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Flow 1.0.2
Flow project: Full implementation reference.
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Flow module containing miscellaneous general-use facilities that don't fit into any other Flow module. More...
Namespaces | |
| namespace | bind_ns |
Hack namespace alias to enable use of bind and related utilities like cref in the face of strange observed compiler behavior. | |
| namespace | this_thread |
| Short-hand for standard this-thread namespace. | |
Classes | |
| class | Basic_blob |
A hand-optimized and API-tweaked replacement for vector<uint8_t>, i.e., buffer of bytes inside an allocated area of equal or larger size; also optionally supports limited garbage-collected memory pool functionality and SHM-friendly custom-allocator support. More... | |
| class | Basic_string_view |
Essentially alias for a C++17-conforming string-view class template, which is a very lightweight std::string-like representation of a character sequence already in memory. More... | |
| class | Blob_with_log_context |
| Basic_blob that works in regular heap (and is itself placed in heap or stack) and memorizes a log::Logger, enabling easier logging albeit with a small perf trade-off. More... | |
| class | Container_traits |
| Properties of various container types. More... | |
| class | Container_traits< boost::unordered_set< T > > |
Traits of boost::unordered_set. More... | |
| class | Container_traits< std::map< K, V > > |
Traits of std::map. More... | |
| class | Container_traits< std::set< T > > |
Traits of std::set. More... | |
| class | Container_traits< util::Linked_hash_map< K, V > > |
| Traits of flow::util::Linked_hash_map. More... | |
| class | Container_traits< util::Linked_hash_set< T, Hash, Pred > > |
| Traits of flow::util::Linked_hash_set. More... | |
| class | Duration_units_beautified |
| Internally used class that enables some of the activities of beautify_chrono_ostream() API. More... | |
| class | Linked_hash_map |
An object of this class is a map that combines the lookup speed of a boost::unordered_map<> and ordering and iterator stability capabilities of an std::list<>. More... | |
| class | Linked_hash_set |
An object of this class is a set that combines the lookup speed of an unordered_set<> and ordering and iterator stability capabilities of an std::list<>. More... | |
| class | Null_interface |
An empty interface, consisting of nothing but a default virtual destructor, intended as a boiler-plate-reducing base for any other (presumably virtual-method-having) class that would otherwise require a default virtual destructor. More... | |
| class | Rnd_gen_uniform_range |
| Simple, non-thread-safe uniform-range random number generator. More... | |
| class | Rnd_gen_uniform_range_base |
| Base class for Rnd_gen_uniform_range and Rnd_gen_uniform_range_mt for various aliases and similar, so template arguments need not be involved. More... | |
| class | Rnd_gen_uniform_range_mt |
| Identical to Rnd_gen_uniform_range but safe for concurrent RNG given a single object. More... | |
| struct | Scheduled_task_handle_state |
Internal-use data store used by schedule[d]_task_*(), each object containing the state relevant to a single call to either schedule_task_from_now() or schedule_task_at(). More... | |
| class | Scoped_setter |
| A simple RAII-pattern class template that, at construction, sets the specified location in memory to a specified value, memorizing the previous contents; and at destruction restores the value. More... | |
| class | Shared_ptr_alias_holder |
Convenience class template that endows the given subclass T with nested aliases Ptr and Const_ptr aliased to shared_ptr<T> and shared_ptr<const T> respectively. More... | |
| class | String_ostream |
Similar to ostringstream but allows fast read-only access directly into the std::string being written; and some limited write access to that string. More... | |
| class | Unique_id_holder |
| Each object of this class stores (at construction) and returns (on demand) a numeric ID unique from all other objects of the same class ever constructed, across all time from program start to end. More... | |
Typedefs | |
| using | Blob_sans_log_context = Basic_blob<> |
| Short-hand for a Basic_blob that allocates/deallocates in regular heap and is itself assumed to be stored in heap or on stack; sharing feature compile-time-disabled (with perf boost as a result). More... | |
| using | Sharing_blob_sans_log_context = Basic_blob< std::allocator< uint8_t >, true > |
| Identical to Blob_sans_log_context but with sharing feature compile-time-enabled. More... | |
| using | Blob = Blob_with_log_context<> |
| A concrete Blob_with_log_context that compile-time-disables Basic_blob::share() and the sharing API derived from it. More... | |
| using | Sharing_blob = Blob_with_log_context< true > |
| A concrete Blob_with_log_context that compile-time-enables Basic_blob::share() and the sharing API derived from it. More... | |
| using | Scheduled_task_handle = boost::shared_ptr< Scheduled_task_handle_state > |
| Black-box type that represents a handle to a scheduled task as scheduled by schedule_task_at() or schedule_task_from_now() or similar, which can be (optionally) used to control the scheduled task after it has been thus scheduled. More... | |
| using | Scheduled_task_const_handle = boost::shared_ptr< const Scheduled_task_handle_state > |
Equivalent to Scheduled_task_handle but refers to immutable version of a task. More... | |
| using | Scheduled_task = Function< void(bool short_fire)> |
| Short-hand for tasks that can be scheduled/fired by schedule_task_from_now() and similar. More... | |
| using | String_view = Basic_string_view< char > |
Commonly used char-based Basic_string_view. See its doc header. More... | |
| using | Thread = boost::thread |
| Short-hand for standard thread class. More... | |
| using | Thread_id = Thread::id |
| Short-hand for an OS-provided ID of a util::Thread. More... | |
| using | Task_engine = boost::asio::io_service |
| Short-hand for boost.asio event service, the central class of boost.asio. More... | |
| using | Strand = Task_engine::strand |
| Short-hand for boost.asio strand, an ancillary class that works with Task_engine for advanced task scheduling. More... | |
| using | Timer = boost::asio::basic_waitable_timer< Fine_clock > |
| boost.asio timer. More... | |
| using | Auto_cleanup = boost::shared_ptr< void > |
| Helper type for setup_auto_cleanup(). More... | |
| using | Udp_endpoint = boost::asio::ip::udp::endpoint |
| Short-hand for the UDP endpoint (IP/port) type. More... | |
| using | Ip_address_v4 = boost::asio::ip::address_v4 |
| Short-hand for the IPv4 address type. More... | |
| using | Ip_address_v6 = boost::asio::ip::address_v6 |
| Short-hand for the IPv6 address type. More... | |
| using | Mutex_non_recursive = boost::mutex |
| Short-hand for non-reentrant, exclusive mutex. ("Reentrant" = one can lock an already-locked-in-that-thread mutex.) More... | |
| using | Mutex_recursive = boost::recursive_mutex |
| Short-hand for reentrant, exclusive mutex. More... | |
| using | Mutex_shared_non_recursive = boost::shared_mutex |
| Short-hand for non-reentrant, shared-or-exclusive mutex. More... | |
| using | Mutex_noop_shared_non_recursive = boost::null_mutex |
| Short-hand for a mutex type equivalent to util::Mutex_shared_non_recursive – except that the lock/unlock mutex ops all do nothing. More... | |
| template<typename Mutex > | |
| using | Lock_guard = boost::unique_lock< Mutex > |
| Short-hand for advanced-capability RAII lock guard for any mutex, ensuring exclusive ownership of that mutex. More... | |
| template<typename Shared_mutex > | |
| using | Shared_lock_guard = boost::shared_lock< Shared_mutex > |
| Short-hand for shared mode advanced-capability RAII lock guard, particuarly for Mutex_shared_non_recursive mutexes. More... | |
| using | Lock_guard_non_recursive = boost::unique_lock< Mutex_non_recursive > |
| (Deprecated given C++1x) Short-hand for advanced-capability RAII lock guard for Mutex_non_recursive mutexes. More... | |
| using | Lock_guard_recursive = boost::unique_lock< Mutex_recursive > |
| (Deprecated given C++1x) Short-hand for advanced-capability RAII lock guard for Mutex_recursive mutexes. More... | |
| using | Lock_guard_shared_non_recursive_sh = boost::shared_lock< Mutex_shared_non_recursive > |
| (Deprecated given C++1x) Short-hand for shared mode advanced-capability RAII lock guard for Mutex_shared_non_recursive mutexes. More... | |
| using | Lock_guard_shared_non_recursive_ex = boost::unique_lock< Mutex_shared_non_recursive > |
| (Deprecated given C++1x) Short-hand for exclusive mode advanced-capability RAII lock guard for Mutex_shared_non_recursive mutexes. More... | |
| using | Lock_guard_noop_shared_non_recursive_sh = boost::shared_lock< Mutex_noop_shared_non_recursive > |
| (Deprecated given C++1x) Equivalent to Lock_guard_shared_non_recursive_sh but applied to Mutex_noop_shared_non_recursive. More... | |
| using | Lock_guard_noop_shared_non_recursive_ex = boost::unique_lock< Mutex_noop_shared_non_recursive > |
| (Deprecated given C++1x) Equivalent to Lock_guard_shared_non_recursive_ex but applied to Mutex_noop_shared_non_recursive. More... | |
Functions | |
| template<typename Allocator , bool S_SHARING_ALLOWED> | |
| void | swap (Basic_blob< Allocator, S_SHARING_ALLOWED > &blob1, Basic_blob< Allocator, S_SHARING_ALLOWED > &blob2, log::Logger *logger_ptr=0) |
Equivalent to blob1.swap(blob2). More... | |
| template<typename Allocator , bool S_SHARING_ALLOWED> | |
| bool | blobs_sharing (const Basic_blob< Allocator, S_SHARING_ALLOWED > &blob1, const Basic_blob< Allocator, S_SHARING_ALLOWED > &blob2) |
Returns true if and only if both given objects are not zero() == true, and they either co-own a common underlying buffer, or are the same object. More... | |
| template<bool S_SHARING_ALLOWED> | |
| void | swap (Blob_with_log_context< S_SHARING_ALLOWED > &blob1, Blob_with_log_context< S_SHARING_ALLOWED > &blob2) |
On top of the similar Basic_blob related function, logs using the stored log context of blob1. More... | |
| std::string | get_where_am_i_str (String_view file, String_view function, unsigned int line) |
Helper for FLOW_UTIL_WHERE_AM_I(), etc., that, given values for source code file name, function, and line number, returns an std::string equal to what FLOW_UTIL_WHERE_AM_I() would place into an ostream. More... | |
| template<typename Rep , typename Period > | |
| Fine_duration | chrono_duration_to_fine_duration (const boost::chrono::duration< Rep, Period > &dur) |
| Helper that takes a non-negative duration of arbitrary precision/period and converts it to Fine_duration, rounding up. More... | |
| template<typename Rep , typename Period > | |
| Fine_time_pt | chrono_duration_from_now_to_fine_time_pt (const boost::chrono::duration< Rep, Period > &dur) |
Helper that takes a non-negative duration of arbitrary precision/period and converts it to Fine_duration, rounding up; then adds it to Fine_clock::now() and returns the result. More... | |
| constexpr String_view | get_last_path_segment (String_view path) |
| Helper for FLOW_UTIL_WHERE_AM_I() that, given a pointer/length of a string in memory containing a path, returns a pointer/length into that same buffer that comprises the postfix just past the last directory separator or (if none exists) to all of it. More... | |
| template<typename Key , typename Mapped , typename Hash , typename Pred > | |
| void | swap (Linked_hash_map< Key, Mapped, Hash, Pred > &val1, Linked_hash_map< Key, Mapped, Hash, Pred > &val2) |
Equivalent to val1.swap(val2). More... | |
| template<typename Key , typename Hash , typename Pred > | |
| void | swap (Linked_hash_set< Key, Hash, Pred > &val1, Linked_hash_set< Key, Hash, Pred > &val2) |
Equivalent to val1.swap(val2). More... | |
| bool | scheduled_task_cancel (log::Logger *logger_ptr, Scheduled_task_handle task) |
| Attempts to prevent the execution of a previously scheduled (by schedule_task_from_now() or similar) task. More... | |
| bool | scheduled_task_short_fire (log::Logger *logger_ptr, Scheduled_task_handle task) |
| Attempts to reschedule a previously scheduled (by schedule_task_from_now() or similar) task to fire immediately. More... | |
| Fine_duration | scheduled_task_fires_from_now_or_canceled (log::Logger *logger_ptr, Scheduled_task_const_handle task) |
| Returns how long remains until a previously scheduled (by schedule_task_from_now() or similar) task fires; or negative time if that point is in the past; or special value if the task has been canceled. More... | |
| bool | scheduled_task_fired (log::Logger *logger_ptr, Scheduled_task_const_handle task) |
| Returns whether a previously scheduled (by schedule_task_from_now() or similar) task has already fired. More... | |
| bool | scheduled_task_canceled (log::Logger *logger_ptr, Scheduled_task_const_handle task) |
| Returns whether a previously scheduled (by schedule_task_from_now() or similar) task has been canceled. More... | |
| template<typename Scheduled_task_handler > | |
| Scheduled_task_handle | schedule_task_from_now (log::Logger *logger_ptr, const Fine_duration &from_now, bool single_threaded, Task_engine *task_engine, Scheduled_task_handler &&task_body_moved) |
| Schedule the given function to execute in a certain amount of time: A handy wrapper around Timer (asio's timer facility). More... | |
| template<typename Scheduled_task_handler > | |
| Scheduled_task_handle | schedule_task_at (log::Logger *logger_ptr, const Fine_time_pt &at, bool single_threaded, Task_engine *task_engine, Scheduled_task_handler &&task_body_moved) |
| Identical to schedule_task_from_now() except the time is specified in absolute terms. More... | |
| boost::chrono::microseconds | time_since_posix_epoch () |
| Get the current POSIX (Unix) time as a duration from the Epoch time point. More... | |
| void | beautify_chrono_ostream (std::ostream *os) |
Sets certain chrono-related formatting on the given ostream that results in a consistent, desirable output of durations and certain types of time_points. More... | |
| size_t | deep_size (const std::string &val) |
Estimate of memory footprint of the given value, including memory allocated on its behalf – but excluding its shallow sizeof! – in bytes. More... | |
| template<typename Time_unit , typename N_items > | |
| double | to_mbit_per_sec (N_items items_per_time, size_t bits_per_item=8) |
| Utility that converts a bandwidth in arbitrary units in both numerator and denominator to the same bandwidth in megabits per second. More... | |
| template<typename Integer > | |
| Integer | ceil_div (Integer dividend, Integer divisor) |
| Returns the result of the given non-negative integer divided by a positive integer, rounded up to the nearest integer. More... | |
| template<typename T > | |
| bool | in_closed_range (T const &min_val, T const &val, T const &max_val) |
Returns true if and only if the given value is within the given range, inclusive. More... | |
| template<typename T > | |
| bool | in_open_closed_range (T const &min_val, T const &val, T const &max_val) |
Returns true if and only if the given value is within the given range, given as a (low, high] pair. More... | |
| template<typename T > | |
| bool | in_closed_open_range (T const &min_val, T const &val, T const &max_val) |
Returns true if and only if the given value is within the given range, given as a [low, high) pair. More... | |
| template<typename T > | |
| bool | in_open_open_range (T const &min_val, T const &val, T const &max_val) |
Returns true if and only if the given value is within the given range, given as a (low, high) pair. More... | |
| template<typename Container > | |
| bool | key_exists (const Container &container, const typename Container::key_type &key) |
Returns true if and only if the given key is present at least once in the given associative container. More... | |
| template<typename Cleanup_func > | |
| Auto_cleanup | setup_auto_cleanup (const Cleanup_func &func) |
| Provides a way to execute arbitrary (cleanup) code at the exit of the current block. More... | |
| template<typename Minuend , typename Subtrahend > | |
| bool | subtract_with_floor (Minuend *minuend, const Subtrahend &subtrahend, const Minuend &floor=0) |
Performs *minuend -= subtrahend, subject to a floor of floor. More... | |
| template<typename From , typename To > | |
| size_t | size_unit_convert (From num_froms) |
Answers the question what's the smallest integer number of Tos sufficient to verbatim store the given number of Froms?, where From and To are POD types. More... | |
| template<typename T1 , typename ... T_rest> | |
| void | feed_args_to_ostream (std::ostream *os, T1 const &ostream_arg1, T_rest const &... remaining_ostream_args) |
"Induction step" version of variadic function template that simply outputs arguments 2+ via << to the given ostream, in the order given. More... | |
| template<typename T > | |
| void | feed_args_to_ostream (std::ostream *os, T const &only_ostream_arg) |
"Induction base" for a variadic function template, this simply outputs given item to given ostream via <<. More... | |
| template<typename ... T> | |
| void | ostream_op_to_string (std::string *target_str, T const &... ostream_args) |
Writes to the specified string, as if the given arguments were each passed, via << in sequence, to an ostringstream, and then the result were appended to the aforementioned string variable. More... | |
| template<typename ... T> | |
| std::string | ostream_op_string (T const &... ostream_args) |
Equivalent to ostream_op_to_string() but returns a new string by value instead of writing to the caller's string. More... | |
| template<typename Map , typename Sequence > | |
| void | sequence_to_inverted_lookup_map (Sequence const &src_seq, Map *target_map, const Function< typename Map::mapped_type(size_t)> &idx_to_map_val_func) |
| Similar to the 2-arg overload of sequence_to_inverted_lookup_map() but with the ability to store a value based on the index into the input sequence instead of that index itself. More... | |
| template<typename Map , typename Sequence > | |
| void | sequence_to_inverted_lookup_map (Sequence const &src_seq, Map *target_map) |
| Given a generic sequence (integer -> object) generates a generic map (object -> integer) providing inverse lookup. More... | |
| template<typename Const_buffer_sequence > | |
| std::ostream & | buffers_to_ostream (std::ostream &os, const Const_buffer_sequence &data, const std::string &indentation, size_t bytes_per_line=0) |
| Writes a multi- or single-line string representation of the provided binary data to an output stream, complete with a printable and hex versions of each byte. More... | |
| template<typename Const_buffer_sequence > | |
| std::string | buffers_dump_string (const Const_buffer_sequence &data, const std::string &indentation, size_t bytes_per_line=0) |
Identical to buffers_to_ostream() but returns an std::string instead of writing to a given ostream. More... | |
| template<typename Enum > | |
| Enum | istream_to_enum (std::istream *is_ptr, Enum enum_default, Enum enum_sentinel, bool accept_num_encoding=true, bool case_sensitive=false, Enum enum_lowest=Enum(0)) |
Deserializes an enum class value from a standard input stream. More... | |
Flow module containing miscellaneous general-use facilities that don't fit into any other Flow module.
Each symbol therein is typically used by at least 1 other Flow module; but all public symbols (except ones under a detail/ subdirectory) are intended for use by Flow user as well.
| using flow::util::Auto_cleanup = typedef boost::shared_ptr<void> |
Helper type for setup_auto_cleanup().
Definition at line 205 of file util_fwd.hpp.
| using flow::util::Blob = typedef Blob_with_log_context<> |
A concrete Blob_with_log_context that compile-time-disables Basic_blob::share() and the sharing API derived from it.
It is likely the user will refer to Blob (or Sharing_blob) rather than Blob_with_log_context.
Definition at line 60 of file blob_fwd.hpp.
| using flow::util::Blob_sans_log_context = typedef Basic_blob<> |
Short-hand for a Basic_blob that allocates/deallocates in regular heap and is itself assumed to be stored in heap or on stack; sharing feature compile-time-disabled (with perf boost as a result).
Definition at line 44 of file blob_fwd.hpp.
| using flow::util::Ip_address_v4 = typedef boost::asio::ip::address_v4 |
Short-hand for the IPv4 address type.
Definition at line 210 of file util_fwd.hpp.
| using flow::util::Ip_address_v6 = typedef boost::asio::ip::address_v6 |
Short-hand for the IPv6 address type.
Definition at line 212 of file util_fwd.hpp.
| using flow::util::Lock_guard = typedef boost::unique_lock<Mutex> |
Short-hand for advanced-capability RAII lock guard for any mutex, ensuring exclusive ownership of that mutex.
Note the advanced API available for the underlying type: it is possible to relinquish ownership without unlocking, gain ownership of a locked mutex; and so on.
| Mutex | A non-recursive or recursive mutex type. Recommend one of: Mutex_non_recursive, Mutex_recursive, Mutex_shared_non_recursive, Mutex_noop_shared_non_recursive. |
Definition at line 265 of file util_fwd.hpp.
| using flow::util::Lock_guard_non_recursive = typedef boost::unique_lock<Mutex_non_recursive> |
(Deprecated given C++1x) Short-hand for advanced-capability RAII lock guard for Mutex_non_recursive mutexes.
Lock_guard<Mutex_non_recursive> possible. Remove it and all (outside) uses eventually. Definition at line 283 of file util_fwd.hpp.
| using flow::util::Lock_guard_noop_shared_non_recursive_ex = typedef boost::unique_lock<Mutex_noop_shared_non_recursive> |
(Deprecated given C++1x) Equivalent to Lock_guard_shared_non_recursive_ex but applied to Mutex_noop_shared_non_recursive.
Lock_guard<Mutex_noop_shared_non_recursive> possible. Remove it and all (outside) uses eventually. Definition at line 327 of file util_fwd.hpp.
| using flow::util::Lock_guard_noop_shared_non_recursive_sh = typedef boost::shared_lock<Mutex_noop_shared_non_recursive> |
(Deprecated given C++1x) Equivalent to Lock_guard_shared_non_recursive_sh but applied to Mutex_noop_shared_non_recursive.
Shared_lock_guard<Mutex_noop_shared_non_recursive> possible. Remove it and all (outside) uses eventually. Definition at line 318 of file util_fwd.hpp.
| using flow::util::Lock_guard_recursive = typedef boost::unique_lock<Mutex_recursive> |
(Deprecated given C++1x) Short-hand for advanced-capability RAII lock guard for Mutex_recursive mutexes.
Lock_guard<Mutex_recursive> possible. Remove it and all (outside) uses eventually. Definition at line 291 of file util_fwd.hpp.
| using flow::util::Lock_guard_shared_non_recursive_ex = typedef boost::unique_lock<Mutex_shared_non_recursive> |
(Deprecated given C++1x) Short-hand for exclusive mode advanced-capability RAII lock guard for Mutex_shared_non_recursive mutexes.
Lock_guard<Mutex_shared_non_recursive> possible. Remove it and all (outside) uses eventually. Definition at line 309 of file util_fwd.hpp.
| using flow::util::Lock_guard_shared_non_recursive_sh = typedef boost::shared_lock<Mutex_shared_non_recursive> |
(Deprecated given C++1x) Short-hand for shared mode advanced-capability RAII lock guard for Mutex_shared_non_recursive mutexes.
Shared_lock_guard<Mutex_shared_non_recursive> possible. Remove it and all (outside) uses eventually. Definition at line 300 of file util_fwd.hpp.
| using flow::util::Mutex_non_recursive = typedef boost::mutex |
Short-hand for non-reentrant, exclusive mutex. ("Reentrant" = one can lock an already-locked-in-that-thread mutex.)
Definition at line 215 of file util_fwd.hpp.
| using flow::util::Mutex_noop_shared_non_recursive = typedef boost::null_mutex |
Short-hand for a mutex type equivalent to util::Mutex_shared_non_recursive – except that the lock/unlock mutex ops all do nothing.
One can parameterize templates accordingly; so that an algorithm can be generically written to work in both single- and multi-threaded contexts without branching into 2 code paths, yet avoid the unnecessary actual locking in the former case.
Definition at line 251 of file util_fwd.hpp.
| using flow::util::Mutex_recursive = typedef boost::recursive_mutex |
Short-hand for reentrant, exclusive mutex.
Definition at line 218 of file util_fwd.hpp.
| using flow::util::Mutex_shared_non_recursive = typedef boost::shared_mutex |
Short-hand for non-reentrant, shared-or-exclusive mutex.
When locking one of these, choose one of: Lock_guard<Mutex_shared_non_recursive>, Shared_lock_guard<Mutex_shared_non_recursive>. The level of locking acquired (shared vs. exclusive) depends on which you chose and is thus highly significant.
boost::shared_mutex to std::shared_mutex, as the former has a long-standing unresolved ticket about its impl being slow and/or outdated (as of Boost-1.80). However see also the note on util::Mutex_shared_non_recursive that explains why it might be best to avoid this type of mutex altogether in the first place (in most cases).Experts suggest fairly strongly that one should be very wary about using a shared mutex, over a simple non-recursive exclusive mutex, in almost any practical application. The reason there's a trade-off at all is that a Mutex_non_recursive is extremely fast to lock and unlock; the entire perf cost is in waiting for another thread to unlock first; so without contention it's almost free. In contrast apparently any real impl of Mutex_shared_non_recursive is much slower to lock/unlock. The trade-off is against allowing reads to proceed in parallel; but experts say this is "worth it" only when these read critical sections are lengthy and very frequently invoked. So, for example, if the lock/unlock is around an unordered_map lookup with a quick hashing function, it would be quite difficult to induce enough lock contention to make a shared mutex better than an exclusive one. (Note this is assuming even no perf issue with boost::shared_mutex specifically.)
Definition at line 243 of file util_fwd.hpp.
| using flow::util::Scheduled_task = typedef Function<void (bool short_fire)> |
Short-hand for tasks that can be scheduled/fired by schedule_task_from_now() and similar.
short_fire shall be set to false if the task executed based on its scheduled time; true if it is fired early due to scheduled_task_short_fire().
Definition at line 59 of file sched_task_fwd.hpp.
| using flow::util::Scheduled_task_const_handle = typedef boost::shared_ptr<const Scheduled_task_handle_state> |
Equivalent to Scheduled_task_handle but refers to immutable version of a task.
One can safely construct a Scheduled_task_const_handle directly from Scheduled_task_handle (but not vice versa; nor would that compile without some kind of frowned-upon const_cast or equivalent).
Definition at line 52 of file sched_task_fwd.hpp.
| using flow::util::Scheduled_task_handle = typedef boost::shared_ptr<Scheduled_task_handle_state> |
Black-box type that represents a handle to a scheduled task as scheduled by schedule_task_at() or schedule_task_from_now() or similar, which can be (optionally) used to control the scheduled task after it has been thus scheduled.
Special value Scheduled_task_handle() represents an invalid task and can be used as a sentinel, as with a null pointer.
Values of this type are to be passed around by value, not reference. They are light-weight. Officially, passing it by reference results in undefined behavior. Unofficially, it will probably work (just haven't thought super-hard about it to make sure) but will bring no performance benefit.
Definition at line 45 of file sched_task_fwd.hpp.
| using flow::util::Shared_lock_guard = typedef boost::shared_lock<Shared_mutex> |
Short-hand for shared mode advanced-capability RAII lock guard, particuarly for Mutex_shared_non_recursive mutexes.
| Shared_mutex | Typically Mutex_shared_non_recursive, but any mutex type with that both-exclusive-and-shared API will work. |
Definition at line 275 of file util_fwd.hpp.
| using flow::util::Sharing_blob = typedef Blob_with_log_context<true> |
A concrete Blob_with_log_context that compile-time-enables Basic_blob::share() and the sharing API derived from it.
It is likely the user will refer to Sharing_blob (or Blob) rather than Blob_with_log_context.
Definition at line 68 of file blob_fwd.hpp.
| using flow::util::Sharing_blob_sans_log_context = typedef Basic_blob<std::allocator<uint8_t>, true> |
Identical to Blob_sans_log_context but with sharing feature compile-time-enabled.
The latter fact implies a small perf hit; see details in Basic_blob doc header.
Definition at line 52 of file blob_fwd.hpp.
| using flow::util::Strand = typedef Task_engine::strand |
Short-hand for boost.asio strand, an ancillary class that works with Task_engine for advanced task scheduling.
Definition at line 138 of file util_fwd.hpp.
| using flow::util::String_view = typedef Basic_string_view<char> |
Commonly used char-based Basic_string_view. See its doc header.
Definition at line 191 of file string_view.hpp.
| using flow::util::Task_engine = typedef boost::asio::io_service |
Short-hand for boost.asio event service, the central class of boost.asio.
The reasons for the rename – as opposed to simply calling it Io_service (historically it was indeed so named) – are as follows. To start, a later version of Boost (to which we eventually moved) realigned boost.asio's API to match the feedback boost.asio received when submitted as a candidate for inclusion into the official STL (sometime after C++17); in this reorg they renamed it from io_service to io_context. That's not the actual reason but more of a symptom of similar reasoning to the following:
io_service actually doesn't; it can (and typically is) used to take over at least one thread, but that's not a part of its "essence," so to speak. I've noticed that when boost.asio neophytes see "service" they intuitively draw incorrect assumptions about what it does, and then one must repeatedly dash those assumptions.io_service is all about working with various input/output (especially networking). While it's true that roughly 50% of the utility of boost.asio is its portable sockets/networking API, the other 50% is about its ability to flexibly execute user tasks in various threads; and, indeed, io_service itself is more about the latter 50% rather than the former. Its two most basic and arguably oft-used features are simply io_service::post() (which executes the given task ASAP); and the basic_waitable_timer set of classes (which execute task at some specified point in the future). Note these have nothing to do with networking or I/O of any kind. The I/O comes from the "I/O object" classes/etc., such as tcp::socket, but those are not io_service; they merely work together with it to execute the user-specified success/failure handlers.So, neither "I/O" nor "service" is accurate. To fix both, then, we used this rename reasoning:
post() – what is it handling?)io_service does provide immense algorithmic value.io_service::run()ning then to the extent there are any queues there might be multiple.Task_qs – of which there could be multiple (plural) – was clumsy. (An early proof-of-concept used Task_qs; people were not fans.) Definition at line 135 of file util_fwd.hpp.
| using flow::util::Thread = typedef boost::thread |
Short-hand for standard thread class.
We use/encourage use of boost.thread threads (and other boost.thread facilities) over std.thread counterparts – simply because it tends to be more full-featured. However, reminder: boost.thread IS (API-wise at least) std.thread, plus more (advanced?) stuff. Generally, boost.thread-using code can be converted to std.thread with little pain, unless one of the "advanced?" features is used.
Definition at line 78 of file util_fwd.hpp.
| using flow::util::Thread_id = typedef Thread::id |
Short-hand for an OS-provided ID of a util::Thread.
Definition at line 90 of file util_fwd.hpp.
| using flow::util::Timer = typedef boost::asio::basic_waitable_timer<Fine_clock> |
boost.asio timer.
Can schedule a function to get called within a set amount of time or at a certain specific time relative to some Epoch.
Timer). The notes below still apply however. Please read them even if you won't useTimer` directly.Important: While one can schedule events using very precise units using Fine_duration, the timer may not actually have that resolution. That is, I may schedule something to happen in 1 millisecond and then measure the time passed, using a high-res clock like Fine_clock, and discover that the wait was actually 15 milliseconds. This is not a problem for most timers. (In Flow itself, the most advanced use of timers by far is in flow::net_flow. Timers used in flow::net_flow – delayed ACK timer, Drop Timer, simulated latency timer – typically are for n x 50 milliseconds time periods or coarser.) However that may not be the case for all timers. (In particular, flow::net_flow packet pacing may use finer time periods.)
net_flow user. I leave them in this public doc header for practical purposes, as examples needed to discuss some Inside-Baseball topics involved.So I looked into what boost.asio provides. deadline_timer uses the system clock (universal_time()) as the time reference, while basic_waitable_timer<Fine_clock> uses the high-resolution clock (see Fine_clock). I tested both (using wait()s of various lengths and using Fine_clock to measure duration) and observed the following resolutions on certain OS (not listing the hardware):
glibc is too old to provide the timerfd API, therefore Boost falls back to using epoll_wait() directly; on a newer Linux this may get better results.)These results were observed for BOTH deadline_timer and basic_waitable_timer<Fine_clock> in Boost 1.50. Thus, there was no resolution advantage to using the latter – only an interface advantage. Conclusion: we'd be well-advised not to rely on anything much smaller than 20 milliseconds when scheduling timer events. One technique might be, given any time T < 20 ms, to assume T = 0 (i.e., execute immediately). This may or may not be appropriate depending on the situation.
However, using basic_waitable_timer<Fine_clock> may get an additional nice property: Fine_clock always goes forward and cannot be affected by NTP or user changes. deadline_timer may or may not be affected by such tomfoolery (untested, but the potential is clearly there). Therefore we do the best we can by using the Fine_clock-based timer.
cancel()ing it does not always cause the handler to fire with operation_aborted error code. Sometimes it was already "just
about" to fire at cancel() time, so the handler will run with no error code regardless of the cancel(). Personally I have never once found this behavior useful, and there is much code currently written to work around this "feature." Furthermore, even a "successful" cancel still runs the handler but with operation_aborted; 99.999% of the time one would want to just not run it at all. Finally, in many cases, even having to create a timer object (and then the multiple steps required to actually schedule a thing) feels like more boiler-plate than should be necessary. To avoid all of these usability issues, see schedule_task_from_now() (and similar), which is a facility that wraps Timer for a boiler-plate-free experience sufficient in the majority of practical situations. Timer is to be used directly when that simpler facility is insufficient.b_w_t<Fine_clock> happens to equal boost::asio::high_resolution_timer. We chose to alias in terms of Fine_clock merely to ensure that Fine_duration is one-to-one compatible with it, as it is defined in terms of Fine_clock also. Definition at line 202 of file util_fwd.hpp.
| using flow::util::Udp_endpoint = typedef boost::asio::ip::udp::endpoint |
Short-hand for the UDP endpoint (IP/port) type.
Definition at line 208 of file util_fwd.hpp.
| void flow::util::beautify_chrono_ostream | ( | std::ostream * | os | ) |
Sets certain chrono-related formatting on the given ostream that results in a consistent, desirable output of durations and certain types of time_points.
As of this writing this includes enabling short unit format (e.g., "ms" instead of "milliseconds") and avoiding Unicode characters (the Greek letter for micro becomes a similar-looking "u" instead).
| os | The stream to affect. |
Definition at line 173 of file util.cpp.
References flow::util::Duration_units_beautified::beautified_locale().
Referenced by flow::log::beautify_chrono_logger_this_thread().
| bool blobs_sharing | ( | const Basic_blob< Allocator, S_SHARING_ALLOWED > & | blob1, |
| const Basic_blob< Allocator, S_SHARING_ALLOWED > & | blob2 | ||
| ) |
Returns true if and only if both given objects are not zero() == true, and they either co-own a common underlying buffer, or are the same object.
Note: by the nature of Basic_blob::share(), a true returned value is orthogonal to whether Basic_blob::start() and Basic_blob::size() values are respectively equal; true may be returned even if their [begin(), end()) ranges don't overlap at all – as long as the allocated buffer is co-owned by the 2 Basic_blobs.
If &blob1 != &blob2, true indicates blob1 was obtained from blob2 via a chain of Basic_blob::share() (or wrapper thereof) calls, or vice versa.
| blob1 | Object. |
| blob2 | Object. |
blob1 and blob2 both operate on the same underlying buffer. Definition at line 1825 of file basic_blob.hpp.
Referenced by flow::util::Basic_blob< Allocator, S_SHARING_ALLOWED >::assign().
| std::string flow::util::buffers_dump_string | ( | const Const_buffer_sequence & | data, |
| const std::string & | indentation, | ||
| size_t | bytes_per_line = 0 |
||
| ) |
Identical to buffers_to_ostream() but returns an std::string instead of writing to a given ostream.
| Const_buffer_sequence | See buffers_to_ostream(). |
| data | See buffers_to_ostream(). |
| indentation | See buffers_to_ostream(). |
| bytes_per_line | See buffers_to_ostream(). |
Definition at line 481 of file util.hpp.
References buffers_to_ostream(), and flow::util::String_ostream::os().
Referenced by flow::net_flow::Socket_buffer::consume_buf_move(), flow::net_flow::Socket_buffer::consume_bufs_copy(), flow::net_flow::Low_lvl_packet::create_from_raw_data_packet(), flow::net_flow::Socket_buffer::feed_buf_move(), flow::net_flow::Socket_buffer::feed_bufs_copy(), flow::net_flow::Node::handle_data_to_established(), and flow::net_flow::Low_lvl_packet::serialize_to_raw_data_and_log().
| std::ostream & flow::util::buffers_to_ostream | ( | std::ostream & | os, |
| const Const_buffer_sequence & | data, | ||
| const std::string & | indentation, | ||
| size_t | bytes_per_line = 0 |
||
| ) |
Writes a multi- or single-line string representation of the provided binary data to an output stream, complete with a printable and hex versions of each byte.
bytes_per_line to special value -1. In this mode, the output consists of indentation, followed by a pretty-printed hex dump of every byte in data (no matter how many), followed by a pretty-printed ASCII-printable (or '.' if not so printable) character for each byte; that's it. No newline is added, and indentation is included only the one time. It is recommended to therefore print "in-line" inside log messages (etc.) without surrounding newlines, etc., when using this mode.bytes_per_line to a positive value; or 0 which auto-selects a decent default positive value. Then, each line represents up to that many bytes, which are pretty-printed similarly to single-line mode, in order of appearance in data (with the last such line representing the last few bytes, formatting nicely including accounting for potentially fewer than the desired # of bytes per line). Every line starts with indentation and ends with a newline – including the last line. Therefore, it is recommended to precede this call with an output of a newline and to avoid doing so after that call (unless blank line is desired).Example with a single contiguous memory area, multi-line mode:
See also buffers_dump_string() which returns a string and can thus be more easily used directly inside FLOW_LOG_DATA() and similar log macros.
This thing is slow... it's not trying to be fast and can't be all that fast anyway. As usual, though, if used in FLOW_LOG_DATA() (etc.) its slowness will only come into play if the log filter passes which (esp. for log::Severity::S_DATA) it usually won't.
That said buffers_dump_string() is even slower, because it'll use an intermediate ostream independent of whatever ostream you may or may not be placing the resulting string. However it's easier to use with FLOW_LOG_...(), and since in that case perf is typically not an issue, it makes sense to use the easier thing typically.
However, if you do want to avoid that extra copy and need to also use buffers_to_ostream() directly inside FLOW_LOG_...() then the following technique isn't too wordy and works:
The reason it returns os and takes a reference-to-mutable instead of the customary (for this project's style, to indicate modification potential at call sites) pointer-to-mutable is in order to be bind()able in such a way as to make an ostream manipulator. In the example above we use a lambda instead of bind() however.
| Const_buffer_sequence | Type that models the boost.asio ConstBufferSequence concept (see Boost docs) which represents 1 or more scattered buffers in memory (only 1 buffer in a sequence is common). In particular boost::asio::const_buffer works when dumping a single buffer. |
| os | The output stream to which to write. |
| data | The data to write, given as an immutable sequence of buffers each of which is essentially a pointer and length. (Reminder: it is trivial to make such an object from a single buffer as well; for example given array<uint8_t, 256> data (an array of 256 bytes), you can just pass boost::asio::buffer(data), as the latter returns an object whose type satisfies requirements of Const_buffer_sequence despite the original memory area being nothing more than a single byte array.) |
| indentation | The indentation to use at the start of every line of output. |
| bytes_per_line | If 0, act as-if a certain default positive value were passed; and then: If -1, single-line mode is invoked. If a positive value, multi-line mode is invoked, with all lines but the last one consisting of a dump of that many contiguous bytes of data. (Yes, multi-line mode is still in force, even if there are only enough bytes in data for one line of output anyway.) |
os. Definition at line 388 of file util.hpp.
Referenced by buffers_dump_string(), flow::net_flow::Syn_packet::to_ostream(), and flow::net_flow::Data_packet::to_ostream().
| Integer flow::util::ceil_div | ( | Integer | dividend, |
| Integer | divisor | ||
| ) |
Returns the result of the given non-negative integer divided by a positive integer, rounded up to the nearest integer.
Internally, it avoids floating-point math for performance.
| Integer | A signed or unsigned integral type. |
| dividend | Dividend; non-negative or assertion trips. |
| divisor | Divisor; positive or assertion trips. |
(dividend / divisor). Definition at line 233 of file util.hpp.
Referenced by flow::net_flow::Peer_socket::max_block_size_multiple().
| Fine_time_pt flow::util::chrono_duration_from_now_to_fine_time_pt | ( | const boost::chrono::duration< Rep, Period > & | dur | ) |
Helper that takes a non-negative duration of arbitrary precision/period and converts it to Fine_duration, rounding up; then adds it to Fine_clock::now() and returns the result.
Also, the input type's max() is translated to Fine_time_pt() (Epoch-valued – i.e., zero-valued – time point).
| Rep | See boost::chrono::duration documentation. |
| Period | See boost::chrono::duration documentation. |
| dur | A non-negative duration (or assertion trips). |
Definition at line 42 of file util.hpp.
Referenced by flow::net_flow::asio::Server_socket::async_accept(), flow::net_flow::asio::Peer_socket::async_receive(), flow::net_flow::asio::Peer_socket::async_send(), flow::net_flow::Server_socket::sync_accept(), flow::net_flow::Peer_socket::sync_receive(), and flow::net_flow::Peer_socket::sync_send().
| Fine_duration flow::util::chrono_duration_to_fine_duration | ( | const boost::chrono::duration< Rep, Period > & | dur | ) |
Helper that takes a non-negative duration of arbitrary precision/period and converts it to Fine_duration, rounding up.
Also, the input type's max() is translated to Fine_duration::max().
| Rep | See boost::chrono::duration documentation. |
| Period | See boost::chrono::duration documentation. |
| dur | A non-negative duration (or assertion trips). |
Definition at line 31 of file util.hpp.
Referenced by flow::net_flow::Node::sync_connect_with_metadata(), and flow::net_flow::Event_set::sync_wait().
| size_t flow::util::deep_size | ( | const std::string & | val | ) |
Estimate of memory footprint of the given value, including memory allocated on its behalf – but excluding its shallow sizeof! – in bytes.
| val | Value. |
Definition at line 186 of file util.cpp.
Referenced by flow::log::deep_size().
| void flow::util::feed_args_to_ostream | ( | std::ostream * | os, |
| T const & | only_ostream_arg | ||
| ) |
"Induction base" for a variadic function template, this simply outputs given item to given ostream via <<.
| T | See each of ...T in ostream_op_to_string(). |
| os | Pointer to stream to which to sequentially send arguments for output. |
| only_ostream_arg | See each of ostream_args in ostream_op_to_string(). |
| void flow::util::feed_args_to_ostream | ( | std::ostream * | os, |
| T1 const & | ostream_arg1, | ||
| T_rest const &... | remaining_ostream_args | ||
| ) |
"Induction step" version of variadic function template that simply outputs arguments 2+ via << to the given ostream, in the order given.
| ...T_rest | See ...T in ostream_op_to_string(). |
| remaining_ostream_args | See ostream_args in ostream_op_to_string(). |
| T1 | Same as each of ...T_rest. |
| ostream_arg1 | Same as each of remaining_ostream_args. |
| os | Pointer to stream to which to sequentially send arguments for output. |
Definition at line 327 of file util.hpp.
References feed_args_to_ostream().
Referenced by feed_args_to_ostream(), and ostream_op_to_string().
|
constexpr |
Helper for FLOW_UTIL_WHERE_AM_I() that, given a pointer/length of a string in memory containing a path, returns a pointer/length into that same buffer that comprises the postfix just past the last directory separator or (if none exists) to all of it.
There are 2 other alternatives. One is essentially to take std::string (or String_view) and return new std::string (or some variation). That is un-great, because the main use case is to use this at log call sites, and creating temporary std::strings is best avoided; the ability to simply return a pointer into existing memory, – particularly since it is likely to come from __FILE__ (which is in static memory) – might represent significant perf savings. So that leaves either the alternative we chose or a variation (which, historically, used to be the case) which is to take a const char* and return same, into that memory. The latter is an acceptable approach. String_view, by comparison, does involve storing an extra bit of data, namely the length stored inside String_view. We stipulate this is negligible in terms of RAM and copying costs when compared to doing same with the pointers alone... but what's the advantage? Answer: it may be small; but in order to search for the right-most dir separator character, one needs to internally find the NUL (a/k/a strlen()); with String_view it is already available, so the linear search is unnecessary. Doesn't it cost cycles to set the length though? you ask. Answer: Not if one constructs the #String_views involved cleverly. To wit:
String_view path from __FILE__For max performance, do it in the same way as recommended when setting log::Msg_metadata::m_msg_src_file. Spoiler alert: Use sizeof(__FILE__) to obtain a compile-time length.
constexprUpdate: This function is now constexpr, so path must be known at compile-time; hence the above instructions (while still valid) apply in a different way. The raw performance doesn't necessarily matter (since it's "executed" by the compiler now). However, following those instructions (1) will help make constexprness easier to achieve (as the NUL-terminated String_view ctor is less likely to be effectively constexpr depending on compiler; while the pointer+length ctor is more likely so); and (2) is good for perf in case constexprness is dropped in the future. It's less fragile is the point. Anyway, just do it!
| path | String containing a path from a __FILE__ macro. See instructions above for max perf. |
| std::string flow::util::get_where_am_i_str | ( | String_view | file, |
| String_view | function, | ||
| unsigned int | line | ||
| ) |
Helper for FLOW_UTIL_WHERE_AM_I(), etc., that, given values for source code file name, function, and line number, returns an std::string equal to what FLOW_UTIL_WHERE_AM_I() would place into an ostream.
For rationale of using String_view instead of const char* for the string args see similar reasoning in get_last_path_segment() doc header. See also practical instructions on how to performantly obtain these args, in the doc header for ARG_file for FLOW_UTIL_WHERE_AM_I_FROM_ARGS().
| file | See ARG_file in FLOW_UTIL_WHERE_AM_I_FROM_ARGS(). |
| function | Full function name, as from __FUNCTION__. See instructions above for max perf. |
| line | Line number, as from __LINE__. |
X (suitable for, for example: std::cout << X << ": Hi!"). Definition at line 27 of file util.cpp.
References FLOW_UTIL_WHERE_AM_I_FROM_ARGS_TO_ARGS, and ostream_op_to_string().
| bool flow::util::in_closed_open_range | ( | T const & | min_val, |
| T const & | val, | ||
| T const & | max_val | ||
| ) |
Returns true if and only if the given value is within the given range, given as a [low, high) pair.
| min_val | Lower part of the range. |
| val | Value to check. |
| max_val | Higher part of the range. Must be greater than min_val, or behavior is undefined. |
| T | A type for which the operation x < y is defined and makes sense. Examples: double, char, unsigned int, Fine_duration. |
true if and only if val is in [min_val, max_val), i.e., min_val <= val < max_val. Definition at line 262 of file util.hpp.
Referenced by flow::util::Basic_blob< Allocator, S_SHARING_ALLOWED >::derefable_iterator(), flow::net_flow::Port_space::is_service_port(), and flow::net_flow::Port_space::return_port().
| bool flow::util::in_closed_range | ( | T const & | min_val, |
| T const & | val, | ||
| T const & | max_val | ||
| ) |
Returns true if and only if the given value is within the given range, inclusive.
| min_val | Lower part of the range. |
| val | Value to check. |
| max_val | Higher part of the range. Must be greater than or equal to min_val, or behavior is undefined. |
| T | A type for which the operation x < y is defined and makes sense. Examples: double, char, unsigned int, Fine_duration. |
true if and only if val is in [min_val, max_val]. Definition at line 246 of file util.hpp.
Referenced by flow::net_flow::Peer_socket_info::output(), flow::net_flow::Node::sock_validate_options(), and flow::util::Basic_blob< Allocator, S_SHARING_ALLOWED >::valid_iterator().
| bool flow::util::in_open_closed_range | ( | T const & | min_val, |
| T const & | val, | ||
| T const & | max_val | ||
| ) |
Returns true if and only if the given value is within the given range, given as a (low, high] pair.
| min_val | Lower part of the range. |
| val | Value to check. |
| max_val | Higher part of the range. Must be greater than min_val, or behavior is undefined. |
| T | A type for which the operation x < y is defined and makes sense. Examples: double, char, unsigned int, Fine_duration. |
true if and only if val is in (min_val, max_val], i.e., min_val < val <= max_val. Definition at line 254 of file util.hpp.
Referenced by flow::net_flow::Node::sock_validate_options().
| bool flow::util::in_open_open_range | ( | T const & | min_val, |
| T const & | val, | ||
| T const & | max_val | ||
| ) |
Returns true if and only if the given value is within the given range, given as a (low, high) pair.
| min_val | Lower part of the range. |
| val | Value to check. |
| max_val | Higher part of the range. Must be at least 2 greater than min_val, or behavior is undefined. |
| T | A type for which the operation x < y is defined and makes sense. Examples: double, char, unsigned int, Fine_duration. |
true if and only if val is in (min_val, max_val), i.e., min_val < val < max_val. Definition at line 270 of file util.hpp.
Referenced by flow::net_flow::Node::categorize_individual_ack().
| Enum flow::util::istream_to_enum | ( | std::istream * | is_ptr, |
| Enum | enum_default, | ||
| Enum | enum_sentinel, | ||
| bool | accept_num_encoding = true, |
||
| bool | case_sensitive = false, |
||
| Enum | enum_lowest = Enum(0) |
||
| ) |
Deserializes an enum class value from a standard input stream.
Reads up to but not including the next non-alphanumeric-or-underscore character; the resulting string is then mapped to an Enum. If none is recognized, enum_default is the result. The recognized values are:
Enum. (Can be disabled optionally.)Enum, as determined by operator<<(ostream&) – which must exist (or this will not compile). Informally we recommend the encoding to be the non-S_-prefix part of the actual Enum member; e.g., "WARNING" for log::Sev::S_WARNING. If the scanned token does not map to any of these, or if end-of-input is encountered immediately (empty token), then enum_default is returned.Error semantics: There are no invalid values or exceptions thrown; enum_default returned is the worst case. Do note *is_ptr may not be good() == true after return.
Tip: It is convenient to implement operator>>(istream&) in terms of istream_to_enum(). With both >> and << available, serialization/deserialization of the enum class will work; this enables a few key things to work, including parsing from config file/command line via and conversion from string via lexical_cast.
Informal convention suggestion: S_END_SENTINEL should be the sentinel member of Enum. E.g., see log::Sev.
| Enum | An enum class which must satisfy the following requirements or else risk undefined behavior (if it compiles): An element, enum_lowest, has a non-negative integer value. Subsequent elements are strictly monotonically increasing with increment 1, up to and including enum_sentinel. (Elements outside [enum_lowest, enum_sentinel] may exist, as long as their numeric values don't conflict with those in-range, but informally we recommend against this.) ostream << Enum exists and works without throwing for all values in range [enum_lowest, enum_sentinel). Each <<-serialized string must be distinct from the others. Each <<-serialized string must start with a non-digit and must consist only of alphanumerics and underscores. Exception: digit-leading is allowed if and only if !accept_num_encoding, though informally we recommend against it as a convention. |
| is_ptr | Stream from which to deserialize. |
| enum_default | Value to return if the token does not match either the numeric encoding (if enabled) or the << encoding. enum_sentinel is a sensible (but not the only sensible) choice. |
| enum_sentinel | Enum value such that all valid deserializable values have numeric conversions strictly lower than it. |
| accept_num_encoding | If true, a numeric value is accepted as an encoding; otherwise it is not (and will yield enum_default like any other non-matching token). |
| case_sensitive | If true, then the token must exactly equal an ostream<< encoding of a non-sentinel Enum; otherwise it may equal it modulo different case. |
| enum_lowest | The lowest Enum value. Its integer value is very often 0, sometimes 1. Behavior undefined if it is negative. |
Definition at line 498 of file util.hpp.
Referenced by flow::log::operator>>().
| bool flow::util::key_exists | ( | const Container & | container, |
| const typename Container::key_type & | key | ||
| ) |
Returns true if and only if the given key is present at least once in the given associative container.
| Container | Associative container type (boost::unordered_map, std::set, etc.). In particular must have the members find(), end(), and key_type. |
| container | Container to search. |
| key | Key to find. |
Definition at line 276 of file util.hpp.
Referenced by flow::cfg::Option_set< Value_set >::canonicalize_candidate(), flow::net_flow::Node::connect_worker(), flow::net_flow::Drop_timer::end_contemporaneous_events(), flow::net_flow::Node::event_set_all_check_delta(), flow::net_flow::Node::handle_syn_to_listening_server(), flow::log::Config::init_component_names(), flow::log::Config::init_component_to_union_idx_mapping(), flow::net_flow::Node::listen_worker(), flow::net_flow::Drop_timer::on_ack(), and flow::cfg::Option_set< Value_set >::parse_config_file().
| std::string flow::util::ostream_op_string | ( | T const &... | ostream_args | ) |
Equivalent to ostream_op_to_string() but returns a new string by value instead of writing to the caller's string.
This is useful at least in constructor initializers, where it is not possible to first declare a stack variable.
With the C++11-y use of move semantics in STL it should be no slower than using ostream_op_to_string() – meaning, it is no slower, period, as this library now requires C++11.
| ...T | See ostream_op_to_string(). |
| ostream_args | See ostream_op_to_string(). |
std::string. Definition at line 356 of file util.hpp.
References ostream_op_to_string().
Referenced by flow::log::Verbosity_config::apply_to_config(), flow::perf::Checkpointing_timer::Checkpointing_timer(), flow::cfg::Config_manager< S_d_value_set >::Config_manager(), flow::async::optimize_pinning_in_thread_pool(), flow::log::Verbosity_config::parse(), flow::cfg::Option_set< Value_set >::parse_config_file(), flow::async::Segregated_thread_task_loop::start(), flow::async::Cross_thread_task_loop::start(), flow::log::Logger::this_thread_set_logged_nickname(), boost::filesystem::validate(), flow::cfg::value_set_member_id_to_opt_name_keyed(), and flow::cfg::value_to_ostream().
| void flow::util::ostream_op_to_string | ( | std::string * | target_str, |
| T const &... | ostream_args | ||
| ) |
Writes to the specified string, as if the given arguments were each passed, via << in sequence, to an ostringstream, and then the result were appended to the aforementioned string variable.
Tip: It works nicely, 99% as nicely as simply <<ing an ostream; but certain language subtleties mean you may have to fully qualify some template instances among ostream_args. Do so if you receive a "deduced incomplete pack" (clang) or similar error, as I have seen when using, e.g., chrono::symbol_format formatter (which the compile error forced me to qualify as: symbol_format<char, ostream::traits_type>).
| ...T | Each type T is such that os << t, with types T const & t and ostream& os, builds and writes t to os, returning lvalue os. Usually in practice this means the existence of ostream& operator<<(ostream&, T const &) or ostream& operator<<(ostream&, T) overload, the latter usually for basic types T. See also tip above, if compiler is unable to deduce a given T (even when it would deduce it in os << t). |
| target_str | Pointer to the string to which to append. |
| ostream_args | One or more arguments, such that each argument arg is suitable for os << arg, where os is an ostream. |
Definition at line 342 of file util.hpp.
References feed_args_to_ostream(), and flow::util::String_ostream::os().
Referenced by flow::net_flow::Event_set::ev_type_to_socks_map_sizes_to_str(), get_where_am_i_str(), flow::net_flow::Node::log_rcv_window(), flow::net_flow::Node::log_snd_window(), flow::net_flow::error::Category::message(), flow::perf::Duration_set::operator<<(), ostream_op_string(), flow::net_flow::Event_set::sock_as_any_to_str(), and flow::net_flow::Node::this_thread_init_logger_setup().
| Scheduled_task_handle flow::util::schedule_task_at | ( | log::Logger * | logger_ptr, |
| const Fine_time_pt & | at, | ||
| bool | single_threaded, | ||
| Task_engine * | task_engine, | ||
| Scheduled_task_handler && | task_body_moved | ||
| ) |
Identical to schedule_task_from_now() except the time is specified in absolute terms.
The current implementation is such that there is no performance benefit to using schedule_task_from_now(at - Fine_clock::now(), ...) over schedule_task_at(at, ...). Therefore, if it is convenient for caller's code reuse to do the former, there is no perf downside to it, so feel free.
Ensure the "Performance note" is accurate w/r/t to the body of the function; as of this writing it is; keep the two places in sync with each other.
| logger_ptr | See schedule_task_from_now(). |
| at | Fire at this absolute time. If this is in the past, it will fire ASAP. |
| single_threaded | See schedule_task_from_now(). |
| task_engine | See schedule_task_from_now(). |
| task_body_moved | See schedule_task_from_now(). |
| Scheduled_task_handler | See schedule_task_from_now(). |
Definition at line 245 of file sched_task.hpp.
Referenced by flow::net_flow::asio::Node::async_op().
| Scheduled_task_handle flow::util::schedule_task_from_now | ( | log::Logger * | logger_ptr, |
| const Fine_duration & | from_now, | ||
| bool | single_threaded, | ||
| Task_engine * | task_engine, | ||
| Scheduled_task_handler && | task_body_moved | ||
| ) |
Schedule the given function to execute in a certain amount of time: A handy wrapper around Timer (asio's timer facility).
Compared to using Timer, this has far simplified semantics at the cost of certain less-used features of Timer. Recommend using this facility when sufficient; otherwise use Timer directly. The trade-offs are explained below, but first:
Conceptually this is similar to JavaScript's ubiquitous (albeit single-threaded) setTimeout() feature. The given function shall execute as if post()ed onto the given Task_engine; unless successfully canceled by scheduled_task_cancel(X), where X is the (optionally used and entirely ignorable) returned handle. Barring unrelated crashes/etc. there are exactly three mutually exclusive outcomes of this function executing:
bool short_fire arg to it set to false.short_fire == true. To trigger this, use scheduled_task_short_fire() before the scheduled time.All related functions are thread-safe w/r/t a given returned Scheduled_task_handle, if single_threaded == false. In addition, for extra performance (internally, by omitting certain locking), set single_threaded = true only if you can guarantee the following:
*task_engine is run()ning in no more than one thread throughout all work with the returned Scheduled_task_handle including the present function.Scheduled_task_handle are also – if at all – called from that one thread.The minimum is step 1: Call schedule_task_at() or schedule_task_from_now(). Optionally, if one saves the return value X from either, one can do step 2: scheduled_task_short_fire(X) or scheduled_task_cancel(X), which will succeed (return true) if called sufficiently early. There is no step 3; any subsequent calls on X will fail (return false).
scheduled_task_*() function on it.)Error_code passed in to your task function.Timer::cancel() means it will still execute but with operation_aborted code.)Timer::cancel() can result in ~3 behaviors: it already executed, so it does nothing; it has not yet executed but was JUST about to execute, so it will still execute with non-operation_aborted code; it has not yet executed, so now it will execute but with operation_aborted. With this facility, it's simpler: it either succeeds (so acts per previous bullet – does not execute); or it fails, hence it will have executed (and there is no Error_code to decipher).cancel() actually means short-firing (firing ASAP) but with a special Error_code. One can also change the expiration time to the past to short-fire in a different way. With this facility, cancellation means it won't run; and scheduled_task_short_fire() means it will fire early; that's it.Timer for performance?': It might not be fine if and only if timer firings and/or cancellations occur many times a second in a performance-sensitive environment. E.g., if it's something fired and/or canceled every second repeatedly, it's fine; it it's packet pacing that must sensitively fire near the resolution limit of the native Timer facility, it might not be fine, and it's safer to use Timer repeatedly.Timer has certain informational accessors (like one that returns the scheduled firing time) that we lack. (Again, we could provide this also – but why?)
Timers can be internally maintained to implement this. This may or may not be worth the complexity, but if the API can remain identically simple while cleanly eliminating the one perf-related reason to choose Timer over this simpler facility, then that is a clean win from the API user's point of view. By comparison, other possible improvements mentioned complicate the API which makes them less attractive.from_now values). class. The picture is slightly muddled because we DO provide some "methods" – so why not make it a class after all, just a simpler one than Timer? Answer: I believe this keeps the API simple: Step 1: Schedule it. Step 2 (optional): Short-fire or cancel it. There are no corner cases introduced as might have been via increased potential statefulness inherent with a class. But see the following to-do.Serial_task_timer). I believe it internally uses integer "task ID" to distinguish between scheduled tasks issued in some chronological order, so that boost.asio firing a task after it has been canceled/pre-fired can be easily detected.| logger_ptr | Logging, if any – including in the background – will be done via this logger. |
| from_now | Fire ASAP once this time period passes (0 to fire ASAP). A negative value has the same effect as 0. |
| single_threaded | Set to a true value if and only if, basically, *task_engine is single-threaded, and you promise not to call anything on the returned Scheduled_task_handle except from that same thread. More formally, see above. |
| task_engine | The Task_engine onto which the given task may be post()ed (or equivalent). |
| task_body_moved | The task to execute within *task_engine unless successfully canceled. See template param doc below also regarding Strand and other executor binding. |
| Scheduled_task_handler | Completion handler with signature compatible with void (bool short_fired). This allows for standard boost.asio semantics, including associating with an executor such as a boost::asio::strand. In particular you may pass in: bind_executor(S, F), where F(bool short_fire) is the handler, and S is a Strand (or other executor). Binding to a Strand will ensure the fired or short-fired body will not execute concurrently with any other handler also bound to it. |
Definition at line 34 of file sched_task.hpp.
References flow::util::Unique_id_holder::create_unique_id(), FLOW_ERROR_SYS_ERROR_LOG_WARNING, FLOW_LOG_SET_CONTEXT, FLOW_LOG_TRACE, and FLOW_LOG_WARNING.
Referenced by flow::net_flow::Node::async_rcv_wnd_recovery(), flow::net_flow::Node::async_wait_latency_then_handle_incoming(), flow::net_flow::Node::perform_regular_infrequent_tasks(), flow::async::Cross_thread_task_loop::schedule_from_now(), flow::async::Segregated_thread_task_loop::schedule_from_now_impl(), flow::net_flow::Node::setup_connection_timers(), and flow::net_flow::Node::worker_run().
| bool flow::util::scheduled_task_cancel | ( | log::Logger * | logger_ptr, |
| Scheduled_task_handle | task | ||
| ) |
Attempts to prevent the execution of a previously scheduled (by schedule_task_from_now() or similar) task.
For semantics, in the context of the entire facility, see schedule_task_from_now() doc header.
| logger_ptr | See scheduled_task_short_fire(). |
| task | See scheduled_task_short_fire(). |
true if the task has not executed and will NEVER have executed, AND no other scheduled_task_cancel() with the same arg has succeeded before this. false if it has or will soon have executed because the present call occurred too late to stop it. Namely, it may have fired or short-fired already. Definition at line 26 of file sched_task.cpp.
References FLOW_ERROR_SYS_ERROR_LOG_WARNING, FLOW_LOG_SET_CONTEXT, and FLOW_LOG_TRACE.
Referenced by flow::net_flow::asio::Node::async_op(), flow::net_flow::Node::cancel_timers(), and flow::net_flow::Node::receive_wnd_recovery_data_received().
| bool flow::util::scheduled_task_canceled | ( | log::Logger * | logger_ptr, |
| Scheduled_task_const_handle | task | ||
| ) |
Returns whether a previously scheduled (by schedule_task_from_now() or similar) task has been canceled.
Note that this cannot be true while scheduled_task_fired() is false and vice versa (but see thread safety note below).
Thread safety notes in the scheduled_task_fired() doc header apply equally here.
| logger_ptr | See scheduled_task_fired(). |
| task | See scheduled_task_fired(). |
Definition at line 259 of file sched_task.cpp.
References FLOW_LOG_SET_CONTEXT, and FLOW_LOG_TRACE.
| bool flow::util::scheduled_task_fired | ( | log::Logger * | logger_ptr, |
| Scheduled_task_const_handle | task | ||
| ) |
Returns whether a previously scheduled (by schedule_task_from_now() or similar) task has already fired.
Note that this cannot be true while scheduled_task_canceled() is false and vice versa (but see thread safety note below).
Also note that, while thread-safe, if !single_threaded in the original scheduling call, then the value returned might be different even if checked immediately after this function exits, in the same thread. However, if single_threaded (and one indeed properly uses task from one thread only) then it is guaranteed this value is consistent/correct synchronously in the caller's thread, until code in that thread actively changes it (e.g., by canceling task).
| logger_ptr | See scheduled_task_fires_from_now_or_canceled(). |
| task | See scheduled_task_fires_from_now_or_canceled(). |
Definition at line 238 of file sched_task.cpp.
References FLOW_LOG_SET_CONTEXT, and FLOW_LOG_TRACE.
Referenced by flow::net_flow::Node::setup_connection_timers().
| Fine_duration flow::util::scheduled_task_fires_from_now_or_canceled | ( | log::Logger * | logger_ptr, |
| Scheduled_task_const_handle | task | ||
| ) |
Returns how long remains until a previously scheduled (by schedule_task_from_now() or similar) task fires; or negative time if that point is in the past; or special value if the task has been canceled.
This is based solely on what was specified when scheduling it; it may be different from when it will actually fire or has fired. However, a special value (see below) is returned, if the task has been canceled (scheduled_task_cancel()).
| logger_ptr | Logging, if any, will be done synchronously via this logger. |
| task | (Copy of) the handle returned by a previous schedule_task_*() call. |
Fine_duration::max() to indicate the task has been canceled. Note a non-max() (probably negative) duration will be returned even if it has already fired. Definition at line 200 of file sched_task.cpp.
References FLOW_LOG_SET_CONTEXT, and FLOW_LOG_TRACE.
Referenced by flow::net_flow::Node::setup_connection_timers().
| bool flow::util::scheduled_task_short_fire | ( | log::Logger * | logger_ptr, |
| Scheduled_task_handle | task | ||
| ) |
Attempts to reschedule a previously scheduled (by schedule_task_from_now() or similar) task to fire immediately.
For semantics, in the context of the entire facility, see schedule_task_from_now() doc header.
| logger_ptr | See schedule_task_from_now(). |
| task | (Copy of) the handle returned by a previous schedule_task_*() call. |
true if the task will indeed have executed soon with short_fire == true. false if it has or will soon have executed with short_file == false; or if it has already been successfully canceled via scheduled_task_cancel(). Definition at line 95 of file sched_task.cpp.
References FLOW_ERROR_SYS_ERROR_LOG_WARNING, FLOW_LOG_SET_CONTEXT, and FLOW_LOG_TRACE.
| void flow::util::sequence_to_inverted_lookup_map | ( | Sequence const & | src_seq, |
| Map * | target_map | ||
| ) |
Given a generic sequence (integer -> object) generates a generic map (object -> integer) providing inverse lookup.
See the 3-arg overload if you want to provide a more complex lookup function to store something else based on each index.
A naive way of implementing lookups otherwise would be a linear search for the object; using this will use RAM to avoid the slow searches.
| Sequence | Sequence such as std::vector<T> or std::array<T>. Informally, T should be something light-weight and hence usable as a key type for a map type (Map). |
| Map | Map that maps T from Sequence to size_t. Example: std::map<T, size_t>. |
| src_seq | Input sequence. |
| target_map | Output map. Note it will not be pre-cleared; informally, this means one can shove 2+ lookup maps into one. If null behavior undefined (assertion may trip). |
Definition at line 379 of file util.hpp.
References sequence_to_inverted_lookup_map().
| void flow::util::sequence_to_inverted_lookup_map | ( | Sequence const & | src_seq, |
| Map * | target_map, | ||
| const Function< typename Map::mapped_type(size_t)> & | idx_to_map_val_func | ||
| ) |
Similar to the 2-arg overload of sequence_to_inverted_lookup_map() but with the ability to store a value based on the index into the input sequence instead of that index itself.
See the 2-arg overload.
| Sequence | Sequence such as std::vector<T> or std::array<T>. Informally, T should be something light-weight and hence usable as a key type for a map type (Map). |
| Map | Map that maps T from Sequence to another type X. Example: unordered_map<T, X>, where an X can be computed from a size_t index. |
| src_seq | See 2-arg overload. |
| target_map | See 2-arg overload. |
| idx_to_map_val_func | Given an index idx into src_seq, (*target_map)[] shall contain idx_to_map_val_func(idx). Use this arg to instead perform a second lookup before storing a value in *target_map. Use the 2-arg overload if you'd like to store the index itself. |
Definition at line 366 of file util.hpp.
Referenced by sequence_to_inverted_lookup_map().
| Auto_cleanup flow::util::setup_auto_cleanup | ( | const Cleanup_func & | func | ) |
Provides a way to execute arbitrary (cleanup) code at the exit of the current block.
Simply save the returned object into a local variable that will go out of scope when your code block exits. Example:
| Cleanup_func | Any type such that given an instance Cleanup_func f, the expression f() is valid. |
| func | func() will be called when cleanup is needed. |
func() to be called. Definition at line 282 of file util.hpp.
Referenced by flow::net_flow::Node::handle_accumulated_acks(), flow::net_flow::Node::sync_connect_impl(), and flow::net_flow::Node::sync_op().
| size_t flow::util::size_unit_convert | ( | From | num_froms | ) |
Answers the question what's the smallest integer number of Tos sufficient to verbatim store the given number of Froms?, where From and To are POD types.
For example, one needs 1 uint64_t to store 1, 2, 3, or 4 uint16_ts, hence size_unit_convert<uint16_t, uint64_t>(1 or 2 or 3 or 4) == 1. Similarly, 5 or 6 or 7 or 8 -> 2. It works in the opposite direction, too; if we are storing uint64_ts in multiples of uint16_t, then 1 -> 4, 2 -> 8, 3 -> 12, etc.
To be clear, when From bit width is smaller than To bit width, some of the bits will be padding and presumably unused. For example, raw data buffers of arbitrary bytes are often arranged in multi-byte "words."
| From | The POD type of the values that must be encoded in Froms. |
| To | The POD type of the array that would store the Froms. |
| num_froms | How many Froms does one want to encode in an array of Tos? |
Tos are sufficient to encode num_from Froms verbatim? | bool flow::util::subtract_with_floor | ( | Minuend * | minuend, |
| const Subtrahend & | subtrahend, | ||
| const Minuend & | floor = 0 |
||
| ) |
Performs *minuend -= subtrahend, subject to a floor of floor.
Avoids underflow/overflow to the extent it's reasonably possible, but no more. The return value indicates whether the floor was hit; this allows one to chain high-performance subtractions like this:
| Minuend | Numeric type. |
| Subtrahend | Numeric type, such that given Subtrahend s, Minuend(s) is something reasonable for all s involved. |
| minuend | *minuend is set to either (*minuend - subtrahend) or floor, whichever is higher. |
| subtrahend | Ditto. |
| floor | Ditto. Negatives are OK. Typically it's best to keep the magnitude of this small. |
true if *minuend == floor at function exit; false if *minuend > floor. Definition at line 299 of file util.hpp.
Referenced by flow::net_flow::Node::sock_data_to_reassembly_q_unless_overflow().
| void swap | ( | Basic_blob< Allocator, S_SHARING_ALLOWED > & | blob1, |
| Basic_blob< Allocator, S_SHARING_ALLOWED > & | blob2, | ||
| log::Logger * | logger_ptr = 0 |
||
| ) |
Equivalent to blob1.swap(blob2).
| blob1 | Object. |
| blob2 | Object. |
| logger_ptr | The Logger implementation to use in this routine (synchronously) only. Null allowed. |
Definition at line 1665 of file basic_blob.hpp.
Referenced by flow::util::Linked_hash_map< Key, Mapped, Hash, Pred >::operator=(), flow::util::Linked_hash_set< Key, Hash, Pred >::operator=(), flow::util::Basic_blob< Allocator, S_SHARING_ALLOWED >::swap(), flow::util::Blob_with_log_context< S_SHARING_ALLOWED >::swap(), flow::util::Linked_hash_map< Key, Mapped, Hash, Pred >::swap(), flow::util::Linked_hash_set< Key, Hash, Pred >::swap(), and flow::util::Basic_blob< Allocator, S_SHARING_ALLOWED >::swap_impl().
| void swap | ( | Blob_with_log_context< S_SHARING_ALLOWED > & | blob1, |
| Blob_with_log_context< S_SHARING_ALLOWED > & | blob2 | ||
| ) |
On top of the similar Basic_blob related function, logs using the stored log context of blob1.
| blob1 | See super-class related API. |
| blob2 | See super-class related API. |
Definition at line 419 of file blob.hpp.
Referenced by flow::util::Blob_with_log_context< S_SHARING_ALLOWED >::swap().
| void swap | ( | Linked_hash_map< Key, Mapped, Hash, Pred > & | val1, |
| Linked_hash_map< Key, Mapped, Hash, Pred > & | val2 | ||
| ) |
Equivalent to val1.swap(val2).
| val1 | Object. |
| val2 | Object. |
Definition at line 1089 of file linked_hash_map.hpp.
Referenced by flow::util::Linked_hash_map< Key, Mapped, Hash, Pred >::swap().
| void swap | ( | Linked_hash_set< Key, Hash, Pred > & | val1, |
| Linked_hash_set< Key, Hash, Pred > & | val2 | ||
| ) |
Equivalent to val1.swap(val2).
| val1 | Object. |
| val2 | Object. |
Definition at line 871 of file linked_hash_set.hpp.
Referenced by flow::util::Linked_hash_set< Key, Hash, Pred >::swap().
| boost::chrono::microseconds flow::util::time_since_posix_epoch | ( | ) |
Get the current POSIX (Unix) time as a duration from the Epoch time point.
This is the amount of time – according to the user-settable system clock time – to have passed since the POSIX (Unix) Epoch – January 1st, 1970, 00:00:00 UTC – not counting leap seconds to have been inserted or deleted between then and now.
The boost::chrono duration type is chosen so as to support the entire supported resolution of the OS-exposed system clock (but probably no more than that).
ceil<seconds>() in the desired human-friendly form, splicing in the left-over microseconds where desired (boost.locale lacks formatters for sub-second-resolution time points). However see below for a typically-superior alternative.Using this for time stamp output is no longer needed or convenient, as a much nicer way presents itself when combined with boost.chrono I/O-v2 time_point-outputting ostream<< overload. Just grab time_point boost::chrono::system_clock::now() (or another system_clock-originated value); its default-formatted ostream<< output will include date, time with microsecond+ precision, and time-zone specifier (one can choose UTC or local time).
However, as of this writing, it is not possible to directly obtain just the microsecond+ part of this, in isolation, according boost.chrono docs. (One could hack it by taking a substring.) Quote: "Unfortunately there are no formatting/parsing sequences which indicate fractional seconds." From: https://www.boost.org/doc/libs/1_76_0/doc/html/chrono/users_guide.html#chrono.users_guide.tutorial.i_o.system_clock_time_point_io)
| double flow::util::to_mbit_per_sec | ( | N_items | items_per_time, |
| size_t | bits_per_item = 8 |
||
| ) |
Utility that converts a bandwidth in arbitrary units in both numerator and denominator to the same bandwidth in megabits per second.
The input bandwidth is given in "items" per Time_unit(1); where Time_unit is an arbitrary boost.chrono duration type that must be explicitly provided as input; and an "item" is defined as bits_per_item bits. Useful at least for logging. It's probably easiest to understand by example; see below; rather than by parsing that description I just wrote.
To be clear (as C++ syntax is not super-expressive in this case) – the template parameter Time_unit is an explicit input to the function template, essentially instructing it as to in what units items_per_time is. Thus all uses of this function should look similar to:
| Time_unit | boost::chrono::duration<Rep, Period> for some specific Rep and Period. See boost::chrono::duration documentation. Example types: boost::chrono::milliseconds; boost::chrono::seconds; see example use code above. |
| N_items | Some (not necessarily integral) numeric type. Strictly speaking, any type convertible to double works. |
| items_per_time | The value, in items per Time_unit(1) (where there are bits_per_item bits in 1 item) to convert to megabits per second. Note this need not be an integer. |
| bits_per_item | Number of bits in an item, where items_per_time is given as a number of items. |
1.9.4