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 = [2, 4, 8, 16]
}%

% for N in sizes:

internal struct _FixedArray${N}<T> {
  // ABI TODO: This makes 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
  )

  var _count: Int8
}

extension _FixedArray${N} {
  internal static var capacity: Int {
    @inline(__always) get { return ${N} }
  }

  internal var capacity: Int {
    @inline(__always) get { return ${N} }
  }

  internal var count: Int {
    @inline(__always) get { return Int(truncatingIfNeeded: _count) }
    @inline(__always) set { _count = Int8(newValue) }
  }
}

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

  internal var startIndex : Index {
    return 0
  }

  internal var endIndex : Index {
    return count
  }

  internal subscript(i: Index) -> T {
    @inline(__always)
    get {
      let count = self.count // for exclusive access
      _internalInvariant(i >= 0 && i < count)
      let res: T = withUnsafeBytes(of: storage) {
        (rawPtr : UnsafeRawBufferPointer) -> T in
        let stride = MemoryLayout<T>.stride
        _internalInvariant(rawPtr.count == ${N}*stride, "layout mismatch?")
        let bufPtr = UnsafeBufferPointer(
          start: rawPtr.baseAddress!.assumingMemoryBound(to: T.self),
          count: count)
        return bufPtr[_unchecked: i]
      }
      return res
    }
    @inline(__always)
    set {
      _internalInvariant(i >= 0 && i < count)
      self.withUnsafeMutableBufferPointer { buffer in
        buffer[_unchecked: i] = newValue
      }
    }
  }

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

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

extension _FixedArray${N} {
  internal mutating func append(_ newElement: T) {
    _internalInvariant(count < capacity)
    _count += 1
    self[count-1] = newElement
  }
}

extension _FixedArray${N} where T : ExpressibleByIntegerLiteral {
  @inline(__always)
  internal init(count: Int) {
    _internalInvariant(count >= 0 && count <= _FixedArray${N}.capacity)
    self.storage = (
% for i in range(0, N-1):
    0,
% end
    0
    )
    self._count = Int8(truncatingIfNeeded: count)
  }

  @inline(__always)
  internal init() {
    self.init(count: 0)
  }

  @inline(__always)
  internal init(allZeros: ()) {
    self.init(count: ${N})
  }
}

extension _FixedArray${N} {
  internal mutating func withUnsafeMutableBufferPointer<R>(
    _ body: (UnsafeMutableBufferPointer<Element>) throws -> R
  ) rethrows -> R {
    let count = self.count // for exclusive access
    return try withUnsafeMutableBytes(of: &storage) { rawBuffer in
      _internalInvariant(rawBuffer.count == ${N}*MemoryLayout<T>.stride,
        "layout mismatch?")
      let buffer = UnsafeMutableBufferPointer<Element>(
        start: rawBuffer.baseAddress._unsafelyUnwrappedUnchecked
          .assumingMemoryBound(to: Element.self),
        count: count)
      return try body(buffer)
    }
  }

  internal mutating func withUnsafeBufferPointer<R>(
    _ body: (UnsafeBufferPointer<Element>) throws -> R
  ) rethrows -> R {
    let count = self.count // for exclusive access
    return try withUnsafeBytes(of: &storage) { rawBuffer in
      _internalInvariant(rawBuffer.count == ${N}*MemoryLayout<T>.stride,
        "layout mismatch?")
      let buffer = UnsafeBufferPointer<Element>(
        start: rawBuffer.baseAddress._unsafelyUnwrappedUnchecked
        .assumingMemoryBound(to: Element.self),
        count: count)
      return try body(buffer)
    }
  }
}

% end

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