---
title: SSLReadFunc
framework: security
role: symbol
role_heading: Type Alias
path: security/sslreadfunc
---

# SSLReadFunc

A pointer to a customized read function that secure transport calls to read data from the connection.

## Declaration

```swift
typealias SSLReadFunc = (SSLConnectionRef, UnsafeMutableRawPointer, UnsafeMutablePointer<Int>) -> OSStatus
```

## Parameters

- `connection`: A connection reference.
- `data`: On return, your callback should overwrite the memory at this location with the data read from the connection.
- `dataLength`: On input, a pointer to an integer representing the length of the data in bytes. On return, your callback should overwrite that integer with the number of bytes actually transferred.

## Mentioned in

Using the Secure Socket Layer for Network Communication

## Return Value

Return Value Your callback must return an appropriate result code. See Secure Transport Result Codes.

## Discussion

Discussion Before using the secure transport API, you must create a read function (conforming to the SSLReadFunc prototype) and a write function (conforming to  the SSLWriteFunc prototype) and provide them to the library by calling the SSLSetIOFuncs(_:_:_:) function. You may configure the underlying connection to operate in a non-blocking manner; in that case, a read operation may well return errSSLWouldBlock, indicating less data than requested was transferred and nothing is wrong except that the requested I/O hasn’t completed. This result is returned to the caller from the functions SSLRead(_:_:_:_:), SSLWrite(_:_:_:_:), or SSLHandshake(_:).