1//===--- CharUnits.h - Character units for sizes and offsets ----*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9//  This file defines the CharUnits class
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_CLANG_AST_CHARUNITS_H
14#define LLVM_CLANG_AST_CHARUNITS_H
15
16#include "llvm/ADT/DenseMapInfo.h"
17#include "llvm/Support/Alignment.h"
18#include "llvm/Support/DataTypes.h"
19#include "llvm/Support/MathExtras.h"
20
21namespace clang {
22
23  /// CharUnits - This is an opaque type for sizes expressed in character units.
24  /// Instances of this type represent a quantity as a multiple of the size
25  /// of the standard C type, char, on the target architecture. As an opaque
26  /// type, CharUnits protects you from accidentally combining operations on
27  /// quantities in bit units and character units.
28  ///
29  /// In both C and C++, an object of type 'char', 'signed char', or 'unsigned
30  /// char' occupies exactly one byte, so 'character unit' and 'byte' refer to
31  /// the same quantity of storage. However, we use the term 'character unit'
32  /// rather than 'byte' to avoid an implication that a character unit is
33  /// exactly 8 bits.
34  ///
35  /// For portability, never assume that a target character is 8 bits wide. Use
36  /// CharUnit values wherever you calculate sizes, offsets, or alignments
37  /// in character units.
38  class CharUnits {
39    public:
40      typedef int64_t QuantityType;
41
42    private:
43      QuantityType Quantity = 0;
44
45      explicit CharUnits(QuantityType C) : Quantity(C) {}
46
47    public:
48
49      /// CharUnits - A default constructor.
50      CharUnits() = default;
51
52      /// Zero - Construct a CharUnits quantity of zero.
53      static CharUnits Zero() {
54        return CharUnits(0);
55      }
56
57      /// One - Construct a CharUnits quantity of one.
58      static CharUnits One() {
59        return CharUnits(1);
60      }
61
62      /// fromQuantity - Construct a CharUnits quantity from a raw integer type.
63      static CharUnits fromQuantity(QuantityType Quantity) {
64        return CharUnits(Quantity);
65      }
66
67      // Compound assignment.
68      CharUnits& operator+= (const CharUnits &Other) {
69        Quantity += Other.Quantity;
70        return *this;
71      }
72      CharUnits& operator++ () {
73        ++Quantity;
74        return *this;
75      }
76      CharUnits operator++ (int) {
77        return CharUnits(Quantity++);
78      }
79      CharUnits& operator-= (const CharUnits &Other) {
80        Quantity -= Other.Quantity;
81        return *this;
82      }
83      CharUnits& operator-- () {
84        --Quantity;
85        return *this;
86      }
87      CharUnits operator-- (int) {
88        return CharUnits(Quantity--);
89      }
90
91      // Comparison operators.
92      bool operator== (const CharUnits &Other) const {
93        return Quantity == Other.Quantity;
94      }
95      bool operator!= (const CharUnits &Other) const {
96        return Quantity != Other.Quantity;
97      }
98
99      // Relational operators.
100      bool operator<  (const CharUnits &Other) const {
101        return Quantity <  Other.Quantity;
102      }
103      bool operator<= (const CharUnits &Other) const {
104        return Quantity <= Other.Quantity;
105      }
106      bool operator>  (const CharUnits &Other) const {
107        return Quantity >  Other.Quantity;
108      }
109      bool operator>= (const CharUnits &Other) const {
110        return Quantity >= Other.Quantity;
111      }
112
113      // Other predicates.
114
115      /// isZero - Test whether the quantity equals zero.
116      bool isZero() const     { return Quantity == 0; }
117
118      /// isOne - Test whether the quantity equals one.
119      bool isOne() const      { return Quantity == 1; }
120
121      /// isPositive - Test whether the quantity is greater than zero.
122      bool isPositive() const { return Quantity  > 0; }
123
124      /// isNegative - Test whether the quantity is less than zero.
125      bool isNegative() const { return Quantity  < 0; }
126
127      /// isPowerOfTwo - Test whether the quantity is a power of two.
128      /// Zero is not a power of two.
129      bool isPowerOfTwo() const {
130        return (Quantity & -Quantity) == Quantity;
131      }
132
133      /// Test whether this is a multiple of the other value.
134      ///
135      /// Among other things, this promises that
136      /// self.alignTo(N) will just return self.
137      bool isMultipleOf(CharUnits N) const {
138        return (*this % N) == 0;
139      }
140
141      // Arithmetic operators.
142      CharUnits operator* (QuantityType N) const {
143        return CharUnits(Quantity * N);
144      }
145      CharUnits &operator*= (QuantityType N) {
146        Quantity *= N;
147        return *this;
148      }
149      CharUnits operator/ (QuantityType N) const {
150        return CharUnits(Quantity / N);
151      }
152      CharUnits &operator/= (QuantityType N) {
153        Quantity /= N;
154        return *this;
155      }
156      QuantityType operator/ (const CharUnits &Other) const {
157        return Quantity / Other.Quantity;
158      }
159      CharUnits operator% (QuantityType N) const {
160        return CharUnits(Quantity % N);
161      }
162      QuantityType operator% (const CharUnits &Other) const {
163        return Quantity % Other.Quantity;
164      }
165      CharUnits operator+ (const CharUnits &Other) const {
166        return CharUnits(Quantity + Other.Quantity);
167      }
168      CharUnits operator- (const CharUnits &Other) const {
169        return CharUnits(Quantity - Other.Quantity);
170      }
171      CharUnits operator- () const {
172        return CharUnits(-Quantity);
173      }
174
175
176      // Conversions.
177
178      /// getQuantity - Get the raw integer representation of this quantity.
179      QuantityType getQuantity() const { return Quantity; }
180
181      /// getAsAlign - Returns Quantity as a valid llvm::Align,
182      /// Beware llvm::Align assumes power of two 8-bit bytes.
183      llvm::Align getAsAlign() const { return llvm::Align(Quantity); }
184
185      /// alignTo - Returns the next integer (mod 2**64) that is
186      /// greater than or equal to this quantity and is a multiple of \p Align.
187      /// Align must be non-zero.
188      CharUnits alignTo(const CharUnits &Align) const {
189        return CharUnits(llvm::alignTo(Quantity, Align.Quantity));
190      }
191
192      /// Given that this is a non-zero alignment value, what is the
193      /// alignment at the given offset?
194      CharUnits alignmentAtOffset(CharUnits offset) const {
195        assert(Quantity != 0 && "offsetting from unknown alignment?");
196        return CharUnits(llvm::MinAlign(Quantity, offset.Quantity));
197      }
198
199      /// Given that this is the alignment of the first element of an
200      /// array, return the minimum alignment of any element in the array.
201      CharUnits alignmentOfArrayElement(CharUnits elementSize) const {
202        // Since we don't track offsetted alignments, the alignment of
203        // the second element (or any odd element) will be minimally
204        // aligned.
205        return alignmentAtOffset(elementSize);
206      }
207
208
209  }; // class CharUnit
210} // namespace clang
211
212inline clang::CharUnits operator* (clang::CharUnits::QuantityType Scale,
213                                   const clang::CharUnits &CU) {
214  return CU * Scale;
215}
216
217namespace llvm {
218
219template<> struct DenseMapInfo<clang::CharUnits> {
220  static clang::CharUnits getEmptyKey() {
221    clang::CharUnits::QuantityType Quantity =
222      DenseMapInfo<clang::CharUnits::QuantityType>::getEmptyKey();
223
224    return clang::CharUnits::fromQuantity(Quantity);
225  }
226
227  static clang::CharUnits getTombstoneKey() {
228    clang::CharUnits::QuantityType Quantity =
229      DenseMapInfo<clang::CharUnits::QuantityType>::getTombstoneKey();
230
231    return clang::CharUnits::fromQuantity(Quantity);
232  }
233
234  static unsigned getHashValue(const clang::CharUnits &CU) {
235    clang::CharUnits::QuantityType Quantity = CU.getQuantity();
236    return DenseMapInfo<clang::CharUnits::QuantityType>::getHashValue(Quantity);
237  }
238
239  static bool isEqual(const clang::CharUnits &LHS,
240                      const clang::CharUnits &RHS) {
241    return LHS == RHS;
242  }
243};
244
245} // end namespace llvm
246
247#endif // LLVM_CLANG_AST_CHARUNITS_H
248