fast_stream.h File Reference

Allocation-light std::ostream backed by a growable string buffer. More...

#include <ostream>
#include <string>
#include <string_view>
#include "./macros.h"

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Classes
class	vlink::FastStream
	Logger-friendly std::ostream with a custom growable string buffer. More...

Namespaces
	vlink

Detailed Description

Allocation-light std::ostream backed by a growable string buffer.

FastStream is the zero-copy log assembly buffer used inside the VLink logger. Inheriting from std::ostream means every operator<< overload and manipulator works unchanged; the difference lies in the StringBuf backing storage and in take_view, which yields a std::string_view directly into the buffer for hand-off to the active sink without an intermediate copy.

Supported operators

Operation	Source	Notes
operator<<	std::ostream interface	All integral, floating, pointer types
Standard manipulators	std::ios_base::fmtflags etc.	std::hex, std::setw, std::setfill, ...
write_raw	direct buffer write	Bypasses locale and format flags
append_to	append current contents	Does not reset the buffer
take_view	hand-off as string_view	View invalidated by the next write

Growth policy

Stage	Capacity
Initial	kDefaultCapacity (256)
Doubling	until kMaxExpandSize (8192)
Linear increments	kMaxExpandSize step thereafter

Example

vlink::FastStream stream;
stream << "sensor_id=" << 42 << " value=" << 3.14;
std::string_view view = stream.take_view();  // valid until next write
write_to_sink(view);
stream.reset();
 
stream.write_raw("LITERAL", 7);              // bypass formatting

Note

Not thread-safe; the logger keeps one FastStream per thread via thread_local. Views returned by take_view become invalid on the next stream operation or reset.