CFDataGetMutableBytePtr

CFDataGetMutableBytePtr is a function in the Core Foundation framework of Apple's operating systems, including macOS and iOS. It is used to obtain a pointer to the mutable byte buffer of a CFMutableData object. A CFMutableData object is a dynamic array of bytes that can be resized and modified. When you call CFDataGetMutableBytePtr, you are given direct access to the raw memory where the data is stored. This allows for efficient, low-level manipulation of the data.

The function signature is typically void *CFDataGetMutableBytePtr(CFMutableDataRef data). It takes a reference to a CFMutableData object as input and returns a void pointer. This void pointer can then be cast to a type such as unsigned char * or char * to work with individual bytes or sequences of bytes. It is important to note that modifying the data through the obtained pointer directly changes the contents of the CFMutableData object.

It is crucial to ensure that the CFMutableData object remains valid while you hold the pointer. If the CFMutableData object is deallocated or resized in a way that invalidates the pointer, using the pointer can lead to undefined behavior, including crashes. Developers should be mindful of the object's lifecycle and avoid holding onto the pointer longer than necessary. CFDataGetMutableBytePtr is a powerful tool for performance-critical operations where direct memory access is beneficial.