Internally used class that enables some of the activities of beautify_chrono_ostream() API. More...

Inheritance diagram for flow::util::Duration_units_beautified:

Collaboration diagram for flow::util::Duration_units_beautified:

Public Member Functions
boost::chrono::duration_units< char_type >::string_type	do_get_ratio_prefix (boost::chrono::duration_style style, boost::micro period_tag) const override
	Returns the prefix string for micro-units; namely the default thing for long-form format ("micro") but the non-default "u" for the short-form. More...

Static Public Member Functions
static const std::locale &	beautified_locale ()
	Returns a reference to a locale that – if imbued onto an `ostream` – equals `std::locale::classic` except beautified by a Duration_units_beautified facet (as described in the class doc header). More...

Private Types
using	Duration_units_default = boost::chrono::duration_units_default< char >
	Short-hand for superclass. More...

Private Member Functions
	Duration_units_beautified ()
	Constructs. More...

Static Private Attributes
static std::locale const *	s_beautified_locale_or_null
	Pointer returned by beautified_locale(), pointing to an object allocated exactly once; or null if that has not yet been called. More...

static boost::once_flag	s_beautified_locale_init_flag
	Helper to initialize s_beautified_locale_or_null at most once. More...

Detailed Description

Internally used class that enables some of the activities of beautify_chrono_ostream() API.

It's a locale facet, whose virtual API can be used to imbue onto an ostream; but even within our own internal code the only public API used is beautified_locale(), which returns a reference to a ready-made such std::locale.

This facet enables the default chrono output behavior, except the "micro" short-form prefix is just "u" instead of the default Unicode Greek letter mu.

Implementation notes

How it does this is fairly self-explanatory, but finding out how to do it was annoyingly tricky due to the inconsistent/outdated boost.chrono docs which only partially explain boost.chrono I/O v2. Ultimately I had to find the actual example french.cpp (not its outdated v1 version directly inside the main doc text, in Boost 1.76); then cross-reference it with the Reference section that described the duration_units_default class.

Definition at line 41 of file util.cpp.

Member Typedef Documentation

◆ Duration_units_default

using flow::util::Duration_units_beautified::Duration_units_default = boost::chrono::duration_units_default<char>

private

Short-hand for superclass.

Definition at line 82 of file util.cpp.

Constructor & Destructor Documentation

◆ Duration_units_beautified()

flow::util::Duration_units_beautified::Duration_units_beautified ( )

explicitprivate

Constructs.

Definition at line 110 of file util.cpp.

Member Function Documentation

◆ beautified_locale()

const std::locale & flow::util::Duration_units_beautified::beautified_locale ( )

static

Returns a reference to a locale that – if imbued onto an ostream – equals std::locale::classic except beautified by a Duration_units_beautified facet (as described in the class doc header).

Thread safety and perf

This (static) method is safe to call concurrently with itself. Internally it achieves this possibly by using a simple mutex. Since it is not expected one would call this frequently, let alone frequently enough for any contention to occur, we consider this acceptable.

Returns: See above.

Definition at line 116 of file util.cpp.

References s_beautified_locale_init_flag, and s_beautified_locale_or_null.

Referenced by flow::util::beautify_chrono_ostream().

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◆ do_get_ratio_prefix()

boost::chrono::duration_units< char >::string_type flow::util::Duration_units_beautified::do_get_ratio_prefix	(	boost::chrono::duration_style	style,
		boost::micro	period_tag
	)		const

override

Returns the prefix string for micro-units; namely the default thing for long-form format ("micro") but the non-default "u" for the short-form.

Hence microseconds are either "microsecond[s]" or "us."

Rationale

This is public only so as to work as a virtual facet interface element invoked by STL ostream machinery upon imbuing *this onto a locale. Since Duration_units_beautified is not exposed as a flow::util public API, leaving this method public (to our internal code in this .cpp file only) is acceptable.

Parameters

style	Either `name_format` or `symbol_format` (the latter being the short-form choice).
period_tag	Tag indicating this method is for the micro prefix.

Returns: The prefix string.

Definition at line 129 of file util.cpp.

Member Data Documentation

◆ s_beautified_locale_init_flag

boost::once_flag flow::util::Duration_units_beautified::s_beautified_locale_init_flag

staticprivate

Helper to initialize s_beautified_locale_or_null at most once.

Definition at line 98 of file util.cpp.

Referenced by beautified_locale().

◆ s_beautified_locale_or_null

std::locale const * flow::util::Duration_units_beautified::s_beautified_locale_or_null

staticprivate

Pointer returned by beautified_locale(), pointing to an object allocated exactly once; or null if that has not yet been called.

The allocated object lives until the process exits.

Definition at line 95 of file util.cpp.