Determines how much data is available to be read.
- iOS 5.0+
- macOS 10.2+
- tvOS 9.0+
- watchOS 2.0+
An SSL session context reference.
On return, the size of the data to be read.
A result code. See Secure Transport Result Codes.
This function determines how much data you can be guaranteed to obtain in a call to the
SSLRead function. This function does not block or cause any low-level read operations to occur.