Apple Platforms

Buffer on iOS, macOS, watchOS, and tvOS wraps Foundation's NSData.

Implementation

Zone	Apple Type
Heap	ByteArray
Direct	NSMutableData
SharedMemory	NSMutableData

NSData Integration

Buffers wrap NSMutableData for seamless Foundation interop:

val buffer = PlatformBuffer.allocate(1024)
buffer.writeString("Hello from Kotlin!")
buffer.resetForRead()

// Access underlying NSData (platform-specific)
// val nsData: NSData = buffer.asNSData()

Swift Interop

When exposing to Swift code:

// In Swift
let buffer = PlatformBuffer.companion.allocate(size: 1024)
buffer.writeInt(value: 42)
buffer.resetForRead()
let value = buffer.readInt()

Memory Management

Memory is managed automatically through Kotlin/Native GC and Objective-C ARC cooperation:

• Kotlin wrapper (MutableDataBuffer/ByteArrayBuffer) - managed by Kotlin/Native GC
• Underlying NSData/NSMutableData - managed by Objective-C ARC

When the Kotlin buffer object is garbage collected, the reference to the underlying NSData is released, allowing ARC to deallocate it.

fun processData(): PlatformBuffer {
    val buffer = PlatformBuffer.allocate(1024)
    buffer.writeBytes(data)
    buffer.resetForRead()
    return buffer  // Kotlin GC + ARC manage lifecycle automatically
}

// No manual cleanup needed - memory is released when buffer is unreachable

Implementation Detail

The close() method on Apple buffers is a no-op since ARC handles cleanup automatically. The SuspendCloseable interface is implemented for API consistency across platforms.

Native Data Conversion

Convert buffers to Apple-native NSData/NSMutableData for Foundation API interop:

val buffer = PlatformBuffer.allocate(1024)
buffer.writeBytes(data)
buffer.resetForRead()

// Get read-only NSData (zero-copy for MutableDataBuffer)
val nativeData = buffer.toNativeData()
val nsData: NSData = nativeData.nsData
NSFileManager.defaultManager.createFileAtPath(path, nsData, null)

// Get mutable NSMutableData
val mutableData = buffer.toMutableNativeData()
val nsMutableData: NSMutableData = mutableData.nsMutableData

Zero-Copy Behavior

Conversion	ByteArrayBuffer	MutableDataBuffer
toNativeData()	Copy	Zero-copy (subdataWithRange)
toMutableNativeData()	Copy	Zero-copy (full buffer only)
toByteArray()	Zero-copy (backing array)	Copy

Partial Views

For toNativeData(), subdataWithRange creates a zero-copy view of the remaining bytes.

For toMutableNativeData(), zero-copy is only possible when position is 0 and the entire buffer is used. Partial views require a copy because NSMutableData needs mutable ownership of its memory.

Wrapping NSData

You can also create buffers from existing NSData:

// Wrap NSData (read-only, zero-copy)
val nsData: NSData = // ... from API ...
val buffer = PlatformBuffer.wrap(nsData)

// Wrap NSMutableData (mutable, zero-copy)
val nsMutableData: NSMutableData = // ... from API ...
val buffer = PlatformBuffer.wrap(nsMutableData)

See Platform Interop for more details.

Best Practices

1. Use Direct (default) - NSMutableData is efficient
2. No manual cleanup needed - Kotlin GC and ARC work together
3. Pool for hot paths - reduce allocation overhead