blocks|key|4399869|text|下面是UnsafeMutableRawPointer到T/UnsafeMutablePointer转换的接口文档：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4399870|///+Binds+the+allocated+memory+to+type+`T`+and+returns+an
///+`UnsafePointer<T>`+to+the+bound+memory+at+`self`.
///
///+-+Precondition:+The+memory+is+uninitialized.
///+-+Postcondition:+The+memory+is+bound+to+'T'+starting+at+`self`+continuing
///+++through+`self`+%2B+`count`+*+`MemoryLayout<T>.stride`
///+-+Warning:+Binding+memory+to+a+type+is+potentially+undefined+if+the
///+++memory+is+ever+accessed+as+an+unrelated+type.
public+func+bindMemory<T>(to+type:+T.Type,+capacity+count:+Int)+->+UnsafePointer<T>

///+Converts+from+an+`UnsafeRawPointer`+to+UnsafePointer<T>+given+that
///+the+region+of+memory+starting+at+`self`+is+already+bound+to+type+`T`.
///
///+-+Precondition:+The+memory+is+bound+to+'T'+starting+at+`self`+for+some
///+++unspecified+capacity.
///
///+-+Warning:+Accessing+memory+via+the+returned+pointer+is+undefined+if+the
///+++if+the+memory+has+not+been+bound+to+`T`.
public+func+assumingMemoryBound<T>(to:+T.Type)+->+UnsafePointer<T>

///+Reads+raw+bytes+from+memory+at+`self+%2B+offset`+and+constructs+a
///+value+of+type+`T`.
///
///+-+Precondition:+The+underlying+pointer+plus+`offset`+is+properly
///+++aligned+for+accessing+`T`.
///
///+-+Precondition:+The+memory+is+initialized+to+a+value+of+some+type,+`U`,
///+++such+that+`T`+is+layout+compatible+with+`U`.
public+func+load<T>(fromByteOffset+offset:+Int+=+default,+as+type:+T.Type)+->+T|code-block|syntax|javascript|4399871|然后可以使用pointee和move+apis将Unsafe[MutablePointer]<T>转换为T|offset|length|style|CODE|4399872|///+Accesses+the+`Pointee`+instance+referenced+by+`self`.
///
///+-+Precondition:+the+pointee+has+been+initialized+with+an+instance+of
///+++type+`Pointee`.
public+var+pointee:+Pointee+{+get+}

///+Retrieves+the+`pointee`,+returning+the+referenced+memory+to+an
///+uninitialized+state.
///
///+Equivalent+to+`{+defer+{+deinitialize()+};+return+pointee+}()`,+but
///+more+efficient.
///
///+-+Precondition:+The+pointee+is+initialized.
///
///+-+Postcondition:+The+memory+is+uninitialized.
public+func+move()+->+Pointee|4399873|entityMap^0|0|0|6|7|E|4|O|P|1G|1|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]|$I|V|J|W|K|L]|$I|X|J|Y|K|L]|$I|Z|J|10|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|P|$]]

Here are the api documentation of Unsafe[Mutable]RawPointer to T/Unsafe[MutablePointer] conversion:

<pre><code>/// Binds the allocated memory to type `T` and returns an
/// `UnsafePointer&lt;T&gt;` to the bound memory at `self`.
///
/// - Precondition: The memory is uninitialized.
/// - Postcondition: The memory is bound to 'T' starting at `self` continuing
/// through `self` + `count` * `MemoryLayout&lt;T&gt;.stride`
/// - Warning: Binding memory to a type is potentially undefined if the
/// memory is ever accessed as an unrelated type.
public func bindMemory&lt;T&gt;(to type: T.Type, capacity count: Int) -&gt; UnsafePointer&lt;T&gt;

/// Converts from an `UnsafeRawPointer` to UnsafePointer&lt;T&gt; given that
/// the region of memory starting at `self` is already bound to type `T`.
///
/// - Precondition: The memory is bound to 'T' starting at `self` for some
/// unspecified capacity.
///
/// - Warning: Accessing memory via the returned pointer is undefined if the
/// if the memory has not been bound to `T`.
public func assumingMemoryBound&lt;T&gt;(to: T.Type) -&gt; UnsafePointer&lt;T&gt;

/// Reads raw bytes from memory at `self + offset` and constructs a
/// value of type `T`.
///
/// - Precondition: The underlying pointer plus `offset` is properly
/// aligned for accessing `T`.
///
/// - Precondition: The memory is initialized to a value of some type, `U`,
/// such that `T` is layout compatible with `U`.
public func load&lt;T&gt;(fromByteOffset offset: Int = default, as type: T.Type) -&gt; T
</code></pre>

and then from <code>Unsafe[MutablePointer]&lt;T&gt;</code> to<code>T</code> can be converted with
<code>pointee</code> and <code>move</code> apis

<pre><code>/// Accesses the `Pointee` instance referenced by `self`.
///
/// - Precondition: the pointee has been initialized with an instance of
/// type `Pointee`.
public var pointee: Pointee { get }

/// Retrieves the `pointee`, returning the referenced memory to an
/// uninitialized state.
///
/// Equivalent to `{ defer { deinitialize() }; return pointee }()`, but
/// more efficient.
///
/// - Precondition: The pointee is initialized.
///
/// - Postcondition: The memory is uninitialized.
public func move() -&gt; Pointee
</code></pre>

blocks|key|4399920|text|下面是一个将文字UInt8数组转换为UnsafeMutableRawPointer数组然后再转换回UInt32数组的Swift+4示例|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4399921|static+func+unsafePointerTest()+{
++++//let+a+:+[UInt8]+=+[0,0,0,4,0,0,0,8,0,0,0,12]
++++let+a+:+[UInt8]+=+[0x04,+0x00,+0x00,+0x00,
+++++++++++++++++++++++0x08,+0x00,+0x00,+0x00,
+++++++++++++++++++++++0x0C,+0x00,+0x00,+0x00]+//little+endian
++++//0xFF,+0xF0,+0xF0,+0x12]++//317780223+=+12F0F0FF
++++let+b:UnsafeMutableRawPointer+=+UnsafeMutableRawPointer(mutating:a)
++++let+bTypedPtr+=+b.bindMemory(to:+UInt32.self,+capacity:+a.count/4)
++++let+UInt32Buffer+=+UnsafeBufferPointer(start:+bTypedPtr,+count:+a.count/4)
++++let+output+=+Array(UInt32Buffer)
++++print(output)
}|code-block|syntax|javascript|4399922|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here's a Swift 4 example of converting a literal UInt8 array to an UnsafeMutableRawPointer and back to an UInt32 array

<pre><code>static func unsafePointerTest() {
 //let a : [UInt8] = [0,0,0,4,0,0,0,8,0,0,0,12]
 let a : [UInt8] = [0x04, 0x00, 0x00, 0x00,
 0x08, 0x00, 0x00, 0x00,
 0x0C, 0x00, 0x00, 0x00] //little endian
 //0xFF, 0xF0, 0xF0, 0x12] //317780223 = 12F0F0FF
 let b:UnsafeMutableRawPointer = UnsafeMutableRawPointer(mutating:a)
 let bTypedPtr = b.bindMemory(to: UInt32.self, capacity: a.count/4)
 let UInt32Buffer = UnsafeBufferPointer(start: bTypedPtr, count: a.count/4)
 let output = Array(UInt32Buffer)
 print(output)
}
</code></pre>

How does one access bytes (or Int16's, floats, etc.) out of memory pointed to by an UnsafeMutableRawPointer (new in Swift 3) handed to a Swift function by a C API (Core Audio, etc.)

How to get bytes out of an UnsafeMutableRawPointer?

Swift

如何访问字节(或Int16、浮点数等)由C应用程序接口(核心音频等)传递给Swift函数的UnsafeMutableRawPointer ( Swift 3中的新功能)指向的内存不足

问如何从UnsafeMutableRawPointer中提取字节？
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