CFDataAppendBytes

CFDataAppendBytes is a function in the Core Foundation framework of Apple's operating systems. It is used to append a specified number of bytes to an existing CFMutableData object. CFMutableData is a mutable data buffer that can grow or shrink in size.

The function takes three arguments: a pointer to the CFMutableData object to which the bytes will be appended, a pointer to the buffer containing the bytes to append, and the number of bytes to append from the buffer. If the operation is successful, the CFMutableData object's contents are updated to include the appended bytes. The function returns void, meaning it does not return any value.

This function is crucial for dynamically building or modifying data structures in memory. For example, it could be used when reading data from a file or network socket and accumulating it into a single data object, or when constructing binary data for transmission. It's important to ensure that the CFMutableData object passed to the function is indeed mutable, as attempting to append bytes to an immutable CFData object would result in an error or undefined behavior. The memory occupied by the appended bytes must be valid for the duration of the append operation.