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#ifndef FISH_ENV_UNIVERSAL_COMMON_H
#define FISH_ENV_UNIVERSAL_COMMON_H
#include <pthread.h>
#include <stdio.h>
#include <memory>
#include <set>
#include <vector>
#include "common.h"
#include "env.h"
#include "wutil.h"
/// The different types of messages found in the fishd file.
typedef enum { SET, SET_EXPORT, ERASE } fish_message_type_t;
/// Callback data, reflecting a change in universal variables.
struct callback_data_t {
fish_message_type_t type;
wcstring key;
wcstring val;
callback_data_t(fish_message_type_t t, const wcstring &k, const wcstring &v)
: type(t), key(k), val(v) {}
};
typedef std::vector<struct callback_data_t> callback_data_list_t;
/// Class representing universal variables.
class env_universal_t {
var_table_t vars; // current values
// Keys that have been modified, and need to be written. A value here that is not present in
// vars indicates a deleted value.
std::set<wcstring> modified;
// Path that we save to. If empty, use the default.
const wcstring explicit_vars_path;
mutable pthread_mutex_t lock;
bool tried_renaming;
bool load_from_path(const wcstring &path, callback_data_list_t *callbacks);
void load_from_fd(int fd, callback_data_list_t *callbacks);
void set_internal(const wcstring &key, const wcstring &val, bool exportv, bool overwrite);
bool remove_internal(const wcstring &name);
// Functions concerned with saving.
bool open_and_acquire_lock(const wcstring &path, int *out_fd);
bool open_temporary_file(const wcstring &directory, wcstring *out_path, int *out_fd);
bool write_to_fd(int fd, const wcstring &path);
bool move_new_vars_file_into_place(const wcstring &src, const wcstring &dst);
// File id from which we last read.
file_id_t last_read_file;
// Given a variable table, generate callbacks representing the difference between our vars and
// the new vars.
void generate_callbacks(const var_table_t &new_vars, callback_data_list_t *callbacks) const;
// Given a variable table, copy unmodified values into self. May destructively modified
// vars_to_acquire.
void acquire_variables(var_table_t *vars_to_acquire);
static void parse_message_internal(const wcstring &msg, var_table_t *vars, wcstring *storage);
static var_table_t read_message_internal(int fd);
public:
explicit env_universal_t(const wcstring &path);
~env_universal_t();
// Get the value of the variable with the specified name.
env_var_t get(const wcstring &name) const;
// Returns whether the variable with the given name is exported, or false if it does not exist.
bool get_export(const wcstring &name) const;
// Sets a variable.
void set(const wcstring &key, const wcstring &val, bool exportv);
// Removes a variable. Returns true if it was found, false if not.
bool remove(const wcstring &name);
// Gets variable names.
wcstring_list_t get_names(bool show_exported, bool show_unexported) const;
/// Loads variables at the correct path.
bool load();
/// Reads and writes variables at the correct path. Returns true if modified variables were
/// written.
bool sync(callback_data_list_t *callbacks);
};
/// The "universal notifier" is an object responsible for broadcasting and receiving universal
/// variable change notifications. These notifications do not contain the change, but merely
/// indicate that the uvar file has changed. It is up to the uvar subsystem to re-read the file.
///
/// We support a few notificatins strategies. Not all strategies are supported on all platforms.
///
/// Notifiers may request polling, and/or provide a file descriptor to be watched for readability in
/// select().
///
/// To request polling, the notifier overrides usec_delay_between_polls() to return a positive
/// value. That value will be used as the timeout in select(). When select returns, the loop invokes
/// poll(). poll() should return true to indicate that the file may have changed.
///
/// To provide a file descriptor, the notifier overrides notification_fd() to return a non-negative
/// fd. This will be added to the "read" file descriptor list in select(). If the fd is readable,
/// notification_fd_became_readable() will be called; that function should be overridden to return
/// true if the file may have changed.
class universal_notifier_t {
public:
enum notifier_strategy_t {
// Default meta-strategy to use the 'best' notifier for the system.
strategy_default,
// Use a value in shared memory. Simple, but requires polling and therefore semi-frequent
// wakeups.
strategy_shmem_polling,
// Strategy that uses a named pipe. Somewhat complex, but portable and doesn't require
// polling most of the time.
strategy_named_pipe,
// Strategy that uses notify(3). Simple and efficient, but OS X only.
strategy_notifyd,
// Null notifier, does nothing.
strategy_null
};
protected:
universal_notifier_t();
private:
// No copying.
universal_notifier_t &operator=(const universal_notifier_t &);
universal_notifier_t(const universal_notifier_t &x);
static notifier_strategy_t resolve_default_strategy();
public:
virtual ~universal_notifier_t();
// Factory constructor. Free with delete.
static universal_notifier_t *new_notifier_for_strategy(notifier_strategy_t strat,
const wchar_t *test_path = NULL);
// Default instance. Other instances are possible for testing.
static universal_notifier_t &default_notifier();
// Does a fast poll(). Returns true if changed.
virtual bool poll();
// Triggers a notification.
virtual void post_notification();
// Recommended delay between polls. A value of 0 means no polling required (so no timeout).
virtual unsigned long usec_delay_between_polls() const;
// Returns the fd from which to watch for events, or -1 if none.
virtual int notification_fd();
// The notification_fd is readable; drain it. Returns true if a notification is considered to
// have been posted.
virtual bool notification_fd_became_readable(int fd);
};
// Environment variable for requesting a particular universal notifier. See
// fetch_default_strategy_from_environment for names.
#define UNIVERSAL_NOTIFIER_ENV_NAME "fish_universal_notifier"
#endif
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