1 files changed, 153 insertions, 0 deletions
diff --git a/js/src/frontend/BytecodeOffset.h b/js/src/frontend/BytecodeOffset.h
new file mode 100644
index 0000000000..cb13e9e79a
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+++ b/js/src/frontend/BytecodeOffset.h
@@ -0,0 +1,153 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef frontend_BytecodeOffset_h
+#define frontend_BytecodeOffset_h
+
+#include "mozilla/Assertions.h"  // MOZ_ASSERT
+#include "mozilla/CheckedInt.h"  // mozilla::CheckedInt
+
+#include <stddef.h>  // ptrdiff_t
+
+namespace js {
+namespace frontend {
+
+class BytecodeOffsetDiff;
+
+// The offset inside bytecode.
+class BytecodeOffset {
+ private:
+  static const ptrdiff_t INVALID_OFFSET = -1;
+
+  ptrdiff_t value_ = 0;
+
+  struct Invalid {};
+  explicit constexpr BytecodeOffset(Invalid) : value_(INVALID_OFFSET) {}
+
+ public:
+  constexpr BytecodeOffset() = default;
+
+  explicit BytecodeOffset(ptrdiff_t value) : value_(value) {
+    MOZ_ASSERT(value >= 0);
+  }
+
+  static constexpr BytecodeOffset invalidOffset() {
+    return BytecodeOffset(Invalid());
+  }
+
+  bool operator==(const BytecodeOffset& rhs) const {
+    return value_ == rhs.value_;
+  }
+
+  bool operator!=(const BytecodeOffset& rhs) const { return !(*this == rhs); }
+
+  inline BytecodeOffsetDiff operator-(const BytecodeOffset& rhs) const;
+  inline BytecodeOffset operator+(const BytecodeOffsetDiff& diff) const;
+
+  inline BytecodeOffset& operator+=(const BytecodeOffsetDiff& diff);
+  inline BytecodeOffset& operator-=(const BytecodeOffsetDiff& diff);
+
+  bool operator<(const BytecodeOffset& rhs) const {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(rhs.valid());
+    return value_ < rhs.value_;
+  }
+  bool operator<=(const BytecodeOffset& rhs) const {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(rhs.valid());
+    return value_ <= rhs.value_;
+  }
+  bool operator>(const BytecodeOffset& rhs) const {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(rhs.valid());
+    return value_ > rhs.value_;
+  }
+  bool operator>=(const BytecodeOffset& rhs) const {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(rhs.valid());
+    return value_ >= rhs.value_;
+  }
+
+  ptrdiff_t value() const { return value_; }
+  uint32_t toUint32() const {
+    MOZ_ASSERT(size_t(uint32_t(value_)) == size_t(value_));
+    return uint32_t(value_);
+  }
+
+  bool valid() const { return value_ != INVALID_OFFSET; }
+};
+
+class BytecodeOffsetDiff {
+ private:
+  friend class BytecodeOffset;
+
+  ptrdiff_t value_ = 0;
+
+ public:
+  constexpr BytecodeOffsetDiff() = default;
+
+  explicit constexpr BytecodeOffsetDiff(ptrdiff_t value_) : value_(value_) {}
+
+  bool operator==(const BytecodeOffsetDiff& rhs) const {
+    return value_ == rhs.value_;
+  }
+
+  bool operator!=(const BytecodeOffsetDiff& rhs) const {
+    return !(*this == rhs);
+  }
+
+  BytecodeOffsetDiff operator+(const BytecodeOffsetDiff& rhs) const {
+    mozilla::CheckedInt<ptrdiff_t> result = value_;
+    result += rhs.value_;
+    return BytecodeOffsetDiff(result.value());
+  }
+
+  ptrdiff_t value() const { return value_; }
+  uint32_t toUint32() const {
+    MOZ_ASSERT(size_t(uint32_t(value_)) == size_t(value_));
+    return uint32_t(value_);
+  }
+};
+
+inline BytecodeOffsetDiff BytecodeOffset::operator-(
+    const BytecodeOffset& rhs) const {
+  MOZ_ASSERT(valid());
+  MOZ_ASSERT(rhs.valid());
+  mozilla::CheckedInt<ptrdiff_t> result = value_;
+  result -= rhs.value_;
+  return BytecodeOffsetDiff(result.value());
+}
+
+inline BytecodeOffset BytecodeOffset::operator+(
+    const BytecodeOffsetDiff& diff) const {
+  MOZ_ASSERT(valid());
+  mozilla::CheckedInt<ptrdiff_t> result = value_;
+  result += diff.value_;
+  return BytecodeOffset(result.value());
+}
+
+inline BytecodeOffset& BytecodeOffset::operator+=(
+    const BytecodeOffsetDiff& diff) {
+  MOZ_ASSERT(valid());
+  mozilla::CheckedInt<ptrdiff_t> result = value_;
+  result += diff.value_;
+  value_ = result.value();
+  return *this;
+}
+
+inline BytecodeOffset& BytecodeOffset::operator-=(
+    const BytecodeOffsetDiff& diff) {
+  MOZ_ASSERT(valid());
+  mozilla::CheckedInt<ptrdiff_t> result = value_;
+  result -= diff.value_;
+  value_ = result.value();
+  return *this;
+}
+
+} /* namespace frontend */
+} /* namespace js */
+
+#endif /* frontend_BytecodeOffset_h */