.. _module-pw_string:

=========
pw_string
=========
.. pigweed-module::
   :name: pw_string

   - **Efficient**: No memory allocation, no pointer indirection.
   - **Easy**: Use the string API you already know.
   - **Safe**: Never worry about buffer overruns or undefined behavior.

   *Pick three!* If you know how to use ``std::string``, just use
   :cc:`pw::InlineString` in the same way:

   .. Note for docs maintainers: the next code example could be built
   .. but is difficult to test because it generates a runtime crash.

   .. code-block:: cpp

      // Create a string from a C-style char array; storage is pre-allocated!
      pw::InlineString<16> my_string = "Literally";

      // We have some space left, so let's add to the string.
      my_string.append('?', 3);  // "Literally???"

      // Let's try something evil and extend this past its capacity 😈
      my_string.append('!', 8);
      // Foiled by a crash! No mysterious bugs or undefined behavior.

   Need to build up a string? :cc:`pw::StringBuilder` works like
   ``std::ostringstream``, but with most of the efficiency and memory benefits
   of :cc:`pw::InlineString`:

   .. DOCSTAG: [contributing-docs-examples]

   .. literalinclude:: ./examples/build_string_in_buffer_test.cc
      :language: cpp
      :dedent:
      :start-after: // DOCSTAG: [build-string-in-buffer]
      :end-before: // DOCSTAG: [build-string-in-buffer]

   .. DOCSTAG: [contributing-docs-examples]

   Check out :ref:`module-pw_string-guide` for more code samples.

String manipulation on embedded systems can be surprisingly challenging.

- **C strings?** They're light-weight but come with many pitfalls for those who
  don't know the standard library deeply.

- **C++ strings?** STL string classes are safe and easy to use, but they consume
  way too much code space and are designed to be used with dynamic memory
  allocation.

- **Roll your own strings?** You don't have time! You have a product to ship!

Embedded systems need string functionality that is both *safe* and *suitable*
for resource-constrained platforms.

.. rst-class:: key-text

   ``pw_string`` provides safe string handling functionality with an API that
   closely matches that of ``std::string``, but without dynamic memory
   allocation and with a *much* smaller :ref:`binary size impact<module-pw_string-size-reports>`.

--------------------
Is it right for you?
--------------------
.. rst-class:: key-text

   ``pw_string`` is useful any time you need to handle strings in embedded C++.

If your project written in C, ``pw_string`` is not a good fit since we don't
currently expose a C API.

On the other hand, for larger platforms where code space isn't in short supply
and dynamic memory allocation isn't a problem, you may find that ``std::string``
meets your needs.

.. tip::
   ``pw_string`` works just as well on larger embedded platforms and host
   systems. Using ``pw_string`` even when you could get away with ``std::string``
   gives you the flexibility to move to smaller platforms later with much less
   rework.

.. toctree::
   :hidden:
   :maxdepth: 1

   guide
   design
   code_size

.. grid:: 2

   .. grid-item-card:: :octicon:`rocket` Get Started & Guides
      :link: module-pw_string-get-started
      :link-type: ref
      :class-item: sales-pitch-cta-primary

      Integrate pw_string into your project and learn common use cases

   .. grid-item-card:: :octicon:`code-square` API Reference
      :link: ../api/cc/group__pw__string.html
      :link-type: url
      :class-item: sales-pitch-cta-secondary

      Detailed description of pw_string's classes and methods

.. grid:: 2

   .. grid-item-card:: :octicon:`code-square` Design & Roadmap
      :link: module-pw_string-design
      :link-type: ref
      :class-item: sales-pitch-cta-secondary

      Learn why pw_string is designed the way it is, and upcoming plans

   .. grid-item-card:: :octicon:`code-square` Code Size Analysis
      :link: module-pw_string-size-reports
      :link-type: ref
      :class-item: sales-pitch-cta-secondary

      Understand pw_string's code footprint and savings potential