swift/Sources/FlatBuffers/ByteBuffer.swift - third_party/flatbuffers - Git at Google

 import Foundation

 public final class ByteBuffer {

     /// pointer to the start of the buffer object in memory
     private var _memory: UnsafeMutableRawPointer
     /// The size of the elements written to the buffer + their paddings
     private var _writerSize: Int = 0
     /// Capacity of UInt8 the buffer can hold
     private var _capacity: Int

     /// Aliginment of the current  memory being written to the buffer
     internal var alignment = 1
     /// Current Index which is being used to write to the buffer, it is written from the end to the start of the buffer
     internal var writerIndex: Int { return _capacity - _writerSize }

     /// Reader is the position of the current Writer Index (capacity - size)
     public var reader: Int { return writerIndex }
     /// Current size of the buffer
     public var size: UOffset { return UOffset(_writerSize) }
     /// Public Pointer to the buffer object in memory. This should NOT be modified for any reason
     public var memory: UnsafeMutableRawPointer { return _memory }
     /// Current capacity for the buffer
     public var capacity: Int { return _capacity }

     /// Constructor that creates a Flatbuffer object from a UInt8
     /// - Parameter bytes: Array of UInt8
     public init(bytes: [UInt8]) {
         let ptr = UnsafePointer(bytes)
         _memory = UnsafeMutableRawPointer.allocate(byteCount: bytes.count, alignment: alignment)
         _memory.copyMemory(from: ptr, byteCount: bytes.count)
         _capacity = bytes.count
         _writerSize = _capacity
     }

     /// Constructor that creates a Flatbuffer from the Swift Data type object
     /// - Parameter data: Swift data Object
     public init(data: Data) {
         let pointer = UnsafeMutablePointer<UInt8>.allocate(capacity: data.count)
         data.copyBytes(to: pointer, count: data.count)
         _memory = UnsafeMutableRawPointer(pointer)
         _capacity = data.count
         _writerSize = _capacity
     }

     /// Constructor that creates a Flatbuffer instance with a size
     /// - Parameter size: Length of the buffer
     init(initialSize size: Int) {
         let size = size.convertToPowerofTwo
         _memory = UnsafeMutableRawPointer.allocate(byteCount: size, alignment: alignment)
         _memory.initializeMemory(as: UInt8.self, repeating: 0, count: size)
         _capacity = size
     }

 #if swift(>=5.0)
     /// Constructor that creates a Flatbuffer object from a ContiguousBytes
     /// - Parameters:
     ///   - contiguousBytes: Binary stripe to use as the buffer
     ///   - count: amount of readable bytes
     public init<Bytes: ContiguousBytes>(
         contiguousBytes: Bytes,
         count: Int
     ) {
         _memory = UnsafeMutableRawPointer.allocate(byteCount: count, alignment: alignment)
         _capacity = count
         _writerSize = _capacity
         contiguousBytes.withUnsafeBytes { buf in
             _memory.copyMemory(from: buf.baseAddress!, byteCount: buf.count)
         }
     }
 #endif

     /// Creates a copy of the buffer that's being built by calling sizedBuffer
     /// - Parameters:
     ///   - memory: Current memory of the buffer
     ///   - count: count of bytes
     internal init(memory: UnsafeMutableRawPointer, count: Int) {
         _memory = UnsafeMutableRawPointer.allocate(byteCount: count, alignment: alignment)
         _memory.copyMemory(from: memory, byteCount: count)
         _capacity = count
         _writerSize = _capacity
     }

     /// Creates a copy of the existing flatbuffer, by copying it to a different memory.
     /// - Parameters:
     ///   - memory: Current memory of the buffer
     ///   - count: count of bytes
     ///   - removeBytes: Removes a number of bytes from the current size
     internal init(memory: UnsafeMutableRawPointer, count: Int, removing removeBytes: Int) {
         _memory = UnsafeMutableRawPointer.allocate(byteCount: count, alignment: alignment)
         _memory.copyMemory(from: memory, byteCount: count)
         _capacity = count
         _writerSize = removeBytes
     }

     deinit { _memory.deallocate() }

     /// Fills the buffer with padding by adding to the writersize
     /// - Parameter padding: Amount of padding between two to be serialized objects
     func fill(padding: UInt32) {
         ensureSpace(size: padding)
         _writerSize += (MemoryLayout<UInt8>.size * Int(padding))
     }

     ///Adds an array of type Scalar to the buffer memory
     /// - Parameter elements: An array of Scalars
     func push<T: Scalar>(elements: [T]) {
         let size = elements.count * MemoryLayout<T>.size
         ensureSpace(size: UInt32(size))
         elements.lazy.reversed().forEach { (s) in
             push(value: s, len: MemoryLayout.size(ofValue: s))
         }
     }

     /// A custom type of structs that are padded according to the flatbuffer padding,
     /// - Parameters:
     ///   - value: Pointer to the object in memory
     ///   - size: Size of Value being written to the buffer
     func push(struct value: UnsafeMutableRawPointer, size: Int) {
         ensureSpace(size: UInt32(size))
         memcpy(_memory.advanced(by: writerIndex - size), value, size)
         defer { value.deallocate() }
         _writerSize += size
     }

     /// Adds an object of type Scalar into the buffer
     /// - Parameters:
     ///   - value: Object  that will be written to the buffer
     ///   - len: Offset to subtract from the WriterIndex
     func push<T: Scalar>(value: T, len: Int) {
         ensureSpace(size: UInt32(len))
         var v = value.convertedEndian
         memcpy(_memory.advanced(by: writerIndex - len), &v, len)
         _writerSize += len
     }

     /// Adds a string to the buffer using swift.utf8 object
     /// - Parameter str: String that will be added to the buffer
     /// - Parameter len: length of the string
     func push(string str: String, len: Int) {
         ensureSpace(size: UInt32(len))
         if str.utf8.withContiguousStorageIfAvailable({ self.push(bytes: $0, len: len) }) != nil {
         } else {
             let utf8View = str.utf8
             for c in utf8View.lazy.reversed() {
                 push(value: c, len: 1)
             }
         }
     }

     /// Writes a string to Bytebuffer using UTF8View
     /// - Parameters:
     ///   - bytes: Pointer to the view
     ///   - len: Size of string
     private func push(bytes: UnsafeBufferPointer<String.UTF8View.Element>, len: Int) -> Bool {
         _memory.advanced(by: writerIndex - len).copyMemory(from:
             UnsafeRawPointer(bytes.baseAddress!), byteCount: len)
         _writerSize += len
         return true
     }

     /// Write stores an object into the buffer directly or indirectly.
     ///
     /// Direct: ignores the capacity of buffer which would mean we are referring to the direct point in memory
     /// indirect: takes into respect the current capacity of the buffer (capacity - index), writing to the buffer from the end
     /// - Parameters:
     ///   - value: Value that needs to be written to the buffer
     ///   - index: index to write to
     ///   - direct: Should take into consideration the capacity of the buffer
     func write<T>(value: T, index: Int, direct: Bool = false) {
         var index = index
         if !direct {
             index = _capacity - index
         }
         _memory.storeBytes(of: value, toByteOffset: index, as: T.self)
     }

     /// Makes sure that buffer has enouch space for each of the objects that will be written into it
     /// - Parameter size: size of object
     @discardableResult
     func ensureSpace(size: UInt32) -> UInt32 {
         if Int(size) + _writerSize > _capacity { reallocate(size) }
         assert(size < FlatBufferMaxSize, "Buffer can't grow beyond 2 Gigabytes")
         return size
     }

     /// Reallocates the buffer incase the object to be written doesnt fit in the current buffer
     /// - Parameter size: Size of the current object
     fileprivate func reallocate(_ size: UInt32) {
         let currentWritingIndex = writerIndex
         while _capacity <= _writerSize + Int(size) {
             _capacity = _capacity << 1
         }

         /// solution take from Apple-NIO
         _capacity = _capacity.convertToPowerofTwo

         let newData = UnsafeMutableRawPointer.allocate(byteCount: _capacity, alignment: alignment)
         newData.initializeMemory(as: UInt8.self, repeating: 0, count: _capacity)
         newData
             .advanced(by: writerIndex)
             .copyMemory(from: _memory.advanced(by: currentWritingIndex), byteCount: _writerSize)
         _memory.deallocate()
         _memory = newData
     }

     /// Clears the current size of the buffer
     public func clearSize() {
         _writerSize = 0
     }

     /// Clears the current instance of the buffer, replacing it with new memory
     public func clear() {
         _writerSize = 0
         alignment = 1
         _memory.deallocate()
         _memory = UnsafeMutableRawPointer.allocate(byteCount: _capacity, alignment: alignment)
     }

     /// Resizes the buffer size
     /// - Parameter size: new size for the buffer
     internal func resize(_ size: Int) {
         _writerSize = size
     }

     /// Reads an object from the buffer
     /// - Parameters:
     ///   - def: Type of the object
     ///   - position: the index of the object in the buffer
     public func read<T>(def: T.Type, position: Int) -> T {
         return _memory.advanced(by: position).load(as: T.self)
     }

     /// Reads a slice from the memory assuming a type of T
     /// - Parameters:
     ///   - index: index of the object to be read from the buffer
     ///   - count: count of bytes in memory
     public func readSlice<T>(index: Int32,
                              count: Int32) -> [T] {
         let start = _memory.advanced(by: Int(index)).assumingMemoryBound(to: T.self)
         let array = UnsafeBufferPointer(start: start, count: Int(count))
         return Array(array)
     }

     /// Reads a string from the buffer and encodes it to a swift string
     /// - Parameters:
     ///   - index: index of the string in the buffer
     ///   - count: length of the string
     ///   - type: Encoding of the string
     public func readString(at index: Int32,
                            count: Int32,
                            type: String.Encoding = .utf8) -> String? {
         let start = _memory.advanced(by: Int(index)).assumingMemoryBound(to: UInt8.self)
         let bufprt = UnsafeBufferPointer(start: start, count: Int(count))
         return String(bytes: Array(bufprt), encoding: type)
     }

     /// Creates a new Flatbuffer object that's duplicated from the current one
     /// - Parameter removeBytes: the amount of bytes to remove from the current Size
     public func duplicate(removing removeBytes: Int = 0) -> ByteBuffer {
         return ByteBuffer(memory: _memory, count: _capacity, removing: _writerSize - removeBytes)
     }
 }

 extension ByteBuffer: CustomDebugStringConvertible {

     public var debugDescription: String {
         """
         buffer located at: \(_memory), with capacity of \(_capacity)
         { writerSize: \(_writerSize), readerSize: \(reader), writerIndex: \(writerIndex) }
         """
     }
 }
	import Foundation

	public final class ByteBuffer {

	/// pointer to the start of the buffer object in memory
	private var _memory: UnsafeMutableRawPointer
	/// The size of the elements written to the buffer + their paddings
	private var _writerSize: Int = 0
	/// Capacity of UInt8 the buffer can hold
	private var _capacity: Int

	/// Aliginment of the current memory being written to the buffer
	internal var alignment = 1
	/// Current Index which is being used to write to the buffer, it is written from the end to the start of the buffer
	internal var writerIndex: Int { return _capacity - _writerSize }

	/// Reader is the position of the current Writer Index (capacity - size)
	public var reader: Int { return writerIndex }
	/// Current size of the buffer
	public var size: UOffset { return UOffset(_writerSize) }
	/// Public Pointer to the buffer object in memory. This should NOT be modified for any reason
	public var memory: UnsafeMutableRawPointer { return _memory }
	/// Current capacity for the buffer
	public var capacity: Int { return _capacity }

	/// Constructor that creates a Flatbuffer object from a UInt8
	/// - Parameter bytes: Array of UInt8
	public init(bytes: [UInt8]) {
	let ptr = UnsafePointer(bytes)
	_memory = UnsafeMutableRawPointer.allocate(byteCount: bytes.count, alignment: alignment)
	_memory.copyMemory(from: ptr, byteCount: bytes.count)
	_capacity = bytes.count
	_writerSize = _capacity
	}

	/// Constructor that creates a Flatbuffer from the Swift Data type object
	/// - Parameter data: Swift data Object
	public init(data: Data) {
	let pointer = UnsafeMutablePointer<UInt8>.allocate(capacity: data.count)
	data.copyBytes(to: pointer, count: data.count)
	_memory = UnsafeMutableRawPointer(pointer)
	_capacity = data.count
	_writerSize = _capacity
	}

	/// Constructor that creates a Flatbuffer instance with a size
	/// - Parameter size: Length of the buffer
	init(initialSize size: Int) {
	let size = size.convertToPowerofTwo
	_memory = UnsafeMutableRawPointer.allocate(byteCount: size, alignment: alignment)
	_memory.initializeMemory(as: UInt8.self, repeating: 0, count: size)
	_capacity = size
	}

	#if swift(>=5.0)
	/// Constructor that creates a Flatbuffer object from a ContiguousBytes
	/// - Parameters:
	/// - contiguousBytes: Binary stripe to use as the buffer
	/// - count: amount of readable bytes
	public init<Bytes: ContiguousBytes>(
	contiguousBytes: Bytes,
	count: Int
	) {
	_memory = UnsafeMutableRawPointer.allocate(byteCount: count, alignment: alignment)
	_capacity = count
	_writerSize = _capacity
	contiguousBytes.withUnsafeBytes { buf in
	_memory.copyMemory(from: buf.baseAddress!, byteCount: buf.count)
	}
	}
	#endif

	/// Creates a copy of the buffer that's being built by calling sizedBuffer
	/// - Parameters:
	/// - memory: Current memory of the buffer
	/// - count: count of bytes
	internal init(memory: UnsafeMutableRawPointer, count: Int) {
	_memory = UnsafeMutableRawPointer.allocate(byteCount: count, alignment: alignment)
	_memory.copyMemory(from: memory, byteCount: count)
	_capacity = count
	_writerSize = _capacity
	}

	/// Creates a copy of the existing flatbuffer, by copying it to a different memory.
	/// - Parameters:
	/// - memory: Current memory of the buffer
	/// - count: count of bytes
	/// - removeBytes: Removes a number of bytes from the current size
	internal init(memory: UnsafeMutableRawPointer, count: Int, removing removeBytes: Int) {
	_memory = UnsafeMutableRawPointer.allocate(byteCount: count, alignment: alignment)
	_memory.copyMemory(from: memory, byteCount: count)
	_capacity = count
	_writerSize = removeBytes
	}

	deinit { _memory.deallocate() }

	/// Fills the buffer with padding by adding to the writersize
	/// - Parameter padding: Amount of padding between two to be serialized objects
	func fill(padding: UInt32) {
	ensureSpace(size: padding)
	_writerSize += (MemoryLayout<UInt8>.size * Int(padding))
	}

	///Adds an array of type Scalar to the buffer memory
	/// - Parameter elements: An array of Scalars
	func push<T: Scalar>(elements: [T]) {
	let size = elements.count * MemoryLayout<T>.size
	ensureSpace(size: UInt32(size))
	elements.lazy.reversed().forEach { (s) in
	push(value: s, len: MemoryLayout.size(ofValue: s))
	}
	}

	/// A custom type of structs that are padded according to the flatbuffer padding,
	/// - Parameters:
	/// - value: Pointer to the object in memory
	/// - size: Size of Value being written to the buffer
	func push(struct value: UnsafeMutableRawPointer, size: Int) {
	ensureSpace(size: UInt32(size))
	memcpy(_memory.advanced(by: writerIndex - size), value, size)
	defer { value.deallocate() }
	_writerSize += size
	}

	/// Adds an object of type Scalar into the buffer
	/// - Parameters:
	/// - value: Object that will be written to the buffer
	/// - len: Offset to subtract from the WriterIndex
	func push<T: Scalar>(value: T, len: Int) {
	ensureSpace(size: UInt32(len))
	var v = value.convertedEndian
	memcpy(_memory.advanced(by: writerIndex - len), &v, len)
	_writerSize += len
	}

	/// Adds a string to the buffer using swift.utf8 object
	/// - Parameter str: String that will be added to the buffer
	/// - Parameter len: length of the string
	func push(string str: String, len: Int) {
	ensureSpace(size: UInt32(len))
	if str.utf8.withContiguousStorageIfAvailable({ self.push(bytes: $0, len: len) }) != nil {
	} else {
	let utf8View = str.utf8
	for c in utf8View.lazy.reversed() {
	push(value: c, len: 1)
	}
	}
	}

	/// Writes a string to Bytebuffer using UTF8View
	/// - Parameters:
	/// - bytes: Pointer to the view
	/// - len: Size of string
	private func push(bytes: UnsafeBufferPointer<String.UTF8View.Element>, len: Int) -> Bool {
	_memory.advanced(by: writerIndex - len).copyMemory(from:
	UnsafeRawPointer(bytes.baseAddress!), byteCount: len)
	_writerSize += len
	return true
	}

	/// Write stores an object into the buffer directly or indirectly.
	///
	/// Direct: ignores the capacity of buffer which would mean we are referring to the direct point in memory
	/// indirect: takes into respect the current capacity of the buffer (capacity - index), writing to the buffer from the end
	/// - Parameters:
	/// - value: Value that needs to be written to the buffer
	/// - index: index to write to
	/// - direct: Should take into consideration the capacity of the buffer
	func write<T>(value: T, index: Int, direct: Bool = false) {
	var index = index
	if !direct {
	index = _capacity - index
	}
	_memory.storeBytes(of: value, toByteOffset: index, as: T.self)
	}

	/// Makes sure that buffer has enouch space for each of the objects that will be written into it
	/// - Parameter size: size of object
	@discardableResult
	func ensureSpace(size: UInt32) -> UInt32 {
	if Int(size) + _writerSize > _capacity { reallocate(size) }
	assert(size < FlatBufferMaxSize, "Buffer can't grow beyond 2 Gigabytes")
	return size
	}

	/// Reallocates the buffer incase the object to be written doesnt fit in the current buffer
	/// - Parameter size: Size of the current object
	fileprivate func reallocate(_ size: UInt32) {
	let currentWritingIndex = writerIndex
	while _capacity <= _writerSize + Int(size) {
	_capacity = _capacity << 1
	}

	/// solution take from Apple-NIO
	_capacity = _capacity.convertToPowerofTwo

	let newData = UnsafeMutableRawPointer.allocate(byteCount: _capacity, alignment: alignment)
	newData.initializeMemory(as: UInt8.self, repeating: 0, count: _capacity)
	newData
	.advanced(by: writerIndex)
	.copyMemory(from: _memory.advanced(by: currentWritingIndex), byteCount: _writerSize)
	_memory.deallocate()
	_memory = newData
	}

	/// Clears the current size of the buffer
	public func clearSize() {
	_writerSize = 0
	}

	/// Clears the current instance of the buffer, replacing it with new memory
	public func clear() {
	_writerSize = 0
	alignment = 1
	_memory.deallocate()
	_memory = UnsafeMutableRawPointer.allocate(byteCount: _capacity, alignment: alignment)
	}

	/// Resizes the buffer size
	/// - Parameter size: new size for the buffer
	internal func resize(_ size: Int) {
	_writerSize = size
	}

	/// Reads an object from the buffer
	/// - Parameters:
	/// - def: Type of the object
	/// - position: the index of the object in the buffer
	public func read<T>(def: T.Type, position: Int) -> T {
	return _memory.advanced(by: position).load(as: T.self)
	}

	/// Reads a slice from the memory assuming a type of T
	/// - Parameters:
	/// - index: index of the object to be read from the buffer
	/// - count: count of bytes in memory
	public func readSlice<T>(index: Int32,
	count: Int32) -> [T] {
	let start = _memory.advanced(by: Int(index)).assumingMemoryBound(to: T.self)
	let array = UnsafeBufferPointer(start: start, count: Int(count))
	return Array(array)
	}

	/// Reads a string from the buffer and encodes it to a swift string
	/// - Parameters:
	/// - index: index of the string in the buffer
	/// - count: length of the string
	/// - type: Encoding of the string
	public func readString(at index: Int32,
	count: Int32,
	type: String.Encoding = .utf8) -> String? {
	let start = _memory.advanced(by: Int(index)).assumingMemoryBound(to: UInt8.self)
	let bufprt = UnsafeBufferPointer(start: start, count: Int(count))
	return String(bytes: Array(bufprt), encoding: type)
	}

	/// Creates a new Flatbuffer object that's duplicated from the current one
	/// - Parameter removeBytes: the amount of bytes to remove from the current Size
	public func duplicate(removing removeBytes: Int = 0) -> ByteBuffer {
	return ByteBuffer(memory: _memory, count: _capacity, removing: _writerSize - removeBytes)
	}
	}

	extension ByteBuffer: CustomDebugStringConvertible {

	public var debugDescription: String {
	"""
	buffer located at: \(_memory), with capacity of \(_capacity)
	{ writerSize: \(_writerSize), readerSize: \(reader), writerIndex: \(writerIndex) }
	"""
	}
	}