std::ostrstream(3)

👑 std::ostrstream 👑 — like, the C++ Standard Library one, bestie (page std::ostrstream(3), C++ Standard Libary, std::ostrstream(3))

Ok so listen. This is std::ostrstream, and no I'm not gonna pretend it's still that girl — it's deprecated and honestly kind of a legacy icon. But we're gonna learn it anyway because your girl does not skip content. Periodt. 💅

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✨ NAME ✨

std::ostrstream — literally std::ostrstream. That's the name. That's the whole thing. 🎀

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🦋 Synopsis 🦋

First of all, where does it live:

Defined in header <strstream>

And here's the class, exactly as it is:

class ostrstream : public std::ostream  (deprecated in C++98)
                                        (removed in C++26)

So real talk: the class ostrstream implements output operations on array-backed streams. Basically it wraps a raw array I/O device implementation (std::strstreambuf) into the higher-level interface of std::basic_ostream. It's giving "glow-up wrapper" energy ✨

And the typical implementation of ostrstream holds only one non-derived data member: an object of type std::strstreambuf. One. Single. Member. Minimalist queen 🫶

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🌸 Notes 🌸

Okay these notes are important, do not scroll past:

• After any call to str(), a call to freeze(false) is required to allow the destructor to deallocate the buffer as necessary. So like, don't forget the freeze(false) or your destructor can't do its job 😭
• Before any call to str() that uses the result as a C-string, the buffer must be null-terminated, typically with std::ends. Get that terminating vibe in there first, iykyk.
• ostrstream has been deprecated since C++98 and removed since C++26. Yeah. It's been over for a minute. 💀
• The recommended replacements are std::ostringstream, std::ospanstream (since C++23), and boost::iostreams::array_sink. Those are the ones eating in 2023+ and beyond. 🍓

Bestie note: the "deprecated since C++98, removed since C++26" thing is not a drill. If you're reaching for this in new code, maybe… don't? The replacements above are right there.

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🔥 Member functions 🔥

The main character lineup, all public members:

• constructor — constructs an ostrstream object, optionally allocating the buffer (public member function)
• destructor — destructs an ostrstream object, optionally deallocating the buffer, and it's marked [virtual] (virtual public member function)
• rdbuf — obtains a pointer to the associated strstreambuf (public member function)
• str — accesses the output buffer (public member function)
• freeze — disables/enables automatic reallocation (public member function)
• pcount — obtains the number of characters written (public member function)

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💜 Inherited from std::basic_ostream 💜

Yeah she inherited all of this. Generous ancestor. 🌈

🎀 Member functions 🎀

💖 Formatted output

• operator<< — inserts formatted data (public member function of std::basic_ostream<CharT,Traits>)

💫 Unformatted output

• put — inserts a character (public member function of std::basic_ostream<CharT,Traits>)
• write — inserts blocks of characters (public member function of std::basic_ostream<CharT,Traits>)

⭐ Positioning

• tellp — returns the output position indicator (public member function of std::basic_ostream<CharT,Traits>)
• seekp — sets the output position indicator (public member function of std::basic_ostream<CharT,Traits>)

🦋 Miscellaneous

• flush — synchronizes with the underlying storage device (public member function of std::basic_ostream<CharT,Traits>)

👑 Member classes

• sentry — implements basic logic for preparation of the stream for output operations (public member class of std::basic_ostream<CharT,Traits>)

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🧚 Inherited from std::basic_ios 🧚

More inheritance, more slay. 🎀

🌟 Member types

Here's the whole mapping, one bullet per type because tables are not the vibe in this terminal:

• char_type → CharT
• traits_type → Traits
• int_type → Traits::int_type
• pos_type → Traits::pos_type
• off_type → Traits::off_type

🌸 Member functions 🌸

🔍 State functions

• good — checks if no error has occurred i.e. I/O operations are available (public member function of std::basic_ios<CharT,Traits>)
• eof — checks if end-of-file has been reached (public member function of std::basic_ios<CharT,Traits>)
• fail — checks if an error has occurred (public member function of std::basic_ios<CharT,Traits>)
• bad — checks if a non-recoverable error has occurred (public member function of std::basic_ios<CharT,Traits>)
• operator! — checks if an error has occurred (synonym of fail()) (public member function of std::basic_ios<CharT,Traits>)
• operator bool — checks if no error has occurred (synonym of !fail()) (public member function of std::basic_ios<CharT,Traits>)
• rdstate — returns state flags (public member function of std::basic_ios<CharT,Traits>)
• setstate — sets state flags (public member function of std::basic_ios<CharT,Traits>)
• clear — modifies state flags (public member function of std::basic_ios<CharT,Traits>)

💅 Formatting

• copyfmt — copies formatting information (public member function of std::basic_ios<CharT,Traits>)
• fill — manages the fill character (public member function of std::basic_ios<CharT,Traits>)

🌈 Miscellaneous

• exceptions — manages exception mask (public member function of std::basic_ios<CharT,Traits>)
• imbue — sets the locale (public member function of std::basic_ios<CharT,Traits>)
• rdbuf — manages associated stream buffer (public member function of std::basic_ios<CharT,Traits>)
• tie — manages tied stream (public member function of std::basic_ios<CharT,Traits>)
• narrow — narrows characters (public member function of std::basic_ios<CharT,Traits>)
• widen — widens characters (public member function of std::basic_ios<CharT,Traits>)

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💜 Inherited from std::ios_base 💜

The OG base class. Everything trickles down from here, bestie. 🫶

🎀 Member functions 🎀

✨ Formatting

• flags — manages format flags (public member function of std::ios_base)
• setf — sets specific format flag (public member function of std::ios_base)
• unsetf — clears specific format flag (public member function of std::ios_base)
• precision — manages decimal precision of floating point operations (public member function of std::ios_base)
• width — manages field width (public member function of std::ios_base)

🌍 Locales

• imbue — sets locale (public member function of std::ios_base)
• getloc — returns current locale (public member function of std::ios_base)

🗂️ Internal extensible array

• xalloc — returns a program-wide unique integer that is safe to use as index to pword() and iword(), and it's marked [static] (public static member function of std::ios_base)
• iword — resizes the private storage if necessary and access to the long element at the given index (public member function of std::ios_base)
• pword — resizes the private storage if necessary and access to the void* element at the given index (public member function of std::ios_base)

🦋 Miscellaneous

• register_callback — registers event callback function (public member function of std::ios_base)
• sync_with_stdio — sets whether C++ and C I/O libraries are interoperable, and it's marked [static] (public static member function of std::ios_base)

👑 Member classes

• failure — stream exception (public member class of std::ios_base)
• Init — initializes standard stream objects (public member class of std::ios_base)

✨ Member types and constants ✨

Okay bestie, this is the type-and-constant cheat sheet 💅 — every single name stays exactly as written, no cap. Let’s go.

🌸 stream open mode type

openmode — (typedef)

The following constants are also defined:

• app — seek to the end of stream before each write
• binary — open in binary mode
• in — open for reading
• out — open for writing
• trunc — discard the contents of the stream when opening
• ate — seek to the end of stream immediately after open
• noreplace (C++23) — open in exclusive mode

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🎀 formatting flags type

fmtflags — (typedef)

The following constants are also defined:

• dec — use decimal base for integer I/O: see std::dec
• oct — use octal base for integer I/O: see std::oct
• hex — use hexadecimal base for integer I/O: see std::hex
• basefield — dec | oct | hex. Useful for masking operations
• left — left adjustment (adds fill characters to the right): see std::left
• right — right adjustment (adds fill characters to the left): see std::right
• internal — internal adjustment (adds fill characters to the internal designated point): see std::internal
• adjustfield — left | right | internal. Useful for masking operations
• scientific — generate floating point types using scientific notation, or hex notation if combined with fixed: see std::scientific
• fixed — generate floating point types using fixed notation, or hex notation if combined with scientific: see std::fixed
• floatfield — scientific | fixed. Useful for masking operations
• boolalpha — insert and extract bool type in alphanumeric format: see std::boolalpha
• showbase — generate a prefix indicating the numeric base for integer output, require the currency indicator in monetary I/O: see std::showbase
• showpoint — generate a decimal-point character unconditionally for floating-point number output: see std::showpoint
• showpos — generate a + character for non-negative numeric output: see std::showpos
• skipws — skip leading whitespace before certain input operations: see std::skipws
• unitbuf — flush the output after each output operation: see std::unitbuf
• uppercase — replace certain lowercase letters with their uppercase equivalents in certain output operations: see std::uppercase

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💜 state of the stream type

iostate — (typedef)

The following constants are also defined:

• goodbit — no error
• badbit — irrecoverable stream error
• failbit — input/output operation failed (formatting or extraction error)
• eofbit — associated input sequence has reached end-of-file

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🦋 seeking direction type

seekdir — (typedef)

The following constants are also defined:

• beg — the beginning of a stream
• end — the ending of a stream
• cur — the current position of stream position indicator

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🌈 event things

• event — (enum) — specifies event type
• event_callback — (typedef) — callback function type

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That’s the whole list, bestie — every type, every constant, every little (typedef) and (enum) accounted for 💖. This page came from http://cppreference.com, dated 2024.06.10, and it’s the std::ostrstream(3) page 🎀.