fish-shell/src/autoload.h

// The classes responsible for autoloading functions and completions.
#ifndef FISH_AUTOLOAD_H
#define FISH_AUTOLOAD_H

#include <pthread.h>
#include <stddef.h>
#include <time.h>
#include <set>
#include "common.h"
#include "lru.h"

// A struct responsible for recording an attempt to access a file.
struct file_access_attempt_t {
    time_t mod_time;      // modification time of the file
    time_t last_checked;  // when we last checked the file
    bool accessible;      // whether we believe we could access this file
    bool stale;           // whether the access attempt is stale
    int error;            // if we could not access the file, the error code
};

file_access_attempt_t access_file(const wcstring &path, int mode);

struct autoload_function_t : public lru_node_t {
    explicit autoload_function_t(const wcstring &key)
        : lru_node_t(key),
          access(),
          is_loaded(false),
          is_placeholder(false),
          is_internalized(false) {}
    file_access_attempt_t access;  // the last access attempt
    bool is_loaded;                // whether we have actually loaded this function
    // Whether we are a placeholder that stands in for "no such function". If this is true, then
    // is_loaded must be false.
    bool is_placeholder;
    // Whether this function came from a builtin "internalized" script.
    bool is_internalized;
};

struct builtin_script_t {
    const wchar_t *name;
    const char *def;
};

class env_vars_snapshot_t;

// A class that represents a path from which we can autoload, and the autoloaded contents.
class autoload_t : private lru_cache_t<autoload_function_t> {
   private:
    // Lock for thread safety.
    pthread_mutex_t lock;
    // The environment variable name.
    const wcstring env_var_name;
    // Builtin script array.
    const struct builtin_script_t *const builtin_scripts;
    // Builtin script count.
    const size_t builtin_script_count;
    // The path from which we most recently autoloaded.
    wcstring last_path;
    // That path, tokenized (split on separators).
    wcstring_list_t last_path_tokenized;

    // A table containing all the files that are currently being loaded. This is here to help
    // prevent recursion.
    std::set<wcstring> is_loading_set;

    void remove_all_functions(void) { this->evict_all_nodes(); }

    bool locate_file_and_maybe_load_it(const wcstring &cmd, bool really_load, bool reload,
                                       const wcstring_list_t &path_list);

    virtual void node_was_evicted(autoload_function_t *node);

    autoload_function_t *get_autoloaded_function_with_creation(const wcstring &cmd,
                                                               bool allow_eviction);

   protected:
    // Overridable callback for when a command is removed.
    virtual void command_removed(const wcstring &cmd) {}

   public:
    // Create an autoload_t for the given environment variable name.
    autoload_t(const wcstring &env_var_name_var, const builtin_script_t *scripts,
               size_t script_count);

    virtual ~autoload_t();  // destructor

    // Autoload the specified file, if it exists in the specified path. Do not load it multiple
    // times unless its timestamp changes or parse_util_unload is called.
    //
    // Autoloading one file may unload another.
    //
    // \param cmd the filename to search for. The suffix '.fish' is always added to this name
    // \param on_unload a callback function to run if a suitable file is found, which has not
    // already been run. unload will also be called for old files which are unloaded.
    // \param reload wheter to recheck file timestamps on already loaded files
    int load(const wcstring &cmd, bool reload);

    // Check whether we have tried loading the given command. Does not do any I/O.
    bool has_tried_loading(const wcstring &cmd);

    // Tell the autoloader that the specified file, in the specified path, is no longer loaded.
    //
    // \param cmd the filename to search for. The suffix '.fish' is always added to this name
    // \param on_unload a callback function which will be called before (re)loading a file, may be
    // used to unload the previous file.
    // \return non-zero if the file was removed, zero if the file had not yet been loaded
    int unload(const wcstring &cmd);

    // Check whether the given command could be loaded, but do not load it.
    bool can_load(const wcstring &cmd, const env_vars_snapshot_t &vars);
};
#endif