, -2);
160 try {
161 config::tree& tree = get_global_tree(state);
162 tree.set_lua(dotted_key, state, -1);
163 } catch (const config::value_error& e) {
164 throw config::value_error(F("Invalid value for key '%s' (%s)") %
165 dotted_key % e.what());
166 }
167
168 // Now really set the key in the Lua table, but prevent direct accesses from
169 // the user by prefixing it. We do this to ensure that re-setting the same
170 // key of the tree results in a call to __newindex instead of __index.
171 state.push_string("_" + state.to_string(-2));
172 state.push_value(-2);
173 state.raw_set(-5);
174
175 return 0;
176 }
177
178
179 /// Indexes a configuration node.
180 ///
181 /// \pre state(-3) The table to index. If this is not _G, then the table
182 /// metadata must contain a tree_key property describing the path to
183 /// current level. If the field does not exist, a new table is created.
184 /// \pre state(-1) The field to index into the table. Must be a string.
185 ///
186 /// \param state The Lua state in which to operate.
187 ///
188 /// \return The number of result values on the Lua stack; always 1.
189 ///
190 /// \throw value_error If the input table or index are invalid.
191 static int
redirect_index(lutok::state & state)192 redirect_index(lutok::state& state)
193 {
194 if (!state.is_table(-2))
195 throw config::value_error("Indexed object is not a table");
196 if (!state.is_string(-1))
197 throw config::value_error("Invalid field in configuration object "
198 "reference; must be a string");
199
200 // Query if the key has already been set by a call to redirect_newindex.
201 state.push_string("_" + state.to_string(-1));
202 state.raw_get(-3);
203 if (!state.is_nil(-1))
204 return 1;
205 state.pop(1);
206
207 state.push_value(-1); // Duplicate the field name.
208 state.raw_get(-3); // Get table[field] to see if it's defined.
209 if (state.is_nil(-1)) {
210 state.pop(1);
211
212 // The stack is now the same as when we entered the function, but we
213 // know that the field is undefined and thus have to create a new
214 // configuration table.
215 INV(state.is_table(-2));
216 INV(state.is_string(-1));
217
218 const config::tree& tree = get_global_tree(state);
219 const std::string tree_key = get_tree_key(state, -2, -1);
220 if (tree.is_set(tree_key)) {
221 // Publish the pre-recorded value in the tree to the Lua state,
222 // instead of considering this table key a new inner node.
223 tree.push_lua(tree_key, state);
224 } else {
225 state.push_string("_" + state.to_string(-1));
226 state.insert(-2);
227 state.pop(1);
228
229 new_table_for_key(state, tree_key);
230
231 // Duplicate the newly created table and place it deep in the stack
232 // so that the raw_set below leaves us with the return value of this
233 // function at the top of the stack.
234 state.push_value(-1);
235 state.insert(-4);
236
237 state.raw_set(-3);
238 state.pop(1);
239 }
240 }
241 return 1;
242 }
243
244
245 } // anonymous namespace
246
247
248 /// Install wrappers for globals to set values in the configuration tree.
249 ///
250 /// This function installs wrappers to capture all accesses to global variables.
251 /// Such wrappers redirect the reads and writes to the out_tree, which is the
252 /// entity that defines what configuration variables exist.
253 ///
254 /// \param state The Lua state into which to install the wrappers.
255 /// \param out_tree The tree with the layout definition and where the
256 /// configuration settings will be collected.
257 void
redirect(lutok::state & state,tree & out_tree)258 config::redirect(lutok::state& state, tree& out_tree)
259 {
260 lutok::stack_cleaner cleaner(state);
261
262 state.get_global_table();
263 {
264 state.push_string("__index");
265 state.push_cxx_function(redirect_index);
266 state.set_table(-3);
267
268 state.push_string("__newindex");
269 state.push_cxx_function(redirect_newindex);
270 state.set_table(-3);
271 }
272 state.set_metatable(-1);
273
274 state.push_value(lutok::registry_index);
275 state.push_string("tree");
276 config::tree** tree = state.new_userdata< config::tree* >();
277 *tree = &out_tree;
278 state.set_table(-3);
279 state.pop(1);
280 }
281