[llvm] r207069 - [ADT] Add a generic iterator utility for adapting iterators much like
Chandler Carruth
chandlerc at gmail.com
Wed Apr 23 20:31:23 PDT 2014
Author: chandlerc
Date: Wed Apr 23 22:31:23 2014
New Revision: 207069
URL: http://llvm.org/viewvc/llvm-project?rev=207069&view=rev
Log:
[ADT] Add a generic iterator utility for adapting iterators much like
Boost's iterator_adaptor, and a specific adaptor which iterates over
pointees when wrapped around an iterator over pointers.
This is the result of a long discussion on IRC with Duncan Smith, Dave
Blaikie, Richard Smith, and myself. Essentially, I could use some subset
of the iterator facade facilities often used from Boost, and everyone
seemed interested in having the functionality in a reasonably generic
form. I've tried to strike a balance between the pragmatism and the
established Boost design. The primary differences are:
1) Delegating to the standard iterator interface names rather than
special names that then make up a second iterator-like API.
2) Using the name 'pointee_iterator' which seems more clear than
'indirect_iterator'. The whole business of calling the '*p' operation
'pointer indirection' in the standard is ... quite confusing. And
'dereference' is no better of a term for moving from a pointer to
a reference.
Hoping Duncan, and others continue to provide comments on this until
we've got a nice, minimal abstraction.
Added:
llvm/trunk/include/llvm/ADT/iterator.h
llvm/trunk/unittests/Support/IteratorTest.cpp
Modified:
llvm/trunk/unittests/Support/CMakeLists.txt
Added: llvm/trunk/include/llvm/ADT/iterator.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/iterator.h?rev=207069&view=auto
==============================================================================
--- llvm/trunk/include/llvm/ADT/iterator.h (added)
+++ llvm/trunk/include/llvm/ADT/iterator.h Wed Apr 23 22:31:23 2014
@@ -0,0 +1,145 @@
+//===- iterator.h - Utilities for using and defining iterators --*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_ITERATOR_H
+#define LLVM_ADT_ITERATOR_H
+
+#include <iterator>
+
+namespace llvm {
+
+/// \brief CRTP base class for adapting an iterator to a different type.
+///
+/// This class can be used through CRTP to adapt one iterator into another.
+/// Typically this is done through providing in the derived class a custom \c
+/// operator* implementation. Other methods can be overridden as well.
+///
+/// FIXME: Factor out the iterator-facade-like aspects into a base class that
+/// can be used for defining completely custom iterators.
+template <typename DerivedT, typename WrappedIteratorT, typename T,
+ typename PointerT = T *, typename ReferenceT = T &,
+ // Don't provide these, they are mostly to act as aliases below.
+ typename WrappedTraitsT = std::iterator_traits<WrappedIteratorT>>
+class iterator_adaptor_base
+ : public std::iterator<typename WrappedTraitsT::iterator_category, T,
+ typename WrappedTraitsT::difference_type, PointerT,
+ ReferenceT> {
+protected:
+ WrappedIteratorT I;
+
+ iterator_adaptor_base() {}
+
+ template <
+ typename U,
+ typename = typename std::enable_if<
+ !std::is_same<typename std::remove_cv<
+ typename std::remove_reference<U>::type>::type,
+ DerivedT>::value>::type>
+ explicit iterator_adaptor_base(U &&u)
+ : I(std::forward<U &&>(u)) {}
+
+public:
+ typedef typename iterator_adaptor_base::iterator::difference_type
+ difference_type;
+
+ DerivedT &operator+=(difference_type n) {
+ I += n;
+ return *static_cast<DerivedT *>(this);
+ }
+ DerivedT &operator-=(difference_type n) {
+ I -= n;
+ return *static_cast<DerivedT *>(this);
+ }
+ DerivedT operator+(difference_type n) const {
+ DerivedT tmp = *this;
+ tmp += n;
+ return tmp;
+ }
+ friend DerivedT operator+(difference_type n, const DerivedT &i) {
+ return i + n;
+ }
+ DerivedT operator-(difference_type n) const {
+ DerivedT tmp = *this;
+ tmp -= n;
+ return tmp;
+ }
+ difference_type operator-(const DerivedT &RHS) const { return I - RHS.I; }
+
+ DerivedT &operator++() {
+ ++I;
+ return *static_cast<DerivedT *>(this);
+ }
+ DerivedT &operator--() {
+ --I;
+ return *static_cast<DerivedT *>(this);
+ }
+ DerivedT operator++(int) {
+ DerivedT tmp = *static_cast<DerivedT *>(this);
+ ++*this;
+ return tmp;
+ }
+ DerivedT operator--(int) {
+ DerivedT tmp = *static_cast<DerivedT *>(this);
+ --*this;
+ return tmp;
+ }
+
+ bool operator==(const DerivedT &RHS) const { return I == RHS.I; }
+ bool operator!=(const DerivedT &RHS) const {
+ return !static_cast<const DerivedT *>(this)->operator==(RHS);
+ }
+
+ bool operator<(const DerivedT &RHS) const { return I < RHS.I; }
+ bool operator>(const DerivedT &RHS) const {
+ return !static_cast<const DerivedT *>(this)->operator<(RHS) &&
+ !static_cast<const DerivedT *>(this)->operator==(RHS);
+ }
+ bool operator<=(const DerivedT &RHS) const {
+ return !static_cast<const DerivedT *>(this)->operator>(RHS);
+ }
+ bool operator>=(const DerivedT &RHS) const {
+ return !static_cast<const DerivedT *>(this)->operator<(RHS);
+ }
+
+ ReferenceT operator*() const { return *I; }
+ PointerT operator->() const {
+ return static_cast<const DerivedT *>(this)->operator*();
+ }
+ ReferenceT operator[](difference_type n) const {
+ return *static_cast<const DerivedT *>(this)->operator+(n);
+ }
+};
+
+/// \brief An iterator type that allows iterating over the pointees via some
+/// other iterator.
+///
+/// The typical usage of this is to expose a type that iterates over Ts, but
+/// which is implemented with some iterator over T*s:
+///
+/// \code
+/// typedef pointee_iterator<SmallVectorImpl<T *>::iterator> iterator;
+/// \endcode
+template <
+ typename WrappedIteratorT,
+ typename T = typename std::remove_pointer<
+ typename std::iterator_traits<WrappedIteratorT>::value_type>::type>
+struct pointee_iterator
+ : iterator_adaptor_base<pointee_iterator<WrappedIteratorT>,
+ WrappedIteratorT, T> {
+ pointee_iterator() {}
+ template <typename U>
+ pointee_iterator(U &&u)
+ : pointee_iterator::iterator_adaptor_base(std::forward<U &&>(u)) {}
+
+ T &operator*() const { return **this->I; }
+};
+
+}
+
+#endif
Modified: llvm/trunk/unittests/Support/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/CMakeLists.txt?rev=207069&r1=207068&r2=207069&view=diff
==============================================================================
--- llvm/trunk/unittests/Support/CMakeLists.txt (original)
+++ llvm/trunk/unittests/Support/CMakeLists.txt Wed Apr 23 22:31:23 2014
@@ -15,12 +15,13 @@ add_llvm_unittest(SupportTests
EndianTest.cpp
ErrorOrTest.cpp
FileOutputBufferTest.cpp
+ IteratorTest.cpp
LEB128Test.cpp
LineIteratorTest.cpp
LockFileManagerTest.cpp
+ MD5Test.cpp
ManagedStatic.cpp
MathExtrasTest.cpp
- MD5Test.cpp
MemoryBufferTest.cpp
MemoryTest.cpp
Path.cpp
Added: llvm/trunk/unittests/Support/IteratorTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/IteratorTest.cpp?rev=207069&view=auto
==============================================================================
--- llvm/trunk/unittests/Support/IteratorTest.cpp (added)
+++ llvm/trunk/unittests/Support/IteratorTest.cpp Wed Apr 23 22:31:23 2014
@@ -0,0 +1,59 @@
+//===- IteratorTest.cpp - Unit tests for iterator utilities ---------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/iterator.h"
+#include "llvm/ADT/SmallVector.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+TEST(PointeeIteratorTest, Basic) {
+ int arr[4] = { 1, 2, 3, 4 };
+ SmallVector<int *, 4> V;
+ V.push_back(&arr[0]);
+ V.push_back(&arr[1]);
+ V.push_back(&arr[2]);
+ V.push_back(&arr[3]);
+
+ typedef pointee_iterator<SmallVectorImpl<int *>::const_iterator> test_iterator;
+
+ test_iterator Begin, End;
+ Begin = V.begin();
+ End = test_iterator(V.end());
+
+ test_iterator I = Begin;
+ for (int i = 0; i < 4; ++i) {
+ EXPECT_EQ(*V[i], *I);
+
+ EXPECT_EQ(I, Begin + i);
+ EXPECT_EQ(I, std::next(Begin, i));
+ test_iterator J = Begin;
+ J += i;
+ EXPECT_EQ(I, J);
+ EXPECT_EQ(*V[i], Begin[i]);
+
+ EXPECT_NE(I, End);
+ EXPECT_GT(End, I);
+ EXPECT_LT(I, End);
+ EXPECT_GE(I, Begin);
+ EXPECT_LE(Begin, I);
+
+ EXPECT_EQ(i, I - Begin);
+ EXPECT_EQ(i, std::distance(Begin, I));
+ EXPECT_EQ(Begin, I - i);
+
+ test_iterator K = I++;
+ EXPECT_EQ(K, std::prev(I));
+ }
+ EXPECT_EQ(End, I);
+}
+
+} // anonymous namespace
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