tor-browser

The Tor Browser
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BytecodeOffset.h (3573B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
      2 * vim: set ts=8 sts=2 et sw=2 tw=80:
      3 * This Source Code Form is subject to the terms of the Mozilla Public
      4 * License, v. 2.0. If a copy of the MPL was not distributed with this
      5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      6 
      7 #ifndef frontend_BytecodeOffset_h
      8 #define frontend_BytecodeOffset_h
      9 
     10 #include "mozilla/Assertions.h"  // MOZ_ASSERT
     11 #include "mozilla/CheckedInt.h"  // mozilla::CheckedInt
     12 
     13 #include <compare>   // std::strong_ordering
     14 #include <stddef.h>  // ptrdiff_t
     15 
     16 namespace js {
     17 namespace frontend {
     18 
     19 class BytecodeOffsetDiff;
     20 
     21 // The offset inside bytecode.
     22 class BytecodeOffset {
     23 private:
     24  static const ptrdiff_t INVALID_OFFSET = -1;
     25 
     26  ptrdiff_t value_ = 0;
     27 
     28  struct Invalid {};
     29  explicit constexpr BytecodeOffset(Invalid) : value_(INVALID_OFFSET) {}
     30 
     31 public:
     32  constexpr BytecodeOffset() = default;
     33 
     34  explicit BytecodeOffset(ptrdiff_t value) : value_(value) {
     35    MOZ_ASSERT(value >= 0);
     36  }
     37 
     38  static constexpr BytecodeOffset invalidOffset() {
     39    return BytecodeOffset(Invalid());
     40  }
     41 
     42  constexpr bool operator==(const BytecodeOffset& rhs) const = default;
     43 
     44  inline BytecodeOffsetDiff operator-(const BytecodeOffset& rhs) const;
     45  inline BytecodeOffset operator+(const BytecodeOffsetDiff& diff) const;
     46 
     47  inline BytecodeOffset& operator+=(const BytecodeOffsetDiff& diff);
     48  inline BytecodeOffset& operator-=(const BytecodeOffsetDiff& diff);
     49 
     50  auto operator<=>(const BytecodeOffset& rhs) const {
     51    MOZ_ASSERT(valid());
     52    MOZ_ASSERT(rhs.valid());
     53    return value_ <=> rhs.value_;
     54  }
     55 
     56  ptrdiff_t value() const { return value_; }
     57  uint32_t toUint32() const {
     58    MOZ_ASSERT(size_t(uint32_t(value_)) == size_t(value_));
     59    return uint32_t(value_);
     60  }
     61 
     62  bool valid() const { return value_ != INVALID_OFFSET; }
     63 };
     64 
     65 class BytecodeOffsetDiff {
     66 private:
     67  friend class BytecodeOffset;
     68 
     69  ptrdiff_t value_ = 0;
     70 
     71 public:
     72  constexpr BytecodeOffsetDiff() = default;
     73 
     74  explicit constexpr BytecodeOffsetDiff(ptrdiff_t value_) : value_(value_) {}
     75 
     76  constexpr bool operator==(const BytecodeOffsetDiff& rhs) const = default;
     77 
     78  BytecodeOffsetDiff operator+(const BytecodeOffsetDiff& rhs) const {
     79    mozilla::CheckedInt<ptrdiff_t> result = value_;
     80    result += rhs.value_;
     81    return BytecodeOffsetDiff(result.value());
     82  }
     83 
     84  ptrdiff_t value() const { return value_; }
     85  uint32_t toUint32() const {
     86    MOZ_ASSERT(size_t(uint32_t(value_)) == size_t(value_));
     87    return uint32_t(value_);
     88  }
     89 };
     90 
     91 inline BytecodeOffsetDiff BytecodeOffset::operator-(
     92    const BytecodeOffset& rhs) const {
     93  MOZ_ASSERT(valid());
     94  MOZ_ASSERT(rhs.valid());
     95  mozilla::CheckedInt<ptrdiff_t> result = value_;
     96  result -= rhs.value_;
     97  return BytecodeOffsetDiff(result.value());
     98 }
     99 
    100 inline BytecodeOffset BytecodeOffset::operator+(
    101    const BytecodeOffsetDiff& diff) const {
    102  MOZ_ASSERT(valid());
    103  mozilla::CheckedInt<ptrdiff_t> result = value_;
    104  result += diff.value_;
    105  return BytecodeOffset(result.value());
    106 }
    107 
    108 inline BytecodeOffset& BytecodeOffset::operator+=(
    109    const BytecodeOffsetDiff& diff) {
    110  MOZ_ASSERT(valid());
    111  mozilla::CheckedInt<ptrdiff_t> result = value_;
    112  result += diff.value_;
    113  value_ = result.value();
    114  return *this;
    115 }
    116 
    117 inline BytecodeOffset& BytecodeOffset::operator-=(
    118    const BytecodeOffsetDiff& diff) {
    119  MOZ_ASSERT(valid());
    120  mozilla::CheckedInt<ptrdiff_t> result = value_;
    121  result -= diff.value_;
    122  value_ = result.value();
    123  return *this;
    124 }
    125 
    126 } /* namespace frontend */
    127 } /* namespace js */
    128 
    129 #endif /* frontend_BytecodeOffset_h */