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Refactor module and node implementation
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topjohnwu
341
native/src/core/node.hpp
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341
native/src/core/node.hpp
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#pragma once
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#include <sys/mount.h>
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#include <map>
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using namespace std;
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#define TYPE_MIRROR (1 << 0) /* mount from mirror */
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#define TYPE_INTER (1 << 1) /* intermediate node */
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#define TYPE_TMPFS (1 << 2) /* replace with tmpfs */
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#define TYPE_MODULE (1 << 3) /* mount from module */
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#define TYPE_ROOT (1 << 4) /* partition root */
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#define TYPE_CUSTOM (1 << 5) /* custom node type overrides all */
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#define TYPE_DIR (TYPE_INTER|TYPE_TMPFS|TYPE_ROOT)
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class node_entry;
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class dir_node;
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class inter_node;
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class mirror_node;
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class tmpfs_node;
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class module_node;
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class root_node;
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// Poor man's dynamic cast without RTTI
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template<class T> static bool isa(node_entry *node);
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template<class T> static T *dyn_cast(node_entry *node);
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template<class T> uint8_t type_id() { return TYPE_CUSTOM; }
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template<> uint8_t type_id<dir_node>() { return TYPE_DIR; }
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template<> uint8_t type_id<inter_node>() { return TYPE_INTER; }
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template<> uint8_t type_id<mirror_node>() { return TYPE_MIRROR; }
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template<> uint8_t type_id<tmpfs_node>() { return TYPE_TMPFS; }
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template<> uint8_t type_id<module_node>() { return TYPE_MODULE; }
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template<> uint8_t type_id<root_node>() { return TYPE_ROOT; }
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class node_entry {
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public:
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virtual ~node_entry() = default;
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// Node info
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bool is_dir() const { return file_type() == DT_DIR; }
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bool is_lnk() const { return file_type() == DT_LNK; }
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bool is_reg() const { return file_type() == DT_REG; }
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const string &name() const { return _name; }
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dir_node *parent() const { return _parent; }
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// Don't call the following two functions before prepare
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const string &node_path();
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string mirror_path() { return mirror_dir + node_path(); }
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virtual void mount() = 0;
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static string module_mnt;
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static string mirror_dir;
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protected:
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template<class T>
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node_entry(const char *name, uint8_t file_type, T*)
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: _name(name), _file_type(file_type), _node_type(type_id<T>()) {}
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template<class T>
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explicit node_entry(T*) : _file_type(0), _node_type(type_id<T>()) {}
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void consume(node_entry *other);
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void create_and_mount(const char *reason, const string &src);
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// Use top bit of _file_type for node exist status
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bool exist() const { return static_cast<bool>(_file_type & (1 << 7)); }
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void set_exist(bool b) { if (b) _file_type |= (1 << 7); else _file_type &= ~(1 << 7); }
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uint8_t file_type() const { return static_cast<uint8_t>(_file_type & ~(1 << 7)); }
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private:
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friend class dir_node;
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template<class T>
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friend bool isa(node_entry *node);
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// Node properties
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string _name;
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uint8_t _file_type;
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const uint8_t _node_type;
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dir_node *_parent = nullptr;
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// Cache, it should only be used within prepare
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string _node_path;
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};
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class dir_node : public node_entry {
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public:
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friend void node_entry::consume(node_entry *other);
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using map_type = map<string_view, node_entry *>;
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using iterator = map_type::iterator;
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~dir_node() override {
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for (auto &it : children)
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delete it.second;
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children.clear();
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}
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// Traverse through module directories to generate a tree of module files
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void collect_module_files(const char *module, int dfd);
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// Traverse through the real filesystem and prepare the tree for magic mount.
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// Return true to indicate that this node needs to be upgraded to tmpfs_node.
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bool prepare();
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// Default directory mount logic
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void mount() override {
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for (auto &pair : children)
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pair.second->mount();
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}
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/***************
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* Tree Methods
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***************/
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bool is_empty() { return children.empty(); }
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template<class T>
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T *get_child(string_view name) { return iterator_to_node<T>(children.find(name)); }
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root_node *root() {
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if (!_root)
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_root = _parent->root();
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return _root;
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}
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// Return child with name or nullptr
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node_entry *extract(string_view name) {
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auto it = children.find(name);
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if (it != children.end()) {
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auto ret = it->second;
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children.erase(it);
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return ret;
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}
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return nullptr;
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}
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// Return false if rejected
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bool insert(node_entry *node) {
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auto fn = [=](auto) { return node; };
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return node && iterator_to_node(insert(node->_name, node->_node_type, fn));
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}
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// Return inserted node or null if rejected
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template<class T, class ...Args>
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T *emplace(string_view name, Args &&...args) {
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auto fn = [&](auto) { return new T(std::forward<Args>(args)...); };
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return iterator_to_node<T>(insert(name, type_id<T>(), fn));
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}
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// Return upgraded node or null if rejected
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template<class T, class ...Args>
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T *upgrade(string_view name, Args &...args) {
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return iterator_to_node<T>(upgrade<T>(children.find(name), args...));
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}
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protected:
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template<class T>
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dir_node(const char *name, T *self) : node_entry(name, DT_DIR, self) {
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if constexpr (std::is_same_v<T, root_node>)
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_root = self;
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}
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template<class T>
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dir_node(node_entry *node, T *self) : node_entry(self) {
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consume(node);
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if constexpr (std::is_same_v<T, root_node>)
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_root = self;
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}
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template<class T = node_entry>
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T *iterator_to_node(iterator it) {
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return static_cast<T*>(it == children.end() ? nullptr : it->second);
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}
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template<typename Func>
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iterator insert(string_view name, uint8_t type, const Func &fn) {
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return insert_at(children.find(name), type, fn);
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}
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// Emplace insert a new node, or upgrade if the requested type has a higher rank.
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// Return iterator to the new/upgraded node, or end() if insertion is rejected.
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// fn is the node builder function. Signature: (node_entry *&) -> node_entry *
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// fn gets a reference to the existing node pointer and returns a new node object.
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// Input is null when there is no existing node. If returns null, the insertion is rejected.
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// If fn consumes the input, it should set the reference to null.
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template<typename Builder>
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iterator insert_at(iterator it, uint8_t type, const Builder &builder) {
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node_entry *node = nullptr;
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if (it != children.end()) {
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// Upgrade existing node only if higher rank
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if (it->second->_node_type < type) {
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node = builder(it->second);
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if (!node)
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return children.end();
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if (it->second)
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node->consume(it->second);
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it = children.erase(it);
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// Minor optimization to make insert O(1) by using hint
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if (it == children.begin())
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it = children.emplace(node->_name, node).first;
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else
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it = children.emplace_hint(--it, node->_name, node);
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} else {
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return children.end();
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}
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} else {
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node = builder(node);
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if (!node)
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return children.end();
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node->_parent = this;
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it = children.emplace(node->_name, node).first;
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}
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return it;
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}
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template<class To, class From = node_entry, class ...Args>
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iterator upgrade(iterator it, Args &&...args) {
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return insert_at(it, type_id<To>(), [&](node_entry *&ex) -> node_entry * {
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if (!ex)
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return nullptr;
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if constexpr (!std::is_same_v<From, node_entry>) {
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// Type check if type is specified
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if (!isa<From>(ex))
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return nullptr;
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}
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auto node = new To(static_cast<From *>(ex), std::forward<Args>(args)...);
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ex = nullptr;
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return node;
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});
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}
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// dir nodes host children
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map_type children;
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// Skip binding mirror for this directory
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bool skip_mirror = false;
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private:
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// Root node lookup cache
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root_node *_root = nullptr;
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// We need to upgrade to tmpfs node if any child:
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// - Target does not exist
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// - Source or target is a symlink (since we cannot bind mount link)
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bool require_tmpfs_upgrade(node_entry *child) {
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struct stat st{};
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if (lstat(child->node_path().data(), &st) != 0) {
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return true;
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} else {
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child->set_exist(true);
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if (child->is_lnk() || S_ISLNK(st.st_mode))
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return true;
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}
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return false;
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}
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};
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class root_node : public dir_node {
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public:
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explicit root_node(const char *name) : dir_node(name, this), prefix("") {
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set_exist(true);
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}
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explicit root_node(node_entry *node) : dir_node(node, this), prefix("/system") {
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set_exist(true);
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}
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const char * const prefix;
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};
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class inter_node : public dir_node {
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public:
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inter_node(const char *name, const char *module) : dir_node(name, this), module(module) {}
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private:
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const char *module;
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friend class module_node;
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};
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class module_node : public node_entry {
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public:
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module_node(const char *module, dirent *entry)
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: node_entry(entry->d_name, entry->d_type, this), module(module) {}
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module_node(node_entry *node, const char *module) : node_entry(this), module(module) {
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consume(node);
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}
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explicit module_node(inter_node *node) : module_node(node, node->module) {}
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void mount() override;
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private:
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const char *module;
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};
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// Don't create the following two nodes before prepare
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class mirror_node : public node_entry {
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public:
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explicit mirror_node(dirent *entry) : node_entry(entry->d_name, entry->d_type, this) {}
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void mount() override {
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create_and_mount("mirror", mirror_path());
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}
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};
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class tmpfs_node : public dir_node {
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public:
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explicit tmpfs_node(node_entry *node);
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void mount() override;
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};
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template<class T>
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static bool isa(node_entry *node) {
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return node && (node->_node_type & type_id<T>());
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}
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template<class T>
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static T *dyn_cast(node_entry *node) {
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return isa<T>(node) ? static_cast<T*>(node) : nullptr;
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}
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const string &node_entry::node_path() {
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if (_parent && _node_path.empty())
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_node_path = _parent->node_path() + '/' + _name;
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return _node_path;
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}
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void node_entry::consume(node_entry *other) {
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_name.swap(other->_name);
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_file_type = other->_file_type;
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_parent = other->_parent;
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// Merge children if both is dir
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if (auto a = dyn_cast<dir_node>(this)) {
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if (auto b = dyn_cast<dir_node>(other)) {
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a->skip_mirror = b->skip_mirror;
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a->children.merge(b->children);
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for (auto &pair : a->children)
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pair.second->_parent = a;
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}
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}
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delete other;
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}
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