//===--- UnsafeBufferPointer.swift.gyb ------------------------*- swift -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

/// A generator for the elements in the buffer referenced by
/// `UnsafeBufferPointer` or `UnsafeMutableBufferPointer`
public struct UnsafeBufferPointerGenerator<T>: GeneratorType, SequenceType {
  /// Advance to the next element and return it, or `nil` if no next
  /// element exists.
  public mutating func next() -> T? {
    return position == end ? nil : (position++).memory
  }

  /// `UnsafeBufferPointerGenerator` is also a `SequenceType`, so it
  /// `generate`\ 's a copy of itself
  public func generate() -> UnsafeBufferPointerGenerator {
    return self
  }
  
  var position, end: UnsafePointer<T>
}

%for Mutable in ('Mutable', ''):
/// A non-owning pointer to buffer of ${Mutable.lower()} `T`\ s stored
/// contiguously in memory, presenting a `Collection` interface to the
/// underlying elements.
public struct Unsafe${Mutable}BufferPointer<T> : ${Mutable}CollectionType {

  /// Always zero, which is the index of the first element in a
  /// non-empty buffer.
  public var startIndex: Int {
    return 0
  }

  /// The "past the end" position; always identical to `count`.
  ///
  /// `endIndex` is not a valid argument to `subscript`, and is always
  /// reachable from `startIndex` by zero or more applications of
  /// `successor()`.
  public var endIndex: Int {
    return _end - _position
  }

  /// Access the `i`\ th element in the buffer.
  public subscript(i: Int) -> T {
    get {
      _debugPrecondition(i >= 0)
      _debugPrecondition(i < endIndex)
      return _position[i]
    }
%if Mutable:
    nonmutating set {
      _debugPrecondition(i >= 0)
      _debugPrecondition(i < endIndex)
      _position[i] = newValue
    }
%end    
  }

  /// Construct an Unsafe${Mutable}Pointer over the `count` contiguous
  /// `T` instances beginning at `start`.
  public init(start: Unsafe${Mutable}Pointer<T>, count: Int) {
    _precondition(
      count >= 0, "Unsafe${Mutable}BufferPointer with negative count")
    _position = start
    _end = start + count
  }

  /// Return a *generator* over the elements of this *sequence*.
  ///
  /// Complexity: O(1)
  public func generate() -> UnsafeBufferPointerGenerator<T> {
    return UnsafeBufferPointerGenerator(position: _position, end: _end)
  }

  /// A pointer to the first element of the buffer
  public var baseAddress: Unsafe${Mutable}Pointer<T> {
    return _position
  }

  /// The number of elements in the buffer
  public var count: Int {
    return _end - _position
  }
  
  var _position, _end: Unsafe${Mutable}Pointer<T>
}

extension Unsafe${Mutable}BufferPointer : DebugPrintable {
  /// A textual representation of `self`, suitable for debugging.
  public var debugDescription: String {
    return "Unsafe${Mutable}BufferPointer"
    + "(start: \(_position), length: \(_end - _position))"
  }
}
%end

// ${'Local Variables'}:
// eval: (read-only-mode 1)
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