Boost.FixedString

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This is currently NOT an official Boost library.

Introduction

This library provides a dynamically resizable string of characters with compile-time fixed capacity and contiguous embedded storage in which the characters are placed within the string object itself. Its API closely resembles that of std::string

Motivation

A fixed capacity string is useful when:

• Memory allocation is not possible, e.g., embedded environments without a free store, where only a stack and the static memory segment are available.
• Memory allocation imposes an unacceptable performance penalty. e.g., with respect to latency.
• Allocation of objects with complex lifetimes in the static-memory segment is required.
• A dynamically-resizable string is required within constexpr functions.
• The storage location of the static_vector elements is required to be within the string object itself (e.g. to support memcpy for serialization purposes).

Design

The over-arching design goal is to resemble the interface and behavior of std::string as much as possible. When any operation would exceed the maximum allowed size of the string, std::length_error is thrown. All algorithms which throw exceptions provide the strong exception safety guarantee. This is intended to be a drop in replacement for std::string. All the operations for fixed_string work when the source is within the string itself.

The API of fixed_string only diverges from std::string in few places, being substr for which this implementation returns a string view instead of fixed_string, and certain functions that will never throw are marked as noexcept, which diverges from those of std::string. Every function that is in the C++20 specification of std::stringis present in this implementation, with the only difference being the lack ofconstexprfor the time being. The avaliable overloads forfixed_stringare identical to those ofstd::string, except for operator+which is explicitly deleted as no reasonable implementation would be possible, due to the difficulty in determining the size of the resultingfixed_string`.

Iterators

The iterator invalidation rules are different than those for std::string, since:

• Moving a string invalidates all iterators
• Swapping two strings invalidates all iterators

License

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)