minix/external/bsd/kyua-cli/dist/utils/config/lua_module.cpp

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// Copyright 2012 Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// * Neither the name of Google Inc. nor the names of its contributors
// may be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "utils/config/lua_module.hpp"
#include <lutok/stack_cleaner.hpp>
#include <lutok/state.ipp>
#include "utils/config/exceptions.hpp"
#include "utils/config/tree.ipp"
namespace config = utils::config;
namespace {
/// Gets the tree singleton stored in the Lua state.
///
/// \param state The Lua state. The metadata of _G must contain a key named
/// "tree" with a pointer to the singleton.
///
/// \return A reference to the tree associated with the Lua state.
///
/// \throw syntax_error If the tree cannot be located.
config::tree&
get_global_tree(lutok::state& state)
{
lutok::stack_cleaner cleaner(state);
if (!state.get_metafield(lutok::globals_index, "tree"))
throw config::syntax_error("Cannot find tree singleton; global state "
"corrupted?");
return **state.to_userdata< config::tree* >();
}
/// Gets a fully-qualified tree key from the state.
///
/// \param state The Lua state.
/// \param table_index An index to the Lua stack pointing to the table being
/// accessed. If this table contains a tree_key metadata property, this is
/// considered to be the prefix of the tree key.
/// \param field_index An index to the Lua stack pointing to the entry
/// containing the name of the field being indexed.
///
/// \return A dotted key.
///
/// \throw invalid_key_error If the name of the key is invalid.
static std::string
get_tree_key(lutok::state& state, const int table_index, const int field_index)
{
PRE(state.is_string(field_index));
const std::string field = state.to_string(field_index);
if (!field.empty() && field[0] == '_')
throw config::invalid_key_error(
F("Configuration key cannot have an underscore as a prefix; "
"found %s") % field);
std::string tree_key;
if (state.get_metafield(table_index, "tree_key")) {
tree_key = state.to_string(-1) + "." + state.to_string(field_index - 1);
state.pop(1);
} else
tree_key = state.to_string(field_index);
return tree_key;
}
static int redirect_newindex(lutok::state&);
static int redirect_index(lutok::state&);
/// Creates a table for a new configuration inner node.
///
/// \post state(-1) Contains the new table.
///
/// \param state The Lua state in which to push the table.
/// \param tree_key The key to which the new table corresponds.
static void
new_table_for_key(lutok::state& state, const std::string& tree_key)
{
state.new_table();
{
state.new_table();
{
state.push_string("__index");
state.push_cxx_function(redirect_index);
state.set_table(-3);
state.push_string("__newindex");
state.push_cxx_function(redirect_newindex);
state.set_table(-3);
state.push_string("tree_key");
state.push_string(tree_key);
state.set_table(-3);
}
state.set_metatable(-2);
}
}
/// Sets the value of an configuration node.
///
/// \pre state(-3) The table to index. If this is not _G, then the table
/// metadata must contain a tree_key property describing the path to
/// current level.
/// \pre state(-2) The field to index into the table. Must be a string.
/// \pre state(-1) The value to set the indexed table field to.
///
/// \param state The Lua state in which to operate.
///
/// \return The number of result values on the Lua stack; always 0.
///
/// \throw invalid_key_error If the provided key is invalid.
/// \throw unknown_key_error If the key cannot be located.
/// \throw value_error If the value has an unsupported type or cannot be
/// set on the key, or if the input table or index are invalid.
static int
redirect_newindex(lutok::state& state)
{
if (!state.is_table(-3))
throw config::value_error("Indexed object is not a table");
if (!state.is_string(-2))
throw config::value_error("Invalid field in configuration object "
"reference; must be a string");
const std::string dotted_key = get_tree_key(state, -3, -2);
try {
config::tree& tree = get_global_tree(state);
tree.set_lua(dotted_key, state, -1);
} catch (const config::value_error& e) {
throw config::value_error(F("Invalid value for key '%s' (%s)") %
dotted_key % e.what());
}
// Now really set the key in the Lua table, but prevent direct accesses from
// the user by prefixing it. We do this to ensure that re-setting the same
// key of the tree results in a call to __newindex instead of __index.
state.push_string("_" + state.to_string(-2));
state.push_value(-2);
state.raw_set(-5);
return 0;
}
/// Indexes a configuration node.
///
/// \pre state(-3) The table to index. If this is not _G, then the table
/// metadata must contain a tree_key property describing the path to
/// current level. If the field does not exist, a new table is created.
/// \pre state(-1) The field to index into the table. Must be a string.
///
/// \param state The Lua state in which to operate.
///
/// \return The number of result values on the Lua stack; always 1.
///
/// \throw value_error If the input table or index are invalid.
static int
redirect_index(lutok::state& state)
{
if (!state.is_table(-2))
throw config::value_error("Indexed object is not a table");
if (!state.is_string(-1))
throw config::value_error("Invalid field in configuration object "
"reference; must be a string");
// Query if the key has already been set by a call to redirect_newindex.
state.push_string("_" + state.to_string(-1));
state.raw_get(-3);
if (!state.is_nil(-1))
return 1;
state.pop(1);
state.push_value(-1); // Duplicate the field name.
state.raw_get(-3); // Get table[field] to see if it's defined.
if (state.is_nil(-1)) {
state.pop(1);
// The stack is now the same as when we entered the function, but we
// know that the field is undefined and thus have to create a new
// configuration table.
INV(state.is_table(-2));
INV(state.is_string(-1));
const config::tree& tree = get_global_tree(state);
const std::string tree_key = get_tree_key(state, -2, -1);
if (tree.is_set(tree_key)) {
// Publish the pre-recorded value in the tree to the Lua state,
// instead of considering this table key a new inner node.
tree.push_lua(tree_key, state);
} else {
state.push_string("_" + state.to_string(-1));
state.insert(-2);
state.pop(1);
new_table_for_key(state, tree_key);
// Duplicate the newly created table and place it deep in the stack
// so that the raw_set below leaves us with the return value of this
// function at the top of the stack.
state.push_value(-1);
state.insert(-4);
state.raw_set(-3);
state.pop(1);
}
}
return 1;
}
} // anonymous namespace
/// Install wrappers for globals to set values in the configuration tree.
///
/// This function installs wrappers to capture all accesses to global variables.
/// Such wrappers redirect the reads and writes to the out_tree, which is the
/// entity that defines what configuration variables exist.
///
/// \param state The Lua state into which to install the wrappers.
/// \param out_tree The tree with the layout definition and where the
/// configuration settings will be collected.
void
config::redirect(lutok::state& state, tree& out_tree)
{
lutok::stack_cleaner cleaner(state);
state.new_table();
{
state.push_string("__index");
state.push_cxx_function(redirect_index);
state.set_table(-3);
state.push_string("__newindex");
state.push_cxx_function(redirect_newindex);
state.set_table(-3);
state.push_string("tree");
config::tree** tree = state.new_userdata< config::tree* >();
*tree = &out_tree;
state.set_table(-3);
}
state.set_metatable(lutok::globals_index);
}