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# Strings and Buffers

For an improved experience when working with strings,
UCX provides an API to work with structures that store a [string](string.h.md) together with its length,
as well as a more sophisticated [buffer](buffer.h.md) API for working with text of dynamic or unknown length.

Additionally, UCX offers several advanced [printf-like functions](printf.h.md) that also allow convenient work
with strings of unknown length.
For example, one the more advanced functions is `cx_sprintf_sa()` which lets you format a string into an existing
pre-allocated buffer (e.g. on the stack) and automatically switches to a fresh buffer allocated by a custom allocator
when the existing buffer is not large enough.

The string API is designed to work with _both_ mutable and constant strings.
The possibility to work with constant strings is especially important when you want to work with string literals
without copying them into a separate memory region - e.g., when you want to get a substring.

By default, UCX assumes strings are constant and stores them in a structure of type `cxstring`.
Mutable strings are stored in a separate structure called `cxmutstr`.
You can conveniently convert any UCX string to a `cxstring` by using `cx_strcast()`.
Several macros throughout UCX already do that for you.
Since this function is usually inlined, this comes with no additional cost when compiled with optimizations enabled.