OSString wraps a C string in a C++ object for use in Libkern collections.
- macOS 10.0+
OSString is a container class for managing arrays of characters. An OSString normally maintains its own character buffer and allows changes, but you can create an "immutable" OSString that references an external C string buffer using the "NoCopy" creator functions. Functions called to change the contents of an immutable OSString will fail.
OSString makes no provisions for different character encodings and assumes that a string is a nul-terminated sequence of single-byte characters. User-space code must either assume an encoding (typically ASCII or UTF-8) or determine it in some other way (such as an IORegistryEntry property).
OSString's indended use is as a reference-counted object container for a C string and little more. While OSString provides full access to the underlying C string, it provides little in the way of string object manipulation; there are no append or insert functions, only a set-character function. If you need to manipulate OSStrings, it's generally best to get the C strings, alter them as necessary, and create a new OSString object from the resulting C string.
With very few exceptions in the I/O Kit, all Libkern-based C++ classes, functions, and macros are unsafe to use in a primary interrupt context. Consult the I/O Kit documentation related to primary interrupts for more information.
OSString provides no concurrency protection; it's up to the usage context to provide any protection necessary. Some portions of the I/O Kit, such as IORegistryEntry, handle synchronization via defined member functions for setting properties.