stdlib/public/core/FixedArray.swift.gyb

//===--- FixedArray.swift.gyb ---------------------------------*- swift -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
//  A helper struct to provide fixed-sized array like functionality
//
//===----------------------------------------------------------------------===//

%{
  # The sizes to generate code for.
  sizes = [16]
}%

% for N in sizes:

internal struct _FixedArray${N}<T> {
  // ABI TODO: The has assumptions about tuple layout in the ABI, namely that
  // they are laid out contiguously and individually addressable (i.e. strided).
  //
  internal var storage: (
    // A ${N}-wide tuple of type T
% for i in range(0, N-1):
    T,
% end
    T
  )

  static var _arraySize : Int { return ${N} }
}

extension _FixedArray${N} : RandomAccessCollection, MutableCollection {
  internal typealias Index = Int
  internal typealias IndexDistance = Int

  internal var startIndex : Index {
    return 0
  }

  internal var endIndex : Index {
    return _FixedArray${N}._arraySize
  }

  internal var count : IndexDistance { return _FixedArray${N}._arraySize }

  internal subscript(i: Index) -> T {
    @_versioned
    @inline(__always)
    get {
      var copy = storage
      let res: T = withUnsafeBytes(of: &copy) {
        (rawPtr : UnsafeRawBufferPointer) -> T in
        let stride = MemoryLayout<T>.stride
        _sanityCheck(rawPtr.count == ${N}*stride, "layout mismatch?")
        let bufPtr = UnsafeBufferPointer(
          start: rawPtr.baseAddress!.assumingMemoryBound(to: T.self),
          count: count)
        return bufPtr[i]
      }
      return res
    }
    @_versioned
    @inline(__always)
    set {
      withUnsafeBytes(of: &storage) {
        (rawPtr : UnsafeRawBufferPointer) -> () in
        let rawPtr = UnsafeMutableRawBufferPointer(mutating: rawPtr)
        let stride = MemoryLayout<T>.stride
        _sanityCheck(rawPtr.count == ${N}*stride, "layout mismatch?")
        let bufPtr = UnsafeMutableBufferPointer(
          start: rawPtr.baseAddress!.assumingMemoryBound(to: T.self),
          count: count)
        bufPtr[i] = newValue
      }
    }
  }

  @_versioned
  @inline(__always)
  internal func index(after i: Index) -> Index {
    return i+1
  }

  @_versioned
  @inline(__always)
  internal func index(before i: Index) -> Index {
    return i-1
  }

  // TODO: Any customization hooks it's profitable to override, e.g. append?

}

extension _FixedArray${N} where T: IntegerLiteralConvertible {
  @inline(__always)
  internal init(allZeros:()) {
    self.storage = (
% for i in range(0, N-1):
    0,
% end
    0
    )
  }
}

% end